Makes light work of speed checks
ROTATIONAL speed can be measured either optically or by direct contact using a tachometer from a St Albans-based firm.
The Graham & White DT2236 meter incorporates an SLR optical system which projects a visible light beam on to the rotating target, from up to 1m (3ft) distance. Light pulses returned from reflective tape attached to the target are counted, and used to calculate the speed.
Rotational speeds from 5-99,999rpm can be displayed on the DT2236 meter, which is priced at £149 (01727-861110).