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Principles of Operation
7.4.4. Synchronous Demodulator (Sync/Demod) Assembly
7.4.4.1. OVERVIEW
56V
Bias
Pre Amp
Photo-
detector
TEC Control
PHT DRIVE
Thermo-Electric
Cooler
Control Circuit
Compact
Programmable
Logic Device
M/R Sensor
From GFC
Wheel
Segment
Sensor
E Test Control
From CPU
via Mother
Dark Switch
Board
Control
210
While the photo-detector converts fluctuations of the IR beam into electronic
signals, the Sync / Demod Board amplifies these signals and converts them into
usable information. Initially the output by the photo-detector is a complex and
continuously changing waveform made up of Measure and Reference pulses.
The sync/demod board demodulates this waveform and outputs two analog DC
voltage signals, corresponding to the peak values of these pulses. CO2 MEAS
and CO2 REF are converted into digital signals by circuitry on the motherboard
then used by the CPU to calculate the CO
Additionally the synch/demod board contains circuitry that controls the photo-
detector's thermoelectric cooler as well as circuitry for performing certain
diagnostic tests on the analyzer.
Dark
Switch
E-Test
Generator
E Test A Gate
E Test B Gate
Dark Test Gate
Measure Gate
Measure Dark Gate
Reference Gate
Reference Dark Gate
Segment Clock
X1 Reference
10
X10 Clock
Phase Lock
Figure 7-15:
T360 Sync / Demod Block Diagram
Teledyne API Model T360/T360M Operation Manual
concentration of the sample gas.
2
Sample &
Variable
Gain Amp
Hold
Circuits
(x4)
Phase
x10
Lock
Loop
CO
MEAS
2
Signal
Conditioner
CO
Reference
2
Signal
Amplifiers
Conditioner
Phase Lock Warning
M/R
Segment
Status LED
Status LED
07272B DCN6552
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