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Teledyne API Model T360/T360M Operation Manual Principles of Operation
207
corruption. In the unlikely event that the flash chip should fail, the analyzer will
continue to operate with just the DOM. However, all configuration information
will be lost, requiring that the unit be recalibrated.
7.4.3. Optical Bench & GFC Wheel
Electronically, the Model T360’s optical bench, GFC wheel and associated
components do more than simply measure the amount of CO
2
present in the
sample chamber. A variety of other critical functions are performed here as well.
7.4.3.1. TEMPERATURE CONTROL
Because the temperature of a gas affects its density and therefore the amount of
light absorbed by that gas it is important to reduce the effect of fluctuations in
ambient temperature on the Model T360’s measurement of CO
2
. To accomplish
this the temperature of both the sample chamber and the GFC Wheel are
maintained at constant temperatures above their normal operating ranges.
Bench Temperature:
To minimize the effects of ambient temperature variations
on the sample measurement, the sample chamber is heated to 48C (8 degrees
above the maximum suggested ambient operating temperature for the analyzer).
The heat source is a strip heater attached to the underside of the chamber housing.
The temperature of the sample chamber is sensed by a thermistor attached to the
sample chamber housing.
Wheel Temperature
: To minimize the effects of temperature variations caused by
the near proximity of the IR Source to the GFC wheel on the gases contained in
the wheel, it is also raised to a high temperature level. Because the IR Source
itself is very hot, the set point for this heat circuit is 68C. The heat source is a
cartridge heater implanted into the heat sync on the motor. The temperature of
the wheel/motor assembly is sensed by a thermistor inserted into the heat sync.
Both heaters operate off of the AC line voltage supplied to the instrument.
7.4.3.2. IR SOURCE
The light used to detect CO
2
in the sample chamber is generated by an element
heated to approximately 1100
o
C producing infrared radiation across a broad band.
This radiation is optically filtered after it has passed through the GFC Wheel and
the sample chamber and just before it reaches the photo-detector to eliminate all
black body radiation and other extraneous IR emitted by the various components
of those components.
07272B DCN6552