Building Electric Energy Sensing
Introduction: In this project, we are developing a stick-on electric energy monitoring system for residential and commercial buildings. The system leverages novel remote sensing technologies to accurately reconstruct electric currents and voltages from the magnetic field and electric field measurements. Giant Magnetoresistive (GMR) sensors are used to measure the magnetic fields produced by the currents in the individual breakers and a conductive plate is employed to capacitively couple to the voltage waveform. These sensors are simply attached to the circuit breakers inside a breaker panel, needing no wiring or electrician, and wirelessly report the individual electric currents — from which the energy consumption of each circuit can be inferred — to a secure repository on the Internet for easy access anywhere. These fine-grained, real-time energy consumption data allows electricity consumers to better manage their energy use for greater energy cost savings.
Stick-on Electric Energy Monitoring Systems
The development and optimization of MEMS AC current sensor:
In order to facilitate deployment of inherently power-constrained wireless sensing nodes, an ultra-low-power MEMS AC Current Sensor is being developed. When a piezoelectric cantilever with a permanent magnet on the free end is placed in proximity to an ac current-carrying wire, the resulting magnetic field coupling will produce a linear and proportional output voltage. Because this technique is based on energy harvesting, such a sensing device will consume orders of magnitude less power than conventional proximity-based sensing techniques. Present designs target 2-5uW of power dissipation (from filter circuitry) and dynamic ranges in excess of 160dB. A vibration-cancelling differential device is presently being designed with tape-out scheduled by early April 2014.
A proposed 3.8mm sensor die
Close-up on a single sensor and magnet
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