GB2470736A

GB2470736A - Counterfeit coin detector

Info

Publication number: GB2470736A
Application number: GB0909451A
Authority: GB
Inventors: Leonard Marmaduke Steele
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-06-02
Filing date: 2009-06-02
Publication date: 2010-12-08
Also published as: GB0909451D0

Abstract

An apparatus used to identify forged, counterfeit and fake coins where a remote inductive element 4 is arranged to fit a test coin 6 and a genuine coin 5 is housed in an enclosure 1 where it is fitted to an inductive element 3. The inductive responses of the coins 5, 6 are measured and if the responses balance using a bridge circuit 2, then the test coin 6 is considered to be valid. The apparatus can give audible and visual indications of the result. The inductive elements 3, 4 are preferably ferrite pot-core inductors which are driven by the same sine-wave generator.

Description

Determining Forged Coins from a Unknown Batch In a method and apparatus for determining the exact metallic property and therefore the authenticity of a coin, and inductive technique is employed wherein a genuine coin housed within an enclosure is balanced against and unknown coin using a remote probe.

Inductive techniques for recognising foreign coins are well established, but suffer from the disadvantage that the air gap between the inductive element and the coin cause significant errors when identifying counterfeit coins.

An object of this invention is to minimise these errors and balance the unknown coin within an inductive bridge such an arrangement allows significant amplification around any minute changes in the alloy composition of a coin.

The magnetic flux generated by a coil is focused onto a sample by use of a ferrite pot core that fits within the rim of the coin.

A preferred embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows the relationship between the enclosure and the remote probe.

Figure 2 shows the internal configuration on the electronics.

Description

This invention relates to an apparatus for determining the exact alloy of a coin employing an inductive technique whereby the sample coin is compared with a reference coin of the same type within an enclosure.

Another object of the invention is to supply a fast indication as to the authenticity of a corn Accordingly, one aspect of the invention relates to employing an inductive technique wherein the sample is compared against a reference and wherein associated apparatus is zeroed or brought into precise balance.

In a preferred arrangement, the magnetic flux generated by the coil is focused using a ferrite pot core. The undulations on the surface of the coin cause significant errors therefore the ferrite core must fit within the rim of a coin only separated by a thin insulating film.

In order that the invention may be more fully understood, the preferred embodiment of the apparatus will now be described by way of example to the accompanying drawings in which; Fig 1 is a diagrammatic view of the apparatus in accordance with the invention.

Fig 2 is a functional view of the apparatus Referring firstly to Fig 1 An enclosure 1 has housed within it a sample coin 5 placed upon one face Is the inductive element 3 between the ferrite core and the coin (5) is an insulating film (7) the electronics module (2) houses the circuit in accordance to Fig 2 From the enclosure is a screened cable (9) a remote probe assembly is connected to the far end The remote assembly consists of a ferrite core (4) the insulating film (8) which can be placed on the unknown coin (6).

Referring to Fig 2 An inductive bridge is constructed and housed within the electronics module Fig 1(2) The reference coin and associated ferrite core (1) form one half of the bridge the unknown coin and Remote probe form the other half (2) resistors (3) and (4) set an equal phase shift between both arms of the bridge it is critical that both arms are the same and in precise balance therefore a potentiometer (5) Is provided to ensure this.

A current of above 1 2OmA is required in both coils to ensure that sufficient penetration if eddy currents within the coin. A high power unity gain amplifier (6) is used to ensure this. The unity gain amplifier is powered by a precision sine wave generator (7) operating at typically 10 kHz.

The output of the bridge is applied to an instrumentation amplifier (8) any minute changes in the balance of the bridge are amplified and processed by a series of voltage comparators housed within the electronics control module (9) an invalid LED (10) is illuminated if the coin is Forged and Valid LED (11) is illuminated if it is genuine.

Claims

CLAIMS1 A method of determining the metallic composition of a coin whereby a genuine coin is balanced against a forged coin.
2 A method according to claim 1 where a genuine coin is housed within an enclosure.
3 A method according to claims 1 and 2 where a remote probe is arranged to test the authenticity of a Coin.
4 A method according to claims I 2 and 3 where the sensing cores can be placed within the rim of the coin.
A method according to the preceding claims where the reference inductive element and the remote inductive element are driven by the same sine wave.
6 An apparatus according to claim 1 where a bridge is brought into balance by the precise adjustment of inductance, resistance and capacitance in each arm of the bridge.
7 A hand held apparatus for the purpose of establishing the authenticity of a coin.