Mars, Incorporated

Keith R Mountfield

Mark H Kryder

Robert E Jones, Jr

Javier I Guzman

Elwood E Barnes

A new and improved unshielded horizontal magnetoresistive head is disclosed which utilizes multiple pairs of magnetoresistive elements. The present invention provides a device which is characterized by reduced output signal undershoot amplitudes, and an increased central peak pulse amplitude, while not significantly affecting the resolution of the device. The device is also characterized by increased signal to noise and signal to interference ratios. Magnetoresistive elements utilized in the device may be fabricated and/or manufactured by simplified processes, resulting in fabrication, manufacturing and cost benefits for the magnetoresistive head. Any number of additional magnetoresistive element pairs may be utilized dependent on the accuracy and resolution required by the specific application.

Unshielded magnetoresistive head with multiple pairs of sensing elements

An apparatus and method for detecting magnetic data on media is disclosed which utilizes an array or arrays of horizontal magnetoresistive sensors. The present invention detects the pitch or separation of magnetic transition data on the magnetic medium under test, and generates a signal that is independent of the velocity of the medium. In one embodiment, the magnetoresistive sensors employed in an array are spaced apart a distance which corresponds to the separation of magnetic transition data of interest, and the output of each sensor is connected to a voltage adder. The signal from the voltage adder is at a maximum when the separation of the magnetic transition data corresponds to the sensor separation. A comparator is connected to the output of the voltage adder, and compares the voltage adder output to a predetermined threshold voltage before indicating that a medium having a particular magnetic transition data pattern is detected. Alternate embodiments contemplate connecting linear circuitry, digital circuitry, fuzzy logic or other electronic circuitry to the array of magnetoresistive sensors. An apparatus according to the present invention is accurate, requires a minimum of parts, is simple and inexpensive to manufacture, and may be employed in a currency validator, magnetic card reader or the like.

Horizontal magnetoresistive head apparatus and method for detecting

An unshielded horizontal magnetoresistive head for magnetic sensing and reading devices. The horizontal unshielded magnetoresistive head is comprised of two magnetoresistive elements separated by a gap and a conductive cross member which electrically connects the magnetoresistive elements together and to a common electrical point such as system ground. A differential voltage sensing circuit is connected across the magnetoresistive elements for sensing voltage variations when magnetic data is sensed by the head. The present invention further facilitates a more simplified fabrication process which results in cost savings and more efficient fabrication methods and procedures.

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Pittsburgh, PA, United States of America

Keith R Mountfield