LI-COR LI-7820, Instruction Manual

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Section 5. Troubleshooting
connector is near the lower left corner of the processor. If it is unplugged from the
circuit board, reattach it and try to connect again.
See Figure B-3 on page B-5
Measurement problems
Here we describe issues related to the display of data or measurements.
Readings drift or step change unexpectedly
Constricted inlet or outlet? If one of these becomes constricted, you will observe
errant measurements, with corresponding status codes that indicate problematic
pressure measurements (see
Status codes on page 2-9). Clear the constriction and
the instrument should return to normal operation in a few minutes. Restart the
instrument if it does not resume normal operation within a few minutes.
Pressure readings are questionable or unstable
Clogged air inlet filter? Check and replace the filter if needed, as described in Repla-
cing the air inlet filter on page 6-4. Otherwise, unstable pressure readings may indic-
ate that the pump is failing. Contact technical support if the issue is not resolved by
replacing the filter.
Gas density measurements appear to have oscillations
Regular, periodic oscillations in the data may appear in circumstances where there
are vibrations that are effectively coupled to the instrument sampling frequency.
Isolating the instrument from potential sources of vibration and having it lay flat
on a solid surface could help avoid these impacts. If the behavior persists in isol-
ation then it could be due to vibration from the internal pump. Generally speaking
the oscillations caused by the internal pump are small and the instrument should
still meet the noise specification. Adjusting the pump speed could decouple the
vibration from the sampling and resolve the oscillations. See
Pump Adjustment
under Operating information on page 4-13 for more details.
Interface issues
Some issues related to the display settings are described here.
5-4 LI-7820 N₂O/H₂O Gas Analyzer