State change detector using inductive or capacitive pickup system - has probe changing its switching state as wheel is rolled along path

摘要

The state of the probe is controlled by the position of a diec element or wheel(2) adjacent to it which is marked with a tapering wedge (1). The probe (7) can move in its working position, so that the time during which it is operated by the disc or wheel (2) has a circular inner wedge on the disc or wheel (2) has a circular inner edge and its outer edge approaches the centre of the disc as the disc rotates. As the wheel is rotated during measurement of a distance the probe is switched on and off and a series of pulses is produced whose frequency is proportional to the speed of rotation of the wheel.