9 Anesthetic Gas Module Introduction
176
O
2
Sensor
Specifications
Measurement Principle
The O
2
sensor uses a fast O
2
measurement technique that utilizes O
2
paramagnetic properties.
Two sealed spheres forming a dumb-bell assembly are filled with N
2
. The dumb-bell assembly is
suspended in a symmetrical non-uniform magnetic field. The spheres take up a position away from the
most intense part of the field, due to the diamagnetic force on the dumbbells. The dumb-bell assembly
is then surrounded by the sample gas.
When the surrounding sample gas contains O
2
, the dumb-bell spheres are forced even further out of
the magnetic field by the relatively stronger paramagnetic O
2
gas. The torque acting on the dumb-bell
is proportional to the paramagnetism of the surrounding gases, and can therefore be taken as a measure
of the oxygen concentration.
This torque is measured by monitoring the current required in a servo system that attempts to return
the dumb-bells to their normal position.
Infrared Measurement Assembly
The measurement assembly measures the IR light absorption of the gases in its sample cell (see Figure
33).
Weight 335 g (0.75 lbs)
Size (HxWxD) 54 x 54 x 56 mm
Calibration Zero: Room Air
Span: Suitable calibrated mixture
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