CONTACTLESS POTENTIOMETER BASED ON GIANT MAGNETORESISTANCE SENSORS

We present a magnetic sensor based on the giant magnetoresistance (GMR ) effect, which can be used as a contactless potentiometer. The sensor consists of a novel GMR sensor scheme with an artificial antiferromag netic subsystem. The sensor gives a sinusoidal signal in dependence on the direction of a rotating external magnetic field H-rot. With two s ensors in a planar setup, the whole 360 degrees angle range can easily be covered. The amplitude Delta R/R of the signal is about 5%. The si gnal amplitude runs through a very flat maximum and changes only by 5% within a field range of about 4.4-27.2 kA/m. This large field range, the magnetic window (H-w), is the main advantage of this sensor compar ed to other magnetic sensor physical principles for contactless potent iometers. Therefore, large mounting tolerances and variations in the f ield strength of the rotating permanent magnet can be accepted. The te mperature dependence of the sensor is linear both for the ground resis tance (R-0) and the signal amplitude (Delta R), allowing simple and ef fective electronic temperature compensation. The sensor can be operate d up to 150 degrees C. (C) 1997 American Institute of Physics.