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Apparatus and method for locating a medical tube in the body of a patient

  • US 5,622,169 A
  • Filed: 09/14/1994
  • Issued: 04/22/1997
  • Est. Priority Date: 09/14/1993
  • Status: Expired due to Term
First Claim
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1. An apparatus for detecting the location of a magnet associated with a medical tube within the body of a patient, comprising:

  • means for sensing a first static magnetic field strength at a first distance from the magnet and providing a first sensor signal which is a function of the first static magnetic field strength;

    means for sensing a second static magnetic field strength at a second distance from the magnet and providing a second sensor signal which is a function of the second static magnetic field strength, wherein the second distance is greater than the first distance;

    means for receiving the first sensor signal and providing a first detection signal which is a function of the first sensor signal, wherein the means for receiving the first sensor signal and providing the first detection signal comprises a first amplifier for receiving the first sensor signal and providing a first amplified signal which is proportional to the first sensor signal, and a first integrator for receiving the first amplified signal and providing the first detection signal;

    means for receiving the second sensor signal and providing a second detection signal which is a function of the second sensor signal, wherein the means for receiving the second sensor signal and providing the second detection signal comprises a second amplifier for receiving the second sensor signal and providing a second amplified signal which is proportional to the second sensor signal, and a second integrator for receiving the second amplified signal and providing the second detection signal;

    means for receiving the first and second detection signals and providing a differential signal which is a function of the difference between the first detection signal and the second detection signal; and

    means for receiving and indicating a value for the differential signal.

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