The generated heat is transferred in the form of radiation or convection to the surrounding gas of filament. The resistance of gauges filament is achieved by measuring the voltage across the wire and the current inside the wire, and using the Wheateston Bridge formula for resistors, and considering that the resistance of wire is a function of temperature, and temperature changes also is a function of the pressure inside the chamber, eventually, it's calculable the chambers gas pressure .
Of course, the measured resistance of the filament is changed non-linearly with pressure. The gauges are built by Marcelo Pirani, and was registered in his name.
Thermocouple and thermistor gauges work like Pirani gauges, except that, in these gauges the pressure is measured directly and according to the changes in wire temperature. Detectable range, by these gauges, is about 10-1 -10-2 Pascal. Figure 3 shows a schematic view of a thermocouple gauge.
The generated heat is transferred in the form of radiation or convection to the surrounding gas of filament. The resistance of gauges filament is achieved by measuring the voltage across the wire and the current inside the wire, and using the Wheateston Bridge formula for resistors, and considering that the resistance of wire is a function of temperature, and temperature changes also is a function of the pressure inside the chamber, eventually, it's calculable the chambers gas pressure .Of course, the measured resistance of the filament is changed non-linearly with pressure. The gauges are built by Marcelo Pirani, and was registered in his name.Thermocouple and thermistor gauges work like Pirani gauges, except that, in these gauges the pressure is measured directly and according to the changes in wire temperature. Detectable range, by these gauges, is about 10-1 -10-2 Pascal. Figure 3 shows a schematic view of a thermocouple gauge.
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