Shock Acceleration

NIST is developing a shock-measurement system optimized for calibrating miniature digital shock sensors that employs a novel approach to system calibration. The system consists of a pendulum exciter, a test block that slides on a V-channel when struck by the pendulum, and a commercial laser-Doppler Velocimeter (LDV). One or more miniature shock sensors are mounted on the test block and the velocity of the test block from before the pendulum strike to after the test block comes to rest is measured by the LDV. Following the shock event the velocity time series is differentiated and filtered off-line to determine the acceleration time series. Rather than calibrate the individual components of the shock measurement system as is customary, the calibration factor is determined as the ratio of the displacement of the test block with SI traceable gauge blocks and a caliper to the displacement obtained by integrating the velocity time series. The advantages of this approach have recently been demonstrated with a bread-board set up and assembly of the final system is commencing.