A simple experiment to determine the characteristics of an NTC thermistor for low-temperature measurement applications

A simple low-cost experiment for undergraduate students to determine the characteristics of a negative temperature coefficient of resistance thermistor is presented. The experiment measures the resistance-temperature and voltage-temperature characteristics of the thermistor. Results of the resistance-temperature experiment are used to determine the sensitivity index of the thermistor material. The experimental sensitivity index of the thermistor material is found to be close to the one from the datasheet of the manufacturer. Two voltage-temperature measurement circuits are tested experimentally, namely the Wheatstone bridge circuit and the operational amplifier (Opamp) bridge circuit. The Wheatstone bridge circuit produces a better sensitivity than the Opamp bridge circuit. The best linearity is obtained with a modified Opamp bridge circuit at an expense of reducing the sensitivity. The low cost of the experimental setup makes it suitable for implementation in universities with very limited resources, especially in developing countries. (paper)