A novel smart interface for voltage-generating sensors

A novel low-cost smart interface for self-generating sensors, e.g., thermopiles and thermocouples, is presented. The proposed interface acts as an asynchronous converter for dc voltages employing a relaxation oscillator which output a period-modulated signal. A microcontroller is used to measure the output signal from the interface, to process data, and to output the measured sensor signal. The system provides an intrinsic A/D converter. Experimental results show that the interface is able to measure voltages in the range of 0 V to 5 V with an accuracy and resolution of /spl plusmn/64/spl times/10/sup -6/ and 20/spl times/10/sup -6/, respectively. The measurement time is less than 100 ms.