An ultrasonic device may include an electromechanical ultrasonic system defined by a predetermined resonant frequency, in which the system may include an ultrasonic transducer coupled to an ultrasonic blade. A method of estimating a state of an end effector of the ultrasonic device may include applying a drive signal defined by a magnitude and a frequency to the ultrasonic transducer, sweeping the frequency of the drive signal from below a first resonance to above the first resonance of the electromagnetic ultrasonic system, measuring and recording, impedance/admittance circle variables Re, Ge, Xe, and Be, comparing, the measured impedance/admittance circle variables Re, Ge, Xe, and Be to reference impedance/admittance circle variables Rref, Gref, Xref, and Bref, and determining, a state or condition of the end effector based on the result of the comparison. An electromechanical ultrasonic system may include a control circuit to effect the method.
