TELEDYNE API T300M - Sync;Demod Status Leds; Table 6-14. Sync DEMOD Sample and Hold Circuits; Table 6-15. Sync;Demod Status LED Activity

158 Theory of Operation 083730300A DCN8101
Table 6-14. 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 6-14. Sample & Hold Timing
6.4.3.2 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 6-15. 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 5.7.7 for more information.