Precision Active Bridge Circuit for Measuring Incremental Resistance with ANN Compensation of Excitation Voltage Variation

The present work deals with the development of low cost, appreciably accurate precision electronic circuit for resistive sensor where measurement of the incremental resistance change with high degree of accuracy is essential. A linear and sensitive active half bridge circuit requiring only few components for its hardware implementation has been proposed for measuring very small resistance change due to change in physical quantity or chemical analytes. Theory of the proposed active bridge circuit has been discussed and experimental results have been compared with conventional bridge circuit. Initial measurements are made with Pt-100 Strain gauge sensor but it can be extended to other resistive sensors of practical importance. Results show that the active bridge circuit is almost four times more sensitive than conventional half bridge circuit and two times more sensitive than full Wheatstone bridge circuit. Studies have also been made to analyze the errors due to ambient temperature, connecting lead resistance and dc excitation voltage. Experimental results show that output of the circuit has negligible effect on ambient temperature and connecting lead resistance. The error due to excitation voltage has been compensated using Artificial Neural Network (ANN) based inverse modeling technique.