PROGRESS IN DEVELOPMENT OF CALIBRATION SYSTEMS FOR ANGULAR VIBRATION PICKUPS

This paper addresses technical challenges unresolved in the calibration of angular vibration pickups. Primary and/or comparison calibration systems for angular vibration pickups can not be realised without the angular vibration exciter and the precision angular accelerometer suitable for the transfer standard. Recent attempts made to tackle these technical challenges and related achievements are introduced in this paper. Several air-bearing supported angular exciters had been machined and tested to improve their background angular vibration levels and instability conditions due to pressurised air flow characteristics A gross level of 0.01 radian/s(2)-rms has been achieved. A new angular exciter whose rotational shaft the precision ball bearings support was designed and machined. This new model includes very improved performance characteristics, such as the reduction of size and mass, the extended frequency range, the efficiency of generated angular acceleration per unit current, much improvement of background vibration, and very low total harmonic distortion characteristics. Experimental results regarding those improved factors are presented in Section 2. The general features, including angular vibration-related, mechanical and electrical parameters, are summarised The first prototype angular accelerometer made by B&K has been used for the measurement of angular vibration in this work after it had been calibrated in KRISS, Recent measurement results of the sensitivity of the prototype angular accelerometer are presented in Section 3. The results are used to obtain the fitted model-based frequency response curve used for frequency compensation of measurements. Finally, test results, obtained to examine the transverse sensitivity characteristics, are presented. They reveal several technical issues that shall be resolved in the future.