Calibration services brochure

Transcription

MIKES METROLOGY
Calibration Service
International competitiveness
and reliability
Copyright © VTT MIKES 2016
Teknologian tutkimuskeskus VTT Oy
PL 1000 (Vuorimiehentie 3, Espoo), 02044 VTT
Puh. +358 20 722 111, faksi +358 722 7001
www.vttresearch.com
2 — VTT MIKES METROLOGY Calibration services
VTT MIKES - metrology
Mass, pressure, flow
Calibration of weights.................................................................................... 6
Calibration of pressure measuring devices.................................................. 8
Calibration of force and torque................................................................... 10
Water flow meter calibrations...................................................................... 12
Calibration of gas flows and density of liquids............................................ 14
Acceleration of free fall............................................................................... 16
Temperature, humidity
Calibration of hygrometers.......................................................................... 18
Calibration of radiation thermometers........................................................ 20
Fixed point calibration of platinum resistance thermometrs....................... 22
Electricity, acoustics
Calibration of direct voltage and current.................................................... 24
Calibration of alternating voltage................................................................ 26
Calibration of capacitance and inductance standards................................ 28
Calibration of resistance............................................................................. 30
Calibration of power and energy at line frequency..................................... 32
RF- and microwave calibrations................................................................. 34
High voltage and high current..................................................................... 36
Acoustic calibrations................................................................................... 38
Time
Calibration of time, time interval,and frequency......................................... 40
Optics
Optical quantities......................................................................................... 42
Length, geometry
Quantitative Microscopy - Atomic force microscope................................... 44
Characterization of nanoparticles............................................................... 46
Calibration of laser interferometers............................................................. 48
Interferometrical calibration of gauge blocks.............................................. 50
Calibration of gauge blocks by mechanical comparison............................ 52
2D- and 3D-measurements of form and surface roughness...................... 54
Optical measurements of surface microstructures..................................... 56
Calibration of tachymeters.......................................................................... 58
Angle and perpendicularity measurements................................................ 60
Measurements of accurate inner and outer dimensions............................ 62
Coordinate measurements......................................................................... 64
Optical coordinate measuring - vision measuring...................................... 66
Calibration of line scales and distance meters........................................... 68
Interferometric measurements of flatness and form................................... 70
Machine tools measurements..................................................................... 72
Measurements of roundness........................................................ ..............74
Calibration of microscopes and calibration standards................................ 76
Length in geodesy....................................................................................... 78
Water quality............................................................................................... 80
VTT MIKES METROLOGY Calibration services 2016 — 3
VTT MIKES - metrology
MIKES
Tekniikantie 1
02150 ESPOO
MIKES-Kajaani
Tehdakatu 15, Puristamo 9P19
87100 KAJAANI
Tel. +358 020 722 111 (call center)
Email: forename.lastname@vtt.fi
www.mikes.fi
Finland has a slightly distributed metrology infrastructure. MIKES is the National Metrology Institute
and it acts as the National Standards Laboratory for most of the quantities. MIKES designates the other
National Standards Laboratories and Contract Laboratories..
MIKES is a specialised research institute for measurement
science and technology. As the National Metrology Institute
of Finland, MIKES is responsible for the implementation and
development of the national measurement standards system
and realisation of the SI units in Finland.
The MIKES building is situated in the city of Espoo and its
branch office in Kajaani is the northernmost National Standards Laboratory in the world. The high-quality laboratories
provide the most accurate measurements and calibrations
– close to 1600 certificates per year – in Finland.
The number of staff is 65 supported by VTT Ltd. administration.
MIKES also performs high-level metrological research and
develops measuring applications in partnership with industry.
The activities of MIKES aim to improve industrial competitiveness, the national innovative environment, and public safety.
• We realize SI-system of units in Finland
• We do high level research in the field of
metrology
• We develop measurement methods for
industry and society
• We offer high level calibration servive, expert
service and training
4 — VTT MIKES METROLOGY C alibration services 2016
MIKES is a signatory to CIPM MRA (International Committee
for Weights and Measures, Mutual Recognition Arrangement)
and a member of EURAMET (European Association of National Metrology Institutes). Through international collaboration,
MIKES is linked to the international measurement system and
to the European and international metrology research community. MIKES takes actively part in the European Metrology
Research Programme (EMRP and EMPIR).
The Metre Convention
The National Measurement Standards System
Electricity, acoustics, time, frequency, temperature,
humidity, pressure, mass, force, torque, flow and length
Photometry and
radiometry
Water quality
Air quality
Ionising radiation
Length in geodesy and
acceleration of free fall
Figure 1. National measurement standards system in Finland. MIKES=VTT MIKES Metrology, Aalto=MIKES Aalto Metrology Insitute,
SYKE=Finnish Environment Institute, FMI=Finnish Meterological Institute, STUK=Radiation and Nuclear Safety Authority and FGI=Finnish Geospatial Research Institute.
Calibration and MeasurementCapabilities (CMCs)recorded in the BIPM
keycomparison database,KCDB
Acoustics: 30
Length: 59
Time and frequency: 11
Thermometry: 44
Optics: 53
Mass and related quantities: 28
Electricity: 99
Ionising radiation: 30
Chemistry: 5
Total Finland: 359 / total 24031 entries.
Voluntary peer review project
MIKES is a coordinator in the EURAMET TC-Q project Peer
reviews of Quality Management Systems (QMSs). The other partners in the project are CMI (CZ), GUM (PL) and
SMU (SK). The project supports the evaluation and improvement of QMS processes and procedures of the participating institutes. Learning from each other and sharing
the best practice for QMS implementation are other goals
of the project. The QMSs of the institutes are based on
ISO/IEC 17025. A programme with on-site visits by peers
is planned on an annual basis and one or twofields in each
institute are reviewed every year. In 2012, the QMS of MIKES in the field of length metrology was peer reviewed by
an expert from GUM, and vice versa. Also the humidity laboratory of MIKES was peer reviewed by a GUM expert.
Source: BIPM, July 1, 2015, kcdb.bipm.org
Figure 2. CIPM MRA -logo
tells us, that our measurement results are accepted
globally.
Mass, pressure
flow
Temperature
humidity
Electricity, time
acoustics
Length
geometry
Optics
Chemistry
Calibration of weights
Maija Ojanen-Saloranta, Senior Research
Scientist, Tel. +358 50 443 4214 (Espoo)
maija.ojanen@vtt.fi
Kari Kyllönen, Research Technician Tel +358 50 4434180
(Kajaani), kari.kyllonen@vtt.fi
MIKES, Tekniikantie 1, 02150 Espoo
MIKES-Kajaani, Tehdaskatu 15, 87100
Kajaani, Tel. +358 20 722 111.
Traceability
Measure methods
The weight standards of MIKES mass laboratory are traceable
via the Pt-Ir prototype number 23 of kilogram to the international prototype of kilogram kept at the BIPM. The comparability
of measurement standards of mass laboratory is maintained
by international comparisons (e.g. EURAMET key comparisons). We carry out research and development related to
scales and weights and offer expert services on the usage
of scales and weights. Our mass laboratories are of high
quality and we have scales equipped with automatic weight
handlers. Our laboratories are located in Espoo and Kajaani.
The measurement range of mass at MIKES is 1 mg ... 2000
kg. The calibrations of weights are performed by using generally accepted
weighing methods: the direct comparison method and the
subdivision method. In the first method, the weight is directly compared
to a standard and in the latter a set of weights is calibrated
by using one or several weight standards.
6 — VTT MIKES METROLOGY Calibration services 2016
Calibration of weights
Table 1. Measurement uncertainties of weight calibrations.
Mass
Measurement uncertainty
(k=2)
2000 kg *)
3000 mg
1000 kg *)
1500 mg
500 kg *)
750 mg
200 kg *)
300 mg
100 kg *)
200 mg
50 kg *)
30 mg
20 kg
3.0 mg
10 kg
1.5 mg
5 kg
1.0 mg
Calibration services
2 kg
0.3 mg
1 kg
0.05 mg
500 g
0.03 mg
200 g
0.02 mg
100 g
0.015 mg
50 g
0.010 mg
20 g
0.008 mg
10 g
0.007 mg
5g
0.005 mg
2g
0.004 mg
1g
0.003 mg
500 mg
0.003 mg
200 mg
0.002 mg
100 mg
0.0015 mg
50 mg
0.0015 mg
20 mg
0.0010 mg
10 mg
0.0008 mg
5 mg
0.0008 mg
2 mg
0.0008 mg
1 mg
0.0008 mg
MIKES is capable to calibrate weights of OIML classes E1, E2,
and F1, whose nominal masses are at most 20 kg (E1), 50 kg
(E2) and 2000 kg (F1). In addition, MIKES offers calibration
services for weights of lower OIML classes, whose masses
are between 10 kg and 2000 kg. MIKES also calibrates other
weights such as weights of pressure balances. In the calibration
certificate, the masses are given as conventional masses
or as true masses. The smallest achievable measurement
uncertainties in mass calibrations are presented in table 1.
Weights whose nominal mass is 50 kg or bigger are calibrated
at MIKES Kajaani.
Calibration of volume of weights
When calibrating a weight, a correction due to the air buoyancy
has to be made to the weighing result. The magnitude of
the correction depends on the volume of the weight and on
the density of air. In order to be able to make the correction
accurately enough, the volumes of the most accurate weights
have to be known. Mass laboratory calibrates volumes and
densities of solid artefacts. The density standard is either
distilled water or silicon. The measurement methods is
hydrostatic weighing. The measuring equipment is suitable
for volume calibration of 2-kg weights or lighter. If needed,
volumes of bigger weights can be determined by using e.g.
dimensional measurements. The measurement uncertainties
of volume calibrations of weights are presented in table 2.
*) Calibration in MIKES-Kajaani
Table 2. Measurement uncertainties of calibrations of weight
volumes.
Mass
1 g – 2 kg
Uncertainty (k=2)
Volume
0.1 – 255 cm
3
0.000 3 – 0.008 cm3
Mass, pressure
flow
Temperature
humidity
Electricity, time
acoustics
Optics
Length
geometry
Chemistry
Calibration of pressure
measuring devices
Monika Lecklin, Research technician, Tel. +358 50 410 5516
monika.lecklin@vtt.fi
Sari Saxholm, Senior Research
Scientist, Tel +358 50 410 5499,
sari.saxholm@vtt.fi
Figure 1. Pressure balance is used for the traceable realization of pressure unit.
MIKES has good capabilities to calibrate different
measuring devices of pressure. The measuring range
for gauge pressure is 0 ... 500 MPa and for absolute
pressure 0.0005 Pa ... 1.75 MPa. The best measurement
MIKES, Tekniikantie 1,
02150 Espoo Tel +358 20 722 111
www.mikes.fi
standards at MIKES are pressure balances, which are
used to realise pressure according to its definition p =
F / A, i.e. pressure is force divided by area. The force
is produced by the mass of the piston of the pressure
balance and by the masses of weights loaded over
the piston. The local value for the acceleration of free
fall must be known. The area A is the effective area of
the piston cylinder assembly of the pressure balance.
Pressure balances are used for gauge and negative
gauge pressure measurements and for absolute pressure measurements. To cover a wide range of pressures, several piston cylinder assemblies of different
sizes are needed in order to be able to realise different pressures and to keep the number of weights still
easy to handle. In pressure ranges below the range of
pressure balances, capacitive sensors and spinning
rotor gauges are used as measurement standards.
The lowest pressures (absolute pressures 0.0005 Pa
... 2 Pa) are calibrated by using spinning rotor gauges.
These measurements are demanding as they require
long stabilisation and measurement times. Measurement methods and devices used for pressure depend
on the pressure range.
Figure 2. Pressure measurements are made in a very broad pressure range, for instance from 10-9 Pascals required in
particle accelerators to over 109 Pascals, i.e. 1 GPa, pressures used in powder met-allurgy. Measuring devices and their
operational principles are very different in different pressure ranges. The measurement range in MIKES is from 0.5mPa to
500 MPa and is marked with blue bar in the figure.
Calibration of pressure
Absolute pressure
Gauge pressure
Differential pressure
Gauge pressure
The reference point is the atmospheric pressure. E.g.,
the tyre pressure of a car is gauge pressure. Any gauge
pressure can be converted to an absolute pressure by
adding the momentary atmospheric pressure
Atmospheric
pressure
Absolut pressure
P=0
Figure 3. In practice, measurement of pressure is always measuring differential pressure. Depending on the reference point
various names are used for pressure and diverse devices used.
Absolute pressure
The ideal vacuum as reference point (vacuum gauges).
Atmospheric pressure
Atmospheric pressure is the absolute pressure caused by the atmosphere so the reference is the ideal
vacuum (barometers).
Absolute pressure
gaseous medium
Pressure range (Pa)
Relative measurement
uncertainty
k = 2 (%)
Negative gauge pressure
The reference point is the atmospheric pressure. When
converted to absolute pressures, negative gauge pressure is thereby lower than the atmospheric pressure.
Thus, negative gauge pressure means that the objects
pressure is lower than the pressure in its environment.
Differential pressure
Pressure is called as differential pressure especially
when the reference pressure is other than the vacuum
or the atmospheric pressure. The reference pressure
is then usually called as
a line pressure.
Gauge pressure
gaseous medium
Pressure range (Pa)
uncertainty
k = 2 (%)
0.0005
9
100
0.03
0.001
6
1000
0.01
0.01
3
10 000
0.004
0,.
3
100 000 (0.1 MPa)
0.003
1
2
1 000 000 (1 MPa)
0.002
10
0.5
10 000 000 (10 MPa)
0.004
100
0.1
16 000 000 (16 MPa)
0.004
1000
0.01
10 000
0.005
100 000 (0,1 MPa)
0.004
1 000 000 (1 MPa)
0.004
1 750 000 (1.75 MPa)
0.003
Negative gauge pressure gaseous medium
Pressure range (Pa)
uncertainty
k = 2 (%)
Figure 4. Piston cylinder assemblies of different size for pressure
balances.
Gauge pressure
in oil medium
Pressure range (Pa)
uncertainty
k = 2 (%)
-100
0.03
500 000 (0,5 MPa)
0.005
-1000
0.01
1 000 000 (1 MPa)
0.004
-10 000
0.005
10 000 000 (10 MPa)
0.003
-100 000 (-0.1 MPa)
0.004
100 000 000 (100 MPa)
0.003
500 000 000 (500 MPa)
0.01
Mass, pressure
flow
Temperature
humidity
Electricity, time
acoustics
Length
geometry
Optics
Chemistry
Calibration of force
and torque
Sauli Kilponen, Research Engineer, Tel. +358 50 443 4178
sauli.kilponen@vtt.fi
Jani Korhonen, Research Engineer Tel. +35850 443 4206
jani.korhonen@vtt.fi
MIKES, Tehdaskatu 15, Puristamo 9P19,
87100 Kajaani, Tel. +358 50 443 4213
www.mikes.fi
Traceability and
calibration of force
VTT MIKES-Kajaani performs force calibrations from
1 N to 1.1 MN. Calibrated measurement devices are
usually force transducers, force measurement devices, balances (eg. hook, wheel weight and airplane)
and pull force testers. The smallest measurement uncertainty is 2×10-5.
The calibration of force is based on the ISO 376 standard. The force calibration from 1 N to 110 kN is carried out in dead weight force standard machines. A
dead weight machine is a mechanical structure that
generates force by subjecting dead weights to the local gravitational field. Hydraulic force standard can be
used in the calibrations from 20 kN to 1.1 MN.
The masses that are used in VTT MIKES-Kajaani are
traceable to the national standard of mass, which is
in turn traceable to the international prototype of the
kilogram held in the BIPM. Force traceability is realised from mass calibrations and international comparisons.
Figure 1. A 1-MN hydraulic force standard and a 100-kN:n
direct load force standard. The total height of the equipment is eight meters, including the load masses below floor
level.
Table 1. Measurement ranges for force.
Load method
Measurement range
Measurement uncertainty (k=2)
Direct load
Compression/pulling: 10 nm ... 10 kN
2 . 10-5
Direct load
Compression/pulling: 10 kN ... 100 kN
5 . 10-5
Hydraulic load
Compression/pulling: 20 kN ... 1 MN
1 . 10-4
Field calibration of force
1 N ... 1 MN
5 10-4
Calibration of force and torque
Traceability and
calibration of torque
MIKES-Kajaani performs calibrations of torque in the
range 0.1 Nm ... 20 kNm, the smallest uncertainty
being 5×10–4. The calibration of torque is carried out
using reference standards for torque or standards
based on reference sensors.
The need for torque calibrations can be classified
in three groups of different types of devices. The
most stringent accuracy requirement (< 0.05 % ...
0.5 %) is for calibration of torque sensors that are
used e.g. in measurement of torque in research of
rotating machines such as pumps and motors. The
second group is devices used for calibration of
torque-controlled assembly tools. In calibration of
these devices, the uncertainty of the torque standard
should not exceed 0.5 %. The third group is calibration
of torque-controlled assembly tools for industries
that do not have their own calibration devices. The
calibration uncertainty for torque-controlled assembly
tools is typically from 1 % to 10 %.
There exist only a few standards for torque calibrations. For torque-controlled assembly tools is
the standard ISO 6789, which however mainly
describes test methods but also defines a cali-bration
procedure. There is no standard for devices used for
calibration of torquecontrolled assembly tools. For
torque sensors there exists the recommendation
Euramet/cg-14.
Torque is a derived quantity that consists of known
masses and a known length of a lever arm. Even
though traceability for masses and length can be
achieved separately, verifying the consistency of
torque in entity is mainly verifying the consistency
of torque in entity is mainly based on interlaboratory comparisons
Figure 2. A 2-kNm torque standard used for comparison
measurements in the range 100 Nm – 2 kNm and for
calibration of torque sensors.
Figure 3. A 20-kNm torque standard based on a
reference sensor.
Table 2. Measurement ranges for torque.
Torque standard
Measurement range
Measurement uncertainty (k=2)
Lever – mass
0.1 ... 10 Nm right/left
5 . 10-4
Lever – mass
10 ... 2000 Nm right/left
5 . 10-4
2 ... 20 kNm right/left
5 . 10-4
Reference standard
Mass, pressure
flow
Temperature
humidity
Electricity, time
acoustics
Optics
Length
geometry
Chemistry
Water flow
meter calibrations
Mika Huovinen, Researcher, Timo Nissilä, Research Engineer,
Tel. +358 50 443 4175
Tel. +358 50 415 5974
timo.nissila@vtt.fi
mika.huovinen@vtt.fi
MIKES, Tehdaskatu 15, Puristamo 9P19,
87100 Kajaani,
Tel. +358 50 443 4213
Calibration provides
reliability
Accurate liquid flow measurements are needed in
many areas of industry, such as process, mining and
energy industry. To maintain global competitiveness
and high quality of the end products, accurate liquid
flow measurements make it possible to optimise different industrial processes and in this way reduce raw
material consumption and emissions to environment.
Regular calibration and stability tracking of liquid flow
meters are essential part of measurement reliability,
regardless of the application.
Figure 1. Graphical user interface of the D200
liquid flow calibration rig.
Water flow meter calibrations
Traceability
The most important activities of MIKES Kajaani are to
implement the traceability of the flow measurements in
Finland, maintain liquid flow measurement standards,
and provide calibration and expert services. These are
achieved by participating in international and domestic
research and intercomparisons projects. The MIKES’s
liquid flow calibration laboratory’s quality management
system is based on the ISO/IEC 17025 standard.
MIKES Kajaani has three different calibration rigs for
liquid flow calibrations. One of the rigs is the national
measurement standard of flow. In this rig, the measuring principle is gravimetric and the measurements
carried out are traceable to the national standards of
mass, temperature and time.
ter is first continuously pumped up to a constant head
tank located 20 m above ground level. The water level is held constant in the tank by sufficient overflow
and by adjusting the water flow in a measuring pipe
section, where the flow meters under test are placed.
The calibration is done by comparing the results of the
balance and the meter under test reading.
In the closed loop type calibration rigs, the referencemeters are usually magnetic or coriolis mass flow
meters. In these rigs, the source of traceaility up to
DN200 is based on the national flow standard. For
pipe sizes DN200 > , the source of traceability is a
foreign NMI, typically PTB from Germany.
The measuring principles, ranges, and reachable
measurement uncertainties are shown in Table 1.
The gravimetric reference standard of water flow is based on weighing the water. In the measurements, waTable 1. Measuring ranges of the liquid flow calibration rigs and the measurement uncertainty.
Equipment
Measuring
principle
Pipe sizes
Volume flow
Pressure
Measurement uncertainty(k=2)
D100
reference
meter
DN 15
DN 50
0.3…20 L/s
<0.7 MPa
0.3 %
D500
reference
meter
DN 150
DN 500
7… 750 L/s
<0.5 MPa
0.3 %
D200
gravimetric
DN 10
DN 50
DN 100
DN 200
0.1 l/s… 200 L/s
0.2 MPa
0.03 %
For pulp and paper industry, MIKES Kajaani has a mass circulating rig applied with a cooling system. Consistency area 0 – 12 % and flow speed 0.5 – 3 m/s.
Figure 2. Part of the D500 liquid flow calibration rig.
Mass, pressure
flow
Temperature
humidity
Electricity, time
acoustics
Optics
Length
geometry
Chemistry
Calibration of gas flows
and density of liquids
Richard Högström, Senior Research
Scientist, Tel +358 50 303 9341
richard.hogstrom@vtt.fi
Heikki Kajastie, Researcher, Martti Heinonen, Principal
Metrologist, Tel. +358 400 686
Tel +358 50 410 5511
553, martti.heinonen@vtt.fi
heikki.kajastie@vtt.fi
Calibration gives
reliability
Nowadays, measurement of small gas flows is needed in various applications. For instance, in health
care and medical industry is very impor-tant to assure the safety of customers. In order to maintain international competiveness and to guarantee the high
quality of products, the accuracy of gas flow measurements in process industry has to be reliably verified. No matter what the application is, the regular
calibration and stability monitoring of gas flowmeters
is an essential part of quality control. MIKES cali-brates gas flowmeters in the flow range 5 ml/min...110
l/min and offers research and expert services in the
field of gas flow meas-urements and their reliability
02150 Espoo Puh. 020 722 111
www.mikes.fi
Traceability
MIKES provides circumstances for traceable gas
flow measurements in Finland by developing and
maintaining standards for gas flows and offers
calibration and expert services.
The traceabiltity of gas flows at MIKES is based
on a dynamic weighing system, DWS developed
at the flow laboratory of MIKES. The measurements performed using this system are traceable
to the national standards of mass and time. The
DWS equipment is used to calibrate measurement standards based on laminar flow elements
(LFE) and customers’ devices whose relative accuracy level is better than 1 %.
The high level of our gas flow measurement activities is maintained by actively participating in
international research projects and compari-sons
and by carrying out own research projects in this
field.
Calibration of gas flow and density of liquids
If the relative accuracy level of a gas flowmeter is
better than 1 %, the DWS equipment will be used in
the calibration. Typical examples of such flowmeters
are high-quality laminar flow elements and some piston-cylinder volume flowmeters.
Most of our customers’ flowmeters are calibrated
at MIKES using the LFE calibration equipment. It is
much more convenient to use than the DWS equipment and it does not have such a strict tolerances
for environmental conditions. Performing of calibrations are thus more flexible and faster. The equipment has proven to be well suited for calibration of
gas flowmeters having relative accuracy above 1 %.
Such meters include thermal mass flowmeters and
controllers.
Furthermore, MIKES performs liquid density measurements. We calibrate for instance areometers and
density meters based on vibra-tions and determine
densities of customers own liquid samples in the
density range 600 kg/m3 ... 2000 kg/m3.
Table 1. Measurement ranges and best achievable
calibration uncertainties at MIKES.
Quantity
Measurement range
Measurement
uncertainty (k=2)
Mass flow (DWS)
0.1 mg/s...625 mg/s
0.3 %...0.8 %
Mass flow (LFE)
0.1 mg/s...625 mg/s
0.4 %...0.9 %
5 ml/min...30 l/min
0.4 %...0.9 %
Density of liquid
(LDCS)
600 kg/m3...2000 kg/m3
15 ppm
Calibration of
areometers (HCS)
600 kg/m3...2000 kg/m3
0.05 %
Volume flow (LFE)
DWS = Dynamic weighing system
LFE = Laminar flow element
LDCS = Liquid density calibration system
HCS = Hydrometer calibration system
Mass, pressure
flow
Temperature
humidity
Electricity, time
acoustics
Optics
Length
geometry
Chemistry
Acceleration of free fall
Markku Poutanen, Prof.,
Tel. +358 29 531 4867,
markku.poutanen@nls.fi
Mirjam Bilker-Koivula,
Senior research scientist
Tel. +358 29 531 4696
mirjam.bilker-koivula@nls.fi
Hannu Ruotsalainen,
Senior research scientist,
Tel. +358 29 531 4876
hannu.ruotsalainen@nls.fi
Finnish Geospatial Research Institute, FGI
Geodeetinrinne 2, 02430 Masala,
Tel. +358 29 530 1100, www.fgi.fi
Finnish Geospatial Research
Institute, FGI
The Finnish Geospatial Research Institute, FGI, of the
National Land Survey of Finland maintains measurement standards for geodetic and photogrammetric
measurements and is the National Standards Laboratory of acceleration of free fall and length. The
FGI takes care of the fundamental measurements in
Finnish cartography and of geographical information
metrology and carries out scientific research in geodesy, geographic information sciences, positioning,
navigation, photogrammetry and remote sensing.
Methods and traceability
The national measurement standard is the absolute
gravimeter FG5-221. Its results are directly traceable
to length and time standards. We have participated in
all international comparisons since the year 1989. At a
customer’s site the measurements are usually performed with a relative gravimeter, measuring the gravity
difference with respect to a point with known gravity.
Acceleration of
free fall and gravity
The acceleration of free fall depends on location and
time. The time dependence originates from tidal forces (variation in Finland 3 μm s–2) and from mass variations of groundwater and atmosphere (at least an
order of magnitude smaller). When the most important time variations are removed from the acceleration
of free fall by using agreed methods, the result is the
acceleration due to gravity, which can be treated as a
time independent quantity..
Figure 1. Acceleration of free fall in Finland, unit m s-2.
Acceleration of free fall
Calibration services and
uncertainty
Research, development
and reporting
We measure gravity at requested sites and report the
value for the acceleration of free fall. The time variation is included in the uncertainty of 4 μm s–2 (k=2). If
needed, we supply an accurate value for gravity (the
smallest uncertainty is 0.008 μm s–2) and methods
to predict the time variation (the smallest uncertainty 0.10 μm s–2). We maintain an open calibration line
where customers can verify their gravimeters.
We carry out research and develop national infrastructure for measurements of gravity and acceleration of free fall for all applications (e.g geodesy,
geophysics and geology). With the help of the 30 000
points in the national gravity grid, the acceleration of
free fall can be estimated with an accuracy of 0.1 mm
s–2 without any new measurements. We have performed measurements using absolute gravimeters in 20
countries.
Figure 2. A measurement using a
relative gravimeter.
Figure 3. The absolute gravimeter FG5X-221 is based on a free fall experiment.
Figure 4. Superconducting gravimeter (Metsähovi, Kirkkonummi) registers
even 0.1 nm s–2 variations in the acceleration of free fall.
Mass, pressure
flow
Temperatue,
humidity
Electricity, time,
acoustic
Optics
Length,
geometry
Chemistry
Calibration
of hygrometers
Martti Heinonen, Pricipal Metrolo- Heikki Kajastie, Researcher,
gist, +358 400 686 553,
Tel +358 50 410 5511
martti.heinonen@vtt.fi
heikki.kajastie@vtt.fi
Hannu Räsänen, Senior Research
Technician, Tel +358 50 410 5497,
hannu.rasanen@vtt.fi
02150 Espoo, Tel +358 20 722 111
www.mikes.fi
Reliability from
calibration
Traceability to humidity
measurements
Reliability of humidity measurements is important,
e.g. in storage of wood, paper, food, etc. in aviation
and environmental monitoring as well as in diverse
fields of industry and research. Cali-bration of hygrometers at regular intervals and monitoring their stability is an essential part of verification of measurements.
MIKES creates conditions for traceable humidity
measurements in Finland by developing and maintaining measurement standards for humidity and by
offering calibration and expert services.
MIKES provides high-quality calibration services for
instruments measuring humidity of gases and expert
services on research and development related to humidity measurements and their reliability..
The high quality of the humidity laboratory is maintained by taking part in international research and comparison projects and by carrying out own research
projects.
Calibration of hygrometers
Traceability
Traceability of humidity measurements is based on
a dew-point temperature scale. The scale is realised
by using a humidity generator, which is the national
measurement standard in Finland.
The core of a dew-point generator is a saturator in
which total saturation of air with respect to water or
ice is reached. The dewpoint temperature of the air
coming out of the generator is calculated from the saturator temperature and from the pressure difference
between the saturator and the device under calibration. When saturated air is led into the measurement
chamber of the generator, the equipment is also suitable for calibration of relative humidity sensors..
The dew-point meter under calibration is directly connected to the dew-point generator. In calibration of a
relative humidity sensor, the sensor is placed in the
measurement chamber system. The reading of the
sensor is compared to the value of relative humidity
that is calculated from the dew-point temperature and
the air temperature inside the chamber.
Most dew-point meters are calibrated using a dewpoint generator. The measurement standards of humidity laboratory at MIKES cover the dew-point temperature range -80 °C to +84 °C. Dew-point calibrations
are also carried out as comparison calibrations in calibrators, for instance for capacitive dew-point meters.
Most relative humidity sensors are calibrated in a climatic chamber. The dew-point temperature and the air
temperature in the chamber are measured by using a
chilled mirror hygrometer and a digital thermometer,
respectively. The relative humidity is calculated from
measured temperature and dew-point temperature. If
the achievable uncertainty is not sufficient or the temperature range extends to below +10 °C, the calibration is performed using a humidity generator. Relative
humidity sensors are calibrated in the range 10 %rh to
95 %rh at temperatures between -20 °C and +85 °C.
In cases of other humidity quantities, calibrations are
performed with the same equipment the relative humidity calibration systems. The values of these quantities are calculated from measured dew point temperature, temperature, and pressure.
Figure 1. Calibration of chilled mirror hygrometers.
Table 1. Measurement ranges and best achievable calibration uncertainties at
Quantity
Measurement range
(k=2)
Dew-point temperature
-80 °C ... -60 °C
-60 °C ... +84 °C
0.2 °C ... 0.1 °C
0.05 °C ... 0.06 °C
Relative humidity
10 %rh ... 95 %rh
(-20 °C ... +85 °C)
0.1 %rh ... 1.0 %rh
(generator)
Relative humidity
10 %rh ... 95 %rh
(+10 °C ... +85 °C)
0.4 %rh ... 2.0 %rh
(climatic chamber)
Mass, pressure
flow
Temperatue,
humidity
Electricity, time,
acoustic
Optics
Length,
geometry
Chemistry
Calibration of radiation
thermometers
Technician, Tel +358 50 410 5497,
Martti Heinonen, Principal Metrologist,
Tel +358 400 686 553
martti.heinonen@vtt.fi
Tel. +358 20 722 111
www.mikes.fi
Measurement methods
Blackbody radiatiors are used in calibration of radiation thermometers. The operation range of MIKES radiators is -40 °C ... 1500 °C.
The temperature of a blackbody radiator can be
measured using e.g. a temperature sensor that is embedded in the radiator wall. When calculating the radiation temperature from the measured temperature,
the emissivity of the wall and bottom materials of the
radiating cavity and the geometry of the blackbody radiator as well as the temperature gradients are taken
into account. The radiation temperature measured by
a radiation thermometer is often lower than the surface temperature of the measured object, since the
surface emissivity is usually lower than the emissivity
of an ideal blackbody (the emissivity of a blackbody is
1 but the emissivity of a glossy copper surface is 0.1).
In MIKES radiation thermometers are calibrated by
using either a calibrated reference pyrometer or reference radiators.
Calibration of radiation thermometers
Traceability Size-of-source-effect
The international temperature scale ITS-90 is realised above the temperature of 962 °C with a reference
pyrometer and fixed-point radiators (962 °C, 1064 °C
and 1085 °C). Of these fixed-points MIKES has the
first and the last one which are the freezing points
of silver (figure 1) and copper. Below the temperature of 962 °C, ITS-90 is realised by using resistance
thermometers instead of a pyrometer. The reference
equipment for radiation temperatures between –40
°C … 962 °C at MIKES are based on resistance thermometers calibrated according to the ITS-90..
The size of the radiation source (size-ofsourceeffect, SSE) affects the calibration results of a
radiation thermometer. A radiation thermometer
detects thermal radiation also outside the blackbody radiator or the object to be measured. The
significance of this additional thermal radiation
depends on the construction of the optics (figure
2).
On demand, the size-of-source-effect is measured at MIKES.
Outer cover graphite
Figure 1. A silver cell that is
used in the calibration of a
reference pyrometer.
Inner cover graphite
Silver
Figure 2. SSE: In this example,
a pyrometer detects lower
temperatures when
the aperture of the radiator
is less than 15 mm and the
temperature of the radiator
is higher than ambient temperature.
Vocabulatory • reference meter: measurement standard • pyrometer: radiation thermometer (infrared
thermometer) • a blackbody radiator does not reflect at all radiation coming from the outside.
The temperature of an object depends only from the heat energy brought to the object and hence its
radiation intensity is proportional to the temperature of the object.
Mass, pressure
flow
Temperatue,
humidity
Electricity, time,
acoustic
Optics
Length,
geometry
Chemistry
Fixed point calibration of platinum resistance thermometers
Ossi Hahtela, Senior Reseach
Scientist, Tel +358 50 303 9340,
ossi.hahtela@vtt.fi
Technician, Tel +358 50 410 5497
Tel +358 20 722 111
www.mikes.fi
Calibration objects
and methods
Standard platinum resistance thermometers (SPRT)
of good quality (i.e. stable) are calibrated at the fixed
points of the ITS-90 temperature scale. A fixed point
cell (Figure 1) usually contains pure metal, e.g. tin,
zinc, aluminium or silver (Table 1) sealed in a crucible
f purified graphite. The purity of the metal is typically
ca. 99.99995 %. The graphite crucible is enclosed in
a fused quartz tube.
The fixed point cell is placed in a vertical tube furnace
and the temperature is slowly raised until the melting
is complete. At this stage the furnace temperature is
reduced to a value slightly below the melt temperature
in order to start solidification. When the metal is in a
su-percooled state, the thermometer to be calibrated
is carefully inserted into the cell. The thermometer is
coupled to a resistance bridge using four wire coupling. The solidification state can be maintained up to
10 hours (Figure 2) and the temperature of the fixed
point cell stays within ±0.5 mK.
The resistance bridge is used to measure the electrical resistance of the thermometer during the solidification state. The thermometers are usually calibrated
using three or five different fixed points.
Figure 1. Pt25-sensor (SPRT) in a fixed point cell.
Fixed point calibration of platinum resistance thermometers
Calculation of
calibration coefficients
The temperature T90 is determined according to the
ITS-90 temperature scale. First a resistance ratio
W(T90) = R(T90) / R(T0.01°C) is calculated by dividing the sensor resistance at a given fixed point by the
resistance value at the water triple point. A deviation
function of the resistance ratio and calibration constants (a, b, …) are de-termined for each sensor under
calibration. The deviation function can be e.g.
W(T90) - Wr(T90) = a[W(T90) - 1] + b[W(T90)-1]2
where Wr(T90) is a reference function given in the
ITS-90 scale. The deviation function to be used and
the number of calibration constants depend on the
temperature range and the used fixed points.
The deviation function can also be used to determine
any temperature between the fixed points when the
constants a and b are known. In this case, W(T90) is
first determined at the unknown temperature and the
resulting Wr is used to calculate T90.
Uncertainties in fixed
point calibration The uncertainties of the fixed points at MIKES are
between 0.0002 ... 0.010 °C. The lower limit is reached
at the triple point of water and the upper limit at the
fixed points of aluminium and silver. The uncertainty
of the resistance thermometer calibrations is larger
since it includes also un-certainties of the calibration
equipment (resis-tance bridge, reference resistor) and
the stability of the thermometer during the calibration.
Traceability
The MIKES fixed points are part of the realisation of
the international ITS-90 temperature scale. The stability of the fixed point cells are monitored and the
temperatures they provide are compared to the temperatures from similar cells at our own and foreign
laboratories.
Table 1. MIKES fixed points for resistance thermometers
Substance
Temperature (°C)
State *
Argon (Ar)
-189.3442
t
Elohopea (Hg)
-38.8344
t
Vesi (H2O)
0.01
t
Gallium (Ga)
29.7646
m
Indium (In)
156.5985
f
Tina (Sn)
231.928
f
Sinkki (Zn)
419.527
f
Alumiini (Al)
660.323
f
Hopea (Ag)
961.78
f
* t = triple point, m = melting point,
f = freezing point
Abbreviations:
Pt25 = 25-ohm platinum resistance thermometer
HTPRT = high temperature platinum resistance
thermometer
Other fixed point
calibrations
Noble metal thermocouples of B-, R- and Stype are
also calibrated at fixed points. The highest fixed point
temperature is the freezing point of copper at 1084.62
°C.
Figure 2. Freezing curve of zinc.
Mass, pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length, geometry
Chemistry
Calibration of direct
voltage and current
Pekka Immonen, Researcher, Risto Rajala, Researcher, Ilkka Iisakka, Researcher,
Tel +358 50 721 8397,
Tel +358 50 410 5519,
Tel +358 50 410 5520
risto.rajala@vtt.fi
ilkka.iisakka@vtt.fi
pekka.immonen@vtt.fi
MIKES, Tekniikantie 1, 02150
Espoo, Tel +358 20 722 111
www.mikes.fi
Accuracy of almost all electrical measuringinstruments is based on traceability of direct voltage and
resistance. MIKES maintains thenational standard of
direct voltage and direct current in Finland. The unit
of direct voltage, volt, is determined very accurately
(repeatability even 10–10) by using Josephson voltage
standard. The volt is transferred from the Josephson
standard to Zener working standards and further to
calibrators and multimeters. The measurement range
is extended above 10 V by using resisive voltage dividers. In practice traceability of direct current comes
from voltage and resistance using Ohm’s law. Traceability of currents smaller than 100 pA can be realized
also by charging a capacitor by a linearly increasing
voltage. One research topic is the development of a
quantum standard for direct current based on singleelectron phenomena in nanostructures.
The methods and measuring instruments developed
at MIKES are of high international level. One demonstration of this is the excellent success in international comparison measurements with other national
metrology institutes. Moreover, MIKES research on
direct current metrology is in the international front
line. Most important research topics are development
of voltage standards based on microelectrome-chanical systems (MEMS) and closing the so-called quantum metrological triangle to prove by Ohm’s law that
there is a mutual agreement between the quantum
standards of electric current, voltage, and resistance..
Figure 1. The traceability of direct current is based on a
Josephson standard cooled in liquid helium.
Calibration of direct voltage and current
In addition to accredited calibration laboratories,
MIKES provides services to all customers requiring
low measurement uncertainty. The most important
calibration subjects in the field of direct current are
solid state voltage standards, dc- and multifunction
calibrators as well as precision multimeters. Zener
standards are calibrated usually by comparison to
MIKES working standards. A relay scanner connects
the voltage difference of the standards to a nanovoltmeter and the results are recorded at regular intervals for a couple of weeks. Routine calibrations of
direct voltage and current ranges of calibrators and
multimeters are carried out using a reference multimeter and a multifunction calibrator. The measuring
ranges and uncertainties of calibrations for voltages
up to 1 kV are presented in table 1.
ficate. Stability or temperature dependence
measurements can be carried out on customer’s request. MIKES follows the longterm
stability of customers’ voltage standards and
can attach follow-up results to the calibration
certificate if needed.
In addition to the calibration, we carry out
special assignments related to voltage and
current measurements and actively participate in research and development projects in
these fields.
Direct current calibrations are usually performed for
currents between 0.1 mA and 1 A with relative uncertainty of 10 μA/A and for 100 fA – 100 μA with
uncertainties varying from 600 μA/A to 20 μA/A.
When lower uncertainties are needed, calibrations
can be performed by using directly the MIKES Josephson standard. On special order, calibrations of
multimeters and calibrators can also be carried out
using directly the Josephson and Zener standards
and a resistive voltage divider. Direct current calibrations requiring lower than 10 μA/A uncertainties and
measurements above 1 A current levels can be performed by measuring the voltage across a resistance standard. The lowest achievable uncertainties of
these measurements can be found in table 2. Resistive voltage dividers are calibrated by comparison to
the MIKES reference divider or with the Josephson
standard. The value of voltage or current together
with its uncertainty is given in the calibration certi-
Figure 2. A Zener direct voltage standard.
Table 1. The smallest measurement uncertainties for the most common direct voltage calibrations. By using special techniques even much lower calibration uncertainties can be achieved.
Device
Zener-standard
Calibrator or multimeter
Voltage (V)
1
1.018
10
0 ... 10
10 ... 100
100 ... 1000
Uncertainty (μV)
0.2
0.2
2
0.3 ... 20
70 ... 610
1000 ... 10000
Table 2. The smallest uncertainties of direct current calibrations for currents less than 20 A.
Current
< 0.1 pA
(0.1 ... 100) pA
(1 ... 100) nA
(0.1 ... 100) μA
(0.1 ... 100) mA
(0.1 ... 20) A
Uncertainty
0.1 fA
(1 ... 0.6) mA/A
(0.1...2) pA
20 μA/A
5 μA/A
(5 ... 20) μA/A
Mass, pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length, geometry
Chemistry
Calibration of alternating
voltage and current
Tapio Mansten, Senior Research
Scientist, Tel +358 400 767 427,
tapio.mansten@vtt.fi
Risto Rajala, Researcher,
Tel +358 50 721 8397,
risto.rajala@vtt.fi
MIKES, Tekniikantie 1,02150 Espoo
Tel +358 20 722 111
www.mikes.fi
In society, many important functions such as the
measurement of electrical energy, which is supplied by electrical power networks to consumers, are
based on the accurate measurement of alternating
voltage and current. MIKES is responsible for the
traceability of alternating voltage and current in Finland. The traceability of the most accurate measurements of AC voltage is based on thermal converters
and range resistors acting as secondary standards.
The traceability of AC voltage and AC current ranges
of multifunctional calibrators and precision multimeters comes from AC voltage standards calibrated at
MIKES or at other national metrology institutes and
from their calibrated range and shunt resistors. The
reliability of results is verified by taking part in international comparisons.
MIKES performs also high level research on AC voltage metrology. Especially, MIKES is at the top of international metrology research in development work
of two different types of AC voltage standards in domestic collaboration with VTT: a primary standard for
AC voltage based on Josephson effect and an AC
voltage working standard based on micromechanical
sensors (MEMS).
Figure 1. Equipment of the national metrology laboratory
for alternating voltage and current.
Calibration of altrnating voltage
MIKES has accurate AC voltage meters and calibrators as working standards. We calibrate voltages
from 1 mV to 1000 V in a frequency range from 10
Hz to 1 MHz and currents from 100 μA to 20 A in a
frequency range from 50 Hz to 10 kHz (up to 8000
A in the frequency range 45 Hz …. 65 Hz). Typical
devices that we calibrate include: thermal converters, precision multimeters and calibrators and current sources and sensors. Also, other devices can
be calibrated in agreement with a customer. Usually customer’s AC voltage and current devices are
calibrated by comparing their AC/DC difference to
the AC/DC difference of a Fluke 5790A working standard and Fluke A40 AC/DC current shunts or by comparing the rms values directly to the rms value of a
MIKES device. The measuring ranges and smallest
achievable uncertainties for these calibrations are
shown in the tables below.
Figure 2. AC-DC-relay and two thermal convertes.
Table 1. Measurement ranges and smallest relative uncertainties in parts per millions from measurement results (μV/V) for
the alternating voltage range of a multifunctional calibrator.
10 Hz
20 Hz
40 Hz
53 Hz 400 Hz
1 kHz
10 kHz
20 kHz
50 kHz
100 kHz 500 kHz 1 MHz
1 mV
1200
1200
1200
-
1200
1200
1200
1200
1200
1400
3300
5000
2 mV
590
590
590
-
590
590
590
590
590
680
1600
4600
20 mV
130
120
120
-
120
120
120
120
120
140
350
580
100 mV
50
50
30
-
30
30
30
30
35
60
220
450
1V
40
40
20
-
15
15
15
15
30
50
110
440
10 V
40
40
20
-
20
20
20
20
30
45
140
400
100 V
40
40
30
-
20
20
20
20
35
40
-
-
1000 V
-
-
50
50
50
-
-
-
-
-
-
-
Table 2. Measurement ranges and smallest relative uncertainties in arts per million of
measurement result (μA/A) for the alternating current range of a multifunctional calibrator.
na mittaustuloksesta (µA/A).
Frequency
Current (rms value)
Voltage (rms value)
Frequency
40 Hz
400 Hz
1 kHz
5 kHz
10 kHz
100 µA
80
80
80
90
110
1 mA
35
35
35
35
40
10 mA
35
35
35
35
50
100 mA
35
35
35
35
60
1A
35
35
35
50
110
10 A
110
110
110
150
210
20 A
110
110
110
180
260
Mass, pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length, geometry
Chemistry
Calibration of capacitance
and inductance standards
Tapio Mansten, Senior Research
Scientist, Tel +358 400 767 427,
tapio.mansten@vtt.fi
Tel +358 50 721 8397,
risto.rajala@vtt.fi
Capacitors and inductors are essential components in
electronics. Moreover, capacitive sensors are used in
many high-precision measurements: e.g. in measurements of position, distance and level. For calibration
of precision LCR meters, inductance and capacitance
standards are needed. Therefore, traceable measurements of capacitance and inductance are of utmost
importance. In Finland, MIKES is responsible for the
traceability of capacitance and inductance.
Tel +358 20 722 111
www.mikes.fi
cy — quantities which are maintained at MIKES. The
reliability of the results is verified by international
comparisons and by taking advantage of capacitance
measurement services at the BIPM. The capacitance
values between calibration points are interpolated by
using measuring bridges based on inductive dividers.
Inductance standards in the range 100 μH – 100 mH
are traceable to the MIKES capacitance and resistance standards.
In MIKES, ac coaxial bridges are used to provide
traceability of the decade capacitance standards in
the range 10 pF – 1 μF to resistance and frequen-
MIKES calibrates capacitance standards in the range
0 pF up to 1 μF by using a very stable capacitance bridge and reference capacitance standards. The
measurements are usually carried out at 1 kHz but
other measurement frequencies are also possible.
The calibration is performed using either two-terminal
or three-terminal method by connecting the calibrated capacitance standard through a 16-channel coaxial relay to the capacitance bridge and by measuring
automatically for about two or three days. The device
under calibration is placed together with a Pt-100
sensor into a volume having a constant temperature.
The temperature is varied during the measurement
by about one or two degrees in order to measure the
temperature coefficient of the device under calibration. The results are corrected to the temperature of
23 °C.
Figure 1. Traceability to capacitance from resistance
and frequency in MIKES impedance laboratory.
Traceability of inductance standards at MIKES is based on the link to the capacitance (100 pF) standards
which are calibrated at BIPM and the resistance standards, calibrated from the Quantum Hall Resistance
in MIKES. The 100 mH inductance is linked to capacitance standards at 1 kHz and 1.59 kHz with the use
of series resonance method, where 253 nF and 100
nF capacitors are used as references.
Calibration of capacitance and inductance standards
Sampling method, which is based on the use of 2
DVM is used to define the values of inductance standards in the range 100 μH – 10 mH. Impedance of
the calibrated inductors is compared with the impedance of the reference resistor, by measurements of
the voltage ratios at frequencies below 1 kHz.
In addition to the calibration of capacitance and inductance standards, we carry out special assignments related to impedance measurements and actively
participate
Figure 2. AH2500A measuring bridge and a 1-nF capacitance standard under calibration.
Table 1. Measuring ranges and smallest calibration uncertainties at MIKES for calibration of capacitive standards at 1 kHz
frequency. The expanded relative uncertainty (k = 2) is expressed as parts per million of measured capacitance.
Capacitance value
10 pF
Relative uncertain- 5
ty (µF/F)
100 pF
1 nF
10 nF
100 nF
5
10
30
100
Table 2. Measuring ranges and smallest calibration uncertainties at MIKES for calibration of capacitive standards that have
capacitance values smaller than 10 pF or larger than 100 nF or whose value is not even decade. The expanded relative
uncertainty (k = 2) is expressed as parts per million of measured capacitance. For capacitances lower than 10 pF a base
apacitance of 5 aF is added to the uncertainty.
Capacitance value
0 pF - 10 pF
10 pF - 1 nF
1 nF - 10 nF
10 nF - 100 nF
100 nF - 1 μF
Relative uncertainty (µF/F)
10 (+ 5 aF)
10
30
200
400
Table 3. Measurement methods, inductance values, and reference standards used in calibration of inductance standards at 1 kHz.
Method
Inductance
Impedance 1 kHz
Reference
Uncertainty 2s
Relative uncertain- 5
ty (µF/F)
5
10
30
2 DVM
1W
1W
50
0.1 mH
2 DVM
1 mH
10 W
10 W
50
2 DVM / SR
10 mH
100 W
100 W
20
SR / 2 DVM
100 mH
1 kW
253 nF / 100 W
20
Mass, pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length, geometry
Chemistry
Calibration of resistance
Ilkka Iisakka, Researcher,
Tel +358 50 410 5519,
Tel +358 50 721 8397,
risto.rajala@vtt.fi
Resistance is the most important quantity of electrical
measurements together with direct voltage. In addition to resistance calibrations, resistance standards
are needed for providing traceability to other electrical quantities. MIKES is the national standards laboratory of resistance. The traceability of resistance
standards at MIKES is based on its own quantum Hall
standard, which connects the unit of resistance to the
values of physical constants with a relative uncertainty of 10–8. The dissemination to secondary and working standards, which are stored in oil or air baths, is
performed by using a cryogenic current comparator
or a direct current comparator resistance bridge. The
Tel +358 20 722 111
www.mikes.fi
traceability of resistance standards with value above
1 GΩ is realized by using a modified Wheatstone bridge.
The accuracy of MIKES’s resistance standard calibrations is at high international level, confirmed by
good results in international resistance comparisons.
MIKES has also participated in coordination of international key comparisons, in which the accurate resistance transfer standards developed at MIKES have
been used.
Calibration of resistance
In addition to accredited calibration laboratories, MIKES provides services to all customers requiring very
low measurement uncertainty. In resistance calibration the resistance of the device under calibration is
measured and the uncertainty of the measurement result is calculated. On demand, temperature, power, or
voltage dependence of resistance standards can be
determined, too. MIKES follows the long-term stability
of customer’s resistance standards and when requested attaches the results to the calibration certificates.
In addition to resistance standards, other calibration
services for calibration of precision multimeters and
multifunction calibrators are offered.
In the range 0.0001 Ω ... 100 MΩ, the resistance standards are calibrated by comparing them to the prima-
ry and working standards of MIKES by using a MI
6242B resistance bridge. When special accuracy
is needed, the measurements can be carried out
by using a cryogenic current comparator. In the
range 1 MΩ ... 100 TΩ, a modified Wheatstone
bridge is used. During the calibration, the resistance standards are placed in a thermal bath.
Either two point or four point measurements are
used and when needed a guarded measurement
is carried out. The resistance ranges of multimeters are calibrated by using MIKES multimeters.
In addition to calibrations, we provide special assignments related to resistance measurements
and actively participate in research and development projects in this field.
Figure 1. Measurement ranges and measurement uncertainties for resistance standards.
Mass, pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length, geometry
Chemistry
Calibration of power and
energy at line frequency
Esa-Pekka Suomalainen,Senior Research
Scientist, Tel +358 50 382 2463,
esa-pekka.suomalainen@vtt.fi
Pekka Immonen, Researcher,
Tel +358 50 410 5520,
pekka.immonen@vtt.fi
The measurement of electric energy consumption
has a huge economic importance. Through the development of electric energy market, the importance
of measurement accuracy and traceability is further
emphasised. Accurate electric power standards are
required in the calibration of energy meters. At MIKES, measurements of electric power at 50 Hz are
traceable to SI units through a sampling power standard. Calibrations are performed using either single-phase or three-phase measurements. Typical devices that we calibrate are electric power meters and
converters.
At MIKES power laboratory, the traceability of electric power at 50 Hz is based on direct voltage from
a Josephson standard and resistance realised by a
quantum Hall equipment. The sampling power standard consists of two 8½ digit voltmeters, which are
accurately synchronised. Currents smaller than 20 A
are converted to voltages using specially constructed shunt resistors, whose resistance values are
traceable to the quantum Hall resistance standard.
As a result of the construction of the shunts, their
frequency dependence is very small. Measurement
results of voltage meters are based on fast sampling
and traceable to the Josephson voltage standard.
The same measurement equipment together with a
current sensor based on a Rogowski coil is used to
measure currents and current ratios up to 8000 A.
The measurement uncertainty of the MIKES power
reference equipment is 0.005 % at its best.
Figure 1. In power and energy measurements traceability for large currents is also needed. Parts of 8000 A
measuring setup based on a Rogowski coil.
Tel +358 20 722 111
www.mikes.fi
The methods and equipment of MIKES power laboratory represent international top quality. The high quality of measurements is verified by taking part in international comparison measurements together with
national metrology laboratories from other countries.
MIKES is also an active member in different expert
working groups at international level and takes part in
national as well as international joint research projects. Several projects are in the European Metrology
Research Programmes EMRP and EMPIR..
Calibration of power and energy at line frequency
MIKES calibrates especially reference standards of
customers who need the best available measuring
accuracy. Typical instruments are power comparators and converters. The calibrations are performed
by connecting the same current and voltage to the
customer’s device and the reference meter of MIKES. If necessary, effect of the power source used in
the calibrations is minimized by accurately synchronising the meters. The reference meter used in the
calibrations is either a single-phase sampling power
standard or a three-phase power comparator.
In addition to power standards, we calibrate current
and voltage transformers and transducers up to 200
kV voltage and 8 kA current. We carry out special
assignments related to the measurement of electric power and energy and take part in research and
development cooperation projects in this field. Moreover, we organise educational opportunities in this
field and custom tailored training.
Figure 2. A coaxial shunt resistor of the sampling power standard.
Table 1. Measuring ranges and calibration uncertainties at MIKES for calibrations of power
and energy at line frequency.
Expanded relative uncertainty (k = 2)
Measured quantity
Single phase, 30 V – 500 V, 5 mA – 10 A
Active power
50 μW/VA
Reactive power
100 μvar/VA
3-vaihe, 50 V – 350 V, 5 mA – 12 A
Active power
120 μW/VA
Reactive power
250 μvar/VA
Active energy
120 μWh/VAh
Reactive energy
250 μvarh/VAh
Mass, pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length, geometry
Chemistry
RF- and microwave
calibrations
Kari Ojasalo, Researcher,
Tel +358 50 410 5557
kari.ojasalo@vtt.fi
The importance of measurement reliability is emphasized along with the continuously increasing amount
of applications in RF- and microwave ranges. MIKES
is the national metrology institute in this field and offers traceability with low uncertainty to internationally
accepted measurement standards in RF and microwave power measurements and measurements of S
parameter (reflection and attenuation). We calibrate
power sensors and attenuators for instance.
Tel +358 20 722 111
www.mikes.fi
of results are mainly automated. The measurements
are carried out in a controlled 23 °C temperature in an
electromagnetically shielded room.
The high standard of the measurements is verified
by actively taking part in international comparisons
together with other national metrology institutes. The
traceability is based on power and attenuation calibrations at NPL (National Physical Laboratory) in U.K.
and on the primary standards at MIKES.
Our calibration equipment is equipped with precision
type N connectors, thus our measu-rement range extends to 18 GHz. The measurements and the analysis
Figure 1. Measurement of power sensors.
RF- and microwave calibrations
Power
The calibration coefficients of sensors are determined with measurement equipment based on a
power divider. Measurement of reflection coefficient
by using a vector network analyzer is included in the
sensor calibration. Typically, calibration takes five
workdays. The calibration of the absolute power of
a power reference in a power meter is performed for
thermocouple and diode power sensors. The reflection coefficient of the power source is determined at
the same time.
Figure 1. Measurement set-up for power sensors.
Attenuation
Attenuation calibrations are carried out by traceable
vector network analyzer measurements. Determination of reflection coefficient by is included in the
calibration. We calibrate fixed value attenuators as
well as step attenuators. The step attenuators can be
controlled by using a GPIB bus, RS-232 connection
or directly using the step attenuator controller Agilent
11713A..
Reflection coefficient
Traceable measurements of reflection coefficient
are performed using a vector network analyzer. The
impedance of the impedance standards used in the
measurements is determined at MIKES with accurate
dimensional measurements. Dimensional measurement services for N-type airlines are offered for customers, also.
Figure 2. Measurement of reference step attenuator.
Table 1. Measurement ranges and uncertainties
Quantity
Measurement
range
Measurement
frequency range
Uncertainty
Calibration coefficients
of power sensors
1 mW
10 MHz – 18 GHz(1)
0.4 % – 1.1 % (k=2)(2)
Absolute power
1 mW
10 MHz – 18 GHz(1)
4 mW/W – 11 mW/W (k=2)
Attenuation
0 dB – 80 dB
300 kHz – 6 GHz
0.02 dB – 0.17 dB (k=2)
Attenuation
0 dB – 60 dB
6 GHz – 18 GHz
0.05 dB – 0.18 dB (k=2)
Reflection coefficient (real
and imaginary parts)
-1 ja 1 välillä
10 MHz – 18 GHz
0.013 – 0.024 (k=2,45)(3)
1) Tehon kalibrointitaajuudet ovat: 10, 30, 50, 100, 300, 500 MHz, 1 GHz, 1.5 GHz, 2 GHz – 18 GHz 1 GHz askelin.
2) Heijastuskertoimen itseisarvo ≤ 0.08
3) Kompleksimuuttujan kompleksiselle epävarmuudelle 95 % kattavuus saadaan, kun k=2.45.
Mass, pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length, geometry
Chemistry
High voltage
and high current
Esa-Pekka Suomalainen, Senior Research
Scientist, Tel +358 50 382 2463
esa-pekka.suomalainen@vtt.fi
Jussi Havunen, Research Scientist,
Tel +358 50 590 6536
jussi.havunen@vtt.fi
Puh. 020 722 111
www.mikes.fi
High voltage quantities
Traceability
The importance of high voltage measurements has
been emphasized with the opening of electricity markets. The quality of electricity, transmission losses
and the sale of electricity for industry and for private
households have become more important measuring and monitoring subjects. In addition to electricity,
electronics and information industries, high voltage
users can be found, in almost every industrial sector. High voltage metrology at MIKES is internationally respected and provides services on traceability
also at customers premises in Finland and globally.
The high voltage measurements at MIKES are traceable to capacitance, resistance and voltage, which in
turn are based on quantum primary standards: quantum Hall resistance standard and Josephson voltage
standard. We have performed well and also acted
as a coordinator in international comparisons in high
voltage metrology. As an example of this is the coordination of broad European and worldwide comparisons of lightning impulse voltage measuring systems.
High voltage and high current
Calibration subjects
MIKES offers calibration services for almost all high
voltage quantities and measuring systems up to 200
kV voltage. The range of alternating current calibrations extends to 6 kA. The measuring range for pulse
quantities covers a voltage range from millivolts up
to megavolts and currents up to tens of kiloamperes.
Our expert services cover different aspects of calibration of measuring systems. If wanted, we evaluate
customer’s measuring systems and modify them to
be more accurate and stable if needed. In future, our
area of qualification will be extended to calibrations
related to measurements on the quality of electricity.
Devices that we calibrate include:
• voltage dividers
• voltage and current transformers
• measuring probes, voltage and current sensors
and current shunts
• high voltage inductors and capacitors
• transient recorders, peak voltage meters
• surge-, EFT- ja ESD- test devices
• voltage testers
• pulse calibrators
• partial discharge calibrators
The best calibration uncertain y is achieved when
calibrations are performed in a laboratory at MIKES
but calibrations can be carried out at customer’s premises, also. Measuring systems can be calibrated
on-site when the voltage level, the size of the system,
grounding conditions or proximity effects necessitate it.
Table 1. Calibration services of high voltage
Quantity
Measurement range
Uncertainty (k=2)
Direct voltage
1 kV - 1000 kV
0.0005 - 0.01 %
Alternating voltage, voltage ratio
1 kV - 200 kV
0.002 - 0.01 %
– angle error
0 - 100 mrad
0.02 mrad
Alternating current, current ratio
1 A - 6 kA
0.025 - 0.02 %
– angle error
0 - 100 mrad
0.2 - 0.4 mrad
Capacitance
1 - 100 kV / 10 pF - 200 µF
0.002 - 0.05 %
-– loss coefficient tan δ
1.10-5 - 2
1 % (1.10-5 abs)
Inductance / losses
1 µH - 10 H
0.03 % / 0.2 mrad
Lightning impulse
50 mV - 400 kV
0.1 - 0.5 %
Switching impulse
1 V - 200 kV
0.1 - 0.2 %
Other voltage impulses (e.g. surge)
1 V - 400 kV
0.1 - 0.5 %
Current impulses
1 A - 10 kA
3%
ESD-pulssi
1 A - 50 A
5%
Time parameters of pulses
0.7 ns - 100 ms
0.5 - 5 %
Apparent charge of a pulse (partial discharge)
1 pC - 1 nC
2 % (0.2 pC abs)
Mass, pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length, geometry
Chemistry
Acoustic calibrations
Kari Ojasalo, Researcher,
Tel +358 50 410 5557
kari.ojasalo@vtt.fi
Jussi Hämäläinen, Researcher,
Tel +358 50 410 5518
jussi.hamalainen@vtt.fi
The need of accurate acoustic measurements is growing for instance due to regulations and legislations
concerning noise emissions and exposure to vibrations. A good measurement accuracy requires, in addition to high-quality measurement devices, regular
and traceable calibrations. In Finland, MIKES is responsible for the traceability of the acoustic quantities:
sound pressure and acceleration.
Sound pressure is transformed into an electrical signal by using accurate condenser microphones, whose primary calibration equipment is in use at MIKES.
Sound level calibrators are calibrated using these
condenser microphones. The traceability chain of
sound pressure level starts from the calibration of
laboratory grade microphones by using a so-called
reciprocity calibration system. This calibration gives
Figure 1. A reciprocity calibration of microphones is
starting in the soundproof
laboratory at MIKES.
Tel +358 20 722 111
www.mikes.fi
the voltage-pressure sensitivities of the microphones.
The method is described in the standard IEC 610942 (1992-03) and it is in use in severalother national
metrology institutes.
A vibration transducer produces a signal, typically a
voltage or a charge, which is proportional to the acceleration of mechanical motion. Therefore, in the
calibration of a vibration transducer, the sensitivity
(typically mV/(m/s2) or pC/(m/s2) of the sensor is determined as a function of frequency. MIKES calibrates
vibration transducers by comparing their readings to
a known vibration produced with a vibration exciter.
The real amplitude of acceleration and frequency is simultaneously measured by using a reference sensor.
The method is described in the standard ISO 1606321:2003.
Acoustic calibrations
Vibration transducers and loggers
Microphones
We calibrate ½ (LS2P) and 1 (LS1P) inch condenser
microphones described in the standard IEC 61094-1
(Table 1). The calibration method depends on the accuracy required by the customer. The smallest calibration uncertainties can be achieved by using the reciprocity method. In many cases, a comparison with
a reference microphone by a sound level calibrator is
adequate.
We calibrate vibration transducers, loggers and
vibration measurement devices in the frequency
range 1 Hz – 10 kHz. Typical nominal acceleration
is 10 m/s2. The calibration gives the magnitude and
the phase of the sensitivity of the vibration transducer. The uncertainty of the calibration depends
on the transducer under calibration. Typical uncertainties for the magnitude are 1–3 % and for the
phase 1–2° depending on the frequency (Figure 2).
Table 1. Uncertainties of calibration for measurement
microphones.
Type of
microphone
LS 1
LS 2
Taajuus [kHz]
Uncertainty [dB]
0.0315
0.06
0.063 ... 2
0.04
4
0.05
5
0.06
8
0.08
10
0.10
0.0315
0.08
0.063
0.06
0.125 ... 8
0.05
10
0.06
12.5
0.08
16
0.10
20
0.14
Sound level calibrators
The most common devices calibrated at MIKES
acoustics laboratory are sound level calibrators
and pistonphones. We calibrate the sound pressure
levels at fixed frequency points. At the same time,
the distortion and frequency of the sound source is
measured (Table 2).
Figure 2: The measurement ranges and uncertainties of calibration of vibration transducers.
Table 2. Calibration ranges and uncertainties for sound level calibrators. The type of the measurement
Frequency (Hz)
Sound level [dB re 20 μPa]
Uncertainty [dB]
Single-frequency
125 – 1000
70 – 130
0.08
31,5
94 – 114
0.15
Multi-frequency
63 – 4000
94 – 114
0.10
8000 - 12500
94 - 114
0.15
Type of calibrator
Mass, pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length, geometry
Chemistry
Calibration of time,
time interval,and frequency
Ilkka Iisakka, Researcher,
Tel 358+50 410 5519,
Mikko Merimaa, Principal Metrologist,
Tel 358+ 50 410 5517
mikko.merimaa@vtt.fi
Measurements of frequency and time interval are
needed in various direct and indirect measurements,
e.g., in telecommunication; therefore, precise and
traceable frequency and time interval measurements
are important nationally. The importance of absolute
time is increasing, too (e.g. time stamps).
Tel 358+ 20 722 111
www.mikes.fi
MIKES is responsible for the traceability of time,
time interval, and frequency in Finland. MIKES
time laboratory maintains the official time in Finland with an uncertainty of 10 ns in relation to the
coordinated universal time (UTC) and national
frequency with a 1•10-13 relative uncertainty. The
reference standards for time and frequency are
one caesium atomic clock, four hydrogen masers
and several GPS receivers. Finland participates
in maintaining of the UTC with its five reference
standards through GPS based time comparison.
Figure 1. The traceability of time and
frequency is based on hydrogen masers (in the figure above) and on caesium atomic clocks, which are located
in enclosures having with a special
climate control.
Calibration of time, time interval, and frequency
We calibrate e.g. GPS receivers (frequency), oscillators, time interval counters, stopwatches, stroboscopes, and optical tachometers. The frequency
range is 1 mHz to 5 GHz. We make time interval
measurements according to customer’s need, with
a lower limit of approximately one nanosecond. Furthermore, MIKES has a transmitter for time code and
precise 25 MHz frequency for those near the Helsinki metropolitan area who need precise time and frequency.
In addition to calibration, we carry out special assignments related to time and frequency measurements
and participate in research and development collaboration projects in this field.
NTP - network time service
Computer clocks can be synchronised with the national time in Finland maintained by MIKES by using
Network Time Protocol, NTP. The achievable uncertainty depends on network connections but it is around
one millisecond at its best. MIKES maintains NTP servers subject to charge for institutions and companies.
We have four servers of the highest level (stratum-1):
two of them are synchronised directly to MIKES atomic clocks and two to GPS receivers. Moreover, we
control two public NTP servers that are locked to
MIKES servers. These servers are available free of
charge for public use.
Figure 3. Stabilities of various frequency standards as a function of integration time.
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Optical quantities
Farshid Manoocheri, TkT,
Tel +358 9 470 22337,
farshid.manoocheri@aalto.fi
Petri Kärhä, TkT,
Tel +358 9 470 22289,
petri.karha@aalto.fi
MIKES-Aalto Metrology
Research Institute
Metrology Research Institute (MIKES-Aalto Mittaustekniikka) is a joint laboratory of Aalto University and
MIKES. It is the national standards laboratory of optical quantities in Finland. The laboratory is a research
and education unit belonging to the Department of
Signal Processing and Acoustics at the Aalto University. The laboratory carries out basic research on LED
measurements, temperature measurements, optical
properties of materials, measurement electronics and
on various measurement methods of photometry and
radiometry. In addition to calibration services, the laboratory offers expert services and educates Diploma
Engineers (M. Sc.) and Doctors of Technology for demanding professional tasks in academy and industry.
Figure 1. Integrating sphere is used as a light source
in calibration of luminance
and radiance. The sphere
has a uniform spatial distribution of the outcoming
light intensity.
MIKES Aalto Mittaustekniikka,
Otakaari 5A, 02150 Espoo
http://metrology.tkk.fi
Research activities
Research activities and assignments of a national
standards laboratory require continuous international cooperation. International comparisons have an
essential role in creating traceability chains and verifying measurement uncertainties. The laboratory has
an active role in, e.g. EURAMET, CCPR, and CIE organisations and takes actively part in the EU research
programs.
Optical quantities
Metrology Research Institute offers calibration
services to the optical quantities listed in the
following table. All measurements are traceable
to national and international measurement standards. Measurement uncertainties are verified
by international comparison measurements. We
are pleased to give further information, e.g. on
the contents of calibration services and on the
measurement uncertainty in different measurement and wavelength ranges.
Calibration objects
lInstruments that we calibrate include among
others:
Figure 2. The spectral irradiance of a lamp is measured by positioning
the lamp at an accurately determined distance from a radiometer, whose
spectral responsivity and surface area are known.
• illuminance meters
• standard lamps
• radiance and luminace meters
• laser power meters
• optical filters
• reflectance references
• UV-meters
• fluorescent samples
Quantity
Figure 3. Part of the calibrations can be carried out as field calibrations at customer’s
laboratory premises. A filter radiometer developed in our laboratory for calibration of
spectral irradiance or illuminance of standard lamps is shown in the figure.
Measurement range
Wavelength range
Uncertainty (k=2)
Luminous intensity
1 – 10 000 cd
-
0.5 %
Illuminance
Illuminance responsivity
0.1 – 5 000 lx
-
0.5 % - 0.7 %
Luminance
Luminance responsivity
1 – 40 000 cd/m2
-
0.8 % - 1.0 %
Luminous flux
10 – 10 000 lm
-
1.0 %
Spectral irradiance
100 μW m nm –
500 W m-2 nm-1
290 – 900 nm
0.8 % - 2.9 %
Spectral radiance
100 μW m-2 sr -1 nm-1 –
1 W m-2 sr -1 nm-1
360 – 830 nm
1.4 % - 4.2 %
Color coordinates (x, y)
0.1 – 0.9
-
0.0005
Color temperature
2800 – 3250 K
-
5K
Optical power
0.1 – 0.5 mW
325 – 920 nm
0.05 % - 1.0 %
Spectral responsitivity
0.01 – 20 μW
0.05 – 5.0 mW
380 – 1700 nm
250 – 380 nm
0.5 % - 4.0 %
2.0 % - 5.0 %
Transmittance
0.0001 – 1
250 – 1700 nm
0.2 % - 5.0 %
Absorbance
0–4
250 – 1700 nm
0.0009 – 0.022
Regular reflectance (5° – 85°)
0.01 – 1
250 – 1000 nm
1.0 % - 5.0 %
Diffuse reflectance factor
0.1 – 1
360 – 830 nm
0.4 % - 1.0 %
Fiber optic power
(in collaboration with MIKES)
1 nW – 200 mW
1310 – 1550 nm
1.2 % - 2.0 %
-2
-1
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Quantitave Microscopy Atomic Force Microscope
Virpi Korpelainen, Senior Research
Scientist, Tel. +358 050 410 5504
virpi.korpelainen@vtt.fi
Tel +358 20 722 111
www.mikes.fi
Development and research in nanotechnology has increased the need for accurate measurements in research institutes and industry. Different kinds of Scanning Probe Microscope (SPM) measurements are
commonly used in many institutes and companies.
In order to guarantee accurate and reliable dimensional measurements at nanometre range, MIKES has a
traceably calibrated Atomic Force Microscope (AFM).
Thus, MIKES can provide customers with traceable
measurements also at nanometre range.
MIKES provides accurate AFM measurement services to match the needs of customers. In addition we
calibrate SPM transfer standards.
Figure 1. Alignment of laser
beams for interferometric calibration of y axis of the AFM.
Quantitave Microscopy - Atomic Force Microscope
MIKES has a PSIA XE-100 AFM, which is calibrated interferometrically and with grating calibrated by
laser diffraction at MIKES. The AFM is traceable to
the definition of the metre. The xy-movements of the
AFM are mechanically separated from the z-movements. This increases the linearity of the movements,
decreases out of plane movements and eliminates
cross-talk. The structure of the device allows rather
large samples to be measured, also measurements
can be done using the most usual measurement modes: contact, non-contact, tapping and lateral force.
The measurement results can be analysed using
SPIP software 1.
Scale errors of uncalibrated SPMs typically range
from 2 % to 20 %. In addition measurement errors
may cause distortions in the measured figure, which
might be difficult to detect from the figure. Therefore,
the device has to be calibrated. New, more advanced SPMs have increased measurement precision,
but the development does not remove need for calibration. Especially in all quantitative form measurements, the measurements should be traceable to the
definition of the metre. Usually SPMs are calibrated
by using calibrated transfer standards.
1
The Scanning Probe
http://www.imagemet.com
Image
Processor
Property
Data
Sample size
<100 mm × 100 mm
Sample thickness
<20 mm
Sample mass
<500 g
Measurement range (xy)
100 µm × 100 µm
Measurement range (z)
12 µm
Resolution (xy)
0.15 nm
0.02 nm (low voltage mode*)
Resolution (z)
0.05 nm
0.01 nm (low voltage mode*)
Uncertainty (k=2),
x and y directions
Q [3; 2 L/µm] nm
Uncertainty (k=2),
z direction
Q [3; 2 L/µm] nm
Q [x; y] = (x2 + y2)1/2
SPIPTM
Figure 2. 2-D grid standard.
Figure 3. AFM image of Seeman tile type
DNA nano-origami structures.
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Length
geometry
Optics
Chemistry
Characterization of
nanoparticles
Tel +358 20 722 111
www.mikes.fi
Scientist, Tel. +358 050 410 5504
Nanoparticles are widely used in many applications.
Accurate characterization of the nanoparticles is important in research, production and applications in several fields including industry, health, safety and related regulation. At VTT MIKES metrology the particles
can be characterized using two different methods:
Dynamic Light Scattering (DLS) and atomic force microscopy (AFM). The measurements are traceable to
the definition of the metre via MIKES interferometrically traceable metrological atomic force microscope
(IT-MAFM). Both methods have advantages and limitations. DLS is fast method and the results are statistically representative. In DSL measurements even a
small number of large particles can prevent detection
of small particles. AFM can be used to measure both
size and shape of single particles. The disadvantage
of AFM measurements is that only limited number of
particles can be measured which leads to poor statistics. Tip sample interaction is important especially
when measuring small particles. Also sample preparation might be challenging.
Figure 2. DLS measurements
Table 1. VTT MIKES metrology has two instruments suitable for nanoparticle measurements.
Figure 1. AFM image of 100 nm nanoparticles
Instrument
Zetasizer Nano
PSiA XE-100
Measurement method
DLS
AFM
Measurands
Size distribution,
Zeta potential
Size,
Shape
Measurement range
0,3 nm - 10 µm
5 nm – 5 µm
2%
from 1 nm
Characterization of nanoparticles
Zetasizer Nano
Atomic force microscopy (AFM)
Dynamic Light Scattering is used to measure particle
and molecule sizes. This technique measures the diffusion of particles moving under Brownian motion,
and converts this to size and a size distribution using
the Stokes-Einstein relationship.
An AFM uses a cantilever with a very sharp tip to
scan over a sample surface. As the tip approaches
the surface, the close-range, attractive force between
the surface and the tip cause the cantilever to deflect towards the surface. However, as the cantilever is
brought even closer to the surface, such that the tip
makes contact with it, increasingly repulsive force takes over and causes the cantilever to deflect away
from the surface.
Laser Doppler Micro-electrophoresis is used to
measure zeta potential. An electric field is applied to
a solution of molecules or a dispersion of particles,
which then move with a velocity related to their zeta
potential.
The services for nanoparticle characterization at MIKES
In AFM images the topography of a sample surface by
scanning the cantilever over a region of interest. The
raised and lowered features on the sample surface
influence the deflection of the cantilever, which is monitored by a position-sensitive photo diode (PSPD).
By using a feedback loop to control the height of the
tip above the surface the AFM can generate an accurate topographic map of the surface features.
• Nanoparticle size and shape measurements
using AFM
• Nanoparticle size distribution in solution using
DLS
• Nanoparticle surface charge (Zeta-potential)
measurements in solution
Figure 3. DLS results of ~100 nm nanoparticles
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Length
geometry
Optics
Calibration of laser
interferometers
Jeremias Seppä, Senior Research
Scientist, Tel +358 50 410 5503
jeremias.seppa@vtt.fi
Veli-Pekka Esala, Senior Research
Scientist, Tel +358 40 866 7636
veli-pekka.esala@vtt.fi
Laser interferometers together with gauge blocks are
the most important measurement standards in modern length metrology. At 1980s a common understanding was that laser interferometers are accurate
and hence do not need any calibration. However,
ever increasing demand for accuracy and long experience on usage of laser interferometers have shown
that it is necessary to calibrate laser interferometers,
also. At MIKES, we have traceable procedures to calibrate laser interferometers. The calibration of laser
interferometers improves their reliability and accuracy essentially.
Tel +358 20 722 111
www.mikes.fi
Figure 1. Functional testing of a laser interferometer
Figure 2. An iodine-stabile HeNe-laser used for the practical realisation
of the metre.
Chemistry
Calibration of laser interferometers
Calibration and functional testing
of environmental sensors
Calibration procedure
Calibration of laser frequency
The vacuum wavelength of lasers used in laser interferometers is calibrated using iodine-stabilised lasers.
Traceability to the definition of the metre is guaranteed as frequencies (vacuum wavelength) of the iodine-stabilised lasers are determined by an optical frequency comb refer-enced to an atomic clock.
MIKES maintains the following lasers that are locked
to iodine absorption lines according to international
recommendations: He-Ne lasers at wavelengths: 633
nm (Figure 2) and 543.5 nm and a Nd:YAG-laser at
532 nm. These laser have a relative frequency uncertainty better than 10-10 (expanded uncertainty, k=2).
The frequency of the laser under calibration is compared to the frequency of an iodinestabilized laser. The
calibration includes a long term frequency (vacuum
wavelength) calibration and repeatability measurements. Moreover, the frequency difference of the
horizontally and vertically polarised lights is determined and the separation of the polarisation planes
inspected. Together these measurements provide
good indication of the frequency stability of the laser
under calibration. Lasers that operate at wavelengths
not reachable by iodine-stabilized lasers can be calibrated using a frequency comb.
In addition to laser vacuum wavelength calibration the
environmental sensors are calibrated and their operation tested. These measurements are necessary to
achieve the naturally good measurement accuracy of
a laser interferometer. Especially, by calibrating the
environmental sensors order of magnitude better
measurement accuracy can be achieved for a
laser interferometer.
The calibration of environmental sensors includes
the calibration of air temperature sensors, atmospheric pressure sensors and material temperature sensors. The functional testing is performed in a temperature stabilised laboratory room by measuring the
locations of a moving carriage equipped with a retroreflector with the laser interferometer under calibration and with a reference laser interferometer (Figure
1). In these measurements, both laser beams travel through the same optical components and data
is collected with and without the environmental sensors operating. Also, the angle-scale is tested using a
reference laser. If necessary, the quality of the optical
components is tested with a flatness interferometer.
If the readings of the environmental sensors deviate
remarkably from readings of the reference instruments they should be adjusted. By adjusting them,
the accuracy of the laser interferometer can easily be
improved (Figure 3), e.g. the adjustment is relatively
easy to perform in Agilent laser interferometers.
Traceability
Figure 3. Errors in environmental sensors can have remarkable effects on the readings of a laser interferometer..
Quantity
Measuring
range
Uncertainty(k=2)
Wavelength
633 nm; 543,5 nm;
532 nm
~10-9
(suhteellinen)
Air pressure
970…1050 hPa
(730…790 mmHg)
40 Pa
Air temperature
17…25 °C
0.10 °C
Material
temperature
15…25 °C
0.050 °C
The frequencies of the iodine-stabilised lasers which
are national measurement standards of length are
determined using an optical frequency comb referenced to MIKES atomic clocks. The instruments used
in the calibration of environmental sensors are calibrated in the corresponding national standards laboratories. Thus, the measurements are traceable to the
corresponding definitions of the units.
Table 1. Uncertainty of calibration..
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Interferometrical calibration
of gauge blocks
Pasi Laukkanen, Research Engineer, Tel +358 50 382 9674,
pasi.laukkanen@vtt.fi
Antti Lassila, Pricipal Metrologist,
Tel +358 40 767 8584
antti.lassila@vtt.fi
Tel +358 20 722 111
www.mikes.fi
Calibration of gaugeblocks
Gauge blocks are the most important measurement standards of length in industry. Interferometric
measurement of gauge blocks provides an absolute calibration method. By using interferometers, the
practical realisation of the metre is transferred to
a gauge block via the calibrated wavelength of the
frequency-stabilised laser used in the interferometer. Gauge blocks calibrated by comparison must be
traceable to gauge blocks calibrated by interferometry. The length of a gauge block is defined in an ISO
standard as the distance from the centre of the gauge
face to an auxiliary reference plane wrung to the other
end of the gauge block at 20 °C temperature and at
1013.25 hPa barometric pressure. Gauge block sets
calibrated by interferometry give a lower uncertainty
for mechanical calibrations for instance in accredited
calibration laboratories.
Figure 1. Tesa-NPL gauge block interferometer.
Interferometers at MIKES
MIKES have gauge block interferometers for short
(0…300 mm) and for long (100…1000 mm) gauge
blocks and end standards. The interferometers are
located in a laboratory room having well stabilised
environmental conditions and they are equipped with
temperature, humidity and pressure sensors. Low uncertainties for refractive index of air and for thermal
expansion compensation can be achieved with a precise control and monitoring of the environmental conditions. Difference in surface roughness between the
gauge block face and the reference plane is measured and corrected for in results. The parallelism and
flatness of the surfaces can be measured, also.
The MIKES PSIGB interferometer for short gauge
blocks (Fig. 1) uses stabilised He-Ne lasers at 633
nm and 543.5 nm. The interferometer is equipped
with a large wringing bed which enables fast and automated calibration of even 14 gauge blocks in sequence. In the Tesa interferometer, the gauge blocks
are positioned vertically.
The long gauge blockinterferometer (Fig. 2) utilises
white light and 633-nm laser light interference patterns. By using white light, beforehand knowledge of
the length of the end standard is not required. The end
standards and gauge blocks are positioned horizontally and supported at the Bessel points in such a way
that the weight of the reference plane is compensated
for.
Interferometrical calibration of gauge blocks
Traceability
The regular calibration of length standards and
length measuring equipment is a necessary part of
measurement quality control. Traceable calibreations
and knowledge on the measurement uncertainty are
basic demands for good and constant quality. The
traceability to gauge block calibrations is achieved by
calibrating the wavelengths of lasers used in the interferometers against national measurement standards
of length, iodine-stabilised He-Ne lasers. Measuring
devices for temperature, humidity and pressure used
in the interferometers are calibrated in corresponding
MIKES laboratories. The reliability of calibrations are
verified by taking regularly part in international comparisons.
Gauge block interferometers can be used to measure
even other artefacts whose surfaces are flat and
smooth enough; for instance to determine the thermal expansion coefficient of ceramic sealings and
to measure the air gap between two parallel glass
plates. Interferometric calibration sets also demands
for gauge blocks: their end surfaces must be parallel,
flat and without scratches. MIKES calibrates gauge
blocks of grades K (00) and O and end standards,
e.g. quartz metres, according to the following table.
Figure 2. MIKES length bar interferometer for calibration of long gauge
blocks.
Table 1. Calibration subjects and measurement uncertainties
Device
Measurement range
Uncertainty (k=2)
Gauge blocks, small
0.5 mm ... 300 mm
Q[20; 0,3L] nm
Gauge blocks, long
100 mm ... 1000 mm
Q[30; 0,11L] nm
Quartz meters
1000 mm
72 nm
2
2 1/2
L is measured in millimetres Q[x; y] = (x + y )
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Length
geometry
Optics
Chemistry
Calibration of gauge blocks
by mechanical comparison
Ilkka Raeluoto, Senior Research
Technician, Tel +358 050 410 5562,
ilkka.raeluoto@vtt.fi
Scientist, Tel +358 40 866 7636
Tel +358 20 722 111
www.mikes.fi
Mechanical comparison measurement is the most
common way to determine the length of a gauge
block. In this method, the length of the gauge block
under calibration is compared to the length of a calibrated gauge block with same nominal length by using
a specific comparator, Figure 1.
Gauge block measurement
Comparison measurements of gauge blocks that
have the same nominal length and that are of the
same material are simple, reliable, fast and inexpensive. The method is also applicable to gauge blocks
whose surfaces have been wornout in use. MIKES
calibrates steel, hard-metal, and ceramic gauge
blocks in lengths 0.1....1000 mm (Table 1). In calibration we check the flatness of the surfaces and remove
splatters that could prevent reliable use of the gauge
blocks. A regular inspection of gauge blocks prevents
a possible damage to affect the whole set. The use
of uncalibrated gauge blocks in production quality
control and in calibration of measurement equipment
causes extra risks and costs.
Figure 1. The sensor of the gauge block comparator identifies the location of the surface by
using 0.6 Nm measurement force.
Table 1. Calibration of gauge blocks by mechanical comparison..
Measurement device
Measurement range
Uncertainty (k=2)
Tesa gauge block comparator
0,1 mm …100 mm
Q[0,050; 0,00087L] µm
MIKES comparator for long
gauge blocks
100 mm …1000 mm
Q[0,20; 0,00087L] µm
L is the nominal length in millimeters
Calibration of gauge blocks by mechanical comparison
Traceability
The reference gauge blocks used in mechanical comparison measurements are regularly calibrated using
MIKES gauge block interfereometers. The wavelengths of lasers used in these interferometers are calibrated by national measurement standard of length,
iodine-stabilised He-Ne lasers.
Table 2. Accuracy grades of ISO 3650:1998 standard:.
Nominal length range
mm
Calibration grade
K
μm
Grade
0
μm
Grade
1
μm
Grade
2
μm
Alaraja
Yläraja
±te
tv
±te
tv
±te
tv
±te
tv
0.5
10
0.20
0.05
0.12
0.10
0.20
0.16
0.45
0.30
10
25
0.30
0.05
0.14
0.10
0.30
0.16
0.60
0.30
25
50
0.40
0.06
0.20
0.10
0.40
0.18
0.80
0.30
50
75
0.50
0.06
0.25
0.12
0.50
0.18
1.00
0.35
75
100
0.60
0.07
0.30
0.12
0.60
0.20
1.20
0.35
100
150
0.80
0.08
0.40
0.14
0.80
0.20
1.60
0.40
150
200
1.00
0.09
0.50
0.16
1.00
0.25
2.00
0.40
200
250
1.20
0.10
0.60
0.16
1.20
0.25
2.40
0.45
250
300
1.40
0.10
0.70
0.18
1.40
0.25
2.80
0.50
300
400
1.80
0.12
0.90
0.20
1.80
0.30
3.60
0.50
400
500
2.20
0.14
1.10
0.25
2.20
0.35
4.40
0.60
500
600
2.60
0.16
1.30
0.25
2.60
0.40
5.00
0.70
600
700
3.00
0.18
1.50
0.30
3.00
0.45
6.00
0.70
700
800
3.40
0.20
1.70
0.30
3.40
0.50
6.50
0.80
800
900
3.80
0.20
1.90
0.35
3.80
0.50
7.50
0.90
900
1000
4.20
0.25
2.00
0.40
4.20
0.60
8.00
1.00
Note: The calibration ISO grades 0, 1, and 2 correspond to accuracy classes A, B, and C in OIML standard nr. 30, respectively.
Abbreviations in the table 2::
te = deviation of length from nominal length
tv = variation in length
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
2D- and 3D- measurement of
form and surface roughness
Björn Hemming, Senior Research
Scientist, Tel +358 50 773 5744
bjorn.hemming@vtt.fi
Maksim Sphak, Researcher,
Tel. +358 504155976
maksim.shpak@vtt.fi”
Tel +358 20 722 111
www.mikes.fi
The manufacturing tolerances of modern products and
the aim to high quality require the ability to measure
different form measurands of small artefacts having
complicated shapes. Examples of such form measurands are straightness, parallelism, radius of curvature and surface roughness. MIKES measurement and
calibration services using a computer controlled form
and surface texture instrument provides one solution
to these measurement problems.
Form measurements
The form measurement instrument can detect form
deviations even as small as 0.6 nm. Examples of typical form measurements are accurate measurements
of straightness, inner and outer determinations of radiation of curvatures and diverse dimensional measurements of small artefacts (Figure 1). These include
determinations of grooves lengths and depths and
inner and outer angle measurements. The most important technical specifications of the Taylor Hobson
Form Talysurf instrument are gathered in table 1..
Figure 1. Straightness measurement on a cylindrical surface.
2D- and 3D- measurement of form and surface roughness
Surface roughness
measurements
In addition to calibration of surface roughness normals, the surface texture instrument at MIKES is
used for tasks related to quality control and product
development. The surface roughness measurements
at MIKES are based on the following standards: ISO
5436-1 and ISO 4287.
Traceability
Traceability to the form measurement instrument
comes from interferometrically calibrated gauge
blocks, a line scale, an optical flat and a sphere.
Measurement subjects
• traceable calibration of surface roughness
standards
• divers measurements in development of
prosthesis in health care industry
• measurement of tribological samples
• profile measurements of blades of
excavation machinery
• geometrical measurements in product
development and quality control of electronic
components
• product development and quality control
measurements of metal packings and
components in hydraulics and pneumatics.
Figure 2. Measurement of sideline.
Taulukko 1. The most important technical specifications of the Taylor Hobson Form Talysurf instrument.
Ominaisuus
Tiedot
Instrument and operational principle
Taylor Hobson Form Taly-surf Ser. 2, Type 112/2815-02,
inductive
Measurement tips
Tdiamond tip, radius 0.002 mm; spherical sapphire tip,
radius 0.397 mm
Measurement forces
1.0 mN (using diamond tip), 15-20 mN (sapphire tip)
Surface texture parameters
R3y, R3z, Ra, Rc, Rda, Rdc, Rdq, RHSC, Rku, Rln, RLo,
Rlq, Rmr, Rmr(c), Rp, RPc, Rq, RS, Rsk, RSm, Rt , Rv,
RVo, Rz, Rz(JIS). In addition, a series of waviness parameters.
Longest measurement length
120 mm
Maximum height of artefact
700 mm, maximum width in 2D measurements is 50 mm
Largest allowed from deviation
28 mm (120 mm arm)
Measurement speed
1 mm/s
Resolution
0.0006 µm
Lowest uncertainty
Q[10; 70P] nm where P is the deviation from flatness in
micrometers
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Optical measurement of
surface microstructures
Ville Heikkinen, Researcher,
Puh. +358 50 415 5980
ville.heikkinen@vtt.fi
Scientist, Tel +358 50 773 5744
Puh. +358 20 722 111
www.mikes.fi
Micro to millimeter range structures can be measured
at MIKES using scanning white light interference microscope (SWLI).
The SWLI has sub-nm vertical and µm level horizontal resolution. It can measure square mm areas in a
single scan. Benefit of SWLI compared to other instruments with similar vertical resolution include large
measurement area ability to measure high steps and
ability to measure overlapping surfaces inside of transparent structures. See table 1 for more properties of
the instrument.
Real life measurement uncertainty is case dependent and depends on measurement environment,
properties of instrument and properties of measured
sample. At MIKES we take care that the sample is
clean, sample temperature is known, sample is well
attached and properly aligned. Measurements are
done traceably under consistent conditions and results are well documented.
Figure 1. Bruker ContourGT-K Scanning white light
interferometer
We do different measurements
using the SWLI
Examples of potential measured
objects
• Bearings, contact surfaces, surface topography
and wear
• Semiconductors and MEMS
• Medical instruments and implants
• Optical components
• Precision machined components
• different type of objects
o surface shape measurements
o x,y,z dimensions of details on surface
o film thickness measurement, layer separation
o surface roughness (2D and 3D ISO roughness
parameters), flatness, deviation from a shape
• calibration of different instruments
• calibration of reference artefacts
o step heights, air gap artefacts, film thickness
artefacts
• calibration of reference artefacts
o step heights, air gap artefacts, film thickness
artefacts
Optical measurements of surface microstructures
Figure 2. Measurement of machined aluminium surface.
Figure 3. Measurement of a groove on a glass surface.
Optimal measurement condition
Traceability
SWLI is in underground measurement room with 20 ± 0,1 °C temperature. Most heat sources in the room have been eliminated by
venting warm air out.
SWLI is traceable to SI-metre through MIKES’s own transfer standards such as step height standards, gauge blocks and laser-interferometry.
Table 1. Properties of SWLI
Property
Information
Optical x-y resolution
Pixel size
Vertical resolution
Step height measurement:
• repeatability
• accuracy
Sample reflectivity:
Maximum surface tilt (smooth samples):
3.8 – 0.7 µm
7.2 – 0.2 µm
< 0.1 nm
< 0.1 %
< 0.75 %
0.05 % - 100 %
3 ° (2.5× objective), 18.9 ° (20× objective)
Magnifications
2.5× and 20× objectives, 0.55×, 1× ja 2× zoom lenses
3
Measurement area (X × Y × Z mm ):
smallest magnification 3.5 × 4.6 × 3.5
largest magnification
0.4 × 0.6 × 3.5
Measurement area in pixels
640 × 480
Programs
Vision64 Analysis Software, MountainsMap, MatLab
Maximum size of measured object
10 cm high × 20 cm wide, one dimension can be long
Ability to measure overlapping surfaces
2 surfaces in single measurement
Maximum depth is dependent on refractive index, geometry and
magnification, e.g. it is possible to measure through 0.3 mm thick
glass
7 mm maximum depth limited by working distance
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Calibration of tachymeters
Jarkko Unkuri, Research Scientist,
Tel +358 50 410 5506
jarkko.unkuri@vtt.fi
Antti Lassila, Pricipal Metrologist,
Tel +358 40 767 8584
Tel +358 20 722 111
www.mikes.fi
MIKES calibrates angle and distance measurements
functions of tacheometers.
Calibration of a distance meter
in a 30-metre measuring rail
Readings from a distance meter of a tachymeter is
compared to readings from a laser interferometer of
the 30 meter measuring rail. The measurement axis
of the tachymeter and the laser interferometer are
aligned to be parallel. The reading of the interferometer is set to zero at the beginning of the measuring
rail. The observed reading of the distance meter at
the zero point of the interferometer is subtracted from
Figure 1. MIKES 30-m
measuring rail.
the readings of the distance meter. In the calibration
certificate, the deviations from the references distances and the expanded measurement uncertainty are
given for each target point. The target point can be a
prism, a reflector tape or a target plate. The measurement uncertainty depends on the scatter of the
measurement results and is typically between 0.05 –
0.25 mm for accurate distance meters..
Calibration of tachymeters
Calibration of angle measurements by using a rotary
table and collimation tubes
The vertical and horizontal scales of a tachymeter
are calibrated by using a Eimeldingen rotary table as
a reference. The rotary table is calibrated using polygons and collimation tubes.
In the calibration of the horizontal scale, the tachymeter is placed to the rotary table in such a way that
the vertical axis is aligned to the rotational axis of the
table (Figure 2). The table is rotated 360° in 30° steps
and at each step the reading of the tachymeter that
has been targeted to the collimation tube are recorded.
The vertical scale of the tachymeter is calibrated in
the same way but now the rotary table is turned to
vertical position by using optomechanics that have
been designed especially for this purpose.
Contents of tacheometer calibration
Figure 2. Calibration of the horizontal plane of a tachymeter
in an Eimeldingen rotary table with a collimation tube as a
target point.
Typical measurement uncertainty
calibration of length scale
deviation from reference
precision target
0.15 mm
spherical target
0.15 mm
reflector tape
0.20 mm
without target
calibration of angle scale
scale error of the vertical circle
2-3”
scale error of the horizontal circle
1-2“
tilting axis error
1-2“
index error of the vertical circle
0.5 - 1.5 “
line-of-sight error
0.5 - 1.5 “
crosshair alignment and perpendicularity
influence of focussing
checking the readings of the environmental sensors
divergence test of automatic targeting
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Angle and perpendicularity
measurements
Asko Rantanen, Senior Research
asko.rantanen@vtt.fi
Scientist, Tel +358 50 773 5744
Angle measurements are important in all me-chanical
engineering and construction industry. The significance of angle measurements is increased also in dimensional measurements when dimensions increase. Perpendicularity that is related to right angles and square
blocks is an important special case of angle mesurement.
Tel +358 20 722 111
www.mikes.fi
• As a result the width t of tolerance zone
is given
• One side is defined as the reference side
and only against this side the perpendicularity
is determined.
The SI-unit for angle is radian (rad) but depending on
the branch of industry and the measurement subject
other unist of angle are commonly used. In mechanical engineering angles are normally expressed in
degrees [°], minutes [’] and seconds [”], in geodesy
the most commonly used unit is gon (also referred to
as grade) [gon]. In earth-moving work and for small
angles the unit [mm/m] is generally used. The diverse
group of units for angle include also the following ways
to express the angle: percent [%] and length ratios.
Perrpendicularity according to the ISO1101
standard:
Figure 1. Polygon attached to a rotary table.
Errors from the rotary
table and the polyhedron can be separated by
performing a measurement series using a Moller Wedel HPR autocollimator.
Angle and perpendicularity measurements
Instruments for measuring angle Measurement uncertainty
The most typical objects of calibration in mechanical
workshops are rotary tables of machine tools and
measuring machines, universal bevel proctractors,
angle blocks, and different kinds of spirit (bubble) levels. Typical angle measurement instruments used in
machine installation and in construction engineering
are e.g. electronic levels, theodolites, levelling instruments, tacheometers, laser interferometers, autocollimators and polygons.
Figure 2. Calibration of the horizontal scale of a tacheometer using an Eimeldingen rotary table and an autocollimator
as a target point.
All measurements are performed in a well-controlled
laboratory room at temperature +20 °C ± 0.1°C. The
achievable measurement uncertainty depends critically on the artefact under calibration and its properties (e.g. its form errors and surface roughness).
Figure 3. Calibration of a granite square using a measuring
machine developed at MIKES.
Table 1. Examples of lowest uncertainties for angle measurement instruments.
Instrument
Measuring
range
(k=2)
Limitations
Optical polygons
0 ° - 360 °
0.2 ”
Rotary indexing table
0 ° - 360 °
0.5 ”
Rotary table
0 ° - 360 °
0.2 ”
Autocollimator
0°-1°
0.02 ”
Electronic level
0 ° - 360 °
0.2 ”
Theodolite
0 ° - 360 °
0.2 ”
Angle block
0 ° - 360 °
0.2 ”
Steel or granite squares
90 °
0.5 ”
max. length 1 m
Cylinder square
90 °
0.5 ”
max. length 1 m
Optical right angle
90 °
0.5 ”
indexing angle n x 15°
instrument limits
the vertical angle
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Length
geometry
Optics
Measurements of accurate inner
and outer dimensions
Ilkka Raeluoto, Senior Research
Technician, Tel +358 50 410 5562,
ilkka.raeluoto@vtt.fi
Scientist, Tel +358 40 866 7636
Measurements using SIP
length measuring machine
Precise measurements of inner and outer diameters
are performed using SIP length measuring machine
either by using its own scale or by referencing to a
standard of equal length (Figure 2). In the measurement a contact is made using a ceramic spherical
measuring probe, a flat tip or in inner measurements
a lever probe. If the measurement depth in inner
measurements is over 15 mm, special hook-shaped
jaws are used. The measuring force can be tuned
between 0.3…11 N. By measuring with several different forces, the deformations due to the measuring
forces can be eliminated from calculations and the
result can be given at so-called zero-force. This is
essential when the reference and the artefact under
calibration are made of different materials or have
Tel +358 20 722 111
www.mikes.fi
shapes. The accuracy of the length scale in SIP
length measuring machine can be improved by
using a laser interferometer (5528A) and a separate readout program. Measurements are performed in a well-controlled laboratory room at
temperature + 20 °C ± 0.1 °C. Different types of
heat sources are eliminated by using vent pipes,
heat shields, and when necessary with a separate laminar flow. In addition to the measurement
length, the measurement uncertainty depends
on the measured artefact (shape and surface
texture), on measuring instrument, measurement
conditions, and on the method used.
In addition to diameter measurements, the SIP
length measuring machine is used for thread
measurements and tolerance comparisons. The
inner threads are measured using spherical probes and in outer thread measurements three
wire method is used.
Figure 1. Measurement using SIP length measuring machine.
Chemistry
Measurements of accurate inner and outer dimensions
Measurements
supplementing diameter
measurements
In order to get a precise picture of the features of an
axially symmetrical artefact that is under measurement, one should also measure its roundness, surface roughness and straightness of sides using appropriate instruments.
Traceability
Measurements made using the SIP length measuring
machine are traceable to corre-sponding transfer standards that are calibrated at MIKES. The linear scale is
calibrated using a laser interferometer, the reference
gauge blocks are calibrated interferometrically, and
the temperature sensors are calibrated in temperature
baths against reference Pt25 thermocouples.
Figure 2. Mounting side by side the artefact under calibration and
the reference in a comparison measurement.
Table 1. Measurement uncertainties achievable in diameter
measurements.
Measurement artefact
(k=2)
Thread plug 0 mm - 550 mm
Q[0,2; 0,87L] µm
Ring gauge 1 mm - 500 mm
Q[0,2; 0,87L] µm
Sphere 0.2 mm …200 mm
Q[0,15; 0,7L] µm
L in metres
Figure 3. SIP 550M length measuring machine.
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Length
geometry
Optics
Coordinate measurement
Pasi Laukkanen, Research Engineer, Tel +358 50 382 9674,
pasi.laukkanen@vtt.fi
Scientist, Tel +358 40 866 7636
The coordinate measuring services at MIKES include
measurements with an optical coordinate measuring
machine and with a high-accuracy industrial size contact probe coordinate measuring machine.
Contacting coordinate measurement
The basic properties of MIKES coordinate measuring
machine are accuracy, flexibility, speed, and automatic calculation of results.
The MIKES 3D coordinate measuring machine is a Mitutoyo Legex 9106 with portal structure (Figure 1). Further information on this
machine can be found in Table 1. The true
measurement uncertainty is always case-specific and depends on the environmental conditions, on the machine, and on the properties
of the work piece. We pay special attention in
our working on surface cleanliness, temperature, mounting (Figure 2), alignment, measuring
system, and on the documentation of results.
Figure 1. Mitutoyo Legex coordinate measuring machine.
Tel +358 20 722 111
www.mikes.fi
Chemistry
Coordinate measurement
The coordinate measuring machine is used for:
• pcustom measurements of 3D workpieces
(Figure 3) and difficult shapes
- scanning
- digitizing of point clouds
• various calibration of measurement
devices
- rulers, surface plates, gauges, cones,
squares
• calibration of transfer standards for
coordinate machines
- step gauges, ball cubes,
Optimal measurement
conditions underground
The coordinate measuring machine is located in a
large volume underground laboratory room held at
+ 20 °C ± 0.2 °C constant temperature. Most of the
heat sources in the laboratory are eliminated using
vent pipes. Moreover, the room is equipped with a
1000-kg load lifter on rails and a lift with 4000 kg maximum load capacity can be used to haul the goods
into the laboratory.tauksena (substitution method) .
Jäljitettävyys
In commissioning, various laser and gauge block
measurement were carried out on the coordinate
measuring machine. Furthermore, the machine is
regularly calibrated using our own measurement
standards: step gauges, ball plates, and a laser
interferometer. The measurement uncertainty and
traceability are verified in each case separately
using so-called substitute method, i.e. results are
corrected using the results of a calibrated standard.
Figure 3. A typical artefact that can be measured using a
coordinate measuring machine.
Figure 2. The proper mounting of work pieces is important.
Table 1. The main properties of the coordinate measuring machine.
Property
Performance checked according
to ISO 10360-2:
• maximum error in lengtmeasurements
• maximum 3D contact deviation
• maximum error in scanningmeasurement
Data
MPEe = (0.35 + L /1000) µm, L =
mm
MPEP = 0.35 µm
MPEthp = 1.4 µm
Scales
Mitutoyo Zerodur scales with floating
mounting, reolution 0.01 μm.
Travelling length
X-910 mm, Y-1010 mm ja Z-610
mm
Contact probe
Renishaw indexing head PH10MQ,
Renishaw SP25M contact and scanning probe.
Software
Mitotoyo COSMOS-software pakage
• Geopak-Win geometry program
• Statpak-Win geostatistical
analysis for quality control
• Scanpak-Win form measurement
program 3Dtol-Win/MCAD300
comparison with CAD models
and importing CAD data for
programmingi
Measuring force
0.03 N…0.09 N
Maximum work piece mass
800 kg
Diameters of probes
0.5 mm…30 mm
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Optical coordinate measuring –
vision measuring
Ville Byman, Research Scientist,
Tel +358 50 386 9327,
ville.byman@vtt.fi
Scientist, Tel +358 50 773 5744
Tel +358 20 722 111
www.mikes.fi
The manufacturing tolerances of modern products
and the aim for high quality require ability to make
precise measurement of dimensional measurands
on small artefacts of complicated shapes. The use
of vision measuring machines and machine vision is
wellestablished in non-contact high-precision measurement.
MIKES have a Mitutoyo Quickvision Hyper QV-350
vision measuring machine (optical CMM or video
measuring machine) that is equipped with a CCD-camera as well as with a contact probe. In non-contact
optical measurements, the machine takes advantage
of the measurement point location detected by the
CCDcamera and location information from the precise scales attached to mechanical guides.sta.
Figure 1. The artefact under study can be illuminated with
ring, coaxial or stage light.
Optical coordinate measuring – vision measuring
The machine is computer-controlled and measurements are fully automated. The machine is capable to measure length, diameter, angle, straightness,
flatness, parallelism, and roundness.
The machine is especially suitable for measurements
of circuit boards, thin-walled fragile plastic and metallic artefacts, and other artefacts that are inconvenient
or impossible to measure with techniques using contact probes.
The artefact under study can be illuminated with ring,
coaxial or stage light. There are four controllable segments in the ring light and its height can be adjusted.
MIKES provides precise optical and contact dimensional measurements tailored according to customers’
needs. Depending on the work order a calibration
certificate or a field log is provided.
Table 1. Properties of the vision measuring machine.
Property
Data
Measuring volume
350 mm x 350 mm x 150 mm
Size of the bench
490 mm x 550 mm
Maximum work piece mass
15 kg
Lowest measurement uncertainty (k=2) , optical mode
U1XY = (0.8 + 2 L/1000) µm *
U2XY = (1.4 + 3 L/1000) µm *
U1Z = (3 + 2 L/1000) µm *
Lowest measurement uncertainty (k=2) , contact probe
U1XY = (1.8 + 2 L/1000) µm *
Maximum speed (rapid travel)
100 mm/s
MMaximum acceleration
490 mm/s2
* L is length in mm. U1 is uncertainty along to one axel and U2
along two axels.
Figure 2. A contact probe complements the vision measuring machine.
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Calibration of line scales and
distance meters
Jarkko Unkuri, Researcher,
Tel +358 50 410 5506
jarkko.unkuri@vtt.fi
Antti Lassila, Pricipal Metrologist, Tel +358 40 767 8584
Calibration services at interferometric
measuring rails
Line scale interferometer
MIKES calibration equipment for precision line scales
allows calibration of up to 1.12-m long line scales with
best possible accuracy. The measuring instrument is
located in an air-conditioned laboratory room in which
the tem-perature is held at + 20 ± 0.05 °C and the
relative humidity at 45±5 %. The instrument performs
computer-controlled measurements of distances
between the graduation lines using a micro-scope
equipped with a CCD camera for line detection and a
Michelson interferometer for position measurement of
the microscope. The line scales are supported at Airy
points which minimizes bendings. The refractive index of air is calculated from the measured air temperature, pressure and humidity data by using updated
Edlen’s equation. Thermal expansion is corrected to
20 °C using material temperature measured with four
Pt100 sensors attached to the line scale. The graduation line distances can be between 10 μm ... 1.12 m.
The line scale interferometer is suitable for calibrations of me-tallic or glass graduated line scales.
Tel +358 20 722 111
www.mikes.fi
carriage. A microscope, a CCD camera and a monitor
used in line scale measurements are mounted on the
carriage, The position of the microscope is measured
using a laser interfereometer.
The temperature stability of the measurement room
and precise gauges and sensors allow precise thermal expansion and refractive index of air compensation. The rail is suitable for calibration of various length
standards. The calibrated devices can be physical
artefacts like tapes and machinist scales or e.g. optical distance meters. Tapes and other flexible length
standards are tensioned using a standardized force,
a force given by the manufacturer or a force separately agreed with customer. Most commonly a 50-Nm
force of is used for tapes.
For thermal expansion compensation, a measured
temperature and a coefficient given by the manufacturer or by the customer are used.
Calibration of line scales and distance meters
30-m measuring rail
MIKES 30-m measuring rail (Figure 2) offers good
possibilities for calibration of precise length measuring
devices. The temperature of the measurement room
is kept at a + 20 °C ± 0.5 °C and the relative humidity
at 45±5 %. The 30-m rail is realised using a highquality linear motion guide and a movable measurement
Kuva 1. Piirtomittainterferometri.
Calibration of line scales and distance meters
Traceability
The wavelengths of the lasers used in the line scale
interferometer and in the 30-m measuring rail are
calibrated using national measurement standard of
length, iodine-stabilized He-Ne laser. The temperature, pressure, and humidity sensors used in the
measuring rail are calibrated at MIKES.
Table 1. Line scales, measuring ranges and measurement uncertainties..
Device
Measuring
range
Uncertainty (k=2)
Precision line
10 µm ... 1 m
scales, microscope
scales
Q[6,2; 82L] nm**
Tapes, wires
Q[35; 2L] µm
0.001 m ... 30, (60,
90 ...) m
Machinist scales
0.001 m... 5 m
Q[4; 1L] mm**
Circometer
0.1 m ... 9,55 m
(diameter)
Q[7; 2D] mm**
Plumb tapes
1 m ... 30, (60,
90) m
Q[250; 5L] mm**
Other devices
0 m ... 30 m
(case dependent)
L, D = measured length or corresponding diameter in meters
*The uncertainty of calibration is usually larger than the aforementioned uncertainties due to the uncertainty resulting from
the device to be calibrated.
**Calculation of uncertainty Q[x; y]=(x2+y2)½
Figure 2. 30-m measuring rail..
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Interferometric measurement of
flatness and form
Scientist, Tel +358 50 773 5744
Ville Byman, Research Scientist,
Tel +358 50 386 9327,
ville.byman@vtt.fi
Tasomaisuus
The surface structure and especially the flatness of
the surface are important features of various components used in different areas of technology and
physics. Examples of these include silicon wafers in
semiconductor industry, sealing faces, bearing areas,
contact surfaces in contact measurement methods,
and surfaces of optical flats and lenses used for reflecting and refracting light.
An optical flat is an easy to use transfer standard for
flatness. In industry, optical flats are used, e.g. for
Figure 1. Calibration of an optical flat.
+358 20 722 111
www.mikes.fi
flatness measurements of gau ge blocks and contact
surfaces of micrometer gauges. In these cases, the
quality of the surfaces of optical flats is of essential
importance for successful measurements of subject
sur-faces. Moreover, optical flats are used to transfer
flatness to interferometers measuring flatness and to
other devices inspecting flatness in industry.
MIKES provides a measurement place for aforementioned measurements and metrological traceability
with its equipment for flatness and form measurements (Figure 1).
Interferometric measurement of flatness and form
Measurement method
The measurement device for flatness at MIKES is
a Fizeau interferometer that uses a He-Ne laser at
wavelength 633nm as a light source. Interference fringes are obtained by adjusting a small angle between
the reference plane and the plane to be measured.
The shapes of the inter-ference fringes are analysed by using a so-called phase stepping method. As
a result, one receives deviations of the plane under
inspec-tion from the reference plane (Figure 2). The
advantages of the method are speed, precision, and
the fact that the entire measurement area is measured at once.
Figure 2. Examples of measured surface profiles of optical flats.
Traceability
The reference plane of the optical flat used in the interferometer is of high-quality: deviations from a perfect
plane are less than 20 nm. The reference plane is calculated either by using an absolute three-point method or by comparing it to a liquid plane. Optical flats
having different reflection coefficients are available
which allows inspections of mirror surfaces as well as
glass surfaces.
Measurement services
The MIKES equipment (Zygo GPi) can be used for
surface profile measurements of objects that have
diameters below 150 mm, best available measurement precision being 45 nm. A prerequi-site for such
measurements is that the height variations of the artefact are less than 12 μm and slowly varying. As the
method is based on interference of light and thus it is a
non-contacting method it is also applicable for fragile
materials. Moreover, it is applicable for very demanding measurement tasks due to its precision.
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Machine tool
measurements
Asko Rantanen, Senior Research
asko.rantanen@vtt.fi
Scientist, Tel +358 40 866 7636
Tel +358 20 722 111
www.mikes.fi
Machine tool measurements
Demands of production and quality systems require
knowledge on the precision of machine tools. Different
measurement are performed on machine tools during
acceptance inspection, in connection with transfers,
and when striving for preventive maintenance. MIKES
provides its wide experience on dimensional and geometrical measurements, positioning and repeatability accuracy measurements, and measurements on
machine tooled test work pieces.
The competent and experienced personnel of MIKES,
modern equipment and continuous development of
new measurement methods guarantee customers
precise measurements performed according standards.
Figure 2. Setup for machine tool measurements.
Figure 1. Scale measurement for a machine tool..
Machine tool measurements
Geometrical measurements
Geometrical measurements are used for finding out
the form defects in the most important organs of a
machine tool and the mutual locations and positions
of the organs. MIKES performs geometrical measurements according to ISO and DIN standards. The
most important measurements subjects are: measurement of spindle runout, the parallelism between the
spindle and the machine, perpendicularity measurements, and straightness and perpendicularity measurements of machine movements.
Positioning and repeatability
accuracy measurements
Spindle positioning and repeatability measurements
reveal errors at different points of the spindle. Errors
in spindle movement can be compensated for by
giving the compensation values to the control unit
memory of the machine tool. The positioning measurement performed using MIKES laser interferometer
is a fast and precise way to adjust the spindle movements of a machine (Figure 3). By using this method,
the measurement precision is at its best below 0.001
mm/m.
Table 1. Devices used in machine tool measurements
Geometrical and
positioning and
repeatability accuracy
measurements::
Measurements of test work
pieces:
- laser interferometers
- surface structure, form, roundness
and length measuring
machines
- autocollimators
- iinductive sensors
- electronic spirit level
- common workshop measurement
devices
- inductive sensors
- coordinate measuring machine
- plumb
- other devices
Traceability
All measurement standards used in machine tool
measureentsare calibrated using similar but more accurateMIKES transfer standards.
Measurements on test work
pieces
Machine-tooling tests are used to find out the precision of the machine in true machining circumstances. MIKES geometrical measurements and measurements on work pieces made in machine-tooling
tests complement each other. The work pieces are
measured in a temperature-controlled laboratory
room using versatile and modern measurement devices and methods. MIKES have a variety of the most
common workshop measurement equipment and a
selection of special tools (see Table 1).
Figure 3. X-axis errors of a broaching machine before laser
measurement and adjustment and after.
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Length
geometry
Optics
Chemistry
Measurement of roundness
Scientist, Tel +358 50 773 5744
scientist, Tel +358 40 866 7636
Tel +358 20 722 111
www.mikes.fi
Roundness in mechanical
engineering industry
Approximately 80 % of machined work pieces have
elements with surfaces of revolution. Roundness has
an important role for guaran-teeing faultless operation
of machines and devices. This is even emphasized
when reli-ability, longevity, low operating costs, and
friendliness to the environmental are required.
At MIKES we perform measurements of roundness
on ring gauges, screw-plug gauges, slide bearings,
metallic packings and hydraulic and pneumatic components. We also measure runout eccentricity, coaxiality, parallelism and straightness (Figure 1).
Figure 1. Roundness measurement is an essential part of
workshop manufacturing.
Measurement of roundness
Measurement potential
Roundness is measured either by using a rotating
spindle or using a roundness measurement instrument equipped with a rotating table. Measurements
can be performed using several different filters according to the ISO 1101 standard’s definition (MZ) or
other computing methods (MC, MI, and LS). The use
of two alternative machines guarantees the customer
that the artefacts can be measured properly and cost
effectively. More information on the machines can be
found in table 1.
Cylindricity is measured using a machine equipped
with a rotating table (Figure 2), with almost the same
settings also the following measurement can be performed: coaxiality, runout eccentricity, parallelism
and straightness. Cylindricity measurements are a
part of the calibration of ring gauges and screw-plug
gauges.
Traceability
Traceability to the sensors in both machines comes
from magnification standards that are calibrated
using MIKES form measurement instrument which in
turn gets it traceability from gauge blocks calibrated Figure 2. Measurement instrument Talyrond 262 for roundness
using an interferometer. The guide bars and shafts in and cylindricity.
the machines are calibrated using error separation.
Table 1. MIKES roundness and cylindricity measurement instruments
Model
Rotating
part
Maximum
height of
the artefact
/ mm
Maximum
inner/ outer
diameter of
the artefact
/ mm
Maximum
mass of the
artefact
/ kg
Other
Expanded uncertainty
(k=2)
Talyrond 73 HR
roundness
spindle
400
175 / 300
100
surface can
be discontinuous or
asymmetrical
Q[0,01; 0,01R ] µm
Talyrond 262
cylindricity
table
500
-
50
surface can
be discontinuous
Q[0,1; 0,5L] µm
/ 350
R is the deviation from roundness in micrometers; L is the height of the cylinder in meters
Q[x; y]=√(x2+y2)
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Calibration of microscpes and
calibration standards
Scientist, Tel. +358 50 410 5504
Reliable measurement results in research, manufacture and quality control require knowledge of accuracy of measurement intruments. Calibration is the
best way to check the accuracy and stability of the
instrument. The calibration can be done with calibrated transfer standards. Official calibration certificate
guarantees traceability to the definition of the metre.
Tel +358 20 722 111
www.mikes.fi
2], which can be calibrated at MIKES. 1-D and 2-D
gratings are calibrated either by laser diffraction or by
metrology atomic force microscope (MAFM). Pitch
and orthogonality of the grid can be measured. Step
height standards or z scale of 1-D or 2-D gratings can
be calibrated.
For optical microscopes MIKES provides calibration
of high quality line scales.
Scanning probe microscopes (SPMs) can be calibrated using several kinds of transfer standards [1,
[1] Guideline VDI/VDE 2656 Part 1 (Draft): Determination of geometric quantities by Scanning Probe Microscopes - Calibration of
Measurement Systems
[2] V. Korpelainen and A. Lassila, Calibration of a commercial AFM:
traceability for a coordinate system, Meas. Sci. Technol. 18 (2007)
395–403
Figure 1. MIKES interferometrically traceable
metrology AFM (MIKES IT-MAFM).
Calibration of microscopes and calibration standards
measured using a flatness standard. In the most
accurate calibrations also some other error types
has to be measured and corrected; e.g. orthogonality of z axis, rotational and other guiding errors.
There are also other error sources which should
be taken into account, e.g. tip-sample interactions,
vibrations, noise and thermal drift. Calibration
period depends on the stability of the device, e.g.
microscopes with open loop scanner need calibration before and after each measurement.
Calibration itself gives information about the accuracy of the instrument. Accuracy of the measurement
can be increased by corrections of the errors detected in the calibration either directly in the measurement software or after the measurement with separate software.
The first step in the calibration is measurement of
x and y scale errors by 1-D or 2-D gratings and z
scale errors by step height standards. The calibration of the x and y scales gives also information
about the linearity of the scales. The linearity of the
z scale needs to be checked by several different
step height standards. Orthogonality errors can be
detected by 2-D grids. Out-of-plane errors can be
Figure 3. Some error types of SPMs.
Table 1. Calibration services for SPM standards.
Uncertainty
Range
1-D grid (diffraction measurement)
Pitch
300 nm - 10 µm
50 - 100 pm
300 nm - 10 µm
50 - 100 pm
100 nm - 10 µm
Q [3.4; 0.2 p/µm] nm
2-D grid (diffraction measurement)
Pitch
Orthogonality
1-D grid (AFM measurement)
Pitch, p
Orthogonality
14 mrad
Step height, h
10 nm - 2 µm
Q [2; 0.2 h/µm] nm
Flatness
100 µm × 100 µm
5 nm
Step height standard
10 nm - 2 µm
Q [2; 0.2 h/µm] nm
Flatness standard
100 µm × 100 µm
5 nm
Mass pressure
flow
Temperature
humidity
Electricity time
acoustics
Optics
Length
geometry
Chemistry
Length in geodesy
Markku Poutanen, Prof.,
Tel. +358 29 531 4867,
markku.poutanen@nls.fi
Paavo Rouhiainen,
Senior research scientist,
Tel +358 29 531 4875
paavo.rouhiainen@nls.fi
Jorma Jokela,
Research manager,
Tel +358 29 531 4743
jorma.jokela@nls.fi
Finnish Geospatial Research Institute, FGI,
Geodeetinrinne 2, 02430 Masala,
Tel. +358 29 530 1100, www.fgi.fi
Finnish Geospatial Research
Institute, FGI
The Finnish Geospatial Research Institute, FGI, of the
National Land Survey of Finland maintains measurement standards for geodetic and photogrammetric
measurements and is the National Standards Laboratory of acceleration of free fall and length. The
FGI takes care of the fundamental measurements in
Finnish cartography and of geographical information
metrology and carries out scientific research in geodesy, geographic information sciences, positioning,
navigation, photogrammetry and remote sensing.
The FGI calibrates high precision electronic distance
measurement (EDM) instruments, geodetic baselines
and photogrammetric test fields. Moreover, we calibrate precise levelling rods, digital and traditional, and
system calibration of digital level instruments. The
calibrations are performed in addition to the Masala
laboratories at Nummela Standard Baseline and at
Metsähovi Fundamental station. Most of our work is
carried out in field conditions or conditions analogous
to operating situations.
Figure 1 and 2. The Nummela standard baseline measured
by using the Väisälä comparator has been one of the most
accurate and stable lengths over the past half decade.
Length in geodesy
Traceability and uncertainty
Research and development
National measurement standards for length at the FGI
are a Väisälä interference comparator with a quartz
meter system and a levelling rod comparator system
with a laser interferometer. All the measurements are
traceable with a known uncertainty. Baselines (864 m
and 432 m) measured with the Väisälä interference
comparator have typically a measurement uncertainty
ranging from 0.1 ppm to 0.2 ppm (k=2) and the measurement uncertainty for other baselines (1 m - 10 km)
is at its best 0.2 ppm. The measurement uncertainty
for calibration of levelling rods is 1 ppm and 5 ppm for
calibration of levelling systems.
The FGI carries out research and development on
methods and equipment for the measurements for
geodesy and geospatial information science. In addition to length measurements, we perform other precision measurement in surveying, e.g. measurements
of angle, azimuths, determination of coordinates and
satellite positioning. We also participate in GNSS
metrology related projects. International cooperation
is a central part of our work and we have measured
baselines in about 20 countries.
Figure 3. Calibration of the most accurate distance meters of
the world can be done at the Nummela Standard Baseline.
Nummela scale has been transferred also to several foreign
baselines.
Figure 4. Calibration of a digital precise level instrument
and system calibration of a barcode rod.
Figure 5. Research on the accuracy of GNSS antennas can be made at the test field
of the Metsähovi observatory.
Massa,
paine ja virtaus
Lämpötila,
kosteus
Sähkö, aika ja
akustiikka
Optiikka
Pituus,
geometria
Kemia
Water quality
Teemu Näykki, PhD, Associate Professor,
Senior research scientist
Tel. +358 29 525 1471,
teemu.naykki@ymparisto.fi
Timo Sara-Aho,
Researcher,
Tel. +358 29 525 1618
timo.sara-aho@ymparisto.fi
ENVICAL SYKE is focusing on the research and
development of metrology in chemistry. Our activities include development of accurate and
traceable calibration methods, testing the reliability of new measurement techniques and validation of methods of analysis and quality assurance.
Traceable calibrations
The SYKE accredited calibration laboratory (K054:
EN ISO/IEC 17025) produces calibration results with
high accuracy and traceability and is responsible for
developing methods based on primary techniques.
In general, Isotope Dilution Mass Spectrometry
(IDMS) can be regarded as one of the main referen-
Finnish Environment Institute
Hakuninmaantie 6, 00430 Helsinki,
Tel. +358 29 525 1000,
www.syke.fi/envical/en
ce methods for elemental analysis, and appropriately
applied it offers the highest accuracy and smallest
measurement uncertainty.
This method is used to measure the elemental
content (usually mass fraction) of an unknown test
sample, which has natural isotopic composition. This
sample is mixed with another sample (spike) containing a known amount of the same element under investifgation. Isotopic composition of the spike
sample is known and it is different from the isotopic
composition of the test sample; usually such a way
that the rarer isotopes of the element are enriched.
When the test sample and the spike are completely
mixed, the resulting mixture (blend) has a new (isotope diluted) isotopic composition, where the isotope ratios are between the test sample and the spike
Photo Timo Vänni
80 — VTT MIKES METROLOGIA Kalibrointipalvelut 2016
Water quality
sample added. The isotope ratios of the mixture are
measured and the result is directly proportional to
the mass fraction or concentration of the element in
the sample.
At present, the scope of SYKE’s calibration laboratory accreditation includes measurement of lead (Pb)
in natural water and mercury (Hg) in natural and waste water. The methods are based on the isotope dilution inductively coupled plasma mass spectrometric
(ICP-MS) technique. The range of measurements is
being complemented with tests for dissolved oxygen
and also nickel and cadmium, listed as priority substances in the Water Framework Directive. The isotope dilution mass spectrometric technique is widely
utilized by SYKE also for measurement of organic
chemical contaminants.
Our customer base consists of public and private
parties requiring accurate and reliable measurement
results for their environmental samples. For instance, we have produced traceable reference values for
proficiency tests (PTs).
Research Activities
The comparability of the measurement results is internationally very important. Reliability and comparability
of the measurement results can be improved with the
realistic measurement uncertainty estimation, validation of the measurement methods, and ensuring the
traceability of the measurement results.
ENVICAL SYKE is an experienced in research
and development of the instrument’s reliability and
procedures for measurement uncertainty estimation.
We have constructed new tools for both laboratory
measurements as well as for portable and continuous
field water quality measuring devices to indicate and
improve the reliability of the measurement results.
Examples of these tools are MUkit- and AutoMUkitmeasurement uncertainty calculation software.
We also actively participate in organizing proficiency
tests for water quality sensor measurements.
In addition to maintenance of measurement standards’ international traceability, our activities include
national and international communication, publication,
and training in the field of metrology. Upon request,
we arrange customized training in the estimation of
measurement uncertainties in chemical measurements or validation of analytical methods.
Table 1. CMC data..
Quantity / method /
object
Measurement
range
CMC, Expressed as
Expanded Uncertainty (k=2) )
Chemical analyses; amount of substance
Mass fraction of soluble
total mercury (Hg) in synthetic water, fresh natural
water (not sea water) and
waste water
Photo Timo Vänni
Mass fraction of soluble
total lead (Pb) in synthetic
water and fresh natural
water (not sea water)
30 - 125 ng/kg
>125 - 5 000 ng/kg
6%
3%
0,200 – 1,00 μg/kg
>1,00 - 100 μg/kg
0,030 μg/kg
3%
MIKES
Tekniikantie 1
02150 ESPOO
MIKES-Kajaani
Tehdakatu 15, Puristamo 9P19
87100 KAJAANI
Tel +358 20 722 111
email: forename.surname@vtt.fi
www.mikes.fi

Calibration services brochure

Transcription

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