Input Gas Pressure / Flow Sensor Assembly - Teledyne T700 Operation Manual

Troubleshooting and Service

9.4.9. INPUT GAS PRESSURE / FLOW SENSOR ASSEMBLY

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The input gas pressure/flow sensor PCA, located at the front of the instrument to the left
of the MFCs (see Figure 3-6) can be checked with a Voltmeter.
procedure assumes that the wiring is intact and that the motherboard as well as the
power supplies is operating properly:
BASIC PCA OPERATION:

Measure the voltage across C1 it should be 5 VDC ± 0.25 VDC. If not, then the
board is bad
CAL GAS PRESSURE SENSOR:
1. Measure the pressure on the inlet side of S1 with an external pressure meter.
2. Measure the voltage across TP4 and TP1.

The expected value for this signal should be:
EXAMPLE: If the measured pressure is 25 PSIG, the expected voltage level between
TP4 and TP1 would be between 3470 mVDC and 4245 mVDC.
EXAMPLE: If the measured pressure is 30 PSIG, the expected voltage level between
TP4 and TP1 would be between 4030 mVDC and 4930 mVDC.

If this voltage is out of range, then either pressure transducer S1 is bad, the
board is bad, or there is a pneumatic failure preventing the pressure transducer
from sensing the absorption cell pressure properly.
DILUENT PRESSURE SENSOR:
1. Measure the pressure on the inlet side of S2 with an external pressure meter.
2. Measure the voltage across TP5 and TP1.

Evaluate the reading in the same manner as for the cal gas pressure sensor.
Teledyne API – Model T700 Dynamic Dilution Calibrator
The following
06873B DCN6388