A Low-Cost Smart Measurement System for Resistive (Bridge) or Capacitive Sensors

A low-cost smart measurement system for resistive (bridge) or capacitive sensors is presented. The measurement system consists of three main parts: the sensor element, a universal transducer interface (UTI) and a microcontroller. The Universal Transducer Interface (UTI) is equipped with front-ends for many types of resistive (bridge) and capacitive sensors. It is a sensor-signal-to-time converter, based on a period-modulated oscillator, which generates a microcontroller-compatible output signal. The microcontroller performs data acquisition of the output signals from the UTI, controls the operating conditions and communicates with a personal computer. Continuous auto-calibration is applied to eliminate the influences of offset and gain errors. According to the experimental results the accuracy and resolution amounts to 13 bits and 16 bits, respectively, for a measurement time of about 100 ms.