Carnegie Mellon University's Niranjini Rajagopal and colleagues have designed an inexpensive wireless device that can monitor the power consumption of home appliances.
The smart meter uses electromagnetic waves to monitor the electric current flowing through the wires that plug appliances into walls. The system runs on two AA batteries, but it does not have the drawbacks of other plug-in electricity monitors, which can be tricky to install on large appliances and are rated up to a maximum power per appliance.
When an appliance changes the amount of power it is using by turning on or off, the sensors pick up the corresponding fluctuations in the electromagnetic field (EMF) around the wire that supplies the electricity. The sensors use a wireless network to send switching information back to a central power-monitoring system for the whole house, which can measure the increase in power use and link it to the appliance that tripped the EMF sensor.
Rajagopal installed the device in a family residence and ran it for a week, monitoring a liquid crystal display TV, washing machine, toaster oven, air-conditioning unit, laser printer, refrigerator, and iron with the EMF sensors. The system achieved a 98-percent accuracy rate in testing.
From New Scientist
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