Storing the LI-840A
The LI-840A can be stored in non-condensing conditions, but if it is exposed to high humidity
or moderate humidity for a long period of time while it is powered off, the humidity can tem-
porarily affect measurements. You can identify this issue by observing unexpected drift that sta-
bilizes after several days of operation, an offset in measurements, or unresponsiveness. If your
instrument exhibits these characteristics, verify the issue by comparing raw detector outputs in
data that was collected before and after storage. If you don't have these data, contact LI-COR and
we will provide the calibration data set for your instrument. In the PC interface software, click
View > Diagnostics and observe the values for Raw CO2 Reference and Raw H2O Reference. If
these values are lower than the original values, power on the instrument and let it run (with the
heaters on) for several hours to several days. If the instrument has not fully recovered after sev-
eral days, you may need to disassemble the optical bench and heat the detector in an oven at 65
°C (150 °F) for several hours. Reassemble the instrument and check the measurements.
5-7Section 5. Maintenance
Section 5
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