Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
1999-03-05
2001-05-08
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S661000, C324S658000, C324S674000
Reexamination Certificate
active
06229317
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to validators having sensors for evaluating dielectric properties of specialized papers. The invention has particular application for paper currency evaluation and security appear evaluation.
BACKGROUND OF THE INVENTION
Currency validators are designed to receive a banknote and move the banknote through an evaluator channel prior to accepting and storing of the accepted banknote. From time to time a banknote can become jammed in the validator which creates problems, particularly for unsupervised installations.
Jamming of a validator often is due to a wet or high humidity banknote or due to high density paper sometimes found in fraudulent banknotes. These conditions can be recognized by a capacitor sensor.
When the currency bill passes between capacitor electrodes, the capacitor capacitance increases according to the effect of the dielectric properties of the currency note. The deviations from this value will be observed when the samples with higher or lower density are tested in the validator.
Water has a dielectric constant almost ten times higher than the dielectric constant of currency paper. When we, currency paper passes between the capacitor plates, its capacitance is higher than dry paper, the wetter the paper, the larger the capacitance (as compared to the authentic currency paper). Therefore, the capacitive sensor can determine the “humidity” of currency paper and can be used to evaluate the authenticity of the paper, as the currency paper is being evaluated by the validator.
Many validators are used in a generally non-supervised application such as a vending machine. Fraudulent bills often have a high density and if fully processed by a validator, can become jammed or damage the validator.
It is important in validators to reject fraudulent bills, however, it is also important to reject bills which may become jammed in the validator or which may damage the validator. A jammed validator causes the operator problems and also frustrates the user.
Information about the humidity and other parameters of the paper, evaluated by a validator, are important for the validator's operation.
The design of automatic validators makes contradictory demands. The size of the sensor should be small. It should be designed in such a way that it can be placed anywhere inside the validator channel. Rigid mechanical and electrical connections between the sensor elements placed on the opposite sides of the validator channel lead to complex configurations. The measurement results should not significantly vary with wobble of the paper in the validator channel. It is also desirable for the validator to reject bills which are likely to become jammed in the validator.
SUMMARY OF THE INVENTION
The present invention is directed to an arrangement for sensing the dielectric properties of a paper substrate as the paper substrate moves through an evaluation channel.
The arrangement includes a generating electrode on a first side of the channel; a receiving electrode located on the first side of the channel and spaced from the generating electrode; a passive conducting electrode situated on a second side of the channel opposite the first side and overlapping with the generating electrode and the receiving electrode; and a electronic processing arrangement connected to the generating electrode and the receiving electrode which evaluates the signals thereof for changes in the detected capacitance sensed by coupling of the electrodes via the passive conducting electrode.
According to an aspect of the invention, the arrangement further includes a screening electrode located on the first side of the channel and connected to the electronic processing arrangement in a manner to diminish capacitance due to direct coupling of the generating electrode and the receiving electrode.
According to a further aspect of the invention, the generating electrode is provided with an alternating voltage high frequency signal.
According to yet a further aspect of the invention, the passive conducting electrode has no electrical connection with the electronic processing arrangement.
According to yet a further aspect of the invention, the processing arrangement converts any high frequency signal received by the receiving electrode into a d.c. voltage which provides a measure of the capacitive coupling of the generating and receiving electrodes which is greatly changed in accordance with the banknote currency.
According to yet a further aspect of the invention, the electronic processing arrangement uses the d.c. voltage to assess the humidity of a substrate located in the evaluation channel.
The electronic processing arrangement in a preferred aspect of the invention uses a measurement of capacitance for determining the humidity of the substrate and rejects the substrate when the determined humidity is grater than a predetermined level. It also rejects dry fraudulent bills with deviations of the dielectric properties relative to known dielectric properties of authentic bills.
REFERENCES:
patent: 4355300 (1982-10-01), Weber
patent: 5122754 (1992-06-01), Gotaas
patent: 5308992 (1994-05-01), Crane et al.
patent: 5309110 (1994-05-01), O'Neill et al.
patent: 5510779 (1996-04-01), Maltby et al.
patent: 42 32 185 (1994-03-01), None
patent: 0 097 570 (1984-01-01), None
Cashcode Company Inc.
Deb Anjan K
Metjahic Safet
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