30 May 1997

Hand-held meter monitors shaft

SHAFT speeds can be checked with the hand-held PT-231 optical tachometer from Graham & White Instruments.

Used to measure speeds from 5-99,999rpm, the instrument operates by directing a beam of light onto a piece of reflective tape, fitted onto the shaft.

Reflected light pulses are counted and the rotational speed is displayed. The company says the beam of light is effective from a distance of 60cm, and accuracy is within one rpm at 5000rpm.

The tachometer is supplied with protective case, batteries and reflective tape, and costs £128. (01727-861110).