Answer / manish kumar

For low pressure measurement around 0.01 pa to .1 pa
preassure can be measured by pirani gauge.

Answer / s parth sarathi

in case of pressure measurement pirani gauges are used in
two wire filament , one filament serves as a reference in
an evacuated glass,while the other filament is kept in
aontainer connected to the source of pressure.

Answer / anand soni

The application of the Pirani gauge to the measurement of small pressure changes is discussed. Both nickel and tungsten wires are used as filaments in the gauge. Nickel wire not only has the greater sensitivity but possesses several other advantages. The theory of the gauge is developed so that it is possible to predict the effect of change in length or diameter of the wire upon the sensitivity of the gauge. The theory also predicts that there is an optimum temperature to which the wire should be heated for maximum sensitivity of the gauge. The observed and computed values of the optimum temperature are compared. In some cases the agreement is as good as can be expected and in the others the discrepancy is easily explained. The maximum sensitivity attained is a galvanometer deflection of 1 mm for a pressure change of air equivalent to 5×10-9 mm of mercury.

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