Buffer-less system for thermistor temperature measurement

This paper presents a temperature measurement system without the input buffer. A voltage follower or a buffer is required to minimize the influence of the ADC input impedance in the thermistor temperature measurement system. A high performance operational amplifier is usually required to prevent the noise and distortion due to the additional circuit. Negative power is also necessary to prevent the distortion of the low voltage input signal. This paper introduces a buffer-less system with a calibration method to resolve such problems. The low temperature coefficient precision resistors were employed to calibrate the input resistance and the leakage current of ADC. The experimental results show that the calibrated error decreased from 240mK to 30mK.