RKI Instruments EAGLE 2 Manual - Manual (Page 19)

EAGLE 2 Operator’s Manual Instrument Description • 9
Oxygen Sensor
The O
2
sensor is a galvanic type of sensor. A membrane behind the openings
on the sensor face allows gas to diffuse into the sensor at a rate proportional
to the partial pressure of oxygen. The oxygen reacts in the sensor and
produces a voltage proportional to the concentration of oxygen. The voltage
is measured by the EAGLE 2’s circuitry, converted to a measurement of gas
concentration, and displayed on the LCD.
The sensor includes a short cable that terminates in a round 7-position
connector. It mates with the OXY pins on the main PCB (see “Main PCB” on
page 12).
CO and H
2
S Sensors
The CO and H
2
S sensors are electrochemical sensors that consist of three
precious metal electrodes in a dilute acid electrolyte. A gas permeable
membrane covers the sensor face and allows gas to diffuse into the
electrolyte. The gas reacts in the sensor and produces a current proportional
to the concentration of the target gas. The current is amplified by the EAGLE
2’s circuitry, converted to a measurement of gas concentration, and displayed
on the LCD.
The CO and H
2
S sensors are physically very similar. Except for their
markings and wire colors, they look almost identical. A three-position
connector at the end of a 2-wire cable from each sensor plugs into a socket on
the main PCB. The sockets on the main PCB for the CO and H
2
S sensors are
labeled CO and H2S. Normally, the CO connector plugs into the CO socket
and the H2S plugs into the H2S socket. However, because of the way that the
main PCB circuitry is arranged, if the CO sensor is plugged into the H2S
socket and the H2S sensor is plugged into the CO socket, the sensors will still
operate properly and the CO and H2S readings will still appear on the
channels that are programmed for those gases.
LCD
A digital LCD (liquid crystal display) is visible through a clear plastic
window in the top case. The LCD simultaneously shows the gas reading for
all installed sensors. The LCD also shows information for each of the
EAGLE 2’s operating modes.