GX-2012 Operator’s Manual Instrument Description • 11
Pump
A diaphragm pump inside the GX-2012 draws the sample to the sensors. It
can draw sample from as far as 50 feet from the GX-2012. The pump is not
user serviceable.
CAUTION: Sample hose lengths of more than 50 feet are not recommended
for the GX-2012 because of flow rate reduction.
Flow Chamber
The flow chamber is on the back of the GX-2012 and is held in place by three
phillips screws. The flow chamber seals to the rubber sensor gasket which
seals to the sensor faces inside the GX-2012 and routes flow from the pump
to the sensors and to the exhaust port (also a part of the flow chamber).
Sensors and Filters
The sensors are located underneath the flow chamber and are only accessible
if you remove the flow chamber and the sensor gasket.
An H
2
S removal filter disk is placed into a recess in the sensor gasket over
the %LEL sensor. It prevents H
2
S in the ambient air from reaching the unit’s
combustible gas sensor. Removing H
2
S that is present in the monitored air
prolongs the life of the sensor. The H
2
S filter disk is dark red in color and
although it may darken over time, its color is not indicative of remaining
filter life. The H
2
S filter disk can absorb H
2
S for 33 ppm hours and should be
replaced after that much exposure. With this many ppm hours of absorption,
the H
2
S filter disk should be replaced after 80 minutes of exposure to 25 ppm
H
2
S. This equates to replacing the H
2
S filter disk after 40 2-minute
calibrations with a cylinder containing 25 ppm H
2
S. If H
2
S exists in the
monitoring environment, the H
2
S filter disk will have to be replaced more
frequently.
A charcoal filter is placed into a recess in the sensor gasket over the CO
sensor. The charcoal filter is black, has a woven texture, and is impregnated
with an H
2
S absorbing material. The CO sensor will respond if exposed to
H
2
S and certain hydrocarbon gases. The charcoal filter disk scrubs these
gases out of the sample to avoid false CO readings. If false or elevated CO
readings are noticed, especially in the presence of H
2
S, change the charcoal
filter.
Inlet Filter Holder
The filter holder is a clear plastic dome shaped piece on the top of the case. A
male quick connect fitting is located on the inlet filter holder. This is the GX-
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