THE CONSTRUCTION AND CALIBRATION OF AN INEXPENSIVE PVDF STRESS GAUGE FOR FAST PRESSURE MEASUREMENTS

Commercial polyvinylidene difluoride (PVDF) piezoelectric film was use d to produce an inexpensive stress sensor with good spatial accuracy t o measure the stress state behind a shock wave. The PVDF gauge was fou nd to respond within similar to 100 ns to fast-rising pulses. Since th e gauge is piezoelectric no power supply or amplifier was required for the gauge. In order to measure fast signals the gauge was found to pe rform best in the current mode in which the derivative of the stress w as measured; the signal was then numerically integrated, Signals were recorded on a fast (100 MS s(-1)) storage oscilloscope. The gauges wer e calibrated against thin-foil manganin stress gauges to similar to 2% . An application in which the gauges were used to measure the response of an alumina to shock loading is described.