Device for measuring the velocity of a magnetically receptive object

摘要

A device for measuring the speed of a golf club has a pair of coils spaced a given distance apart with each of the coils forming an oscillating electro-magnetic field which are positioned to interrupt the course of the head of a golf club. When a golf club head successively passes through the first and second oscillating magnetic fields, the natural frequency of the combined fields is altered. A detector circuit including a phase locked loop detects the change in frequency as the club successively pass through the two fields and the time elapsed is measured by a clock and recorded in the memory of a microprocessor which uses the information, along with the given distance between the fields to calculate the speed of the club.