Theory of Operation
Teledyne API – Model T300/T300M CO Analyzer
296
The four sample and hold circuits are designated as follows:
Table 12-2:
Sync DEMOD Sample and Hold Circuits
Designation
Active When:
IR BEAM PASSING THROUGH
Segment Sensor Pulse is:
Measure Gate
MEASUREMENT cell of GFC Wheel
HIGH
Measure Dark Gate
MEASUREMENT Cell of GFC Wheel
LOW
Reference Gate
REFERENCE cell of GFC Wheel
HIGH
Reference Dark Gate
REFERENCE cell of GFC Wheel
LOW
Timing for activating the Sample and Hold Circuits is provided by a Phase Lock Loop
(PLL) circuit. Using the segment sensor output as a reference signal the PLL generates
clock signal at ten times that frequency. This faster clock signal is used by the PLD to
make the Sample and Hold Circuits capture the signal during the center portions of the
detected waveform, ignore the rising and falling edges of the detector signal.
Sample & Hold
Active
Detector
Output
Sample & Hold
Inactive
Figure 12-14: Sample & Hold Timing
12.4.3.2.
SYNC/DEMOD STATUS LEDS
The following two status LEDs located on the sync/demod board provide additional
diagnostic tools for checking the GFC Wheel rotation.
Table 12-3:
Sync/Demod Status LED Activity
LED
Function
Status OK
Fault Status
D1
M/R Sensor Status
LED flashes approximately
2/second
LED is stuck
ON or OFF
D2
Segment Sensor Status
LED flashes approximately
6/second
LED is stuck
ON or OFF
See Section 11.1.4.2 for more information.
06864D DCN7562
Summary of Contents for T300
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