Demo abstract: Scaling the wireless AC power meter

Abstract

We explore the seemingly trivial problem of scaling the AC power meter to a cubic-inch form factor. This small volume, necessary for unobtrusive inline plug-load monitoring, requires aggressive electromechanical codesign and 3-D electronics packaging. However, the key scaling challenge across both size and efficiency lies in the power supply architecture and load power. Hence, contrary to conventional wisdom, power is not free, even if a device is attached to wall power. Since many existing power supplies exhibit high baseline power draw, this leads to poor efficiency and runs counter to the green goals of many applications. We claim there are two paths to scaling the plug-load meter to a space-and power-efficient design point without sacrificing measurement fidelity: (i) by duty cycling in some cases and (ii) by using an off-line switching regulator that is not capacitor-fed. To evaluate our claims, we design a modular power meter architecture, implement several design alternatives, and evaluate their size, efficiency, and cost. We show that an energy-efficient, cubic-inch-sized wireless power meter is viable. Our design is 10× smaller, draws 3× less standby power, and still offers equivalent measurement fidelity as the best previously reported results.