Instrumentation techniques for measuring large, high rate strains with foil resistance strain gages

Instrumentation for measuring large, high strain rate strains with foil type resistance strain gages was designed, constructed, and evaluated in terms of signal to noise ratio, strain rate response characteristics, and overall accuracy of measurement. Complete design procedures and component specifications for the Wheatstone bridge, pulsed power supply, and control circuit, as well as calibration and data reduction procedures are included. The apparatus has a signal to noise ratio up to six times that which can be obtained with conventional strain gage signal conditioning equipment, and can measure to plus/minus 0.20 strain at strain rates up to 10 to the 4th power s to the -1 power over a 35 to 200 microsecond sample time. Pulsed power density limits for annealed constantan foil strain gages were also investigated and are reported.