An ultrasonic device may include an electromechanical ultrasonic system defined by a predetermined resonant frequency, the electromechanical ultrasonic system further including an ultrasonic transducer coupled to an ultrasonic blade. A method of delivering energy to the ultrasonic device may include measuring a complex impedance of the ultrasonic blade coupled to the ultrasonic transducer, comparing the measured complex impedance to stored values of complex impedance patterns associated with ultrasonic blade functions, and applying, an algorithm to control a power output to the ultrasonic transducer based on the comparison. The method may further include delivering energy to the ultrasonic device based on a state or condition of an end effector, in which the state or condition of the end effector corresponds to a state of only sealing a tissue or of spot coagulating the tissue.
