Disclosed herein are methods and systems for adjusting the power level of an external reader of an electronic device. The external reader transmits power to the electronic device with a radio frequency electromagnetic signal. The electronic device may rectify the radio frequency electromagnetic signal and create a rectified voltage. The rectified voltage may be positively correlated to the power level transmitted by the external device. The rectified power can be used to power a component of the electronic device, such as a component configured to measure either a voltage or power associated with the rectified voltage. The electronic device may communicate the measured voltage or power back to the external reader. Based on the communicated voltage or power, the external reader may adjust its power level of the transmitted power.