Method of determining the rotational speed of a brushless DC-motor
 A method of determining the rotational speed of a three-phase brushless DC-motor, which comprises scanning at least one signal trace disposed on a revolving rotor of a three-phase brushless DC-motor by means of three sensors, each emitting a signal having two possible signal states, the signal trace and the sensors being of such construction and arrangement that eight values are realized by a logical combination of the two possible signal states, respectively, of the three sensors; detecting the rotor position with six of the values; and determining the rotational speed with the other two values. 
Heidelberger Druckmaschinen AG
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inventional inventional inventional inventional
Peter T. Helmut Jurgen Michael
Blaser Meyer Maass Kruger