Home/Technical Glossary/Feedback Modes Feedback Modes Closed loop resistance spot welding technologies can deliver energy in the form of constant current, constant voltage, or constant power. These feedback modes are derived from data collected by internal pick-up coils to measure weld current, pick-up cables to measure voltage, or a calculation based on those two values to measure power. Feedback modes are used to monitor and adjust the spot welding process; the appropriate feedback mode to use depends on the part and process challenges associated with the application. Constant current is great for welding flat parts where the part-to-part and electrode-to-part contact is controlled and consistent. Constant voltage mode is best for welding non-flat parts and wires. And constant power mode is especially useful for breaking through surface oxides and plating. For more information, read High Frequency Inverter Feedback Modes and Closed Loop Resistance Welding Control: WIFM?