
Fault Isolation
Chapter Five: Maintenance
34
How To Calibrate the Engineering Units Circuit
Equipment Required:
1 DVM, 5½ place
1 Precision Variable Voltage Source, 10 Volts
Miscellaneous Bus Wire
Schematic
PC Layout
1. Turn off power to the PDR-C unit.
2. Short the Pressure Input to the Signal GND terminal on the rear panel terminal block
(CH 1).
3. Attach the DVM between Analog GND and the zeroed CH 1 signal, available at front panel
switch S3 or at one end of R43.
4. Apply power to the PDR unit.
5. Adjust the front panel ZERO trimmer for a 0.000
±
0.0005 Volt DVM reading.
6. Shut off power to the PDR.
7. Attach the voltage source between the Pressure Input and Signal GND terminals.
8. Apply power and a voltage source of 10.0000
±
0.0005 Volts, as measured by the DVM.
9. Ignore the decimal point on the front panel display and use Table 10 to set the appropriate
trimmer for a correct display of the chosen engineering units.
Correct Trimmer for Selected Engineering Units
Engineering Units
Trimmer
Front Panel DVM
mbar
R47
13332
kPa
R47
13332
mmHg
R49
10000
psi
R44
19337
cmH
2
O
R55
13597
inH
2
O
R51
5353
in Hg
R53
3937
Table 10: Correct Trimmer for Selected Engineering Units
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