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O
monitor theory of
2
operation
1009-0633-000
Oxygen
Display range:
Display resolution:
Sensor type:
Measurement range:
Measurement accuracy:
Cell response time:
Low O
alarm range:
2
High O
alarm setting:
2
Expected cell life:
The O
monitor measures and displays O
2
The O
sensor assembly contains an oxygen sensor that produces a voltage
2
proportional to the oxygen partial pressure (concentration) at its detecting
surface.
The O
sensor is an electrochemical device (galvanic cell). Oxygen diffuses
2
through a membrane into the device and oxidizes a base metal electrode. This
oxidation produces an electrical current proportional to the partial pressure of
the oxygen at the electrode's sensing surface. The base metal electrode
gradually wears out from the oxidation process.
The voltage from the sensor cartridge is affected by the temperature of the
monitored gas mixture. A thermistor in the sensor's housing automatically
compensates for temperature changes in the sensor.
The O
monitor uses signal processing and analyzing circuitry to convert the
2
sensor signal into a corresponding % oxygen value. The system displays this
value and compares it to saved alarm limits. If the value falls outside the
limits, the monitor produces the appropriate alarms.
6 Specifications and Theory of Operation
5 to 110% O
2
1% increments
Galvanic fuel cell
0 to 100% O
2
± 3% of full scale
35 seconds, 10 - 90%
Response time of cell and adapter as measured using the
test method described in ISO 7767 (1988-12-15), clause
50.9
18% to 100%
21% to 100%
Note: Low O
limit may not be set above the high O
2
nor may the high O
limit be set below the low O
2
Four months of shelf life (23 °C room air) and one year of
normal operation
concentration in the patient circuit.
2
limit,
2
limit.
2
6-25
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