Campbell Scientific CPEC200 Closed-Path Eddy-Covariance System - Manual (Page 62)

Appendix A. CPEC200 Diagnostics
The purpose of the deadband (the gap between the shutdown voltage and the
turn-on voltage) is to protect the CPEC200 from repeated power cycles when
the battery voltage is very near the shutdown limit.
There are two possible values for cpec_status when BattVolt_OK = False. If
the battery voltage is below the shutdown limit, cpec_status will report
ERROR: Battery voltage is too low. In this case, the battery must be recharged
before the CPEC200 will resume normal operation.
If BattVolt_OK = False and the battery voltage is in the deadband,
cpec_status will report ERROR: Battery voltage is in deadband. This situation
can arise if the battery voltage was previously below the shutdown limit
causing the CPEC200 to set the battery voltage error flag and shut the system
down. Subsequently the battery voltage recovered enough to be in the
deadband (above the shutdown limit but below the turn-on limit).
If BattVolt_OK = False and BattVolt is in the deadband, manually set
BattVolt_OK = True which may allow the CPEC200 to power up. However,
the increased current drawn upon powerup may cause the battery voltage to fall
below the shutdown limit causing the CPEC200 to shut down again. In this
case, the battery may need to be further recharged.
The voltage at the CPEC200 power input terminals can also be measured and
compared to BattVolt.
BattVolt is measured in the datalogger which has a diode for
reverse voltage protection. The actual voltage at the input
terminals will be approximately 0.3V higher than the value
reported by BattVolt.
The CPEC200 supply voltage must be 10.5 Vdc to 16.0 Vdc. See Section 4.3,
Specifications, for details on the power required, especially the extra power
required for a cold startup.
Bit 8: IRGA
If the remainder of diag_cpec (after subtracting the numeric value for higher
bits that are set) is greater than 127, this means that bit 8 of diag_cpec is set.
To decode other diagnostic bits, subtract 128 from diag_cpec and compare the
remainder to the bit values below.
Bit 8 of diag_cpec is equivalent to irga_OK = False. This indicates either a
diagnostic has been set in the EC100 or that the signal levels are too low:
1. Check the value of diag_irga. If it is NAN, this indicates the CR3000
is not receiving data from the EC100. Check the SDM cable
connection between the EC100 and the CR3000, and make sure power
is supplied to the EC100.
2. If diag_irga is −1, this indicates the EC100 does not recognize that an
IRGA is connected. Make sure the EC155 sensor head cable is
connected to the EC100. (Remove power from the EC100 before
connecting or disconnecting the EC155).
NOTE
A-10