65-2643-05SS-4S M2A Transmitter Operator’s Manual
21
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” on page 35.
Verify that the M2A is in a fresh air environment (environment known to be free of combustible or toxic gas
vapors and of normal oxygen content, 20.9%).
CAUTION:
If you suspect an abnormal oxygen concentration 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” on page 35 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 17.4 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:
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 26 for instructions to change
the calibration time-out.
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
.
2. Press and release the UP/YES button to continue. The display will indicate
OXYGEN CAL Mode
for a few
seconds before showing
FreshAir Adjust?
.
3. Press and release the UP/YES button.
ENTER
will alternate with
FreshAir
on the top display line and the
current oxygen reading will be on the bottom display line.
4. Press and release the ENTER button. The M2A will perform a span operation and then the display will
indicate
ZERO w/Cal Gas?
.
5. Press and release the DOWN/NO button. The display will indicate
Leaving CAL Mode
and the M2A will
return to normal operation.
Calib?
YES/NO
