Yu-Chung Huang, Jiun-Kai Chen, Hsin-Chia Ho, Chung-Sheng Tu, Chao-Jung Chen
THE SET UP OF PRIMARY CALIBRATION SYSTEM FOR SHOCK ACCELERATION IN NML

This paper mainly describes Taiwan's metrology NML (National Measurement Laboratory) 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 lowpass 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 10000 m/s² for various customers in the future.

Gustavo P. Ripper, Cauê D. Ferreira, Dimas B. Teixeira, Ronaldo S. Dias, Giancarlo B. Micheli
A NEW SYSTEM FOR PRIMARY INTERFEROMETRIC CALIBRATION OF VIBRATION TRANSDUCERS AT LOW FREQUENCIES

This paper presents a primary interferometric calibration system that was developed in the Vibration Laboratory at INMETRO for the calibration of vibration transducers and measuring instruments at low frequencies. This system is based on a long-stroke air bearing shaker, and on a data acquisition board. It has been used for calibration of accelerometers and servo-accelerometers within the frequency range from 0.4 Hz to 160 Hz. Optionally, the system can be adapted to calibrate laser vibrometers for their further use as comparison reference transducers. Fully automated calibrations are carried out in compliance with the international standard ISO 16063-11 employing the fringe counting method. Some experimental results obtained with this system will be presented herein.

Qiao Sun, Chenguang Cai
STUDY ON A SIMPLIFIED IMPLEMENTATION OF HOMODYNE TIA METHOD FOR LOW FREQUENCY PRIMARY VIBRATION CALIBRATION

In this paper, the shortcomings and their causes of the conventional homodyne time interval analysis (TIA) method is described with respect to its software algorithm and hardware implementation, based on which a simplified TIA method is proposed with the help of virtual instrument technology. Equipped with an ordinary Michelson interferometer and dual channel synchronous data acquisition card, the primary vibration calibration system using the simplified method can perform measurements of complex sensitivity of accelerometers accurately, meeting the uncertainty requirements laid down in pertaining ISO standard. The validity and accuracy of the simplified TIA method is verified by simulation and comparison experiments with its performance analyzed. This simplified method is recommended to apply in national metrology institute of developing countries and industrial primary vibration calibration labs for its simplified algorithm and low requirements on hardware.

N.Ruetaiworraseth, W.Suntiamorntut, B.Thummawut, P. Rattanangkul
LOW FREQUENCY VIBRATION MONITORING SYSTEM USING WIRELESS SENSOR NETWORK

This paper presents a wireless sensor network technology for low frequency vibration monitoring system. Sensor node collects the data from accelerometer and transmits the data back to base station through wireless communication. The data has been computed and converted into acceleration information that is stored in database. Then users can monitor using a web application. The experiments were carried out by collecting the acceleration data from three-axis accelerometer. The data from each axis was measured and verified by vertically aligning with a Very Low Frequency Primary Calibration System. The experimental parameters are the vibration frequency between 0.4Hz and 10Hz and the amplitude between 0.0981m/s² and 17.6580m/s². The calibration results of the low frequency vibration monitoring system using wireless sensor network are conformed with the wire vibration monitoring system.

Hideaki Nozato, Takashi Usuda, Akihiro Oota, Seiji Okamoto, Ken Yamamoto, Hiroshi Unejima, Kazuaki Kawaguchi, Ishigami Tamio
A ROUND ROBIN TEST OF SHOCK ACCELERATION CALIBRATION AMONG TWO PRIVATE LABORATORIES AND NMIJ

Shock acceleration measurements are required for evaluating product drop tests and automobile collision tests, and the need for precise shock acceleration measurements continue to increase in the Japanese industries. Thus, it is important to confirm the equivalence of measurement technology among manufacturing corporations, private testing laboratories and national metrology institutes. For this purpose, a round robin test of shock acceleration calibration was carried out among the two Japanese private laboratories (“Foresight Techno”, “Shinyei Technology”) and the National Metrology Institute of Japan (NMIJ). In the round robin test, the calibrated sensitivities were compared in shock accelerations from 500 m/s² to 5000 m/s², and agreed with a difference of less than 0.17% and E_n < 0.1.