OPERATING MANUAL OXYGEN MONITORING SYSTEM
OMS 420
10
6
COe sensor – operating theory
A solid ceramic electrolyte with thin-layer technology is used to measure the combustible gases (CxHy equivalent CO
2
). The ce-
ramic electrolyte is a good oxygen ion conductor at temperatures of approximately 1.300
o
F (700 °C) generated by an internal,
low power (10 W) self regulating heater element.
The heated electrolyte has an initial voltage (U
0
approximately zero mV) in the absence of combustible gases (H
2
, CO or CH
4
or
C
3
H
8
, etc). In presence of these gases, the output voltage increases (see chart below) as these gases are oxidized at the hot sur-
face of sensor
The cell voltage is measured by micro-controller based transmitter electronics and converted into a standard, linearized 4 – 20 mA
signal for combustibles equivalent carbon monoxide (COe) in the range of approximate 0 – 1000 ppm.
Since the sensor is reacting to the presence of any combustible gas, but calibrated with CO+H
2
, equivalent CO measurements will
be reported.
The expected lifetime of this sensor is about 5 years + under normal operating conditions, and is not dependent on fuel type, but:
CAUTION:
•
Exposure to corrosive gases (silicone vapor, alkaline and heavy metals, P, Pb, high SO
2
, etc.)
will shorten the life of the sensor.
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