Energy harvesting circuits power measuring system

The paper proposes a simple and low-cost technique of a power measuring system for the characterization and evaluation of harvesters, harvesting circuits or switching converters. The system is a lab instrument and it can measure the power that is drawn from or provided to it, by measuring the time duration for a specific voltage difference to occur on a capacitor of known capacitance (V-T). This way, it is easier to measure low power values in comparison with the most straightforward method that depends on voltage and current measurements. The system is using only commercially available discrete components and is optimized for measuring power in the uW range with uW accuracy as supported with experimental results. It was tested to compare different solar harvesting circuits and to measure the available power levels for various light intensities.