Energy is one of the most critical resources in Wireless Sensor Networks (WSN). For any WSN deployment, being it for a productive use case or for a testbed, the ability to perform energy measurements is of major importance, e.g., to estimate the status of the WSN, the need for maintenance, or for remaining lifetime. This paper presents a distributed energy measurement system for outdoor applications. An existing testbed has been extended by the micro controller unit (MCU)- based oscilloscope PotatoScope. Measuring voltage and current of the sensor node, undervolting effects and energy consumption of realtime applications can be observed. The PotatoScope is capable of capturing the power dissipation precisely at a high temperature range of 100 K. Using high sample rates with up to 500 kHz, the system needs to be capable of storing and archiving the measured data. A final evaluation shows a 0.9% drift for voltage measurements and a 1.6% drift for current measurements over the range of 100K. Using an SD card, long-term measurements can be made with up to 500 kHz. Nevertheless, a live mode allows sample rates up to 2 MHz when using the PotatoScope with a computer.
