Fluke`s Artifact Calibration and Its Use in Calibration of 8.5 Digit DMMs

Fluke's Artifact Calibration
and Its Use in Calibration
of 8.5 Digit DMMs
Jack Somppi
Product Marketing Manager
Fluke Calibration
NCSLI 2014, Orlando, Florida
1
Today’s Objectives
• Review the concept of artifact calibration as seen in
various commercial instruments
• Evaluate its history as an effective method of maximizing
performance of a calibrator
• Present the performance improvements it offers over
traditional periodic calibration with higher level primary
standards
• Offer an approach to use to make calibration of 8.5 digit
dmms more efficient with improved confidence
2
Today’s challenge with 7½ & 8½ digit dmms
• Supporting anything better than a 6½ digital multimeter
requires more from a calibrator than the performance
based on it’s normal “1-year” specifications.
3
The practical challenge – supporting
commonly used digital multimeters
Manufacturer’s Specifications (parts in 106)
Example Cal.
Points
Popular 6½ & 8½ Digit DMMs
Calibrator
Agilent
34401A
(1 year)
Fluke
8846A
(1 year)
Agilent
3458A
(1 year)
Fluke
8508A
(1 year)
Fluke 5730A
(95% conf.
1 year)
1.0 V dc
47
32
10.3
5.0
5.7
10.0 V dc
40
29
10.05
5.0
3.75
10.0V 1 kHz ac
900
900
92.0
102.0
47.0
100 Ω
110
140
20.0
10.6
10.0
10 kΩ
110
110
13.5
10.6
6.5
10 mA dc
550
700
30.0
22.0
39.0
0.14%
0.21%
505
610
138
10 mA 1 kHz ac
4
Tools to address this challenge…
• Common tools:
– Manual verification of the
calibrator using primary
lab class standards
– Improved a calibrator’s
specs by more frequent
calibration
– Improved specs +
guardbanding the test
limits
– Custom specs through
control charting &
characterization of the
calibrator
• A less commonly used tool:
– Using Artifact Calibration on a
frequent basis to operate at
improved 90 day specs or even
24 hour spec levels.
Benefits from Artifact Calibration
• Artifact Cal will give a 25% to 30% spec improvement
Support a shortened calibration interval to utilize a better standard
specification – calibrate every 90 days with Artifact Cal
Selected as the most
practical specs to use
Up to 2 X better, often
preferred, but not usually used
6
What is this “Artifact Calibration”?
Simplified calibration using self adjustment through
primary level standards
Fluke’s Technique:
• A traceable full calibration & optimized “self
adjustment” of all functions and ranges
• Traceable to the SI through 3 primary level standards
• With Artifact calibration the “As Left” condition of the
instrument will meet its best specified performance (24
hour specs) – and is documented
• Every 57XX calibrator uses Artifact Calibration, it is the
only way to adjust and compensate for natural
performance errors.
First introduced in 1988 with
the 5700A and continued with
the new 5730A in 2013
Agilent’s similar use of self adjustment
• At about the same time
(~1988) Agilent (Hewlett
Packard at that time)
introduced a dmm with self
adjusting capabilities – the
HP 3458A
• Both instruments intended to
simplify the
calibration/adjustment
process of their high end
dmms and calibrators
Using “self adjustment”
• Agilent 3458A DMM – a “must do” to keep performance at the level
of its published specs
– “ACAL” –
• Used daily to maintain standard performance to its published specs within any
24 hour period or corrects for temperature shifts larger than +/-1 degree
– “Calibration” –
• Routinely used for a full calibration to correct any and all output errors and
return instrument to its 24 hour spec level – using a 10V and a 10kΩ artifacts
• Fluke 5700 Calibrator Series – a discretionary technique intended to
optimize performance at a better specified level
– “Artifact Cal” –
• Adjust: To correct for any and all output errors and return instrument
uncertainty to its 24 hour spec level
– “Cal Check” –
• Measure only: To test and document all changes in the output levels since its
last Artifact Cal
Traditional Adjustment through measuring output
parameters with primary lab standards
Requires a
primary lab
type of
measurement
process with
basic,
traceable,
primary
standards,
~ 235 tests,
taking many
manhours of
time
Primary
Voltage
Standards
Primary
Resistance
Standards
Primary
AC:DC
Transfer
Standards
Linear
Ratio
Devices
Comparison
Measurement
Volts
Amps
&Ω
Working
Standards
10
Artifact Calibration Innovation #1 –
A primary level measurement system in the working standard
Benefit: Now full performance verification becomes a
routine part of the calibrator’s quality system.
11
Artifact Calibration Innovation #1 –
A primary level measurement system in the working standard
Volts
Amps
&Ω
Working
Standards
Calibrator
Circuitry
12
Artifact Calibration Innovation #1 –
A primary level measurement system in the working standard
6.5 V DC
Reference.
13 V DC
Reference
1 Ohm
Reference
1.9 Ohm
Reference
10 k Ohm
Reference
Ultra Linear
Ratios with a
26 Bit DAC
Volt Meter for
Measurement
& Comparison
(2)
Multi-Range
TVC
Standards
10Hz -1MHz
Volts
Amps
&Ω
Working
Standards
Calibrator
Circuitry
All the necessary
measurement
standards are built
in, to fully measure
& properly verify
the calibrator’s full
specified
performance
13
Artifact Calibration Innovation #2 –
Traceable adjustments use external primary level standards to
calibrate through the internal measurement system
6.5 V DC
Reference.
10 V DC
Standard
1 Ohm
Standard
13 V DC
Reference
1 Ohm
Reference
1.9 Ohm
Reference
10 kOhm
Standard
10 k Ohm
Reference
Ultra Linear
Ratios with a
26 Bit DAC
Volt Meter for
Measurement
& Comparison
(2)
Multi-Range
TVC
Standards
10Hz -1MHz
Volts
Amps
&Ω
Working
Standards
Calibrator
Circuitry
Benefit: Self support of the best performance becomes very practical
14
A Documented Traceability Chain
The electrical
traceability chain
15
The documentation of traceability
A Laboratory Verification Report
DC VOLTAGE
DC
DC
DC
DC
DC
DC
DC
DC
DC
DC
DC
DC
Range
220 mV
220 mV
2.2V
2.2V
11V
11V
22V
22V
220V
220V
1100V
1100V
Zero Shift Magnitude
1.16E-07
2.20E-01
1.16E-07
-2.20E-01
4.07E-09
2.20E+00
5.81E-12 -2.20E+00
2.03E-08
1.10E+01
0.00E+00 -1.10E+01
-2.85E-07
2.20E+01
5.29E-07 -2.20E+01
-2.66E-05
2.20E+02
-2.70E-05 -2.20E+02
-4.81E-11
1.10E+03
-2.03E-06 -1.10E+03
Abs Shift
-3.60E-07
5.93E-07
-3.01E-06
3.01E-06
-7.85E-06
7.87E-06
-9.79E-06
1.00E-05
7.24E-06
-6.09E-05
7.78E-04
-7.80E-04
V
V
V
V
V
V
V
V
V
V
V
V
Rel Shift
Spec
-1.637
9.2727
2.6932
9.2727
-1.3684
4.3636
1.3702
4.3636
-0.714
3.2727
0.7158
3.2727
-0.4452
3.2273
0.4563
3.2273
0.0329
4.2273
-0.2766
4.2273
0.7071
6.4545
-0.7089
6.4545
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
Pct of Spec
-17.654
29.0446
-31.3585
31.4009
-21.8166
21.873
-13.7948
14.1385
0.7781
-6.5433
10.9546
-10.9833
AC VOLTAGE
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
Range
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV
Magnitude Frequency
2.20E-03 All Freqs.
2.20E-03
2.00E+04
2.20E-03
5.00E+04
2.20E-03
1.00E+05
2.20E-03
1.20E+05
2.20E-03
1.20E+05
2.20E-03
2.00E+05
2.20E-03
3.00E+05
2.20E-03
4.00E+05
2.20E-03
5.00E+05
2.20E-03
6.00E+05
2.20E-03
7.00E+05
2.20E-03
8.00E+05
2.20E-03
9.00E+05
2.20E-03
1.00E+06
Abs Shift
-5.39E-09
5.59E-09
-1.20E-08
-1.10E-08
-6.27E-09
-1.07E-08
1.33E-08
-2.41E-08
1.48E-08
3.59E-08
-1.73E-08
-1.65E-08
-2.70E-08
-1.30E-08
-1.91E-08
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
Rel Shift
Spec
-0.0002
0.2363
0.0003
0.2363
-0.0005
0.2503
-0.0005
0.3267
-0.0003
0.6655
-0.0005
0.6655
0.0006
0.6655
-0.0011
0.6655
0.0007
1.2864
0.0016
1.2864
-0.0008
1.4464
-0.0007
1.4464
-0.0012
1.4464
-0.0006
1.4464
-0.0009
1.4464
%
%
%
%
%
%
%
%
%
%
%
%
%
%
%
Pct of Spec
-0.1036
0.1075
-0.2174
-0.1531
-0.0428
-0.0728
0.0906
-0.165
0.0521
0.1268
-0.0543
-0.0518
-0.0847
-0.0408
-0.0599
DC CURRENT
DC
DC
DC
DC
DC
DC
DC
DC
DC
DC
Range
220 uA
220 uA
2.2 mA
2.2 mA
22 mA
22 mA
220 mA
220 mA
2.2A
2.2A
Zero Shift Magnitude
5.83E-11
2.20E-04
6.64E-11
-2.20E-04
9.81E-10
2.20E-03
1.06E-09
-2.20E-03
2.27E-09
2.20E-02
3.08E-09
-2.20E-02
4.52E-08
2.20E-01
5.33E-08
-2.20E-01
-1.12E-07
2.20E+00
-3.04E-08 -2.20E+00
Abs Shift
-1.63E-10
2.88E-10
-1.23E-09
3.28E-09
1.11E-08
-5.71E-09
1.11E-07
-1.21E-08
1.16E-06
-1.30E-06
A
A
A
A
A
A
A
A
A
A
Rel Shift
Spec
-0.7415 73.8182
1.3081 73.8182
-0.5608 38.6364
1.4896 38.6364
0.5026 37.2727
-0.2595 37.2727
0.5025 58.3164
-0.0548 58.3164
0.5264 125.2182
-0.5911 125.2182
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
Pct of Spec
-1.0044
1.772
-1.4515
3.8553
1.3485
-0.6963
0.8617
-0.094
0.4204
-0.472
AC CURRENT
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
AC
Range
220 uA
220 uA
220 uA
220 uA
220 uA
220 uA
220 uA
2.2 mA
2.2 mA
2.2 mA
2.2 mA
2.2 mA
Magnitude Frequency
2.20E-04 All Freqs.
2.20E-04
5.00E+02
2.20E-04
1.00E+03
2.20E-04
2.00E+03
2.20E-04
5.00E+03
2.20E-04
7.00E+03
2.20E-04
1.00E+04
2.20E-03 All Freqs.
2.20E-03
5.00E+02
2.20E-03
1.00E+03
2.20E-03
2.00E+03
2.20E-03
5.00E+03
Abs Shift
-2.68E-10
-3.61E-08
-7.77E-10
-6.01E-10
3.35E-10
1.14E-09
2.88E-09
-2.68E-09
-1.36E-09
2.34E-09
-6.47E-10
-5.03E-09
A
A
A
A
A
A
A
A
A
A
A
A
Rel Shift
-1.2192
-164.091
-3.5299
-2.7309
1.5229
0.0005
0.0013
-1.2196
-0.6189
1.0645
-0.2941
-2.2845
ppm
ppm
ppm
ppm
ppm
%
%
ppm
ppm
ppm
ppm
ppm
Pct of Spec
-0.7505
-101.0073
-2.1729
-0.7035
0.3923
0.3555
0.8947
-0.9022
-0.4578
0.7875
-0.1054
-0.8185
Spec
162.4545
162.4545
162.4545
388.1818
388.1818
0.1464
0.1464
135.1818
135.1818
135.1818
279.0909
279.0909
16
A 5730A “Cal Check” Verification Report
That is the Artifact Calibration
• Artifact Calibration is the process of traceably adjusting the assigned value(s) of a
large array of multidimensional parameters with full documentation
• Standards required
–
10 Volt DC reference (±1.5 µV/V)
–
1 Ω resistor (±10 µΩ/Ω)
–
10 kΩ resistor (±2 µΩ/Ω)
• Measures > 390 internal points & calibrates 182 operating function/range points
• Performance is adjusted to well within the 24 hour specifications
• ~1 Hour of time to artifact calibrate an entire calibrator
• Also has a “measure only” capability to evaluate and report all drift since the
previous calibration (called Cal Check)
–
no adjustments are made if not desired
17
Artifact Calibration Philosophy
• External references are used to establish values for internal
references through built-in comparator and scaling circuitry
• The same circuitry is used to check all of the other functions
and ranges of the 5700A
• This duplicates the metrology tasks and techniques done in a
primary lab
• Full measurement and shift analysis information is recorded for
every function, range, and specification point
• The information is available for view and stored for review.
• If desired the 5700A stores internal calibration factors for each
function and range during artifact calibration making the
adjustment permanent.
18
Benefits of Artifact Calibration
• Performance Benefit:
• Once complete, allows use of 24hour, 90-day, 180-day or 1 year
specs for up to 2 years between
external measurements
• Economical Traceability Benefit:
• 3 external standards check drift of
internal standards, calibration
constants are adjusted, and record
is kept internally to maintain
traceability
Artifact Cal - does it work?
• Yes, the concept works by design
• Yes, every individual calibrator is proven by testing
– Fluke tests each and every calibrator for adjustment accuracy and
time stability
– Testing continues, a two year cycle of external verification is
recommended (measure only with external standards)
• Yes, the process works and has been proven by ongoing Fluke
and other independent evaluations
– Fluke has performed many studies of large samples (several
hundred) units by comparing the artifact calibration results to the full
external performance verification of 5700A’s in for calibration
– The national measurement institutes including Germany, Netherlands
and Sweden performed numerous studies that thoroughly studied
and validated Artifact Calibration
• Yes, it’s proven performance is a historical fact
– And 20+ years and thousands of 57XX’s prove the technology works
20
International NMI studies
• In 1999 it was evaluated and
confirmed by multiple
European NMI’s
– The Artifact Calibration process
– The detailed calibration results
• Confirmed it works equal to or
better than required
• Report is available for review
from the www.flukecal.com
website
Recent Published Data from PTB
5730A Measured by a Quantum AC JV System
Spec Limit
Spec Limit is ± 53 to 78 µV/V
measured error was less than ±15 µV/V
Different amplitudes are
consistent and in spec
Operation is consistent over
the full bandwidth
Fluke’s Process Metrology – Artifact Cal
Example of As Left Measurements
A recent histogram of tests on 59 Calibrators
1 Year guaranteed Specs are ± 43 µV or (4.3 ppm)
24 hour guaranteed specs are ± 28 µV or (2.8 ppm)
Production Pass/Fail limits are at 80% of 24 hour spec or ± 22.4 µV
23
Fluke’s Process Metrology – Artifact Cal
As Left Measurements of ACV, I & Ohms
Pass/Fail limits are at 80% of 24 hour spec
Histogram of 59 Calibrators
24
Benefits from internal measurements
Use of Cal Check for in depth drift analysis & control charting
• Cal Check is designed to measure that small changes are well within the spec limits
• On newly made 57X0A calibrators Fluke uses Cal Check to confirm proper noise
performance and stability over a 1 to 2 week period
25
Back to the 8½ digit dmm challenge
• What Artifact Cal offers as an improved approach to make
calibration of 8.5 digit dmms more efficient with improved
confidence
26
A solution for the Agilent 3458A
• A calibration process jointly developed by
Agilent & Fluke
• Multi Function Calibrator with specs
based on a 90 day calibration interval
• Plus guardbanding the test to insure
confident decisions
– Refer to this Fluke Calibration application note
for details
The best approach to efficiently use 90
day specs for the calibrator is…
Rather than send it out for
calibration every 3
months….
The solution for simple
support of 90 day specs
is using the Artifact
Calibration capabilities of
Fluke’s 5700 Series of
calibrators.
Benefits from Artifact Calibration
• Artifact Cal can give a 25% to 30% spec improvement
Support a shortened calibration interval to utilize a better standard
specification – calibrate every 90 days with Artifact Cal
Selected as the most
practical specs to use
Up to 2 X better, often
preferred, but not usually used
29
Test Accuracy Ratio Improvements of
60% or more
• Examples of DC volts and Resistance Verification Points
Setting
100 mV
1.0 V
10 V
100 V
1000 V
10 ohms
100 ohms
1k ohms
10k ohms
100k ohms
1M ohms
100M ohms
1 year
1.84
1.75
2.38
2.06
3.47
1.22
2.31
2.18
2.18
1.67
1.61
1.76
TAR 5730A vs. 3458A
90 day improvement
2.12
15%
2.38
36%
3.24
36%
2.86
38%
4.89
41%
1.33
10%
2.57
11%
2.49
14%
2.58
18%
1.89
13%
1.90
18%
2.27
29%
improvement
10% to 41%
24 hour improvement
2.65
44%
2.70
54%
3.96
67%
3.28
59%
5.45
57%
1.40
15%
2.89
25%
2.58
18%
2.84
30%
2.58
55%
2.09
30%
2.60
48%
improvement
30
15% to 67%
To summarize Artifact Calibration’s benefits
• Frequent Use of Cal Check
–
Measurement Assurance – be sure your calibrator performs at expected levels every day,
week, and/or month during the time between calibrations through regular Cal Checks
• Use Artifact Cal to self support your calibrator
–
Self support your 57XX series calibrator with the 3 artifacts – an economical way to reduce
calibration down time
• Use Artifact Cal Regularly
–
Support a shortened calibration interval to utilize a better standard specification – calibrate
every 90 days or even daily as needed with Artifact Cal
• Improve your specs by control charting your calibrators true output over time
using Cal Check
–
Let Cal Check track the changes over time and confirm your calibrator’s true performance
31
Thank You
Any questions or comments?
• You may reach me at:
Jack Somppi
Fluke Calibration
jack.somppi@flukecal.com
32