Simple Measurement Method for Resistive Sensors Based on ADCs of Microcontrollers

A new, complete measurement method for resistance measurement of resistive sensors for systems based on microcontrollers equipped with analog-to-digital converters (ADCs) is proposed. The interface circuit consists of only four resistors, including a resistive sensor and a reference resistor, connected directly to the microcontroller pins. It is activated only during measurements, which significantly reduces power consumption. The measurement procedure consists of measuring three voltages via the ADC. Thanks to this, the measurement results of the resistance are independent of the supply and reference voltages, the ON-resistance of the microcontroller pin, and also the offset and gain errors of the ADC. The method is illustrated in the example of a system consisting of an Arduino Micro and a Pt1000. Experimental studies have shown that the relative systematic measurement error of the sensor resistance is less than 0.29%, and the relative random error is less than 0.56%. They result solely from the quantization error of the 10-bit ADC. An oversampling method has also been proposed. With 64 times oversampling, the above errors were reduced to 0.27% and 0.11%, respectively.