抄録
One important and difficult problem in the thermometry of gaseous substances is how to eliminate the error due to radiation.
The purpose of the paper here reported is to construct a thermoelectric thermometer with which the correct temperature of a gas can be obtained by a single measurement regardless of radiation. Two copper-constantan thermopiles are covered with materials of different emissivities. The ratio of the number of couples of the two piles is inversely proportional to the emissivities of the materials.
The error due to radiation is canceled, and the correct temperature of a gas can be obtained by a single measurement. The ratio of emissivities may be estimated experimentally.
Improvements are made for simplification of the equipment and stabilization of the output voltage. The number of couples and reference junctions is considerably reduced.
An improved thermometer of type I is composed of a reflective thermocouple, a reference junction and a set of differential couples.
An improved thermometer of type II is composed of some reflective couples and absorptive couples connected in parallel and a set of compensating differential couples.
The experimental results show that good stability of output voltage and simplification of the setup are obtained fairly well. The error due to radiation is within ±3μV (0.06°C) over the temperature range from 35°C to 45°C. It is recognized that improved thermometers are available for gas temprature measurement.
