RKI Instruments M2 Series - Manual (Page 31)

M2 Transmitter Operator’s Manual 26
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 M2. During normal operation, this signal tracks
the gas concentration on the LCD.
There are several circumstances where the signal output will not track the display reading
but will behave as follows:
• When the M2 is in its warm-up period, the signal output will be fixed at 3.5 mA (zero)
for all gas types except oxygen. For oxygen types, the output will be fixed at 17.4 mA
(20.9% oxygen) while the M2 is in warm-up.
• When the M2’s gas type is changed, the M2 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 M2 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 M2 returns to normal operation.
• If the M2’s input power decreases below 18.5 volts so that the M2 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 M2 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 6 on page 31 for all the factory settings.
Table 5: 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