Device for measuring the true speed of motor-driven vehicles

摘要

The invention relates to a device for measuring the true speed of motor-driven vehicles. Two photoelectric optical devices are used, by means of which a location on the roadway is scanned. They move synchronously with the wheels and are situated next to one another. The two photoelectric parts are connected back to back. Because of the nonuniform surface of the roadway, the photocurrents generated do not cancel one another out. A voltage is produced. In the event of a deviation in the vehicle speed from the circumferential speed of the wheels, this voltage vanishes completely or partially, since similar, blurred images now act on the two photo devices. This effect is used to display the speed or to execute control.