The laser torsional vibrometer: A step forward in rotating machinery diagnostics

This paper describes the development of the laser torsional vibrometer since its invention at the Institute of Sound and Vibration Research, University of Southampton in 1983. The theory of laser vibrometry measurements is first introduced together with a description of early attempts to harness the technology for torsional vibration measurement through use of a cross-beam laser Doppler velocimeter. This is followed by the theory for the laser torsional vibrometer itself. A measurements section then describes results taken by the first prototype built at ISVR and compares these with the cross-beam velocimeter in a controlled experiment. Further tests with the commercial version of the instrument, produced by Bruel and Kjaer Ltd as the Type 2523 Laser Torsional Vibration Meter, are described, involving checks with the well known Hooke's joint. Results from an investigation into torsional vibration damper performance are also presented. The sensitivity of the instrument is dealt with in detail before practical considerations are described. The laser torsional vibrometer has solved a particularly difficult metrology problem and is now used on a worldwide basis. It is rapidly gaining acceptance as the standard means of measuring torsional vibration. (C) 1996 Academic Press Limited