Teledyne 300E Instruction Manual page 167

Model 300E Carbon Monoxide Analyzer
Instruction Manual
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 68°C. In this case a cartridge heater is
implanted into the heat sync on the motor is the source. The temperature of the
wheel/motor assembly is sensed by a thermistor also inserted into the heat sync.
Both heaters operate off of the AC line voltage supplied to the instrument.
IR Source
The light used to detect CO in the Sample Chamber is generated by a element
heated to approximately 1100
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.
GFC Wheel
A synchronous AC motor turns the GFC Wheel motor. For analyzers operating on
60Hz line power this motor turns at 1800 rpm. For those operating on 50Hz line
power the spin rate is 1500 rpm. The actual spin rate is unimportant within a large
rate since a Phase Lock Loop circuit is used to generate timing pulses for signal
processing (see Section 6.3.4).
In order to accurately interpret the fluctuations of the IR beam after it has passed
through the Sample Gas, the GFC Wheel several other timing signals are produced
by other photo emitters/detectors. These devices consist of a combination LED and
detector mounted so that the light emitted by the LED shines through the same
mask on the GFC Wheel that chops the IR beam.
P/N 04288 Rev: A
o
C producing infrared radiation across a broad band.
THEORY OF OPERATION
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