Pressure/Flow Sensor Assembly - Teledyne T400 User Manual

5.7.9.7 PRESSURE/FLOW SENSOR ASSEMBLY

This assembly is only present in analyzers with O
installed. The pressure/flow sensor PCA, located at the rear of the instrument between
the photometer and the pump, can be checked with a voltmeter. The following procedure
assumes that the wiring is intact and that the motherboard as well as the power supplies
are operating properly:
BASIC PCA OPERATION:
• Measure the voltage across C2: it should be 5 VDC ± 0.25 VDC. If not, then the board is
bad
• Measure the voltage between TP2 and TP1 and also across C1: it should be 10 VDC ±
0.25 VDC. If not, then the board is bad.
PHOTOMETER 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:
Expected mVDC
EXAMPLE: If the measured pressure is 20 In-Hg-A, the expected voltage level between
TP4 and TP1 would be between 2870 mVDC and 3510 mVDC.
EXAMPLE: If the measured pressure is 25 In-Hg-A, the expected voltage level between
TP4 and TP1 would be between 3533 mVDC and 4318 mVDC.
• If this voltage is out of range, then pressure transducer S1 is bad, or the board is
PHOTOMETER FLOW SENSOR:
Measure the voltage across TP3 and TP1.
•
• With proper flow (800 cc
• With flow stopped (photometer inlet disconnected or pump turned OFF) the voltage
• If the voltage is incorrect, the flow sensor S3 is bad, the board is bad or there is a
128
(
Pressure
=
30.0
bad, or there is a pneumatic failure preventing the pressure transducer from sensing
the absorption cell pressure properly.
/min through the photometer), this should be approximately
3
4.5V (this voltage will vary with altitude).
should be approximately 1V.
leak upstream of the sensor.
Teledyne API – Model T400 O
generator and/or photometer options
3
)
x +
4660 250
mvDC
In-Hg-A
Analyzer
3
± 10%
rdg
mvDC
083730400A DCN8130