Campbell Scientific AP200 CO2/H2O Atmospheric Profile System - Manual (Page 23)

AP200 CO
2
/H
2
O Atmospheric Profile System
Humidity Indicator Card: The replacement humidity indicator (FIGURE
4-15) card is pn 28878.
FIGURE 4-15. Humidity indicator card
Diaphragm Pump: The pump module for the AP200 includes a small double-
head diaphragm pump with a brushless DC motor. The pump includes a speed-
control input and a tachometer to measure actual pumping speed. It is mounted
in an insulated, temperature-controlled box inside the AP200 system enclosure.
If the pump fails, the replacement pump (FIGURE 4-16) is available as pn
26402. See Appendix J, AP200 Pump Replacement, for instructions on
replacing the pump. The part includes the connector for easy installation.
FIGURE 4-16. Diaphragm pump used in AP200
4.2 Theory of Operation
The AP200 system measures CO
2
and H
2
O concentrations at multiple locations
by pulling a continuous sample flow from each of several (four to eight) intake
assemblies. Solenoid valves direct sample flow from one intake assembly at a
time, through a CO
2
/H
2
O IRGA. A CR1000 datalogger records data, selects
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