Construction of Pressure and Photo Sensors Using Ferrite Thick Films

This paper describes the preparation of ferrite thick films (FTFs) and their application to pressure and photo sensors. The FTFs are composed of ferrite powder with various Curie temperatures, polymers and solvents. A magnetic semiconductor fluid mixture was dried at 120°C after printing onto a plastic substrate. A pressure sensor was constructed using a high-Curie temperature FTF and a pressure-sensitive element. The FTF converts pressure into reluctance, and a Hall element reads out small changes in flux as the pressure and reluctance vary. When a photosensing PFTF, which is a low-Curie temperature FTF coated with a radiant flux absorbent, absorbs light energy, the PFTF reluctance increases, effecting an optomagnetic conversion. Thus FTFs can be used for measurement of pressure, position, fluid flow, and luminance.