Environmental and Process Impacts on Thermal Conductivity Gauges

Environmental and Process Impacts on Thermal Conductivity Gauges 

Small changes in the above-mentioned pressure independent offset can lead to appreciable measurement errors. Especially a good compensation of ambient temperature effects has to be provided to keep the specified measurement uncertainty in the operating temperature range. For this purpose a temperature-dependent resistor is often installed at the measurement tube. 

An increase of heat radiation induced by blackening of the filament in the process environment can also lead to a considerable increase of zero signal. After a prolonged operation of a heat conductivity gauge it is not unusual that its offset rises by deposition of hydrocarbons on the filament resulting in a constant indication of 10 mbar with the real pressure being much lower. 

In corrosive process fluids one has to use a corrosion resistive measurement cell. Such systems use nickel or platinum instead of tungsten as filament material. 

Compensated heat conductivity gauge naturai output signai 

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