A coin tester includes a coin sensor which outputs a measurement signal which is influenced by the presence of a coin. A memory device stores an impedence model of the coin sensor and the model representing an expected influence of a coin configuration model on the measurement signal. A processor computes and applies acceptance criteria to determine whether the coin falls within a predetermined coin configuration.
1. A coin tester apparatus comprising:
a broadband signal generator configured to output a driving signal;
a coin sensor coupled to said driving signal, said coin sensor configured to output a measurement signal in response to said driving signal, wherein said measurement signal is configured to be influenced by the presence of a coin;
a computer-readable storage medium configured to store an impedance model of said coin sensor, said impedance model representing an expected influence of at least one coin configuration parameter on said measurement signal; and
a processor configured to compute a coefficient of said model in the presence of said coin and apply acceptance criteria to said coefficient to determine whether said coin falls within a predetermined coin classification.
2. The coin tester apparatus of claim 1 wherein said driving signal comprises a pseudorandom sequence.
3. The coin tester apparatus of claim 1 wherein said driving signal comprises a pseudorandom pulse train.
4. The coin tester apparatus of claim 1 wherein said measurement signals represent an effect of inducing eddy currents in said coin.
5. The coin tester apparatus of claim 1 wherein said measurement signal comprises a digital signal.
6. The coin tester apparatus of claim 1 wherein said coin sensor comprises a coil.
7. The coin tester apparatus of claim 6 wherein said coin configuration radius is less than said coil radius.
8. The coin tester apparatus of claim 6 wherein said impedance model accounts for edge effects of said coin configuration on said expected influence to said measurement signals.
9. The coin tester apparatus of claim 1 wherein said coin sensor comprises a driver coil and a pickup coil.
10. The coin tester apparatus of claim 1 wherein said storage media comprises a non-volatile memory device coupled to said processor.
11. The coin tester apparatus of claim 1 wherein said impedance model is initially computed in the absence of having a physical coin sample.
12. The coin tester apparatus of claim 1 further comprising a temperature sensor configured to sense an ambient temperature, wherein said processor is further configured to compute the effect of said ambient temperature on said coefficient.
13. The coin tester apparatus of claim 1 wherein said coin configuration comprises a total number of layers.
14. The coin tester apparatus of claim 1 wherein said at least one coin configuration parameter comprises permeability of a layer.
15. The coin tester apparatus of claim 1 wherein said at least one coin configuration parameter comprises conductivity of a layer.
16. The coin tester apparatus of claim 1 wherein said at least one coin configuration parameter comprises homogeneity of a layer.
17. The coin tester apparatus of claim 1 wherein said predetermined coin classification comprises a non-genuine coin classification.
18. The coin tester apparatus of claim 1 wherein said at least one coin configuration parameter comprises layer material properties.
19. The coin tester apparatus of claim 1 wherein said at least one coin configuration parameter comprises a lift-off dimension between said coil and said coin.
20. A method of testing a coin using a coin tester, the method comprising:
driving a coin sensor using a broadband signal;
obtaining measurement samples from said coin sensor in the presence of a coin, wherein said measurement samples represent an influence of said coin on a field generated by said coin sensor in response to said driving signal;
solving for, via a processor, coefficients of an impedance model of said coin sensor, said impedance model representing an expected influence of at least one coin configuration parameter on said measurement signal;
applying acceptance criteria to said coefficients to determine whether said coin falls within a predetermined classification of coins.
21. The method of claim 20 wherein said broadband signal comprises a pseudorandom sequence.
22. The method of claim 20 wherein said broadband signal comprises a pseudorandom pulse train.
23. The method of claim 20 wherein said measurement samples represent an effect of inducing eddy currents in said coin.
24. The method of claim 20 wherein said measurement samples comprise a digital signal.
25. The method of claim 20 wherein said coin sensor comprises a coil.
26. The method of claim 25 wherein said coin configuration radius is less than said coil radius.
27. The method of claim 25 wherein said impedance model accounts for edge effects of said coin on said coin sensor.
28. The method of claim 20 wherein said coin sensor comprises a driver coil and a pickup coil.
29. The method of claim 20 wherein said storage media comprises a non-volatile memory device coupled to said processor.
30. The method of claim 20 wherein said impedance model is initially computed in the absence of having a physical coin sample.
31. The method of claim 20 further comprising measuring an ambient temperature using a temperature a temperature sensor and computing the effect of said ambient temperature on said coefficient.
32. The method of claim 20 wherein said at least one coin configuration parameter comprises a total number of layers.
33. The method of claim 20 wherein said at least one coin configuration parameter comprises permeability of a layer.
34. The method of claim 20 wherein said at least one coin configuration parameter comprises conductivity of a layer.
35. The method of claim 20 wherein said at least one coin configuration parameter comprises homogeneity of a layer.
36. The method of claim 20 wherein said predetermined coin classification comprises a non-genuine coin classification.
37. The method of claim 20 wherein said at least one coin configuration parameter comprises layer material properties.
38. The method of claim 20 wherein said at least one coin configuration parameter comprises a lift-off dimension between said coil and said coin.