μMonitor: In-situ energy monitoring with microwatt power consumption

Knowledge of energy flow in a microwatt-class energy harvesting system is essential to reliable deployment and scheduling of sensing, computation, communication, and actuation tasks. However, existing techniques for monitoring energy flow fail to meet the basic requirements for in-situ realtime monitoring systems by failing to be efficient and failing to perform accurately across a wide dynamic range. The proposed system, μMonitor, makes use of a highly power-optimized "Coulomb counting" implementation to achieve less than 1.7 microampere current draw, 94% efficiency in-situ, and high energy flow measurement accuracy across four orders of magnitude.