Ultrasonic device for cutting and coagulating

A surgical instrument, comprising:

• (a) at least one variable voltage drop feature configured to provide a variable voltage drop;
• (b) a reference circuit in communication with the at least one variable voltage drop feature, wherein the reference circuit includes at least one predetermined voltage drop feature configured to provide a predetermined voltage drop;
• and
• (b) a power source in communication with the at least one variable voltage drop feature and the reference circuit, wherein the power source is configured to provide power to the surgical instrument, wherein the power source is configured to generate an interrogation signal at a cycle, wherein the cycle includes a first cycle portion and a second cycle portion;
• and
• wherein the power source is configured to read the at least one predetermined voltage drop feature of the reference circuit with the first cycle portion of the interrogation signal,
• wherein the power source is configured to read the at least one voltage drop feature with the second cycle portion of the interrogation signal, and
• wherein the power source is configured to subtract out the variable voltage drop from the at least one variable voltage drop feature based on the predetermined voltage drop from the at least one predetermined voltage drop feature.

A surgical instrument comprising:

• (a) an electrical circuit, including:
• (i) a reference feature to provide a predetermined voltage drop during operation of the surgical instrument, wherein the reference feature is positioned on a first leg of the electrical circuit;
• and
• (ii) a variable feature to provide a variable voltage drop during operation of the surgical instrument, wherein the variable feature comprises at least one switch electrically connected with a resistor, wherein the variable feature further comprises a pair of diodes, wherein the variable feature is positioned on a second leg of the electrical circuit;
• and
• (b) a power source in communication with the electrical circuit, wherein the variable feature and the reference feature are electrically connected with the power source in parallel,
• wherein the variable voltage drop from the variable feature is determinable based on the predetermined voltage drop from the reference feature during operation of the surgical instrument, and
• wherein the power source is configured to generate an interrogation signal at a cycle, wherein the cycle includes a first cycle portion and a second cycle portion, wherein the power source is configured to read the reference feature of the circuit with the first cycle portion of the interrogation signal, wherein the power source is configured to read the variable feature with the second cycle portion of the interrogation signal, and wherein the power source is configured to subtract out the variable voltage drop from the variable feature based on the predetermined voltage drop from the reference feature during operation.