Contactless measurement of temperature based on transient wireless energy transmission

A new method of contactless temperature measurement is presented in this paper. Through analysis of the transient process of the wireless energy transfer, a linear function of the thermistor resistance is obtained, which could be employed to measure the variation of the resistance and the corresponding fluctuation of the temperature. Compared with the conventional temperature measurement, this method provides convenience to measure the environmental variations in the inaccessible or enclosed environment. In the proposed scheme, the sensor circuit consists of only three passive components: a resistance thermometer, a resonant capacitor and a magnetic coupled inductor. It makes the volume of the sensor small and extra battery supply unnecessary. In addition, by applying a variety of resistance sensors, this method has potential to measure other physical quantities including moisture, pressure or lumen without wire connection. The experimental results are provided to verify the effectiveness of the method. An overall resistance resolution of ±1 Ω is realized in experiments, and temperature resolution of ±5°C can be expected with the available thermistor.