Method and apparatus for testing coins
AssigneeMars, Incorporated
InventorDavid M. Furneaux
Life of this patent
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Abstract
A method and apparatus for testing coins is described. In particular, the resistance introduced into a tuned circuit by the proximity of a coin while it is moving past an inductor of the circuit is determined by changing the amount of phase shift present in a feedback path associated with the circuit and measuring the resulting change in frequency of oscillation, which is dependent upon the resistance in the tune circuit.
Claims16
A method of testing coins using an oscillating tuned circuit which includes an inductor, three parameters of the tuned circuit being interdependent, namely:
- a) the effective resistance in the circuit
- b) the phase of a signal in the circuit, and
- c) the frequency of oscillation of the circuit, the method comprising imposing a change in said phase when a coin is adjacent to the inductor, deriving from the resulting frequency change a value dependent on the effective resistance in the tuned circuit as influenced by the coin, and using the derived value in a coin acceptability check,
- characterised by causing the coin to move past the inductor during said phase change and the resulting frequency change.
Apparatus for testing coins, comprising a tuned circuit including an inductor and means for causing the tuned circuit to oscillate, three parameters of the tuned circuit being interdependent, namely:
- a) the effective resistance in the circuit
- b) the phase of a signal in the circuit, and
- c) the frequency of oscillation of the circuit,
- means for positioning a coin adjacent to said inductor so as to influence the effective resistance in the tuned circuit,
- means for imposing a change in said phase,
- means for deriving from the resulting change in said frequency a value dependent on the effective resistance in the tuned circuit as influenced by the coin, and
- means for using the derived value in a coin acceptability check,
- characterised in that the means for positioning the coin is a coin passageway arranged to permit the coin to move freely past the inductor while said phase change is being imposed.
Dependencies are inferred from the claim text.