A microcontroller-based interface circuit for non-linear resistive sensors

Abstract

Abstract This article proposes a circuit based on a microcontroller unit (MCU) for the direct measurement and linearization of non-linear resistive sensors, such as thermistors. The measurement relies on an embedded digital timer and does not require (either embedded or external) operational amplifiers or an analog-to-digital converter, thus resulting in a low-cost, low-power design solution. The circuit includes a known resistor with a twofold function: it is a reference for circuit auto-calibration purposes, and it is in parallel with the non-linear resistive sensor for linearization purposes. A prototype is implemented with an 8-bit MCU (ATtiny 2313) applied to a commercial thermistor, and the results show a non-linearity error smaller than 1% full-scale span.