2-7
Multi-Channel Combustible Monitor
Operational Theory 2
Teledyne Analytical Instruments
2.5.1 Response of Combustible Sensor to Various
Gases
Response factors have been determined to relate the sensor output of a
specific compound to the output obtained using methane. A list of some
typical compounds is given in Table 1, along with their LEL (Lower
Explosive Limit) values. To determine the output of the sensor to any of
the gases listed, compared to the same concentration of methane, multiply
the reading obtained by the factor listed.
For example, if the output is calibrated with methane at 2%, the
output for ethylene at 2% would be 2.0% X 1.26 = 2.52% methane equiva-
lent.
NOTE: The LEL and the response factors cannot be used directly for
calibration. See Table II on page 4-16 for calibration of the
instrument to gases other than Methane.
CAUTION: In most cases, the concentration of any particular
compound that the sensor is exposed to should
not exceed the LEL of that compound, or sensor
damage could occur.
The concentration of combustibles should never
exceed that which will react completely with the
available oxygen present in the sample
(stoichiometric burning), otherwise “coking” (the
deposition of carbon from incomplete combustion)
will occur at the sensor, and drift and a loss of
sensitivity will result.
CAUTION: Exposing the sensor to lead, silicone, or acidic
gases may damage the sensor.
NOTE:
For compounds not listed, consult TAI.