Patent ID: 7529612
Filing Date: 2009-05-05
Classification: G01D,G01P

Abstract:
1. A speedometer and motor vehicle arrangement comprising a motor vehicle and a speedometer installed in said motor vehicle, said motor vehicle comprising at least one revolving shaft, a predetermined quantity of poles equiangularly arranged around the periphery of said at least one revolving shaft, and a sensor device adapted to detect said poles and to output one pulse signal when detected one of said poles, said predetermined quantity being selected from one of the quantity-group of two, four, eight and sixteen; wherein said speedometer comprising: a function storage device having stored therein at least two conversion functions respectively corresponding to at least two of said quantity-group; a selector providing at least two options respectively corresponding to said at least two conversion functions in said function storage device for selection; and a microprocessor electrically connected to said function storage device and said sensor device and adapted to receive and count pulse signals sent by said sensor device during running the at least one revolving shaft of said motor vehicle so as to obtain a counted total value; wherein said microprocessor selects a corresponding conversion function from the at least two conversion functions of said function storage device subject to the option selected through said selector, and then puts said counted total value into the selected corresponding conversion function for calculation to obtain a car speed value, said function storage device has further stored therein a modified parameter that is multiplied by said conversion function when a tire wears after a long use or a large tire is used to substitute for an old tire such that said microprocessor modifies said car speed value subject to said modified parameter to obtain the actual speed of said motor vehicle.