- Eagle Portable Multi-Gas Detector Instruction Manual

Eagle Instruction Manual Description • 7
Sensors
This section describes the Eagle’s standard sensors. Non-standard
sensors are described in Appendices C, D, and E. Your specific Eagle
model may not include all of the sensors described below. Under
normal conditions, the Eagle’s standard sensors have an operating life
of approximately two years.
Combustible gas sensor
The combustible gas (LEL) sensor is mounted with the flame arrestor
down in the sensor block to allow the sample flow to diffuse into the
sensor. Five pins extend from the top of the sensor. The sensor cable
connects to the pins on one end and terminates in a four-position
connector, which plugs into the COMB socket on the analog print
circuit board (PCB).
The LEL sensor detects combustible gas and vapors in the atmosphere
with a catalytic platinum element. The reaction of gas with oxygen on
the catalyst causes a change in the resistance of the element, which is
converted by the Eagle into a reading of combustible gas
concentration.
Oxygen sensor
The oxygen (O
2
) sensor is mounted face down in the sensor block to
allow the sample flow to diffuse into the sensor. A multi-pin plug
connects the O
2
sensor to the CN2 socket on the analog PCB.
The O
2
sensor is an electrochemical cell, which reacts to the oxygen in
the atmosphere and produces a voltage proportional to the oxygen
concentration. This voltage is converted by the Eagle into a reading of
oxygen concentration.
Standard toxics (CO and H2S) sensors
The CO and H
2
S sensors are physically very similar. They have
cylindrical bodies and are mounted face down in the sensor block. A
three-position connector from each sensor plugs into EC1 or EC2
socket on the analog PCB. The sensor connected to the EC1 socket
displays as channel 3; the sensor connected to the EC2 socket displays
as channel 4.
The toxics sensors are electrochemical cells, which react to the target
gas in the atmosphere, producing a current proportional to the
concentration of gas. The current is converted by the Eagle into a
reading of target gas concentration.