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Device for monitoring a neutral electrode during HF surgery

  • US 6,275,786 B1
  • Filed: 12/22/1999
  • Issued: 08/14/2001
  • Est. Priority Date: 04/10/1997
  • Status: Expired due to Term
First Claim
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1. A device for monitoring the application of a unipolar neutral electrode with two separated neutral electrode partial surfaces during unipolar HF surgery, whereby the two separated neutral electrode partial surfaces are respectively connected via a HF input capacitor to source terminal, said device comprising:

  • an impedance sensor comprising an excitation source that excites a resonant circuit by variable frequencies in a range which includes a resonant frequency, the resonant circuit being provided by the HF capacitors to source terminal and a secondary coil of a transformer, the secondary coil being connected between the two separated neutral electrode partial surfaces and serving as excitation input, and the resonant circuit being attenuated by transition impedances of the two separated neutral electrode partial surfaces connected in series to a patients tissues;

    a peak value detector which detects an alternating voltage peak value at the resonant frequency via the secondary coil of the transformer;

    a voltage controlled oscillator for providing the excitation source, said voltage controlled oscillator being controlled by a ramp generator;

    a current asymmetry sensor comprising a compensating transformer, said current asymmetry sensor detecting a mean value of a periodic quantity of a difference in currents flowing through the two separated neutral electrode partial surfaces during the deactivation of a HF output signal; and

    an electronic control and analysis means, said electronic control and analysis means deriving a signal for the quality of the application of the unipolar neutral electrode from signals of the impedance sensor and of the current asymmetry sensor.

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