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65-2661RK-03-04 M2A Transmitter Operator’s Manual
Calibration
This section describes how to calibrate the M2A transmitter. It includes procedures to
prepare for calibration, enter Calibration Mode, adjust the fresh air (zero) setting, adjust
the span setting, and return to normal operation.
WARNING:
The M2A is not an active gas monitoring device during the calibration
procedure. The 4-20 mA output signal will “freeze” at 3.5 mA and all
relays will remain in their non-alarm state while the M2A is in
Calibration Mode. The output signal will not indicate current readings
and the relays will not resume operating normally until the M2A is in
normal operation again.
NOTE:
The following procedure assumes the use of a calibration kit which includes a
calibration gas cylinder, a zero air cylinder and a fixed flow regulator with an
on/off knob.
NOTE:
While in the calibration program, if there is no switch activity for the
calibration time-out period the unit will return to normal operation. See
“Viewing & Changing M2A Parameters” on page 23 for instructions to set the
calibration time-out.
Non-Intrusive Calibration
If the M2A is installed in a classified area and non-intrusive calibration is required, follow
the instructions below, but do not remove the junction box cover. Use the magnetic wand
accessory to actuate the magnetic switches instead of pushing the control switch buttons.
To actuate a magnetic switch and perform the same operation as pressing a control switch
button, touch the magnet in the end of the magnetic wand to the M2A’s glass cover
directly above the magnetic switch you wish to actuate. Touching the glass and removing
the wand is the same as pressing and releasing a button. Touching the glass and keeping
the wand in place is the same as pressing and holding a button.
Calibration Gas Response Memory Feature
The M2A has the capability to “remember” the detector’s response to the calibration gas
after the gas is removed from the detector during the fresh air and span adjustment
procedure. This feature enables one person to perform calibration if the detector is
mounted remotely from the M2A. When zero air is applied to the M2A during a fresh air
adjustment, the M2A will freeze the display reading at the lowest response and the M2A
will continue to display this reading and retain it in its memory until the fresh air
adjustment procedure is completed. When calibration gas is applied to the M2A during a
span adjustment, the M2A will freeze the display reading at the highest response to the
calibration gas. The calibration gas can then be removed and the M2A will continue to
display this reading and retain it in its memory until the span adjustment procedure is
completed.
Adjusting the Fresh Air Reading
Since there is a background of CO
2
in air of typically 300 - 600 ppm (0.03 - 0.06 %volume),
it is necessary to use a calibration kit with a CO
2
free gas to set the zero signal of a low
range CO
2
detector.
