Electric Field Strength Measuring Sensor is Less Prone to Distortion

TU Wien has succeeded in developing a sensor ideal for measuring the strength of electric fields, which is much simpler, smaller and less prone to distortion than comparable devices.

Tiny new sensor - compared to a one-cent-coin. (Image credit: TU Wien)

Accurately measuring electric fields is vital in an extensive range of applications, such as process control on industrial machinery, weather forecasting or guaranteeing the safety of people working on high-voltage power lines. However, this is no easy task from a technological perspective.

A research team at TU Wien, in a break from the design principle that has been followed by all other measuring devices to date, has presently developed a silicon-based sensor as a microelectromechanical system (MEMS). Developed in conjunction with the Department for Integrated Sensor Systems at Danube University Krems, this sensor comprises of the key advantage that it does not distort the extreme electric field it is measuring. An introduction to the new sensor has also been featured in the electronics journal "Nature Electronics".

Distorting Measuring Devices

"The equipment currently used to measure electric field strength has some significant downsides," explains Andreas Kainz from the Institute of Sensor and Actuator Systems (Faculty of Electrical Engineering, TU Wien). "These devices contain parts that become electrically charged. Conductive metallic components can significantly alter the field being measured; an effect that becomes even more pronounced if the device also has to be grounded to provide a reference point for the measurement." Such equipment also tends to be comparatively difficult and impractical to transport.

The team’s sensor is produced from silicon and is based on an extremely simple concept: small, grid-shaped silicon structures measuring only a few micrometers in size are fixed onto a tiny spring. A force is exerted on the silicon crystals, when the silicon is exposed to an electric field, resulting in the spring to slightly extend or compress.

These small movements will now have to be made visible, for which an optical solution has been designed: an extra grid placed above the movable silicon grid is lined so accurately such that the grid openings on one grid are concealed by the other. During the presence of an electric field, the movable structure slightly moves out of perfect alignment with the fixed grid, permitting light to pass via the openings. This light is then measured, from which it is possible to calculate the strength of the electric field by a properly calibrated device.

Prototype Attains Impressive Levels of Precision

The new silicon sensor measures the strength of the electric field instead of measuring its direction. It can be employed for fields of a comparatively low frequency of up to one kilohertz. "Using our prototype, we have been able to reliably measure weak fields of less than 200 volts per meter," says Andreas Kainz. "This means our system is already performing at roughly the same level as existing products, even though it is significantly smaller and much simpler." However, there is still a huge deal of potential for improvement, too: "Other methods of measurement are already mature approaches – we are just starting out. In future it will certainly be possible to achieve even significantly better results with our microelectromechanical sensor," adds Andreas Kainz confidently.

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