M2A-XL Transmitter Operator’s Manual
Chapter 3: Installation & Startup
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39
Adjusting the Fresh Air Reading
When the M2A-XL is shipped from RKI Instruments, Inc., it is factory calibrated. If a full
calibration is desired at startup, see “Calibration, Combustible Gas, CO2, and Toxic Versions” on
page 58 or “Calibration, Oxygen Version” on page 63.
Verify that the M2A-XL is in a fresh air environment (environment known to be free of the target
gas and combustible or toxic gas vapors and of normal oxygen content, 20.9%).
CAUTION:
If you suspect the presence of combustible gas, CO
2
, toxic gas, or that the oxygen
content is not normal in the monitoring environment, use the calibration kit and the
zero air calibration cylinder to introduce “fresh air” to the detector and verify an
accurate fresh air setting. See the “Calibration, Combustible Gas, CO2, and Toxic
Versions” on page 58 or “Calibration, Oxygen Version” on page 63 for instructions
on how to use a zero air cylinder when performing a fresh air adjustment.
Non-Intrusive Fresh Air Signal Adjustment
If the M2A-XL is installed in a classified area and non-intrusive zero adjustment 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-XL’s glass cover directly over 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.
WARNING: The M2A-XL is not an active gas monitoring device during the fresh air
adjustment procedure. The 4-20 mA output signal will “freeze” at 3.5 mA for a
toxic, combustible gas, or CO
2
M2A-XL, or at 17.4 mA for an oxygen M2A-XL,
and all relays will remain in their non-alarm state while the M2A-XL is in
Calibration Mode. The output signal will not indicate current readings and the
relays will not resume operating normally until the M2A-XL is in normal
operation again.
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. The factory set time-out is 15
minutes. If you want a different time-out period, see “Viewing & Changing M2A-XL
Parameters” on page 47 for instructions to change the calibration time-out.
