Clamp-and-measure forever: A MOSFET-based circuit for energy harvesting and measurement targeted for power meters

Smart metering applications for monitoring the power usage of industrial or household appliances are rapidly increasing. At the same time, constraints such as the ease of installation and a long lifetime have boosted the interest in developing dedicated wireless sensor networks combined with energy harvesting systems and contact-less sensors. In this paper we present a hybrid circuit, tailored for wireless current meters, which performs current measurement and power supply extraction from the same non-invasive, clamp-on current transformer. A power saving MOSFET-based switch system (MSwS) connects the current sensor to the harvesting circuit during the node sleep time and to the measurement circuit when the node is active according to a proper operating duty-cycle. Experimental results show that the energy spent during the active phase can be totally recovered during the sleep time interval making the sensor node capable to self-sustain its operations and to operate without batteries indefinitely.