PURPOSE: To prevent lowering of the S/N ratio by setting the the radial generating effective length of a wire element mainly forming a radial component to the width of a frequency generating FG magnet and less and by providing about half of a wire element mainly forming a circumferential component or more at the position corresponding nearly to the center of the width of the FG magnet.
CONSTITUTION: An FG coil 10 is formed on a driving circuit board 11 and has a shape where a rectangular zigzag conductor pattern is arranged in a circle so as to face the magnetized surface of an FG magnet via air gap. The radial generating effective length L4 of wires b, d, f, h of the radial component of the conductor pattern is the width W of the FG magnet 7 and less and about half of wire elements a, c, e, g of the circumferential component thereof is provided at the position corresponding nearly to the center of the width of the FG magnet 7. In this manner, there decreases a possibility that the conductor pattern is subject to an adverse effect (fringing effect) by FG magnet ends, and it is possible to control the undulation of an FG output voltage envelope and to prevent lowering of the S/N.
FUJITANI SAKAE
TAKAHASHI HITOSHI
| JP59122778B | ||||
| JPS6285663A | 1987-04-20 |