Circuit for readout and linearisation of sensor bridges

Abstract

This work presents a general concept for the linearisation of impedance bridges with circuit components changing in only one polarity. The method can be applied for DC or AC bridges using resistive, capacitive or inductive circuit elements. The linearisation can conveniently be integrated with the readout circuit resulting in a highly linear sensor readout. A feedback-loop using a transadmittance amplifier properly designed and matched to the nominal value of the bridge components reduces non-linearity from 9% to 0.4% over /spl plusmn/20% of bridge imbalance. In addition to the linearization of the bridge transfer function itself the method can be applied for the linearization of a range of transducers with a hyperbolic transfer function.