GB1212383A - Moving iron type instruments - Google Patents

Abstract

1,212,383. Moving iron instruments. TOKYO SHIBAURA ELECTRIC CO. Ltd. Feb. 16, 1968 [Feb. 16, 1967; Feb.3, 1968 (3)], No.7750/68. Heading G1Q. In a moving iron type instrument the quantity to be measured is applied to an exciting coil 7 secured within a casing 14 while a fixed vane 9 and a rotatable vane 6 are mounted parallel with one another outside the coil, the rotatable vane being mounted near one end on a shaft 1, to be rotatable about an axis normal to the plane of the vane and the faces of the exciting coil, both vanes being magnetizable by the field produced by current through the coil. The periphery (9a Fig. 3) of the fixed vane has a contour such that the distance between it and the tip 61a of the rotatable vane gradually increases as the rotatable vane turns in response to increases in the quantity being measured. Mutual repulsion between the vanes occurs when N current passes through the coil, but decreases as the rotatable vane turns, until balance with the restoring torque of a spring 5 is achieved. The pointer 4 carried by the rotatable vane then provides the measurement indication. By appropriately shaping the contour of the fixed vane, a linear scale over nearly 360‹ of rotation is achieved. As shown in Fig. 3a, the movable vane 61 may have a radius greater than that of the fixed vane, which progressively reduces. Alternatively Fig. 3b not shown) the movable vane radius may be smaller than that of the fixed vane which progressively increases. In alternative embodiments are variously shown the way in which the periphery of the fixed vane may be varied to ensure that the rotatable vane rotates in the proper initial direction, the addition of a magnetic stop at the end of the travel path, alternative shapes for the rotatable vane, and various types of mounting arrangements for the rotatable and fixed vanes and the exciting coil. The instrument may incorporate two sets of fixed and rotatable names, one at each side of the exciting coil, mounted on a common shaft.