Electronic angular position encoder apparatus

TLDR: In this article, the angular position of a rotating object is produced by an electronic digital counter that is clocked by a programmable frequency source, and the signal strobes the current count into an output buffer register, resets the counter to zero and then activates the processor.

Abstract: The encoded angular position of a rotating object is produced by an electronic digital counter that is clocked by a programmable frequency source. The source frequency is adjusted as necessary by a processor so that the number of counts registered by the counter is the same for each revolution of the rotating object. A sensor provides a signal once during each revolution of the rotating object when it passes some reference angular position. The signal strobes the current count into an output buffer register, resets the counter to zero, and then activates the processor. The processor in turn, checks if the count in the output buffer register is within a given tolerance of the desired count for one revolution, and then, if necessary, programs the source to the correct frequency. Thus, the number of counts for each revolution will remain approximately constant, independent of the angular velocity. At any point during each revolution of the rotating object, the counter can be strobed and the current count transferred to the output buffer register. This output can be used as a measure of the angular position of the rotating object at the time of the strobe signal.