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Troubleshooting and Service Teledyne API – Model T700 Dynamic Dilution Calibrator
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9.4.9. INPUT GAS PRESSURE / FLOW SENSOR ASSEMBLY
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. The following
procedure assum
es 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.
06873B DCN6388