Browse Prior Art Database

Hall Probe Sensor Array for Magnetic Card Read-Out

IP.com Disclosure Number: IPCOM000113178D
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+4]

Abstract

Present technology allows for reading of magnetically encoded strips on magnetic cards, i.e., credit, entry etc, by the location of maximum or minimum flux transitions normal to the surface of the card. The electrical signal from this transition is dependent on the speed of insertion and/or withdrawal in the card reader, that is, the change in flux with respect to time. In addition, the signal is dependent on the physical condition of the card, e.g., bent, warped, contaminated etc., cards generally have decreased signal strength, since read-out is dynamic in nature.

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This is the abbreviated version, containing approximately 52% of the total text.

Hall Probe Sensor Array for Magnetic Card Read-Out

      Present technology allows for reading of magnetically encoded
strips on magnetic cards, i.e., credit, entry etc, by the location of
maximum or minimum flux transitions normal to the surface of the
card.  The electrical signal from this transition is dependent on the
speed of insertion and/or withdrawal in the card reader, that is, the
change in flux with respect to time.  In addition, the signal is
dependent on the physical condition of the card, e.g., bent, warped,
contaminated etc., cards generally have decreased signal strength,
since  read-out is dynamic in nature.

      Disclosed is a device that allows for magnetic card read-out
utilizing an array of Hall probes that are fabricated utilizing
standard semiconductor processing techniques.  The read-out medium
for the Hall probes is made of a vacuum deposited amorphous magnetic
film such as GdTbFeCo that is deposited with a perpendicular magnetic
anisotropy.

      The magnetic squareness and coercivity (Hc) of the hall sensors
can be adjusted to suit the application by varying the composition.
A hall sensor with a square hysteresis loop would latch in one of two
distinct remnant states that are normal to the film and have
opposite magnetization.  The perpendicular component of the fringing
field of a data bit (Hp) would  flip the magnetization of the
adjacent hall element in the same direction when Hp>Hc.  A
perpendicular erase field,provided by a high moment magnetic stripe
on the card or in the device,would reset the hall sensors to prevent
indeterminate states and memory of previous entries.  The memory
feature could be used to lock out repeat ent...