Induction sensor using printed circuit

Abstract

The present invention provides a planar induction sensor for sensing of security features of documents having changing magnetic and (or) conducting properties is of a multilayer printed circuit board design. The sensor comprises a planar current transformer with a spiral-type primary coils and one or several turns of secondary coil in an adjacent layer of the printed circuit board. The secondary coil of the current transformer is connected to an operating coil, which is situated at a sensing edge of the sensor. The operating coil can be formed by external wires or can be incorporated in the circuit board of the current transformer. When a security element, made from the magnetic or conductive material moves past the sensing edge of the sensor, a change in inductance of the induction sensor occurs. In a preferred embodiment, two induction sensors with individual associated electronic circuits were located on opposite sides of validator channel. Analysis of both signals from the sensors allows correction of the signal to reduce variation caused by changing distance of the security document from each sensor.

Description

technical field [0001] The present invention relates to an inductive sensor for detecting magnetic and conductive elements passing in the vicinity of the active part of a planar inductive sensor. This planar inductive sensor is particularly suitable for authentication devices used to verify the authenticity of documents such as banknotes with magnetic or conductive security elements. Background technique [0002] In the case of security documents such as banknotes, many of which include different security elements including security dyes, security inks and security threads. These security elements generally have detectable magnetic and / or conductive properties. Sometimes counterfeit documents will have magnetic properties in areas where the authentic document does not, so that these elements and their positions can be measured to determine if the banknote is genuine. [0003] There are currently several types of inductive sensors that are capable of detecting the magnetic ...

AI Technical Summary

Problems solved by technology

The main problem with this approach is that the two sensing parts are connected by relatively long wires carrying high frequency signals

and these wires will add sources of interference

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