Model CXT-IR
CXT-IR Instruction Manual
Rev. 2.1
Page 27 of 48
Set Gas Factor is used to make the appropriate signal sensitivity adjustment when the target gas is different from
the cal gas. This is necessary because the IR sensor has different signal strengths for each combustible
hydrocarbon gas. The Gas Factor value is adjustable from 0.2 to 5.0. It represents the translation between the
target gas and the cal gas when they are different.
The menu item appears as:
Set Gas Factor
.
To calculate the correct Gas Factor (Table 1), take the Gas Factor of the target gas and divide by the Gas Factor
of the cal gas. The calculated value is the correct number to enter into the menu as the Gas Factor.
For example, if calibrating with methane when propane is the target gas, the correct Gas Factor to enter would
be 0.63/1.0 = 0.63.
For example, if calibrating with butane when ethane is the target gas, the correct Gas Factor to enter would be
0.38/0.72=0.53.
Table 1 shows the Gas Factors of most combustible hydrocarbon gases that will be measured. Find the gas of
interest for the cal gas and the target gas and follow the above instruction. If there is a mixture of target gases,
use a weighted approach to determine the correct Gas Factor.
For example, if the target gas was 50% butane and 50% pentane and the cal gas was methane, the correct Gas
Factor would be calculated and entered as ((0.5 x 0.77) + (0.5 x 0.77)) / 1.0 = 0.77.
Table 1 Gas Factors
Gas
Factor
Gas
Factor
Gas
Factor
Acetic Acid
2.00
Decane
1.53
Naphthalene
Acetone
1.21
Ethyl Alcohol
0.35
n-Nonane
1.53
Benzene
1.00
Ethane
0.38
n-Octane
1.34
1,3-Butadiene
1.80
Ethyl Benzene
1.07
n-Pentane
0.77
Butane
0.77
Ethylene
2.39
Propane
0.63
Iso-Butane
0.72
n-Heptane
0.98
iso-Propyl Alcohol
0.54
Butene-1
0.67
n-Hexane
1.00
Propylene
0.80
n-Butyl Alcohol
0.63
Dimethyl Ether
0.40
Toluene
1.00
iso-Butyl Alcohol
0.63
Methane
1.00
Vinyl Acetate
1.43
Cyclohexane
0.89
Methanol
0.41
Vinyl Chloride
Cyclopropane
0.45
Methyl Ethyl Ketone
0.77
Xylene
1.00
From the Set Gas Factor text scroll, hold the magnet over
PGM1
or
PGM2
until the arrow prompt appears and
continue to hold the magnet in place for an additional 3 to 4 seconds (until the display starts to scroll
Set Factor
).
The display will then switch to
X.XX
(where X.XX is the current gas factor). Swipe the magnet momentarily
over
PGM2
to increase or
PGM1
to decrease the gas factor level until the correct value is displayed. Hold the
magnet over
PGM2
for 3 seconds to accept the new value. The display will scroll
Factor Saved
, and revert to
Set Gas Factor
text scroll.
Move to another menu item by executing a momentary hold, or, return to normal operation via automatic timeout
of about 15 seconds (the display will scroll
Set Gas Factor
four times and then return to normal operation).
