Teledyne gfc 7000ta operation manual Sync/Demod Status LED’s, Four sample and hold circuits are

Theory of Operation Model GFC7000TA Carbon Dioxide Analyzer

The four sample and hold circuits are:

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 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 9-14: Sample & Hold Timing

9.3.4.3. 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 9-1: Sync/Demod Status LED Activity

LED	FUNCTION	STATUS OK	FAULT STATUS
D1	M/R Sensor Status	LED flashes approximately	LED is stuck
		2/second	ON or OFF
D2	Segment Sensor	LED flashes approximately	LED is stuck
	Status	6/second	ON or OFF

See Section 11.1.4 for more information.

Teledyne Analytical Instruments 204