Thermal conductivity gauges rely on the fact that the ability of a gas to conduct heat decreases with pressure. In this type of gauge, a wire filament is heated by running current through it. A thermocouple or Resistance Temperature Detector (RTD) can then be used to measure the temperature of the filament. This temperature is dependent on the rate at which the filament loses heat to the surrounding gas, and therefore on the thermal conductivity. A common variant is the Pirani gauge which uses a single platinum filament as both the heated element and RTD. These gauges are accurate from 10 torr to 10−3 torr, but they are sensitive to the chemical composition of the gases being measured. COUNT 5
QSN1 The fact that gases ability to conduct heat decreases with pressure is used by what form of measurement? ANS1 Thermal conductivity gauges QSN2 How is the wire filament in a Thermal conductivity gauge heated? ANS2 by running current through it QSN3 What is a Pirani gauge sensitive to? ANS3 chemical composition of the gases being measured QSN4 What is a RTD used for on a Thermal Conductivity gauge? ANS4 to measure the temperature of the filament QSN5 A Pirani gauge is accurate within what ranges? ANS5 10 torr to 10−3 torr