Replacing the Source and Detector in
the LI-8x0 Analyzers and LI-8100/A
This document describes how to replace the optical source
and detector on the LI-830, LI-850, and LI-870 gas analyzers,
legacy LI-800, LI-820, LI-840, and LI-840A gas analyzers, and
the LI-8100/A Automated Soil CO
2
Flux System.
Part Numbers
Source
Detector
14 cm
Bench
5 cm
Bench
LI-850 / LI-
870
800-902
800-918
800-904
n/a
LI-830
800-902
800-916
800-904
n/a
LI-840/A
800-902
800-906
800-904
n/a
LI-820
800-902
800-903
800-904
800-905
LI-800
800-902
800-903
800-904
800-905
LI-8100/A
8100-902 800-906
800-904
n/a
Contents
LI-800, LI-820, LI-830, LI-840/A, LI-850, and LI-870
LI-8100/A Source and Detector Replacement
LI-800, LI-820, LI-830, LI-840/A, LI-850,
and LI-870
The optical source and detector may need to be replaced if
one fails. The life expectancy of the source is typically
>20,000 hours, or >2 years of continuous operation, but this
will vary depending upon the number or warm-up cycles,
vibration, and other factors. Typically, detectors need to be
replaced rarely, if ever.
Disassembly
You'll need #1 or #2 Phillips screwdriver and a clippers or
utility knife. The installation, including calibration, may take
an experienced technician 30 minutes to 1 hour. If the instru-
ment has been running recently, the bench may be hot to the
touch. Let it cool for 5 or 10 minutes after powering off if
needed.
Note:
Be sure that you are properly grounded to avoid elec-
trostatic discharge that can damage the electronics. Use an
anti-static wrist strap, electrostatic discharge grounding mat,
or occasionally touch bare metal that has a clear path to
ground, such as an unpainted computer case.
1
Power off the gas analyzer and remove the top cover
(LI-800, LI-820, LI-830, LI-840/A and LI-850) or open
the case (LI-870 only).
The LI-800, LI-820, LI-830, LI-840/A and LI-850 top cover
is held in place by 6 screws. Loosen the screws and lift off
the cover. If there is a ribbon cable connecting the top
panel, be careful not to strain it. The LI-870 is opened by
removing two screws that hold the case closed; then
remove four screws that secure the optical bench cover.
2
Unplug the source and detector ribbon cables from
the source and detector.
3
Lift the optical bench out of the foam insulation.
Replacing the Optical Source
With the optical bench free of the case (except the tubing),
you can remove the source from the optical bench.
1
Remove the tube from the source.
The simplest way is to cut the tubing as close to the hose
barb as possible.
2
Remove the four larger screws from the optical
source.
1
Installation Guide
