38 M2A Transmitter Operator’s Manual
• 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 for LEL and toxic versions and 17.4 mA for oxygen
versions 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 for combustible gas, CO
2
, and toxic versions and 17.4 mA for oxygen versions 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 M2 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 11
on page 43 for all the factory settings.
Table 10: Visual and Audible Alarm Indications
Condition Cause Visual Indication(s)
Alarm 1
1
Increasing (decreasing for O
2
) 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
• The plug-in sensor is not properly plugged
into the socket in the detector housing
body.
NOTE: It could take up to 40 minutes for a
disconnected CT-7 style NH
3
plug-in sensor to
trigger a fail condition.
• 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 condi-
tion.
Low Power DC power source less than 9.5 volts. • F LED is on
• LowPower message and actual voltage of
incoming DC power
*
1
If the M2A is in both an alarm 1 and an alarm 2 condition, both alarm LEDs are on and the display alternates
between the gas reading and the ALMS 1&2 message.
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