A Microcontroller Measuring Resistance Converter

Abstract

A software method is considered for converting a resistance into binary code that makes it possible to control the current flowing through a transformable resistance. The resolving power of the microcontroller measuring converter (MMC) is set by programmatically in the range from 2 to 16 bits. The resistive sensors with different nominal resistance values not lower than 50 Ω can be used as a transformable resistance. A block diagram of an MMC with an explanation of its operation algorithm, an oscillogram of output signals of a double-channel pulse-width modulator (PWM) built into the microcontroller, and an example of MMC calculation are presented. It is found from the calculated and experimental data that the transforming characteristic of MMC is linear in the range of the most relevant resolution from 8 to 16 bits. The operation of two PWM channels at the same frequency when supplying the measuring and reference circuits with current of the same value makes it possible to exclude the negative influence of external factors: temperature, instability of supply voltage, electromagnetic fields, and changes of parameters of elements as a result of their aging.