12 • 35-3001A-10 Oxygen/Carbon Monoxide Sample-Draw Detector
Carbon Monoxide Sensor/CO Amplifier
The carbon monoxide sensor is a plug-in sensor that plugs into the back of the CO amplifier. The
sensor and amplifier are retained in the flow block by two screws. The flow block is mounted to the
middle of the main circuit board. It is the upper of the two flow blocks mounted to the main circuit
board.
Through a series of chemical and electronic reactions, the CO sensor produces a millivolt output that is
proportional to the detection range of the sample-draw detector. A red wire and a blue wire extend
from the CO amplifier and allow connection to the detector/amp terminal strip.
Figure 4: CO Amplifier Component Location
Zero Pot
The zero pot is located in the lower right corner of the amplifier (see Figure 4). Use a small flat blade
screwdriver to turn the zero pot’s adjustment screw and adjust the amplifier’s zero output during the
start up and calibration procedures. Turn the adjustment screw clockwise to increase the zero output
and counterclockwise to decrease the zero output.
Span Pot
The span pot is located to the left of the zero pot (see Figure 4). Use a small flat blade screwdriver to
turn the span pot’s adjustment screw and adjust the amplifier’s gas response during the calibration
procedure. Turn the adjustment screw clockwise to increase the span output and counterclockwise to
decrease the span output.
Test Points
The test points are on the top edge of the amplifier (see Figure 4). 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 (CAL 2) in the upper left corner is the negative (-) test point and the red test point
(CAL 1) in the upper right corner is the positive (+) test point.
Span Pot
Zero Pot
Test Points
100-500 mV Range
