COIN EXAMINATION APPARATUS EMPLOYING AN RL RELAXATION OSCILLATOR

摘要

An apparatus for coin testing including an improved inductive sensing arrangement. A coin to be tested is passed through an electromagnetic field produced by an inductor which is part of a resistor-inductor type relaxation oscillator operating at a frequency in the range of approximately 100 kHz to 1 MHz. The resulting shift in frequency of the relaxation oscillator forms the basis for testing the coin. The resistor-inductor relaxation oscillator has a linear frequency response with respect to changes in the effective inductance in the oscillator over a range of inductance suitable for testing coins and produces an output signal which is digital in nature and requires no amplitude discrimination or shaping to be suitable for counting.