US Patent 9237921 Devices and techniques for cutting and coagulating tissue

Various forms are directed to systems and methods for driving an end effector coupled to an ultrasonic drive system of a surgical instrument. A generator may generate at least one electrical signal. The at least one electrical signal may be monitored against a first set of logic conditions. When an ultrasonic impedance of the surgical instrument exceeds a threshold impedance, a resonant frequency of the at least one electrical signal may be stored as a baseline frequency. A first response of the generator may be triggered upon the occurrence of either the first set of logic conditions being met or the resonant frequency of the at least one electrical signal differing from the baseline frequency by a baseline deviation threshold.