Patent ID: 7104384

Claim:
A method for measuring the diameter of coins in coin validators, comprising: arranging a coin to traverse an electromagnetic field such that the field is at least partially attenuated, also by an upper rim of the coin; the field being generated between at least one transmitter coil and a receiver coil; the transmitter coil periodically providing a short transmission pulse containing a plurality of harmonics, the duration of the pulse being small as compared to the time of coin passage; measuring the maximum attenuation values received by the receiver coil for different time portions of the repeating transmission pulses; forming a time curve (having intensity =f(t)) from the maximum attenuation values extrapolating the time curve to determine a projected curve value at the initiation of the transmission pulse defining the attenuation value at the time σ; comparing the projected curve value determined by extrapolation to a predetermined acceptance band or a predetermined characteristic line for coin diameters for comparison to a stored setting.