Linearization of High Precision Human Body Temperature Measurement Circuit Based on NTC Thermistor

In the micro-climate cloth researching, we usually need to accurate measuring the body temperature, in this paper we choose the constant-voltage temperature measuring system based on the NTC thermistor to measure the temperature. Because the resistance of the thermistor and the temperature is not linear, so this will cause the output of the measurement circuit is not linear. In actual measurement we usually require the output of the circuit varies linearly in the required range. This paper mainly research the linearization problem of the NTC thermistor bridge circuit in the required temperature range.

A Low-Noise Thermistor Bridge for Use in Calorimetry

A precision thermistor bridge and thermistor is described for use in a thermal titration calorimeter or a high-speed stopped- or continuous-flow calorimeter of the Roughton type. These are compared and evaluated with regard to several other types of detectors, including the platinum resistance thermometer, thermocouple, transistor thermometer, and capacitance thermometers. At this time the best detection for our purpose seems to be a specially constructed 20-100 kΩ thermistor used in conjunction with a new ac lock-in amplifier bridge. The sensitivity of the system is equivalent to a peak-to-peak noise of 25 x 10-6 °C, with a 100-ms time constant and 1 µW power dissipation in the thermistor. Long-term drift of the bridge, without an oven, was 1 x 10-6 °C/min.