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Abstract

An automatic circuit measures electrosurgical generator output and controls in accord with impedance between activated movable bipolar electrodes able to contact tissue. Voltage monitor in parallel and current monitor in series with the electrodes measure instantaneous variations and generate proportional signals. First and second calculators receive the signals and find respectively, by dividing the voltage by current, short circuit impedances and impedances other than short circuit impedances between the electrodes. First and second comparators receive the respective outputs from the first and second calculators and assess them against respective first and second references providing signs of short conditions and assessments of changes in impedance between the electrodes. A logic analyzer receives the signs and assessments and evaluates them to permit the instantaneous starting, operating or stopping of the electrosurgical generator. The electrodes include an instrument and a set of cables with a preselected combined impedance so the maximum instantaneous impedance between the electrodes is less than the preselected combined impedance. The second reference is user adjustable. Switches, associated with each of the voltage monitor and the current monitor, choose the gain applied to the proportional signals respectively therefrom. First and second calculator gain changers receive the signals for setting the range across which those respective signals are used. Methods have steps of monitoring voltage and current, generating signals, dividing the voltage signal by current signal to find short circuit impedance between the electrodes and the instantaneous changes in impedance for other than the short circuit impedance, assessing those findings against references and permitting the starting, operating, or stopping of the electrosurgical generator.

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