RKI Instruments M2 for 12 VDC - Manual (Page 30)

25 M2 Transmitter Operator’s Manual, 12 V DC Operation
Calibration Frequency
Although there is no particular calibration frequency that is correct for all applications, a
calibration frequency of every 3 to 6 months is adequate for most M2 applications. Unless
experience in a particular application dictates otherwise, RKI Instruments, Inc.
recommends a calibration frequency of every 3 months.
If an application is not very demanding, for example detection in a clean, temperature
controlled environment where the toxic or combustible target gas is not normally present,
and calibration adjustments are minimal at calibration, then a calibration frequency of
every 6 months is adequate.
If an application is very demanding, for example if a combustible or toxic gas is present
often and in significant concentrations or the environment is not well controlled, then
more frequent calibration than every 3 months may be necessary. For combustible gas
detection, if potential catalyst poisons are known or likely to be present, more frequent
calibration than every 3 months will be necessary.
Calibration
This section describes how to calibrate the M2. 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 M2 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 M2 is in Calibration
Mode. The output signal will not indicate current readings and the relays
will not resume operating normally until the M2 is in normal operation
again.
Preparing for Calibration
NOTE: The following procedure assumes the use of a calibration kit which includes a
calibration gas cylinder, a zero air cylinder, a fixed flow regulator with an on/
off knob, a calibration cup for the appropriate sensor, and a short piece of
sample tubing to connect the regulator to the calibration cup.
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 M2 Parameters” on page 17 for instructions to set the
calibration time-out.
NOTE: The following procedure assumes that the target gas is present in a high
enough concentration to affect the fresh air (zero) reading. If a fresh air
environment can be verified, applying zero air to the detector is not necessary
when setting the zero (span for oxygen) reading.
1. Connect the calibration kit sample tubing to the calibration cup hose barb.