Calibration methods for vibration transducers and their uncertainties

A primary calibration system for vibration transducers within the mid- to high-frequency range (20 Hz to 5 kHz) has been introduced at the National Research Laboratory of Metrology, Japan. We used a recently updated method described in the ISO (International Organization for Standardization) report FDIS 16063-11, called the sine-approximation method. The calibration system is also available for conventional methods such as fringe counting and minimum point, as described in International Standard ISO 5347-1. Each method is carried out simultaneously and the results are compared. Signal-processing procedures and the techniques used in the sine-approximation method (phase-unwrapping algorithm, uncertainty calculation and resolution of the A/D converter), are discussed. Relative deviations within 2 x 10(-3) for frequencies of 160 Hz and 800 Hz in the sine-approximation and conventional methods are obtained in the calibration. Problems with the system are also discussed.