Determination of motor vehicle speed - involves magnets on transmission shaft reacting with sense coil inside vehicle

摘要

An alternating signal whose frequency is proportional to vehicle speed is induced in a coil by permenant magnets. These magnets are arranged around the circumference of a transmission shaft. Curved permanent magnets (11) of moulded ceramic material are mounted on the circumference of a motor vehicle transmission shaft (10). These magnets induce alternating currents in a coil (13) mounted inside the vehicle on transmission shaft tunnel (12a) adjacent to the magnets. Coil output is applied to both inputs of operational amplifier (15) with no feedback to produce constant peak to peak output square wave. Amplifier is located adjacent to coil to reduce lead lengths to the amplifier.