A digital display revolution counter.

The precise reading of revolution frequency is subject to reflective surface and permit an accuracy of up to one human error. The movement of the dial in a Parkinson tenth of a litre. The reflective opto-switch for the Cowan dry spirometer or the fly wheel of a cycle ergorevolution rate of the Muller cycle ergometer was meter are two examples from sports medicine where a mounted on a spindle which rotated in synchrony with digital display may be an advaittage to the experimenter. the movement of the pedals (Fig. 2). The reflective This communication describes an inexpensive electronic opto-switch and counter are linked together by a 2-core unit which is adaptable to many requirements for revolscreened fly lead via a 4 pin-Din plug and socket. This ution counting. The brief for the unit included versameans that a single counter may be used for any applitility, a large digital display and an analog output so that cation, resulting in a considerable saving of cost. a permanent oscillographic record may be obtained.