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Ship's log and speedometer

  • US 4,159,644 A
  • Filed: 05/15/1978
  • Issued: 07/03/1979
  • Est. Priority Date: 05/15/1978
  • Status: Expired due to Term
First Claim
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1. Non-contacting apparatus for measuring the revolutions of a rotating shaft comprising:

  • bearing means supporting said shaft for rotation about its axis;

    a permanent magnet mounted on said shaft with an axis of magnetization oriented substantially transversely with respect to the axis of said shaft;

    electro-magnetic sensing means comprising a balanced magnetometer assembly physically spaced from said magnet and adapted to generate a cyclic electrical output signal whose amplitude and polarity are functions solely of the angular position of said magnet; and

    means responsive to said output signal for counting and indicating said revolutions.

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