Takashi Usuda, Tamio Ishigami, Akihiro Ohta, Hideaki Nozato, Hisayuki Aoyama, Sojun Sato
CURRENT SITUATIONS ON VIBRATION METROLOGY IN JAPAN

We present the current situations and activities related to vibration metrology in Japan. It includes national metrology standard, traceability system, laboratory accreditation scheme, legal metrology regulated by measurement low, and earthquake measurements in Japan.

Wan-Sup Cheung, Cheol-Ung Cheong
ANGLE PRISM-BASED LASER INTERFEROMETER FOR HIGH PRESISION MEASUREMENT OF ANGULAR VIBRATION

This paper introduces a new "angle-prism"-based laser interferometer designed for high-precision measurement of angular vibration. The angle prism, fixed on the centre of the rotating axis, is shown to converter its angular motion into the path difference between two parallel laser beams. Their path difference provides a new way of measuring the angular displacement. This angular displacement measurement method is obviously shown to present a new primary method for the calibration of angular vibration pickups. In comparison to the traditional primary calibration methods in ISO/DIS 16063-15, the suggested one is shown to provide more robustness even for the eccentricity of rotating axis and the unwanted plane motion of the pickup holder. Detailed theoretical and experimental results are presented in this paper.

Gustavo P. Ripper, Guilherme A. Garcia, Ronaldo S. Dias
PRIMARY ACCELEROMETER CALIBRATION PROBLEMS DUE TO VIBRATION EXCITERS

The main purpose of this paper is to discuss the problems that are imposed to primary accelerometer calibration due to the use of imperfect vibration exciters. A review of the main problems is presented. Solutions are discussed and some calibration results are presented.

Torben R. Licht, Sven Erik Salboel
ISO 16063-11: PRIMARY VIBRATION CALIBRATION BY LASER INTERFEROMETRY. EVALUATION OF SINE APPROXIMATION REALISED BY FFT.

Laser interferometry has been used for accelerometer calibration since the late sixties using counters for fringe counting and determination of zeroes at higher frequencies. As the digital techniques evolved during the eighties and nineties it became possible to make more sophisticated treatment of the complex output signals from the interferometer detectors. This was described in the revision of the previous standard ISO 5347-1 resulting in the new ISO 16063-11 in 1999. In this the so-called sine approximation method was introduced. As the input is known to be a sine, a least square fitting of the results calculated from the interferometer output gave good results. The fitting is basically a filtering at the known frequency. Therefore with the advanced high-resolution FFT analysers available today it is logical to use such analysers to do the filtering.
A system has been realised following these ideas. This will be described, and the evaluation of the system’s sensitivity to different imperfections, e.g. noise and gain differences in the interferometer output, will be reported. The evaluation is made using computer generated test signals and the technique can also be used to verify the system whenever needed.

Thorsten Pfister, Lars Büttner, Jürgen Czarske, Richard Schodl, Hartmut Krain
FIBER OPTIC LASER DOPPLER PROBE FOR IN-SITU TIP CLEARANCE AND VIBRATION MONITORING AT TURBO MACHINES

We report about a novel optical method based on laser Doppler techniques for shape and vibration monitoring of fast rotating objects. Tip clearance and vibration measurements on a transonic centrifugal compressor preformed during operation at up to 50,000 rpm and 586 m/s blade tip velocity are presented. The results are in excellent agreement with those of capacitive probes and the achieved accuracy was about 20 µm.