Derk Jan Adelerhof

Robust giant magnetoresistance sensors

Abstract The giant magnetoresistance (GMR) effect offers interesting new possibilities for sensor applications. A short overview is given of the GMR effect in relation to its application in (automotive and industrial) field sensors. In the past the thermal and magnetic stability could not fulfil the requirements for use in automotive and industrial environments. Recently, a new, robust GMR material system has been developed that can withstand high temperatures (>200°C) and large magnetic fields (>200 kA/m). Using this material, GMR sensor elements have been fabricated and measured. Moreover, preliminary measurements on the first robust GMR sensor with a full Wheatstone-bridge configuration will be presented.

Robust GMR sensors for angle detection and rotation speed sensing

Magnetic sensors for automotive applications based on the giant magnetoresistance (GMR) effect have been developed. These sensors combine many of the advantageous properties of the GMR effect for sensor applications. The sensor characteristics have been optimised with respect to two different applications, namely angular position sensing and rotational speed sensing. Robust GMR sensors with a full Wheatstone-bridge configuration have been fabricated. The thermal and magnetic stability of our GMR sensors are excellent. The sensors show reliable performance at temperatures exceeding 170°C and at large magnetic fields (>200 kA/m). Lifetime tests at elevated temperatures also show very promising results.

New position detectors based on AMR sensors

New angular and linear position detectors for automotive applications have been developed: an absolute linear position detector, a full revolution absolute angular position detector, and a discrete crankshaft position detector. The detectors exploit the capability of anisotropic magnetoresistance (AMR) sensors to sense the direction of a magnetic field, independent of the field strength. This capability gives AMR-based detectors clear cost or tolerance advantages over detectors based on field strength measuring sensors, for instance, inductive sensors, Hall effect sensors, or semiconducting magneto-resistive sensors.

Multitrack thin film heads for the DigaMax/sup TM/ tape storage system

The multichannel servo writer and the data read/write heads of the new DigaMax/sup TM/ tape storage system are discussed. These heads enable a storage capacity of 13 GB (uncompressed) on 300 m of 72 kA/m tape using prerecorded buried servo information for dynamic track following during reading and writing of data.