Construction |
|
|---|---|
| Consists of platinum filament wire enclosed in a chamber connected to an unknown pressure source. | |
| Filament forms an arm of a Wheatstone-bridge. | |
| Compensating resistance is placed in the opposite arm. | |
Working |
|
| Pirani gauge operates on 3 modes: Constant current, Constant resistance, and Constant voltage. | |
| Due to constant current, the filament gets heated. | |
| At low pressure, thermal conductivity gets reduced. | |
| Temperature variation leads to resistance variation of the filament and unbalances the Wheatstone bridge. | |
| Change in resistance of the wire filament gives the value of unknown pressure. | |
Advantages |
|
| Simple in design & easy to use. | |
| More accurate than thermocouple gauges. | |
| Remote reading is possible. | |
| Range is between 10^-5 mm to 1 mm of Hg. | |
| Quick and continuous response to pressure changes. | |
Disadvantages |
|
| More expensive than thermocouple type of gauges. | |
| Dependent on electrical power to operate. | |
Applications |
|
| Research and development laboratories | |
| Industrial vacuum furnaces | |
| Sputtering systems | |
| Vacuum pumps | |
| Mass spectrometers | |
| Optical instruments | |
| Semiconductor manufacturing |
