RKI Instruments M2 Series - Manual (Page 45)

M2 Transmitter Operator’s Manual 40
Calibration Frequency
Some M2s have IR (infrared) type detectors, such as an M2 for CO
2
or an LEL M2 with an
IR detector. Most of the M2s do not have an IR detector. For example, an H
2
S M2 has an
electrochemical detector and some of the combustible M2s use catalytic detectors. The
M2s that use IR detectors typically need less frequent calibration as is discussed below.
See Table 1, “M2 Specifications,” on page 2 to see which M2s are IR versions.
Although there is no particular calibration frequency that is correct for all applications, a
calibration frequency of every 3 to 6 months for M2s that do not have an IR detector and
every 6 to 12 months for M2s that have an IR detector 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 for M2s that do
not have an IR detector and every 6 months for M2s that have an IR detector.
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 for a non-IR M2 or 12 months for an IR M2 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 for a non-IR M2 or every 6 months for an
IR M2 may be necessary. For combustible gas detection with an M2 that uses a catalytic
detector, if potential catalyst poisons are known or likely to be present, more frequent
calibration than every 3 months will be necessary.
Calibration, Combustible Gas, CO
2
, and Toxic Versions
This section describes how to calibrate the combustible gas, CO
2
, and toxic gas versions of
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. See the
next section, “Calibration, Oxygen Version” for instructions to calibrate an oxygen M2.
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.