B28050-410-000-RC (MANUAL FOR XD-I).doc
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IS TO APPLY A TEST GAS.
3.1 Poison Resistant Sensors
QEL uses improved catalytic bead sensors, which are very resistant to poison of this sort; however, they
are not proof against poisons and should be tested regularly.
3.2 Filters
QEL has instituted the use of poison filters of activated charcoal impregnated cloth. These supply good
protection against most poisons; however, they are not proof against poisons and should be changed
regularly in an area known to have poisons present. When installing be certain that the filter presses
firmly up against the flame arrestor face.
Activated charcoal filters may not be used when the gas being tested is of a type which will be absorbed
by the filter. General use for methane and Hydrogen detection, use with propane detection is
recommended for non hazardous area such a parking garages, as the response time may be slowed.
Figure 3 Sensor Head Assembly
4. CALIBRATION PROCEDURES
Equipment:
Digital Multimeter c/w Pos and Neg probes with:
a) 20.0 mA scale
b) 200 mV scale
Source of clean air
Source of appropriate span gas (usually 40 - 50 % LEL, Balance air)
Small adjustment screwdriver.
Clean air adjustments:
1.
If sensor is NEW, pull out electronics module slightly and measure voltage between NULL
testpoints TP3 & TP5 (use 200 mV scale) and adjust NULL to get 000.0 mV. (See Figure 1.)
2.
Set multimeter to 20 mA scale, attach probes, and insert Pos probe to "POS" jack, Neg probe to
