Logo PTB

“Growth with High Tech – or helping clever customers do cool things with XMR sensors

Kolloquium der Abteilung 2

The magnetoresistive effect is best known from the read heads of computer hard discs or from magnetic memory (MRAM) applications, but it is also well suited to uses in sensor technology. It has a long history, being first discovered in 1857 by Lord Kelvin. However, the MR-effect did not experience widespread use until the early 1980s, when the first MR-based read heads were implemented in hard disc drives. The first industrial applications for MR-based sensors followed at the beginning of the 1990s, since when the number of applications has increased dramatically. The applications are not only limited to terrestrial use – MR sensors are used to control the electric drives used on “Curiosity”, the Planetary Rover that landed on Mars in August 2012 and has now spent 5 years underway.

 The MR effect is not only used successfully for sensors to measure position or angle, but also for measuring electrical current and magnetic fields. MR sensors offer a number of benefits compared to other sensor technologies. They are more compact than inductive sensors and are more robust than optical encoders, being largely unsusceptible to oil, water and other contaminants. They can be applied over a wider temperature range and with less demanding assembly tolerances. This makes MR sensors particularly well suited to applications with limited available space and demanding operating conditions. Recent developments, such as the trend to electro-mobility and also the Industry 4.0 initiative, are generating additional demands, with respect to even more compact dimensions and energy efficient operation. This combination of demands is leading to the more intensive use of magnetic sensor principles, compared to optical, inductive or capacitive principles.

 This presentation will describe the basic physical principles and will outline the numerous different measurement tasks that are possible and will compare the MR-effect with other physical principles that are used for angle and position sensors.  Numerous practical applications will be described and the presentation concludes with an outlook regarding future sensor applications within the Internet of Things and outlines interesting fields of research for the characterization of magnetic sensors based on the magnetoresistive effect and the associated measurement scales.