Teledyne GFC 7001E User Manual download pdf (Page 291)

Troubleshooting & Repair Model GFC7001E Carbon Dioxide Analyzer

Teledyne Analytical Instruments 291

13.5.6. SENSOR ASSEMBLY

13.5.6.1. Sync/Demodulator Assembly

To verify that the Sync/Demodulator Assembly is working, follow the procedure below:

1. Verify that D1 and D2 are flashing.

 If not check the opto pickup assembly, Section 13.5.6.3 and the GFC Wheel drive, Section 13.5.6.4.

 If the wheel drive and opto pickup are working properly then verify that there is 2.4 ±0.1 VAC and 2.5

±0.15 VDC between digital ground and TP 5 on the sync/demod board. If not then check the wiring

between the sync/demod and opto pickup assembly (see interconnect drawing, P/N 04216). If good

then the sync/demod board is bad.

2. Verify that the IR source is operating, Section 13.5.6.5.

3. With the analyzer connected to zero air, measure between TP11 (measure) and analog ground, and

TP12 (reference) and analog ground.

 If they are similar to values recorded on the factory data sheet then there is likely a problem with the

wiring or the A/D converter.

 If they are not then either the sync demodulator board or the IR-photodetector are bad. See Section

13.4.1.4 for problems with the IR-photodetector TEC drive.

13.5.6.2. Electrical Test

The electric test function substitutes simulated signals for CO MEAS and CO REF, generated by circuitry on the

sync/demod board, for the output of the IR photo-detector. While in this mode the user can also view the same

test functions viewable from the main SAMPLE display. When the test is running, the concentration reported on

the front panel display should be 40.0 ppm. (See Section 9.6.4 to calibrate Electrical Test).

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Teledyne GFC 7001E User Manual Page 291