Constant Current Strain Gauge Bridge

摘要

All the early electrical strain gauge bridge circuits employed constant voltage sources for bridge excitation. The techniques developed for the classical direct-current and alternating-current component-measuring bridges were transferred to the strain gauge bridges with only minor modification. With the introduction of the semi-conductor strain gauges the advantages to be gained by the use of constant current bridge excitation became apparent. While the use of constant current sources does provide a bridge of enhanced stability, the network shares some of the problems of the constant voltage circuit and introduces a few of its own. In this paper an attempt has been made to present some of the formulae for the constant current bridge, to investigate the effects of lead resistance and to examine, for the simplest bridge, the influence of initial offset compensation (initial balance) on the sensitivity of the bridge to strain and on the bridge configurations to be used. A simplified analysis is used to develop expressions for the output of the commonly used strain gauge bridge configurations with Constant Current excitation. Expressions for initial offset compensation, shunt calibration and the influence of lead resistance are developed. Consideration is given to some means for error correction.