Some aspects of the compatibility between strain gauge readout equipment and multi-component wind tunnel balances

In multicomponent strain gauge wind tunnel balances it is common to use four arm bridges of gauges arranged to produce an output from one load component and not from other load components which also cause significant strains under the gauges. This system relies on the fact that there is fundamentally one output producing pattern of strains and three nonoutput producing patterns. It is shown that interactions arise between the various strain patterns and that these interactions, and hence the balance calibration equations, are dependent on the nature of the readout equipment used. Specific precautions which must be observed to obtain 0.01% accuracy levels are investigated.