65-2670-XX-04 M2A Transmitter Operator’s Manual
25
4 - 20 mA Signal Output Operation
The output at the S terminal of the power/signal terminal strip is a 4 - 20 mA signal that corresponds to
the detection range of the M2A. During normal operation, this signal tracks the gas concentration on
the OLED display.
There are several circumstances where the signal output will not track the display reading but will
behave as follows:
•
When the M2A is in its warm-up period, the signal output will be fixed at 3.5 mA (zero).
•
When the M2A’s gas type is changed, the M2A will enter Configuration Mode for you to verify the
parameter settings. When you exit Configuration Mode, the display will indicate
NEEDS
CALIBRATION
and will continue to indicate this until Calibration Mode is entered and a
calibration is performed. In this situation, the signal output will be fixed at 3.5 mA from the time
Gas Type Mode is entered until the M2A is calibrated and returns to normal operation.
•
If you enter Calibration Mode, Configuration Mode, Gas Type Mode, or Modbus Mode, the signal
output will be fixed at 3.5 mA until the M2A returns to normal operation.
•
If the M2A’s input power decreases below 9.5 volts so that the M2A is in a low power alarm, the
signal output is fixed below 2.4 mA until the low power alarm is cleared.
•
If the M2A goes into a fail condition, after a 30 second delay, the signal output is fixed below 2.4
mA until the fail alarm is cleared. During the 30 second delay, the signal output follows the
detector output. In the case of a downscale reading, the display and the signal output continue to
track the reading down to -99% of full scale (1.15 mA).