Prospects for speckle-pattern based vibration sensing in electromechanical equipment

Condition monitoring of heavy electromechanical equipment such as electrical switchgear is increasingly reliant on vibration sensing technology. Of applicable optical methods, electronic speckle-pattern interferometry (ESPI) is established as a sensitive whole-field technique for monitoring surface vibration. Such systems incorporate video signal processing to offer automated real-time measurement of vibrational amplitude and phase. Speckle fluctuations, often a source of noise, may also be utilized within multimode fibres for fast one-dimensional sensing. This paper discusses the optoelectronic processing behind such speckle metrologies, and reviews technological developments suited to vibration monitoring in extreme electromechanical environments. Advances in the technology, particularly in the areas of transient and multiple-frequency response, will be driven by the application and the ability to fabricate industry-compatible system prototypes.