US Patent 11317937 Determining the state of an ultrasonic end effector

Various systems and methods for determining the state of an end effector of an ultrasonic surgical instrument are disclosed. A control circuit can be configured to measure a complex impedance of an ultrasonic electromechanical system including an ultrasonic blade and compare the measured complex impedance to reference complex impedance patterns that each correspond to a state of the end effector. Accordingly, the control circuit can further be configured to determine the state of the end effector according to which of the plurality of reference complex impedance patterns the measured complex impedance corresponds.