RKI Instruments Eagle Series - Manual (Page 14)

Diffusion Eagle Instruction Manual Description: Eagle and Remote Detector • 9
Sensors
Under normal conditions, the Eagle’s standard sensors have an operating life
of approximately two years. To replace the sensors, open the case by
unscrewing the four screws that secure the lid to the case. (See “Replacing
Sensors” on page 52 for more details.)
Combustible gas sensor
The combustible gas (LEL) sensor is mounted with the flame arrestor
extending outside the case to allow the ambient air 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 (CN3) socket on the interconnect printed circuit board (PCB)
inside the Remote Detector.
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 with its face behind a perforated hole
pattern covered by a hydrophobic membrane to allow the ambient air to
diffuse into the sensor. A multi-pin plug connects the O
2
sensor to the OXY
(CN2) socket on the interconnect PCB. This socket sticks up higher than the
rest.
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.