COIN DIAMETER MEASUREMENT

摘要

A coin diameter measuring circuit uses a pair of coils coupled in the feedback path of an oscillator so that the oscillator frequency is dependent upon the inductances of the coils and the mutual inductance therebetween. The coils are switched between aiding and opposing configuration during the time that a coin passes therebetween, the oscillator frequency in each configuration is measured, and the difference therebetween determined to provide an indication of the mutual inductance of the coils, and thence the diameter of the coin. Preferably, the diameter is determined by the difference between the measured mutual inductance with the coin present and with the coin absent.