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Method and apparatus for reducing jitter in a digitizer or other transducer

  • US 4,791,592 A
  • Filed: 04/30/1986
  • Issued: 12/13/1988
  • Est. Priority Date: 04/30/1986
  • Status: Expired due to Term
First Claim
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1. A method of filtering jitter from measured transducer output values, the method comprising the steps of:

  • (a) transducing a physical phenomenon to produce an unfiltered output;

    (b) repeatedly measuring the unfiltered output to produce a sequence of unfiltered output values;

    (c) maintaining a previous filtered output value obtained in accordance with steps (e) and (f) recited below;

    (d) determining if the most recent unfiltered output value from step (b) lies within a preselected interval about the previous filtered output value maintained in step (c);

    (e) subsequent to step (d) and whenever the determination of step (d) is in the negative, discarding the previous filtered output value maintained in step (c) and substituting therefor the most recent unfiltered output value of step (b);

    (f) subsequent to step (d) and whenever the determination of step (d) is in the affirmative, replacing the previous filtered output value maintained in step (c) with a value equal to a first percentage of the most recent unfiltered value of step (b) added to a second percentage of the previous filtered value maintained in step (c), the first and second percentages summing to one hundred percent and the first percentage varying from zero percent to one hundred percent as the most recent unfiltered value of step (b) changes in value from the value of the previous filtered output value maintained in step (c) to the value of an endpoint of the selected interval of step (d); and

    (g) subsequent to steps (e) and (f), supplying the filtered value of step (c) as the measured transducer output value.

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