Field Detection Characteristics of Differential Magnetic Sensor Using Integrated Thin-film MI Sensor Heads.

Abstract

A thin-film MI element made using thin-film integration technology is suitable to fabricate a very small, highly reliable MI sensor head. We developed an integrated thin-film MI sensor head constructed with a combination of a thin-film NiFe MI element and thin-film bias and negative feedback coils using micro-plating technology, in order to solve the problems of an amorphous wire MI head. We also fabricated a differential sensor module using a CMOS multivibrator and a pair of the thin-film MI sensor heads.The differential sensor module using a pair of the thin-film MI heads showed a sensitivity of 25 mV/A/m (2.0V/Oe) with an amplifier having an amplification factor of 10 and good linearity without hysteresis. The sensor module has a thermal drift of less than 0.008%/FS°C at 0 A/m and 0.028%/FS°C at 80 A/m, at temperatures from -25°C to 75°C, and also has good stability in field detection characteristics.