65-2658RK-CH4-4 M2A Transmitter Operator’s Manual
23
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 18.5 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).
Alarm Indications
NOTE:
The M2A includes alarm on and alarm off delay settings for alarm 1 and alarm 2. The alarm
indications described in this section operate according to the factory set alarm settings. See Table 5
on page 27 for all the factory settings.
Table 4: Visual and Audible Alarm Indications
Condition
Cause
Visual Indication(s)
Alarm 1
1
Increasing gas reading at or above the
alarm 1 setpoint
• A1 LED is on
• Gas reading alternates with
ALARM-1
message
Alarm 2
1
Increasing gas reading at or above the
alarm 2 setpoint
• A2 LED is on
• Gas reading alternates with
ALARM-2
message
Fail
• Disconnected or misconnected
detector wiring
• Display reading at -10% of full scale
or lower
• Defective components
• F LED is on
•
FAIL
message replaces gas
reading
NOTE: There is a 30 second
delay on the fail condition.
