Patent ID: 7034495
Filing Date: 2006-04-25
Classification: G01D,G01R

Abstract:
1. An indicating instrument, comprising: a stepping motor having a magnet rotor and a stator provided with two field windings for rotating the magnet rotor; a PWM signal generating device for generating respective PWM signals of an artificial sine-wave and an artificial cosine-wave which are supplied to each of said field windings for rotating said magnet rotor; a pointer rotated in accordance with rotation of said magnet rotor; and a stopper mechanism for stopping rotation of the pointer when said pointer has returned to a zero-reset position, wherein the indicating instrument further comprises: an output port open control device for controlling an output port which outputs the PWM signals to either end of one of said field windings to be in an open state during a period in which the PWM signals supplied to said one of the field windings are in a ground level, at the time when the pointer is rotated to a zero-reset direction by supplying the respective PWM signals which are for rotating said pointer toward the zero-reset direction to each of said field windings; a voltage comparator for comparing magnitude of induced voltage induced in said one of the field windings and previously set threshold value voltage and generating an binary output; and a zero-reset judging device for judging whether said pointer is in the middle of the rotation or said pointer is in contact with said stopper mechanism and the rotation of said pointer is stopped, based on the binary output of said voltage comparator in a period in which said output port is controlled to be in the open state.