Resistance Thermometer for Air Temperature Measurement

Abstract

Air temperature mesurement is very difficult because of the effect of radiation from surrounding bodies. The error due to radiation can be canceled by measuring the temperature with two temperature sensitive resistances of different emissivities.
The resistance thermometer here reported is designed to obtain the air temperature by a single measurement. This resistance thermometer needs no reference junction, different from the thermoelectric thermometer.
The thermometer is composed of two resistance elements covered respectively with different materials of different emissivities, and the two resistances are inversely proportional to the emissivities.
The difference of resistance of the two resistance thermometers gives the correct air temperature, the error due to rediation being canceled.
A modified Wheatstone bridge is used to measure the difference in resistances.
Three resistance thermometers composed of Cu, Ni and Pt respectively are examined. The experimental results show that the errors due to radiation can be reduced to less than 0.1°C between 35°C and 45°C.