Giant Magnetic Resistive Potentiometers with Strong Potentialities

(CORDIS focus, No. 45, October 2003)

The electromechanical product market, having high application in the automotive industry, is claiming reliable and robust sensors for speed measurements, position registration or  electronic  signals  control, through contactless means. Giant magnetoresistance materials provide a low-cost solution for these kinds of contactless measurements.

Sensors are essential components of electronic control systems commonly found in most applications. The sensors transform physical quantities such as pressure or acceleration into a measurable output or signal that can serve as an input to control systems. Their use is steadily growing, as the safety and performance demand grows, inducing new evolutions in sensor technology. Giant Magnetoresistive   (GMR) sensors compose only one of the several existing types of sensors widely used today; however, they provide unique technical advantages.

GMR sensors are based on Giant Magnetoresistive effects - discovered at the end of the 1980s and mainly of a quantum mechanical nature. Stacks of layers, made up of iron and other magnetic  metals,  have demonstrated a magnetoresistance of more than 50% at low temperatures. The layered structure's thickness is in the order of a few nanometers and they react with particular sensitivity to magnetic fields. While conventional magnetic sensors react to the strength of the magnetic field, GMR sensors respond mainly to field orientation and direction rather than field strength. In this way, potential effects of air gaps, commonly present between a sensor and the magnet, are now negligible.

Under the framework of a European research project, a set of companies developed a copper lead frame sensor sensitive to direction and not to the intensity of the magnetic field. The GMR technology was transferred in the construction of new potentiometers with a high exigency of long life in hard working conditions, such as vibrations and accelerations.   The  Application Specific Integrated Circuit (ASIC) potentiometers incorporate Complementary Metal Oxide Semiconductor (CMOS) technology with various outputs and are mainly, but not exclusively, applicable to the automotive sector.

The GMR sensors have a lot of applications in contactless position registration (e.g. distance, speed, annular speed, rotation) and contactless measurements. GMR potentiometers demonstrate strong advantages over contact or conventional magnetic resistive non-contact potentiometers in terms of higher duration, due to non-mechanical wear and, consequently, lower cost.

Programme: Funded within the 4^th Framework Programme INNOVATION (Specific programme for the dissemination and exploitation of RTD results)

Collaboration sought: Further research or development support; Joint venture agreement; Private-public partnership

CATALAN, Enrique

Navarra De Componentes

Electronicos, S.A. (Nacesa)

Poligono Industrial s/n

E-31500 Tudela

Tel: +34-948-820450

E-mail: ecatalan@piher-nacesa.com