A method of ultrasonic sealing includes activating an ultrasonic blade temperature sensing, measuring a first resonant frequency of an ultrasonic electromechanical system that includes a transducer coupled to the blade via a waveguide, making a first comparison between the measured first resonant frequency and a first predetermined resonant frequency, and adjusting a power level applied to the transducer based on the first comparison. The first predetermined frequency may correspond to an optimal tissue coagulation temperature. The method may further include measuring a second resonant frequency of the system, making a second comparison between the measured second frequency and a second predetermined frequency, and adjusting the power level based on the second comparison. The second predetermined frequency may correspond a melting point temperature of a clamp arm pad. An ultrasonic instrument and a generator may implement the method.
