Campbell Scientific AP200 CO2/H2O Atmospheric Profile System - Manual (Page 58)

AP200 CO
2
/H
2
O Atmospheric Profile System
To avoid pulling unfiltered air into the AP200, do not shut down
or disconnect the dewpoint generator until the valve sequence
has been restarted as described in Section 6.2.5, Restart the
Sequence.
Press to return to the Manual Zero/Span menu.
6.2.5 Restart the Sequence
At the conclusion of the manual zero/span process, restart the automatic valve
sequence. Go to the last line of the Manual Zero/Span menu and set
STARTsequence = True. Verify valve_number changes to 1 and look at the
LEDs on the valve module to confirm that valve 1 is active. The AP200 will
stay on valve 1 until it is synchronized with the real-time clock. Then it will
set seq_ACTIVE to True and begin the valve sequence. See Section 5.5,
Starting and Stopping the Sequence, for more details on starting the sequence.
Once the valve_number changes to 1, the dewpoint generator may be shut
down and disconnected. Replace the plug on the AP200 H
2
O Span inlet.
Press to return to the AP200 menu.
6.2.6 Check the System
When the manual zero/span process is complete and the valve sequence is
restarted, select Check Status from the main AP200 menu and verify proper
operation of the system, as described in Section 5.6.1, Quick Status Check
Using a Keyboard Display.
7. Maintenance and Troubleshooting
Most of the basic diagnostic and troubleshooting issues for the AP200 are
covered in Appendix B, AP200 Diagnostics. This section provides additional
detail on some issues.
7.1 Plumbing Leaks
Most of the AP200 plumbing operates at reduced pressure. If there is a leak,
ambient air will be pulled into the air stream, mixing with the intended air
sample and changing the concentration of CO
2
and H
2
O. A large leak can be
easily identified by the higher-than-normal flow rate, but a small leak may be
difficult to detect. One technique that may be helpful to check for leaks is to
breathe on a suspect fitting while observing the measured CO
2
concentration.
Because exhaled breath contains much higher CO
2
than ambient air, breathing
on the location of a leak will cause a rise in measured CO
2
. If near the sample
inlet, take care that a user’s exhalations do not reach the inlet directly. There
may be a substantial time delay when checking for leaks at the intake
assembly. The mixing volume can cause the delay and smooth the response.
A long intake tube will also introduce a significant time delay.
NOTE
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