Campbell CPEC300, Руководство по эксплуатации продукта

Страница: 98 / 175

CPEC300/306/310 Closed-Path Eddy-Covariance Systems
89
The
Prfrm Field H2O Span
menu includes readings of H
2
O molar mixing
ratio in the sample cell. Watch the readings until they indicate that the span gas
has flushed out the sample cell and equilibrium has been reached. Once
equilibrium is attained, highlight Do H2O Span found at the bottom of the
menu, press Enter , highlight TRUE , and press Enter . Setting the H
2
O span
will take a few seconds, during which time the gas analyze measurements ma
not be updated. Upon completion of the H
2
O span, Do H2O Span will return
to FALSE . Throughout the H
2
O span, real-time measurements of H
2
O and
system diagnostic are included in the Prfrm Field H2O Span menu for
convenience. If the system includes a temp/RH probe, the ambient dewpoint
temperature is also reported for reference. If no additional zeros or spans are to
be performed, Pump Off should be set back to FALSE to resume operation of
the pump and resume normal EC field measurements.
8. Maintenance and Troubleshooting
Most of the basic diagnostic and troubleshooting issues for the CPEC300-series
systems are covered in Appendix F , CPEC300 Series Diagnostics
(p. F-1)
. The
section that follows provides additional detail on some issues that may arise
with hardware components.
8.1 Enclosure Desiccant
Check the humidity indicator card in the mesh pocket in the CPEC300-series
system enclosure door and the EC100 enclosure door. The humidity indicator
card has three colored circles that indicate the percentage of humidity (see
FIGURE 4-23 ). Desiccant packets inside the enclosure should be replaced with
fresh packets when the upper dot on the indicator begins to turn pink. The
indicator card does not need to be replaced unless the colored circles overrun.
Both the desiccant packs and humidity cards can be purchase as replacements.
See Section 4.10 , Replacement Parts
(p. 17)
, for more detail.
Campbell Scientific strongly suggests replacing desiccant
instead of reactivating old desiccant. Improper reactivation
can cause the desiccant packets to explode.
If the desiccant packs in a CPEC300-series system enclosure require frequent
replacement, check that the feedthrough cap is properly installed. In very
humid conditions it may be helpful to seal the cable feedthrough with
plumber’s putty as described in Section 5.3.4 , Apply Power
(p. 33)
.
8.2 EC155 Windows
The EC155 gas analyzer reports a signal strength for both CO
2
and H
2
O that
decreases as the optics become contaminated. The factory calibration
procedure allows some tolerance to window contamination. In general, the
tolerance is higher for contaminates that are uniformly distributed on the
windows and have flat spectral characteristics than for contaminates, such as
water droplets, that can greatly disperse or refract the optical beam. The signal
strength should be monitored as part of any quality assurance/quality check of
incoming data. If the signal strength has dropped, CO
2
and H
2
O values should
be checked for validity and windows should be cleaned during the next site
visit. Clean the windows as instructed in the EC155 CO
2
and H
2
O Closed-Path
Gas Analyzer Manual
before the CO
2
and H
2
O signals reach 0.80.
CAUTION