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Acoustic tachometer

  • US 4,452,079 A
  • Filed: 09/27/1982
  • Issued: 06/05/1984
  • Est. Priority Date: 09/27/1982
  • Status: Expired due to Fees
First Claim
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1. Apparatus for measuring the operating speed of a device, said device producing sound waves having components at a number of frequencies, wherein the frequency at which the sound waves are of maximum amplitude is systematically related to said operating speed, said frequency of said maximum occurring in a frequency spectrum of interest which is systematically related to a predetermined range of operating speeds, said apparatus comprisingtransducer means responsive to said sound waves for producing systematically related electrical signals;

  • a band-pass filter having a variable center frequency and a narrow pass band for selectively passing the components of said electrical signals having frequencies within said pass band, said variable center frequency corresponding to the amplitude of an applied control signal;

    sweep means for applying said control signal to said filter with a varying amplitude for cyclically sweeping said center frequency of said filter through said frequency spectrum of interest;

    peak detecting means for selectively detecting the maximum amplitude of the output of said filter during respective sweeping cycles; and

    measuring means responsive to said peak detecting means and said sweep means for measuring the amplitude of said control signal when said peak detecting means detects said maximum amplitude, thereby providing an indication of said operating speed.

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