An accurate, low-cost resistive-sensor interface with a multiple-signal calibration technique

This paper presents an accurate, low-cost 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, also the common-mode effect of the interface is 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 Ω with a resolution of 7 mΩ and an accuracy of 11 mΩ. The measurement time is about 100 ms