# US 10,371,742 B2 · Diagnostics in TMR sensors

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- Number: US 10,371,742 B2
- Document ID: US10371742B2
- Status: Granted
- Kind: B2
- Application number: 15/859,065
- Filed: 2017-12-29
- Published: 2018-04-26
- Granted: 2019-08-06
- Earliest claimed: 2016-06-27
- Assignees: International Business Machines Corporation
- Applicants: International Business Machines Corporation
- Inventors: Robert G. Biskeborn; Wlodzimierz S. Czarnecki; Icko E. T. Iben; Hugo E. Rothuizen
- Web page: https://patentgrep.com/patent/US10371742B2

## CPC

- G01R 31/2829: {Testing of circuits in sensor or actuator systems (testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844)}
- G01R 33/0035: {Calibration of single magnetic sensors, e.g. integrated calibration}
- G01R 33/098: {comprising tunnel junctions, e.g. tunnel magnetoresistance sensors}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A computer-implemented method includes, by one or more processors in electronic communication with a tunneling magnetoresistive sensor, wherein the tunneling magnetoresistive sensor is a component of a magnetic storage drive configured to read magnetic data from a magnetic storage medium, detecting a short across the tunneling magnetoresistive sensor, measuring a change in resistance of the tunneling magnetoresistive sensor, measuring a change in voltage amplitude for the tunneling magnetoresistive sensor, and dividing said change in voltage amplitude by said change in resistance to yield a ratio. The computer-implemented method further includes, responsive to the ratio being greater than a predetermined ratio threshold, determining that the short is caused by a magnetic shunt. A corresponding computer program product and computer system are also disclosed.

## Claims

### Claim 1

A computer-implemented method comprising, by one or more processors in electronic communication with a tunneling magnetoresistive sensor, wherein said tunneling magnetoresistive sensor is a component of a magnetic tape drive configured to read magnetic data from a magnetic tape:
detecting a short across said tunneling magnetoresistive sensor contemporaneously with said tape running across said tunneling magnetoresistive sensor;
measuring a voltage amplitude across said tunneling magnetoresistive sensor as a function of a fractional current through said tunneling magnetoresistive sensor to yield a voltage amplitude data set; and
responsive to said voltage amplitude data set fitting a power law, wherein said power law comprises an exponent, and wherein said exponent is greater than an exponent threshold, determining that said short is caused by a magnetic shunt;
wherein said fractional current is defined as a bias current multiplied by a measured resistance after said short and divided by an initial resistance prior to said short;
wherein said power law comprises an initial voltage amplitude prior to said short multiplied by a ratio raised to said exponent, said ratio comprising said fractional current divided by said bias current;
wherein said exponent threshold is between 2.0 and 2.5; and
responsive determining that said short is caused by said magnetic shunt, setting a bias voltage across said tunneling magnetoresistive sensor to a normal value, said normal value being effective in the absence of said short.