Campbell Scientific CPEC200 Closed-Path Eddy-Covariance System - Manual (Page 64)

Appendix A. CPEC200 Diagnostics
respond by increasing pump_control. This should increase the speed of the
pump and allow pump_flow to rise to the setpoint. Conversely, if the flow is
above the setpoint the CPEC200 will adjust pump_control downward until the
flow matches the setpoint.
If pump_control = 0, this indicates the CPEC200 has turned the pump off.
There are several reasons the CPEC200 may shut the pump off:
• Low supply voltage (see notes on bit 9)
• IRGA has been powered down (see notes on bit 8)
• Pump temperature out of range (see notes on bit 5)
• Pump has been turned off by the user. If public variable pump_ON =
False, then set pump_ON = True to turn the pump on
If the pump flow is too low and pump_control is greater than 0, then verify
the pump is running. If the CPEC200 is physically accessible, listen for the
sound of the pump to confirm it is running. Note that the pump is very quiet,
especially at lower pumping speeds, and may be hard to hear in noisy
environments. If the CPEC200 is remotely located, confirm that the pump is
running by turning the pump on and off and checking the value of
pump_press. If the pump is running, it will pull this pressure down below
ambient pressure. The pressure drop will vary depending on conditions, but 3
kPa is typical for a clean intake filter at the default flow of 7 LPM. If the
pressure drop is significantly smaller than is typical, make sure the pump tube
is connected between the EC155 and the pump module.
If the pressure does not vary when the pump is turned on and off, it is likely the
pump is not running. If the pressure changes, but the value of pump_flow
does not, it is likely that the pump is actually running but there may be a
problem with the pump speed measurement. Contact Campbell Scientific in
either case.
If the pump is running, but the value of pump_control does not change as
expected to control the flow, make sure that datalogger processing is not
lagging (see notes on bit 4).
Bit 5: Pump Temperature
If the remainder of diag_cpec (after subtracting the numeric value for higher
bits that are set) is greater than 15, this means that bit 5 of diag_cpec is set. To
decode other diagnostic bits, subtract 16 from diag_cpec and compare the
remainder to the bit values below.
Bit 5 of diag_cpec indicates the pump temperature is outside its operating
range. This triggers the CPEC200 to shut down the pump to protect the pump
from possible damage. This check is performed even if the pump is turned off.
To confirm the problem, verify that public variable pump_tmpr_OK = False.
This variable is set to True if the valve temperature is within its operating
range (0°C to 55°C) and is set to False if it is outside this range.
The variable pump_tmpr_OK is not available for diagnosing a problem using
data saved in the output tables ( Flux or Zero_Span). Instead, check the value
of PumpTmprOK_Avg. This is a floating point number that represents the
fraction of time (from 0 to 1) that pump_tmpr_OK is true during the
averaging period. A value of 1 indicates no pump temperature problem at any
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