A method of controlling a modular battery powered handheld surgical instrument, the surgical instrument comprising a battery, as user input sensor, a controller, a radio frequency (RF) drive circuit, an ultrasonic transducer, ultrasonic transducer drive circuit, and an end effector, the end effector comprising an electrode electrically coupled to RF drive circuit, an ultrasonic blade acoustically coupled to the ultrasonic transducer, and a sensor to measure tissue parameters, the method comprising:
- applying an RF current drive signal to the electrode by the RF drive circuit;
- applying an ultrasonic drive signal to the ultrasonic transducer by the ultrasonic transducer drive circuit to acoustically excite the ultrasonic blade;
- controlling intensity, wave shape, and/or frequency of the RF current drive signal based on a sensed measure of a tissue or user parameter.