Takaya Nagahata

Triaxis magnetoresistive (MR) sensor using permalloy plate of distorting magnetic field

This paper proposes a triaxis magnetoresistive (MR) sensor of detecting not only x- and y-axes magnetic field intensities but also z-axis one, where all fields are based on the sensor coordinate system. Namely, not only azimuth but also angle of elevation of the sensor can be detected from triaxis components of geomagnetic field. The principle is as follows: a permalloy (FeNi) plate is stood aside MR element. The plate distorts magnetic field and generates x- (or y-) component from originally z-directional field. So, the resistance of MR element changes in proportional to z-axis field intensity, provided that other axes intensities are kept constant. By contriving a processing circuit, three axes components can be separately detected.

Micro accelerometer using screen printed BaTiO 3 film on ceramic substrate

The concept of MEMS sensors directly fabricated on a ceramic substrate, which can be used for a package of end product, was proposed. A micro accelerometer utilizing a fringe capacitance formed in a ferroelectric substrate was focused on. For this sensor, in stead of a previously used bulk PZT plate, a screen-printed BaTiO3 (BTO) film on an alumina substrate was employed in this study. A screen-printing method can save the amount of raw material of the film, because a comparatively thick film can be deposited only on a specified area. Moreover, BTO does not contain harmful lead material. The optimal condition for fabricating a BTO film with minimum unwanted surface defects was experimentally searched. The number of defects was decreased by employing a metal barrier of Pt layer underneath BTO, and by setting the annealing temperature for crystallization to a higher value of 1,400°C. A comparatively high relative dielectric constant of εr =926 was achieved. An accelerometer using a BTO film was practically fabricated. The sensitivity of it was estimated as 0.1 pF/G, the order of which is the same as the previously developed accelerometer using a PZT plate.