Abstract
The magnetic scale system consisting of a strip shaped scale of magnetic substance with equally periodic recorded magnetic grating and a thin film head of nickel-cobalt ferromagnetic alloy with a pattern of folded line and using magneto-resistance effect, has been developed. The arrangement of the pattern keeps a certain phasic relation with the magnetic grating, and a bias magnetic field is applied in the direction of 0°or 45°to the element line. The structure of the magnetic scale system is such that the head surface and the magnetic grating surface are faced to each other in parallel and the head travels, along the grating keeping a constant clearance. Depending on the direction of the bias magnetic field, an approximately sinusoidal output which is equivalent to the signal of 1/2 or 1 wave length recorded is obtained. After execution of harmonic analysis of this output to find the condition to reduce distortion, clarification of the wave selectivity, evaluation of errors and experiments by trial heads, it has been theoretically and experimentally proved that this magnetic scale system can serve as a digital position readout system with sufficient accuracy and high resolution.
