A smart and accurate interface for resistive sensors

This paper presents a smart and accurate interface for resistive sensors based on the use of a relaxation oscillator. To obtain high accuracy, good long-term stability and a reduction of the effects of interference and parasitic elements, some classical and new measurement techniques have been applied in the novel sensor interface. Moreover, all multiplicative and additive errors, and the common-mode effect of the interface are eliminated, using a multiple-signal calibration technique. A prototype has been built and was tested. Experimental results show that the interface is able to measure a resistance of 0 to 400 /spl Omega/, with a resolution of 7 m/spl Omega/ and an accuracy of 11 m/spl Omega/. The measurement time is about 100 ms.