Teledyne Model Vehicle T400 ユーザーズマニュアル

This assembly is only present in analyzers with O

3

 generator and/or photometer options 

installed.  The pressure/flow sensor PCA, located at the rear of the instrument between 
the photometer and the pump (see Figure 3-5) 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: 

  Measure the voltage across C1 it should be 5 VDC ± 0.25 VDC.  If not then the 

board is bad 

  Measure the voltage between TP2 and TP1 C1 it should be 10 VDC ± 0.25 VDC.  If 

not then the board is bad. 

1.  Measure the pressure on the inlet side of S1 with an external pressure meter. 

1.  Measure the voltage across TP4 and TP1.   

  The expected value for this signal should be: 

 

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 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. 

 

  Measure the voltage across TP3 and TP1.   

  With proper flow (800 cc

3

/min through the photometer), this should be 

approximately 4.5V (this voltage will vary with altitude).   

  With flow stopped (photometer inlet disconnected or pump turned OFF) the 

voltage should be approximately 1V.   

  If the voltage is incorrect, the flow sensor S3 is bad, the board is bad or there is 

a leak upstream of the sensor. 

06870C DCN6332