Continental Electric Pirani Vacuum Gauge
Jauge à vide Pirani
Pirani-Vakuummeter
Continental Electric Co. Geneva, IL (later CETRON Electronics Corp.).
A Pirani gauge consists of a metal filament (usually platinum or a platinum alloy) suspended in a tube which is connected to the system whose vacuum is to be measured. Connection is usually made either by a ground glass joint or a flanged metal connector, sealed with an o-ring. The filament is connected to an electrical circuit from which, after calibration, a pressure reading may be taken.
The filament gets heated when electric current flows through it. This wire suspended in a gas will lose heat to the gas as its molecules collide with the wire and remove heat. As the gas pressure is reduced (by the vacuum pumps) the number of molecules present will fall proportionately, the conductivity of the surrounding media will fall and the wire will lose heat more slowly. Measuring the heat loss is an indirect indication of pressure.
The electrical resistance of the wire varies with its temperature, so the measurement of resistance also indicates the temperature of wire. Now the change in resistance of the filament is determined using the bridge. This change in resistance of the pirani gauge filament becomes a measure of the applied pressure when calibrated.
The measurement principle allows these gauges to cover a great total range, from 20 Torr to 10-5 Torr.
Hauteur • Height • Höhe : 74 mm • 2" 7/8
Diamètre • Diameter • Durchmesser : max. 32 mm • 1" 1/4
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