35-3010A-13 Sample-Draw Detector • 9
Flow Block
The flow block is located in the lower right corner of the sample-draw detector. Both sensors are
installed in the flow block. The flow block routes the sampled air to each sensor.
EXHAUST Fitting
The EXHAUST fitting on the bottom of the housing allows the gas sample to exit the sample-draw
detector. The EXHAUST fitting accepts 1/4 in. rigid tubing. See “Installation” on page 14 to connect
tubing to the EXHAUST fitting.
Detection System
The detection system consists of the gas sensors, H
2
and oxygen transmitters, preamp circuit board,
and the main circuit board.
H
2
Sensor
The H
2
sensor is installed in the lower left corner of the flow block.
Sensing Element
The H
2
sensor detects hydrogen in the %volume range. Two sensing elements are protected within the
detector. Through a series of thermal and electronic reactions, these elements produce an electrical
output that is proportional to the detection range of the sample draw detector.
Connector
The top of the sensor includes five pins that plug into the socket connector. This connector allows you
to replace the sensor without disconnecting the wiring. The sensor leads are soldered to the connector.
Sensor Leads
Four color-coded leads extend from the connector. The leads allow you to connect the H
2
sensor to the
main circuit board.
Oxygen Sensor
The oxygen sensor is installed in the lower right corner of the flow block. It consists of a cylindrical
body which houses the detection elements and a cable which terminates in a round 7-pin male
connector. The sensor connector mates to a 7-position socket that is wired to the main PCB.
Carbon Monoxide Sensor
The CO sensor position in the flow block is occupied by a plastic dummy plug in the 35-3010A-13.
Hydrogen Sulfide Gas Sensor
The H
2
S sensor position in the flow block is occupied by a plastic dummy plug in the 35-3010A-13.