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NEC Develops a Compact Sensor that Measures the Power Consumption of Electronic Devices without needing an External Power Supply

February 22, 2011 - Tokyo

NEC Corporation (NEC; TSE: 6701) announced today the development of a compact sensor that measures the power consumption of electronic devices and delivers this information to energy management systems without needing an external power supply or battery.

An independent power supply to the sensor is achieved through energy harvesting(1), a technique that converts energy from a surrounding area into electrical energy without the need of an external power source. Although, this method can be used to convert magnetic fields emitted from power lines into an operating electric supply, energy harvesting can only convert about 1mW of power, which is insufficient for sensors that are used to measure power consumption and send data to an energy management system.

These newly developed sensors, however, consume less than 1mW of power by leveraging an original circuit design that enables them to both measure the power consumption of electric devices and transmit data. As a result, these sensors can provide visibility of electrical device power consumption without the need of an external energy supply. Furthermore, since these sensors do not require data transmission devices, such as wireless interfaces, they may be easily managed and produced in a compact size.

Sensor developments are as follows:

1.Development of a monitoring circuit that can both distinguish between electronic devices and measure their power consumption and operational status

Development of a monitoring sensor that enables high precision, low power, continuous real time monitoring and measurement of current waveforms that are consumed by electronic devices. These measurements identify distinctions between each device and provide detailed information on energy consumption and operational status that also enable the detection of unusual operating conditions.

2. Development of a data transmission circuit that sends power consumption information through power lines

Development of a data transmission circuit that uses the measurement object's AC power line as a transmission path to send current waveform information to a management system in order to calculate power consumption. This has eliminated the need for wireless transmission devices to send data to energy management systems, which has increased usability and enabled the miniaturization of sensors.

3. Development of a control circuit that enables battery free operations

Development of a control circuit that manages the power consumption of sensors by alternately operating the monitoring circuit and data transmission circuit described in points (1) and (2) above. The control circuit ensures that the same level of power is consumed both when the monitoring circuit is operated and when the data transmission circuit is operated. The control circuit accomplishes this by concentrating its operations during the same time as the, relatively low power consuming, monitoring circuit's operations. Conversely, the control circuit's operations are stopped while the, relatively high power consuming, data transmission circuit is operating. As a result, these new sensors can measure current waveforms and transmit data while consuming less than 1mW of power, which enables them to operate without the use of an external power supply.
As the visualization of power consumption within large buildings and factories advances, it is expected that visibility will also become more available within homes and offices through the growing deployment of energy-conscious systems that manage and restrain energy use.

These innovative new sensors, which enable the visualization of power consumption while being free from battery or transmission device maintenance, are suitable for a wide range of electronic devices. Looking forward, NEC will continue to develop power management systems for electronic devices that capitalize on these sensors and contribute to the realization of a low-carbon society.

NEC will present the results of this research on February 22 at the IEEE International Solid State Circuits Conference (ISSCC 2011), held February 20 -24 in San Francisco, California, U.S.A.

(1) Energy Harvest
Energy Harvest is a technique that converts the energy from heat, light and vibrations in a surrounding area into electricity then uses this electricity to power electronic devices without the use of batteries or external power.

About NEC Corporation

NEC Corporation (TSE: 6701) is a leader in the integration of IT and network technologies that benefit businesses and people around the world. By providing a combination of products and solutions that cross utilize the company's experience and global resources, NEC's advanced technologies meet the complex and ever-changing needs of its customers. NEC brings more than 100 years of expertise in technological innovation to empower people, businesses and society. For more information, visit NEC at

Source: NEC Corporation


Joseph Jasper
NEC Corporation

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