Why the LI-7000? A Comparison Between LI-7000 and LI-6262

Why the LI-7000?
A Comparison Between LI-7000 and LI-6262
A Comparison
Between LI-7000
and LI-6262
First introduced in 1990, the LI-6262 CO2/H2O Analyzer quickly became a
favorite of researchers worldwide for a variety of applications (e.g. eddy
covariance measurements) where high speed and precision were required.
The LI-7000 CO2/H2O Analyzer was introduced in 2000 and expanded on
the capabilities of the LI-6262 based on feedback we received from you, our
customers. The LI-6262 is now discontinued. This document is intended to
show why we believe the LI-7000 remains a superior solution for all of your
CO2/H2O measurement needs, and in particular, for those users familiar
with or currently using the LI-6262.
LI-7000
DIFFERENTIAL/ABSOLUTE
MODE OPERATION
Reference cell concentration
can be estimated.
LI-6262
Accuracy depends on reference cell concentration being known.
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OPTICAL BENCH
One optical bench. Sample cell size: 9.53 mm D
x 152.4 mm L (0.375" x 6"). Volume: 10.86 cm3
One optical bench. Sample cell size:
6 mm H x 13 mm D x 152 mm L
(0.25" x 0.5" x 6"). Volume: 11.9 cm3
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OPTICAL CELL CLEANING
Optical cells can be cleaned in the field
without affecting instrument calibration.
Optical cells can be cleaned only at the factory,
and the instrument requires recalibration.
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AUXILIARY PUMP
Software controlled internal air pump is
standard. The chopper housing is scrubbed by
internal chemicals and does not need a pump
for scrubbing. The pump can be used for other
purposes such as scrubbing the reference cell
during absolute mode operation.
Optional auxiliary pump attaches to the back
of the instrument, required for scrubbing water
vapor from the chopper housing when making
water vapor measurements, and used for
scrubbing the reference cell during absolute
mode operation.
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HEAT EXCHANGERS
Heat exchangers equilibrate incoming air
to cell temperature.
Not Available
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PRESSURE SENSOR
Standard 0.1% accuracy pressure sensor
Optional 0.1% accuracy pressure sensor
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MAXIMUM FLOW RATE
Internal diameter of the standard IRGA inlet
and outlet ports is 4.7 mm. A flow rate of
10 liters/min produces a cell pressure of
about 0.01 kPa.
Internal diameter of the standard IRGA inlet
and outlet ports is 2.5 mm. A flow rate of
10 liters/min produces a cell pressure of
about 0.2 kPa.
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From total vacuum to 115 kPa (17 psi)
Max allowable pressure is 115 kPa (17 psi) with
pressure sensor connected and 200 kPa (29 psi)
without pressure sensor connected.
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GAS PRESSURE IN OPTICAL CELL
INTERNAL HUMIDITY SENSOR
Detector housing humidity sensor warns when
to replace internal chemicals.
Not Available
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OPERATING TEMP. RANGE
0–55 °C optical bench
0–50 °C optical bench
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MICROPROCESSOR
400 MHz
9 MHz
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LI-7000
SUPPORT SOFTWARE
LI-6262
Windows® based software for setup, control
and data logging
DOS based software for command line
interrogation and data collection
4 user-scalable DACs, 600 Hz update
frequency (±5v maximum, 14-bit D/A
conversion)
2 user-scalable DACs, update rates of 5 Hz for
CO2 and 3 Hz for H2O (0-100 mV, 0-5V, or
0-20mA full scale, 12-bit D/A conversion). Raw,
non-linearized output for CO2 and H2O at
5 Hz bandwidth.
BACK PANEL CONNECTIONS
Analog Output Channels
1 dedicated presure output
(0-115 kPa = 0-3V)
Auxiliary Input Channels
Two, -2.5 to +2.5V.
One, 0 to +4.096V.
RS-232
9600 to 115,200 baud, 8, N, 1. Supports
XON/XOFF
Baud rates up to 9600, 8, N, 1. Supports
XON/XOFF
USB
Data output rate up to 50 Hz. USB 2.0
compliant.
None
DATA CHECKSUM
USB or RS-232
Yes. Used to ensure integrity of
transmitted data.
No
DISPLAY
8 line by 40 character backlit LCD with
enlarged characters. Real-time graphing
activated by a single keystroke.
2 line by 16 character backlit LCD with
enlarged characters.
POWER REQUIREMENTS
100–240 VAC, 50–60 Hz or 10.5–16 VDC,
1.5–4 amp max depending on temperature
and pump usage
100–130 VAC or 200–260 VAC (47–65 Hz) or
10.5–16 VDC, 1.5 amp max
DIMENSIONS
36.8 cm L x 12.7 cm H x 25 cm D
(14.5" L x 5" H x 9.875" D)
33.5 cm L x 13 cm H x 24 cm D
(13" L x 5" H x 9.5" D)
WEIGHT
8.8 kg (19.4 lbs)
3.5 kg (7.7 lbs)
WARM UP TIME
2 minutes to operation, 2 hours to temperature equilibration
5 minutes to operation, 1/2 hour to
temperature equilibration
CO2 OPERATING RANGE
The factory calibration polynomial is valid
in the range of 0–3,000 ppm; however, the
instrument’s A/D does not over range even at
50,000 ppm, although sensitivity is reduced at
high concentrations.
A/D converter over ranges at about 10,000
ppm when detector output exceeds 7.5 volts.
CO2 NOISE
Typically 0.14 ppm peak-to-peak at
370 ppm with 1 second signal averaging
Typically 0.3 ppm peak-to-peak, at 370 ppm
with 1 second signal averaging
CO2 ZERO DRIFT WITH TEMP.
Typically 0.3 ppm/°C
Typically 0.18 ppm/°C
H2O NOISE
0.01 mmol/mol peak-to-peak at
10 mmol/mol, with 1 second signal averaging
0.015 mmol/mol peak-to-peak at 10 mmol/mol,
with 1 second signal averaging
H2O ZERO DRIFT WITH TEMP.
Typically 0.02 mmol/°C
Typically 0.008 mmol/°C
continued on back
LI-7000 and LI-6262 Similarities
ANALYZER TYPE
Differential, NDIR (non-dispersive infrared) gas analyzer
DETECTOR TYPE
Lead Selenide, solid state (no sensitivity to motion) CO2 detection wavelength: 4.26 microns
H2O detection wavelength: 2.59 microns
INFRARED SOURCE
Single element source with blackbody radiation characteristic; life >20,000 hours
CHOPPER MOTOR LIFE
Chopper motor life is typically >20,000 hours.
DIFFERENTIAL/ABSOLUTE
MODE OPERATION
Operates in absolute or differential mode.
AMBIENT OPERATING TEMP. RANGE
0-50 °C ambient
POWER INPUT
Accepts either AC or DC input.
CO2 CALIBRATION RANGE
Factory calibrated from 0–3,000 ppm using 13 working standard gases which have
been calibrated with WMO standards.
CO2 ACCURACY
Absolute accuracy largely depends on the accuracy of the span gas used to set the
analyzer response. The factory calibrated polynomial fits the 13 calibration gases to
which the typical accuracy is about 1% of reading.
DIRECT SENSITIVITY OF CO2
READING TO WATER VAPOR
Software algorithm corrects for band broadening effects.
H2O CALIBRATION RANGE
0–60 mmol/mol (dry air to 40 °C dew point)
H2O ACCURACY
Absolute accuracy largely depends on the accuracy of the H2O span gas used to set the
analyzer response. The H2O calibration accuracy is typically about 1% of reading.
DIRECT SENSITIVITY OF
H2O READING TO CO2
None
Specifications are subject to change without notice.
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In Germany - LI-COR GmbH: +49 (0) 6172 17 17 771
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Patents and foreign equivalents, and patents pending. LI-COR is a trademark of LI-COR, Inc.
PN980-06623 Rev. 1 10/05