Two methods of approximating nonlinear V-I arc characteristics in electrosurgery

By examining the characteristics of the output voltage (V) versus the output current (I) of the electrical arc during simulated surgery for several input (sinusoidal) voltages, a relationship of these two parameters may possibly be determined. Initially, the relationship is examined by separating each curve into a discharge and a nondischarge region. A linear function is fitted using least squares for each region. By taking the inverse of the slope of each equation estimated, the impedance is studied for increasing input voltage. In addition, by treating each curve as a complete relationship, a nonlinear least squares approximation is executed which estimates the relationship as a third order polynomial. By obtaining a relationship in this manner, one can begin to determine a range of parameters which may be both safe and effective