Thermal Conductivity Gauges with Constant Filament Temperature

Thermal Conductivity Gauges with Constant Filament Temperature 

A better information is given by the correction tables issued by manufacturers, which take into account the geometry and the functional principle of their Pirani cells, too. For gas mixtures it is advisable to set up an individual correction table by comparative measurement against a gas-independent diaphragm gauge. 

---

The sensing filament in the gauge head forms a branch of a Wheatstone bridge. In the TFIERMOTRON thermal conductivity gauges with variable resistance which were commonly used in the past, the sensing filament was heated with a constant current. As gas pressure increases, the temperature of the filament decreases because of the greater thermal... 

A thermal conductivity gauge uses a constant electric current to heat an element whose temperature is a linear function of gas pressure over a limited range. The temperature is typically measured with a thermocouple. In the popular Pirani gauge, a single metal filament is substituted for a thermocouple, and filament resistance is monitored [19]. The range of pressures detected by thermal conductivity gauges is — lO -lO 4 torr, which makes them useful for... 

---