On reciprocating machinery (diesel engine, pump) or any cyclic rotating devices (generator, compressor, transmission), the cause of vibrations often comes from the fluctuations of the angular speed.
The analysis of the instantaneous angular speed inside each shaft revolution provides essential information. The common way to measure such instantaneous velocity is to install a black & white stripe or disk on the shaft as well as an accurate tachometer.
The TAC-O02, an interference-free and noncontact high speed optical fiber sensor providing up to to 50000 imp/sec from an optical fiber probe is the perfect tool for such as measurement.