Improved Strain Gauge Transducer Amplifier for Wind Tunnel Use

摘要

An ac excited self-balancing instrument for measuring low level strain gauge transducer outputs is described. The design of a specific circuit optimized for use with a small wind tunnel force balance is presented with sufficient information to facilitate circuit optimization for other applications. The instrument is intended for applications where the bridge output voltage is below the level that can be conveniently handled by conventional dc amplifier systems. Tests on a prototype instrument showed an input noise in a 0.1 Hz to 0.7 Hz bandwidth of 4 nV RMS, a zero drift of less than 0.1 microvolt per day and negligible drifts.