A DC autonulling bridge for real-time resistance measurement

Abstract

This paper describes a resistance measurement system based on a Wheatstone bridge topology that overcomes the limitations of a direct differential measurement and is suited for monolithic sensor applications. An analog feedback network provides a wide dynamic range and maximizes noise rejection by automatically driving the bridge to null via a voltage-controlled resistor. The circuit also provides transient monitoring of resistance changes in any sensor that produces a resistance change due to an environmental stimulus. The system stability is discussed and analyzed using Liapunov analysis, SPICE simulations, and a prototype circuit implemented using basic off-the-shelf components produces results similar to the theoretical analysis.