The set up of primary calibration system for shock acceleration in NML

This paper mainly describes Taiwan’s metrology National Measurement Laboratory (NML) to set up and evaluate a shock accelerometer calibration system which follows the ISO 16063-13:2001 standard. The environmental shock testing of electro-acoustics or electronic spare parts, the product packing falling impact, the automobile collision and the helmet impact test and so on are more and more important for quality and safety. In consideration of that, NML has started to establish the primary shock calibration system which calibrates the accelerometer sensitivity and trace to the metric unit since 2009. The shock machine structure comprises three parts; they are the electromagnetic high-speed hammer, airborne hammer and airborne anvil. The shock machine impact source of primary shock calibration system is excited by electromagnetic method.The electromagnetic controller inputs a DC voltage to drive electromagnetic high-speed hammer through the DC power source supply. Then the electromagnetic high-speed hammer impacts an airborne hammer, after that, the airborne hammer proceed to impact the PU rubber which is fixed on the end surface of airborne anvil with rigid body motion way. An accelerometer which is mounted on the other end surface of anvil will output the voltage signal during the instantaneous impact. According to different input DC voltage value and different hardness rubber accelerometer will produce different acceleration and duration time. At the same time the accelerometer displacement is measured by combination of modified Michelson and Mach–Zehnder interferometer and acceleration of the accelerometer is derived through two numerical differentiations and two low-pass digital filtering from the displacement.At present the acceleration capability of primary shock calibration system is from 200 m/s2 to 5000 m/s2, the shock pulse duration time is less than 3 ms. The final evaluated relative expanded uncertainty is less than 1.0% within coverage factor k = 1.96. We shall continue to improve and expand the system acceleration from 100 m/s2 to 10,000 m/s2 for various customers in the future.

► In this study the shock machine impact source of primary system is excited by electromagnetic method. ► The repeatability and reproducibility of shock acceleration are very good. ► The acceleration capability of shock system is from 200 m/s2 to 5000 m/s2 and pulse duration time is less than 3 ms. ► The evaluated relative expanded uncertainty is less than 1.0% within coverage factor k = 1.96. ► We have extended the system acceleration from 200 m/s2 to 10,000 m/s2 since May 2011.