Isolation of a piezoresistive accelerometer used in high acceleration tests.

摘要

Both uniaxial and triaxial shock isolation techniques for a piezoresistive accelerometer have been developed for pyroshock and impact tests. The uniaxial shock isolation technique has demonstrated acceptable characteristics for a temperature range of (minus)50(degree)F to +186(degree)F and a frequency bandwidth of DC to 10 kHz. The triaxial shock isolation technique has demonstrated acceptable results for a temperature range of (minus)50(degree)F to 70(degree)F and a frequency bandwidth of DC to 10 kHz. These temperature ranges, that are beyond the accelerometer manufacturer's operational limits of (minus)30(degree)F and +150(degree)F, required the calibration of accelerometers at high shock levels and at the temperature extremes of (minus)50(degree)F and +160(degree)F. The purposes of these calibrations were to insure that the accelerometers operated at the field test temperatures and to provide an accelerometer sensitivity at each test temperature. Since there is no NIST-traceable (National Institute of Standards and Technology traceable) calibration capability at shock levels of 5,000 g - 15,000 g for the temperature extremes of (minus)50(degree)F and +160(degree)F, a method for calibrating and certifying the Hopkinson bar with a transfer standard was developed. Time domain and frequency domain results are given that characterize the Hopkinson bar. The NIST-traceable accuracy for the standard accelerometer in shock is (plus minus)5%. The Hopkinson bar has been certified by the Sandia Secondary Standards Division with an uncertainty of 6%.