APPENDIX
- 21 -
Fig. 5-3 Indication Values – Working Standard
Causes of deviation from measurement accuracy
Ambient temperature
The indication of the Pirani gauge varies with the ambient temperature of the sensor head.
Gas measured
Since the Pirani gauge is a molecular density measuring vacuum gauge, the indication of the
gauge varies with the type of gas (difference in thermal conductivity). The Model GP-1G
has been adjusted with nitrogen gas and its indication is a value converted to nitrogen.
Contamination of sensor head
The indication will be affected if the sensor head filament is contaminated with foreign matter.
0.01 0.1 1 10
0.01
0.1
1
10
-3%
+3%
Working Standard (Torr)
0.003
Indicated Values (Torr)
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