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Chapter 7: Maintenance
M2A-XL Transmitter Operator’s Manual
Calibration Frequency
Some M2As have IR (infrared) type detectors, such as an M2A-XL for CO
2
or an LEL M2A-XL
with an IR detector. Most of the M2As do not have an IR detector. For example, an H
2
S M2A-XL
has an electrochemical detector and some of the combustible M2As use catalytic detectors. The
M2As that use IR detectors typically need less frequent calibration as is discussed below. See
Table , “The table below outlines the M2A-XL part numbers and replacement detector part
numbers for the infrared (IR) detectors.,” on page 12 to see which M2As 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 M2As that do not have an IR detector and every
6 to 12 months for M2As that have an IR detector is adequate for most M2A-XL applications.
Unless experience in a particular application dictates otherwise, RKI Instruments, Inc.
recommends a calibration frequency of every 3 months for M2As that do not have an IR detector
and every 6 months for M2As 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 M2A-XL or 12 months for an IR M2A-XL 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 M2A-XL or every 6 months for an IR M2A-XL may
be necessary. For combustible gas detection with an M2A-XL 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 Ver
-
sions
This section describes how to calibrate the combustible gas, CO
2
, and toxic gas versions of the
M2A-XL. 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 M2A-XL.
NOTE:
The detector must be calibrated with a gas concentration between 10% and 100% of the
channel’s full scale value (ie. a 0 - 300 ppm CO detector must be calibrated with a CO
concentration between 30 and 300 ppm).
WARNING: The M2A-XL 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 M2A-XL is in Calibration Mode. The
output signal will not indicate current readings and the relays will not resume
operating normally until the M2A-XL is in normal operation again.
