Teledyne GFC 7001EM operation manual Pressure/Flow Sensor Assembly

Troubleshooting & Repair Model GFC7001E Carbon Dioxide Analyzer

13.5.6.6.Pressure/Flow Sensor Assembly

The pressure/flow sensor PCA, located on the top of the absorption bench, can be checked with a voltmeter using the following procedure which, assumes that the wiring is intact, and that the motherboard and the power supplies are operating properly:

1.For Pressure related problems:

Measure the voltage across C1 it should be 5 ± 0.25 VDC.

￿If not then the board is bad.

Measure the voltage across TP4 and TP1.

￿With the sample pump disabled it should be 4500 mV ±250 mV.

￿With the pump energized it should be approximately 200 mV less. If not, then S1, the pressure transducer is bad, the board is bad, or there is a pneumatic failure preventing the pressure transducer from sensing the absorption cell pressure properly.

2.For flow related problems:

Measure the voltage across TP2 and TP1 it should be 10 ±0.25 VDC.

￿If not then the board is bad.

￿Measure the voltage across TP3 and TP1.

With proper flow (800 sccm at the sample inlet) this should be approximately 4.5V (this voltage will vary with altitude).

￿With flow stopped (sample inlet blocked) the voltage should be approximately 1V.

￿If the voltage is incorrect, the flow sensor is bad, the board is bad or there is a leak upstream of the sensor.

Teledyne Analytical Instruments 293