Modification of De’ Sauty Bridge Network for Accurate Measurement of Process Variables by Variable Parameter Transducers

Abstract

In variable parameter transducers, the small change in passive parameters such as resistance, capacitance, and inductance, generally changes linearly with the process variable in process plant. The classical method of measurement of passive parameters generally uses an ac bridge circuit. However, this type of bridge measurement technique suffers from errors due to the effect of stray capacitances in between bridge output terminals and ground. These errors can be minimized by using the Wagner-earth technique, but the limitation is the repetition of bridge balance, which is required in every observation so that continuous measurement is not possible, which is the basic needs of a transducer. In this article, a modified De’ Sauty bridge network has been developed by using a high-gain operational amplifier to minimize the stray capacitances in case of measurement of the small change in resistances or capacitances. A potentiometer has been used to adjust the sensitivity of the bridge. For a particular value of bridge sensitivity factor, the change of passive parameters of sensor equivalent and the change of actual process variables have been observed and found good linearity and repeatability.