RKI Instruments M2A - Manual (Page 50)

45 M2A Transmitter Operator’s Manual
Calibration, Oxygen Version
This section describes how to calibrate the oxygen version of the M2A. It includes procedures to
prepare for calibration, enter Calibration Mode, set the fresh air (span) reading, set the zero reading,
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 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.
Preparing for Calibration
NOTE: The following procedure assumes the use of a calibration kit which includes a zero air
(20.9% oxygen) calibration cylinder to set the fresh air reading, a 100% nitrogen (0%
oxygen) calibration gas cylinder to set the zero reading, a fixed flow regulator with an
on/off knob, a calibration cup, and a short piece of sample tubing to connect the
regulator to the calibration cup. A cylinder with up to an 18% oxygen concentration
may be used instead of a 100% nitrogen cylinder to set the zero reading.
NOTE: While in calibration mode, 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 31 for instructions to set the calibration time-out.
NOTE: The following procedure assumes that the oxygen concentration in the calibration area
is not normal, 20.9%, but is oxygen deficient. If a fresh air environment can be verified,
applying zero air to the detector is not necessary when adjusting the fresh air (span)
setting.
1. Connect the calibration kit sample tubing to the calibration cup hose barb.
2. Screw the calibration cup onto the detector.
3. Connect the fixed flow regulator to the calibration cup using the sample tubing.
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 or zero adjustment procedure. This feature
enables one person to perform a 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