Head transducer with multiple resistance temperature sensors for head-medium spacing and contact detection

Patent metadata

Field	Value
Publication number	US-9390741-B2
Application number	US-201514720299-A
Country	US
Kind code	B2
Filing date	May 22, 2015
Priority date	Nov 17, 2010
Publication date	Jul 12, 2016
Grant date	Jul 12, 2016

Abstract

A head transducer, configured to interact with a magnetic recording medium, includes a first sensor having a temperature coefficient of resistance (TCR) and configured to produce a first sensor signal, and a second sensor having a TCR and configured to produce a second sensor signal. One of the first and second sensors is situated at or near a close point of the head transducer in relation to the magnetic recording medium, and the other of the first and second sensors spaced away from the close point. Circuitry is configured to combine the first and second sensor signals and produce a combined sensor signal indicative of one or both of a change in head-medium spacing and head-medium contact. Each of the sensors may have a TCR with the same sign (positive or negative) or each sensor may have a TCR with a different sign.

First claim

What is claimed is:

1. An apparatus, comprising:
a head transducer configured to interact with a magnetic recording medium, a low-modulation or a non-modulation head-to-medium interface defined between the head transducer and the medium;
a heater configured to actuate the head transducer;
a modulator coupled to the heater and configured to modulate power supplied to the heater at a modulation frequency of greater than 10 kHz;
a sensor situated at the head transducer and having a temperature coefficient of resistance, the sensor configured to sense for contact between the head transducer and the medium; and
a detector coupled to the sensor, the detector configured to measure a response of the sensor and detect head-medium contact using a detection metric based on a change in resistance of the sensor and a change in heater power.

2. The apparatus of claim 1 , wherein the detector is configured to measure the response of the sensor at the modulation frequency.

3. The apparatus of claim 1 , wherein the detection metric is based on a rate of change in resistance of the sensor and a rate of change in heater power.

4. The apparatus of claim 1 , wherein the detection metric is defined by a ratio ΔR/ΔP, where ΔR is a rate of change in resistance of the sensor and ΔP is a rate of change in heater power.

5. The apparatus of claim 4 , wherein the detector is configured to make an in situ measurement of ΔR/ΔP.

6. The apparatus of claim 1 , wherein the detector comprises a phase sensitive detector.

7. The apparatus of claim 1 , wherein the detector is configured to detect head-medium contact by detecting a minimum of the detection metric.

8. The apparatus of claim 1 , wherein the detector is configured to detect onset of head-medium contact by detecting a deviation from a linear decrease in the detection metric prior to the detection metric reaching a minimum.

9. The apparatus of claim 1 , wherein the sensor is configured to receive DC current, and the detector is configured to measure a change in sensor resistance using DC sensor current.

10. The apparatus of claim 1 , wherein the heater comprises a heater element and a power circuit comprising a digital-to-analog converter (DAC), the power circuit configured to drive the heater element with alternating current at the modulation frequency controlled by the DAC.

11. The apparatus of claim 1 , wherein the head-to-medium interface defines a beyond contact recording head-to-medium interface.

12. A method, comprising:
modulating, at a modulation frequency of greater than 10 kHz, power supplied to a heater of a head transducer configured to interact with a magnetic recording medium, a low-modulation or a non-modulation head-to-medium interface defined between the head transducer and the medium;
sensing for contact between the head transducer and the medium using a sensor having a temperature coefficient of resistance;
measuring a response of the sensor; and
detecting head-medium contact using a detection metric based on a change in resistance of the sensor and a change in heater power.

13. The method of claim 12 , wherein measuring the sensor response comprises measuring the response of the sensor at the modulation frequency.

14. The method of claim 12 , wherein the detection metric is based on a rate of change in resistance of the sensor and a rate of change in heater power.

15. The method of claim 12 , wherein the detection metric is defined by a ratio ΔR/ΔP, where ΔR is a rate of change in resistance of the sensor and ΔP is a rate of change in heater power.

16. The method of claim 15 , wherein:
the method is performed by a disk drive; and
measuring the sensor response comprises making an in situ measurement of ΔR/ΔP by the disk drive.

17. The method of claim 12 , wherein detecting head-medium contact comprises detecting a minimum of the detection metric.

18. The method of claim 12 , further comprising detecting onset of head-medium contact by detecting a deviation from a linear decrease in the detection metric prior to the detection metric reaching a minimum.

19. The method of claim 12 , wherein:
sensing for contact comprises receiving DC current by the sensor; and
measuring the response of the sensor comprises measuring a change in sensor resistance using DC sensor current.

20. The method of claim 12 , wherein the head-to-medium interface defines a beyond contact recording head-to-medium interface.

21. The apparatus of claim 1 , wherein the modulation frequency ranges between about 50 kHz and about 80 kHz.

22. The method of claim 12 , wherein the modulation frequency ranges between about 50 kHz and about 80 kHz.

Assignees

• Seagate Technology Llc
• Saegate Technology Llc

Inventors

• Johnson Michael Thomas
• Liu Dongming
• Lou Huazhou
• Macken Declan
• Stoebe Timothy William
• Wessel James Gary
• Zheng Xuan

Classifications

• G11B5/6076

  Detecting head-disk contact · CPC title

• G01K13/00

  Thermometers specially adapted for specific purposes · CPC title

• G11B5/607 Primary

  using thermal means · CPC title

• G11B5/6011

  Control of flying height · CPC title

• G11B5/024

  Erasing · CPC title