6 • 35-3001A-07-03 Methane/Hydrogen Sulfide Sample-Draw Detector
IR CH
4
Amplifier
The IR CH
4
amplifier converts the electrical output from the IR CH
4
sensor to a 4 to 20 mA signal
that corresponds to the detection range and transmits the signal to a gas monitoring controller. A
label on the amplifier indicates the detector drive current. This drive current is factory set. The
amplifier is mounted on the top middle edge of the main circuit board. It consists of the zero pot,
span pot, controller terminal strip, detector terminal strip, and test points.
Figure 3: IR CH
4
Amplifier Component Location
Zero Pot
The zero pot is located in the upper right corner of the amplifier (see Figure 3). Use a small flat
blade screwdriver to turn the zero pot’s adjustment screw and adjust the amplifier’s zero (fresh air)
output during the start-up and calibration procedures. Turn the adjustment screw clockwise to
increase the fresh air output and counterclockwise to decrease the fresh air output.
Span Pot
The span pot is located below the zero pot (see Figure 3). Use a small flat blade screwdriver to turn
the span pot’s adjustment screw and adjust the amplifier’s gas response output during the
calibration procedure. Turn the adjustment screw clockwise to increase the span output and
counterclockwise to decrease the span output.
CAUTION:
The amplifier includes additional pots. They are factory-set. Do not adjust them.
Controller and Detector Terminal Strips
The controller terminal strip and detector terminal strip are three- and four-position plug-in style
terminal strips, respectively. The controller terminal strip is located on the right side of the
amplifier and the detector terminal strip is to the left of it. Both terminal strips are factory wired to
the sensor and main circuit board.
Test Points
The test points are on the left side of the amplifier (see Figure 3). The test points produce a 100 mV
to 500 mV output that corresponds to the sample-draw detector’s 4 to 20 mA output. Use the test
points and a voltmeter to measure the amplifier’s output during the start-up and calibration
procedures. The black test point in the upper left corner is the negative (-) test point and the red test
point to the left of the zero and span pots is the positive (+) test point.
W
LEL
G
B
R
Test Points
100-500 mV Range
Controller
Terminal Strip
Span Pot
Zero Pot
Factory Set Pots
S
PWR / SIG
Detector
Terminal Strip
