An apparatus comprising: (a) a reprogramming device comprising an instrument receptacle; (b) an ultrasonic surgical instrument (100, 100) comprising an ultrasonic transducer assembly (102, 210), a generator connection and a memory, wherein the generator connection is configured to be connected to the instrument receptacle, wherein the memory is configured to store an original current value, an original phase margin value, and an original capacitance value of the transducer assembly, wherein the; and (c) a test tip configured to be connected to the ultrasonic surgical instrument, the test tip comprising a phase margin sensor and a capacitance sensor; wherein the reprogramming device is configured to: (i) receive a set of phase margin data and a set of capacitance data from the test tip, (ii) receive the original current value and the original phase margin value, (iii) determine a new current value based upon the set of phase margin data, the original current value, and the original phase margin value by using a transfer function, and (iv) write the new current value to the memory of the ultrasonic surgical instrument. wherein the reprogramming device is further configured to: (i) determine a capacitance difference between the original capacitance value and the set of capacitance data, (ii) where the capacitance difference exceeds a thermal threshold, select a thermal transfer function as the transfer function, (iii) where the capacitance difference does not exceed the thermal threshold, select a non-thermal transfer function as the transfer function, and (iv) determine a displacement value of ultrasonic components of the ultrasonic surgical instrument based upon the original phase margin, the set of phase margin data, and the transfer function. (a) a reprogramming device comprising an instrument receptacle; (b) an ultrasonic surgical instrument (100, 100) comprising an ultrasonic transducer assembly (102, 210), a generator connection and a memory, wherein the generator connection is configured to be connected to the instrument receptacle, wherein the memory is configured to store an original current value, an original phase margin value, and an original capacitance value of the transducer assembly, wherein the; and (c) a test tip configured to be connected to the ultrasonic surgical instrument, the test tip comprising a phase margin sensor and a capacitance sensor; (i) receive a set of phase margin data and a set of capacitance data from the test tip, (ii) receive the original current value and the original phase margin value, (iii) determine a new current value based upon the set of phase margin data, the original current value, and the original phase margin value by using a transfer function, and (iv) write the new current value to the memory of the ultrasonic surgical instrument. (i) determine a capacitance difference between the original capacitance value and the set of capacitance data, (ii) where the capacitance difference exceeds a thermal threshold, select a thermal transfer function as the transfer function, (iii) where the capacitance difference does not exceed the thermal threshold, select a non-thermal transfer function as the transfer function, and (iv) determine a displacement value of ultrasonic components of the ultrasonic surgical instrument based upon the original phase margin, the set of phase margin data, and the transfer function.