pirani gauge

 
 

For pressure measurements in the roughing pump stage of a UHV system, one can use a Pirani gauge.The idea of this instrument is to measure the resistance of a heated wire in the vacuum system. The resistance depends on the temperature of the wire. At high pressures

the wire will be cooled by collisions with the rest gas molecules, i.e. by warming up the rest gas. As the pressure is reduced, this cooling mechanism gets less effective and the temperature of the wire increases. The resistance of the wire can be calibrated as function of

the pressure. Pirani gauges work from ambient pressure down to about 10-5 mbar.

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