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Fundamental frequency and period detector

  • US 5,321,350 A
  • Filed: 08/20/1992
  • Issued: 06/14/1994
  • Est. Priority Date: 03/07/1989
  • Status: Expired due to Fees
First Claim
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1. A process for detecting the fundamental frequency of each cycle of a series of contiguous cycles of an alternating current input wave from an alternating current source, wherein each sequential cycle in the series is treated as the current cycle, and the following contiguous cycle is treated as the succeeding cycle, comprising the steps of:

  • (A) starting to integrate the amplitudes of the current cycle of the input wave when the amplitude of the input wave exceeds a given amplitude in a given polarity;

    (B) continuing to integrate the amplitudes of the current cycle of the input wave for a first given period of time which is less than the shortest expected wave period being detected and during said first period of time ignoring the value of the integral;

    (C) continuing to integrate the amplitudes of the current cycle of the input wave for a second period of time until the value of the integral reaches a threshold voltage set above the highest expected end of cycle value of the integral;

    (D) resetting and maintaining the value of the integral at said starting value prior to the input wave again reaching said given amplitude in said given polarity; and

    (E) again starting to integrate the amplitudes of the input wave when the amplitude of the succeeding cycle of the input wave exceeds said given amplitude in said given polarity;

    (F) measuring the time between any given event in the steps (A) through (D) for the current cycle and the corresponding event in the steps (A) through (D) for the succeeding cycle, whereby said measured time represents the period of the fundamental frequency; and

    (G) dividing one by the period of the fundamental frequency to obtain the fundamental frequency.

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