A low-cost, high-precision sensor interface for platinum temperature sensors

This paper presents a low-cost, high-precision sensor interface for resistive platinum temperature sensors, based on the use of a relaxation oscillator. A high accuracy, good long-term stability and a reduction of the effects of interference and parasitic elements are obtained by applying some classical and new measurement techniques in the sensor interface. Moreover, all multiplicative and additive errors, also the common-mode and charge-injection effects of the interface are eliminated, using a multiple-signal calibration technique. The sensor interface has been fabricated in a 0.7 μm CMOS process. Experimental results show that the sensor interface is able to measure a resistance in the range of 0 Ω to 400 Ω with a resolution of 1.6 mΩ (0.0042°C@Pt100=100 Ω) and a systematic error of 8.6 mΩ (0.022°C@Pt100). The measurement time amounts to 200 ms.