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Model 360E Instruction Manual THEORY OF OPERATION

The four sample and hold circuits are:

ACTIVE WHEN: DESIGNATION

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 circuit (PLL). 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 10-13: Sample & Hold Timing

10.3.4.3. Sync/Demod Status LED’s

The following two status LED’s located on the synch/demod board provide additional diagnostic tools for

checking the GFC wheel rotation.

Table 10-1: Sync/Demod Status LED Activity

LED FUNCTION STATUS OK FAULT STATUS

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 for more information.

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