Authenticity checking of coins using inductive effect - in which resonance is triggered in coil to provide signal for comparison to generate pulse of width specific to coin

摘要

A sensor system is built into a guide channel along which coins are rolled. Built into the channel is an electromagnetic coil (10) with resistance and inductance. The field is activated by switching an FET (11) and a voltage regulator maintains a constant supply voltage. The presence of a metallic coil causes a voltage to be induced that is applied to an amplifier (1) that has integrator (2) feedback. The generated ringing pulses of the induced voltage have a shorter period than the integrator time constant. The pulses are amplified and fed to a comparator (3) for comparison with a reference voltage VREF. The period of the outpt is used to access a set of tabulated values to identify the coin. USE/ADVANTAGE - Simple and reliable identification process.