Interface circuit for resistive sensors utilizing digital potentiometers

In this paper an interface for resistive sensors in a bridge configuration is investigated. The interface utilizes digital potentiometers in order to implement an automatic calibration procedure for the bridge circuit offset. Such an approach facilitates the use of digital signal processing with high flexibility; advantageous in modern instrumentation systems. Commercial digital potentiometers have a very limited resistance range and therefore this method to overcome the discrete nominal resistance values was developed. The system was simulated mathematically and automatic calibration of the offset voltage was demonstrated with a prototype. An important additional advantage was an increase in resolution compared to a simple potentiometer circuit.