Campbell Scientific CPEC200 Closed-Path Eddy-Covariance System User Manual
Page 41
CPEC200 Closed-Path Eddy-Covariance System
CAL_FLOW_SETPT:
Determines the rate at which the zero or CO
2
span gas will flow. The path the
gas takes is from the cylinder, through the valve module to the EC155
analyzer, and out the end of the EC155 intake.
The CPEC200 valve module has a proportional control valve to actively
control the flow of zero and span gas. This flow rate can be changed by
changing the value of public variable
CAL_FLOW_SETPT. The default for
zero and span gas flow is 1.0 LPM, but higher zero/span flow rates may be
required with the long zero/span delivery tubes required for tall tower
installations. The maximum zero/span flow rate is 5.0 LPM.
If a scrub module is used to provide the zero air, this setpoint is ignored and the
flow rate is determined by the pump in the scrub module. The proportional
valve in the valve module will be fully open.
Similarly, during an H
2
O span, this setpoint is ignored and the flow rate is
determined by the pump in the dewpoint generator. The proportional valve
will be fully open.
CO2_SPAN_PPM:
This is the concentration of the CO
2
span cylinder, in ppm (µmol mol
-1
). If
CHECK_ZERO, CHECK_SPAN1, and SET_SPAN_1 all = TRUE, the
system will automatically span the IRGA to this value during the zero/span
sequence. This value is also used during a manual CO
2
span operation.
CO2_SPAN_PPM must be between 300 and 1000.
USE_DIFF_PRESS:
This variable configures the EC100 electronics to use the differential pressure
sensor in the EC155 sample cell. The default is
True. This should be changed
to
False only if the user has connected the EC155 sample cell to some other
pressure sensor. For more details, see the EC155 CO
2
and H
2
O Closed-Path
Gas Analyzer Manual, available at
The next set of system configuration variables determine which steps of the
zero/span sequence are to be performed and which steps will be skipped.
CHECK_ZERO:
Check the gas analyzer zero against the zero gas. This is used as a flag to
completely disable the zero/span sequence. If
CHECK_ZERO = False, the
CPEC200 will not do the automatic sequence.
SET_ZERO:
Set the gas analyzer zero (CO
2
and H
2
O).
CHECK_SPAN1:
Check the gas analyzer span against CO
2
gas number 1.
SET_SPAN_1:
Set the gas analyzer span using CO
2
gas number 1.
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