A-C Excited Self Balancing Equipment for Measuring Strain Gauge Balance Outputs.

摘要

A system for measuring the outputs from A-C excited wind tunnel strain gauge balances is described. The system is a current injection nulling type using integrated circuits. It has excellent noise rejection characteristics, is unaffected by thermal E.M.F.'s, does not require power supplies of extremely high stability and gives a high level D-C output (up to 14 Volts.) suitable for driving an analog to digital converter. Two single channel prototypes were constructed. One of these prototypes incorporated an automatic quadrature rebalancing feature which removed the need for the quadrature balance control required by most A-C systems. The prototypes had good resolution, linearity, drift and gain stability characteristics. The cost of the equipment described is surprisingly small considering its performance. The component cost for the prototype with automatic quadrature rebalancing (excluding, output A to D converter and power supplies) was about $100 per channel. (Author)