RKI Instruments Digester Gas Monitor - Manual (Page 44)

38 • 4 - 20 mA Signal Output Operation Digester Gas Monitor Operator’s Manual
4 - 20 mA Signal Output Operation
The output at the recorder output terminals on the detector/transmitter terminal strip for
each channel is a 4 - 20 mA signal that corresponds to the detection range of the Digester
Gas Monitor. It behaves as follows:
• During the Digester Gas Monitor’s initial 1 minute warm-up period and 1 minute
standby period after being turned on, the signal output will be fixed at 3.5 mA.
• For the first pre-sample purge after the Digester Gas Monitor is turned on, the signal
output will be fixed at 3.5 mA.
• For all pre-sample purge operations after the first presample purge, the output will be
fixed at the last recorded reading from the previous detection cycle.
• During the sampling period, the signal output will track the sensor readings.
• During the post sample purge and the blowback operations, the output will be fixed at
the recorded reading of the cycle.
• During the standby period between detection cycles, the output will be fixed at the last
recorded reading from the previous detection cycle.
• If you enter the Global Menu, the Configuration Menu, the Input Setup Menu, the
Modbus Menu, or Calibration Mode, the signal output will be fixed at 3.5 mA until the
Digester Gas Monitor returns to normal operation.
• If the Digester Gas Monitor’s input power decreases below 18.5 volts so that the
Digester Gas Monitor is in a low power alarm, the signal output is fixed at 2.4 mA until
the low power alarm is cleared.
• If the Digester Gas Monitor goes into a fail condition, after a 30 second delay, the
signal output is fixed at 2.4 mA until the fail alarm is cleared. During the 30 second
delay, the output follows the detector output.
Viewing and Resetting Min/Max Readings
The reset switch may be used to view and reset the minimum and maximum gas readings
for all active channels.
1. While the Digester Gas Monitor is in Standby Mode, press and hold the reset switch
button for 5 seconds.
2. The display will show the following screen for about ten seconds.
The minimum reading is on the left and the maximum is on the right for each channel.
1: 0 45
2: 0.8 20.9
3: 0 500
4: 5.0 37.0