RKI Instruments M2A - Manual (Page 29)

M2A Transmitter Operator’s Manual 24
NOTE: Allow the M2A’s detector to warm up for 15 minutes before you continue with the next
section, “Adjusting the Fresh Air Reading.”
Adjusting the Fresh Air Reading
When the M2A 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 42 or
“Calibration, Oxygen Version” on page 45.
Verify that the M2A 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 42 or “Calibration, Oxygen Version” on page 45 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 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’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 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, or at 17.4 mA for an oxygen M2A, 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: 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
Parameters” on page 31 for instructions to change the calibration time-out.
Combustible Gas, CO
2
, and Toxic Versions, Adjusting the Fresh Air Reading
1. While in normal operation, press and hold the UP/YES button for 5 seconds to enter
Calibration Mode. Release the button when the following screen appears.
Calib?
YES/NO