MEMS sensor measures electric field strength


The tiny sensor compared to a one cent coin

Researchers in Austria have developed a MEMS sensor able to measure the strength of electric fields suitable for use in aerospace applications and testing.

The sensor, which is much smaller, simpler and less prone to distortion than comparable devices, has been developed at TU Wien in Vienna. An introduction to the new sensor has been published in the electronics journal “Nature Electronics”.

According to Andreas Kainz from the Institute of Sensor and Actuator Systems at TU Wien, with further development including increasing the sensitivity of the MEMS sensor, it could replace the conventional systems for electric field measurements, for example in satellite’s monitoring systems for space weather, as a smaller, lower weight device

The sensor could also be used in drones or similar vehicles, for example to prevent collisions with free-standing high-voltage power lines.

Minimal distortion

The silicon-based microelectromechanical system (MEMS) sensor has the benefit that it does not distort the electric field it is currently measuring.

Andreas Kainz said, “The equipment currently used to measure electric field strength has some significant downsides.

“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 relatively impractical and difficult to transport, he added.

The MEMS sensor is based on small, grid-shaped silicon structures measuring just a few micrometres in size, fixed onto a small spring. When the silicon is exposed to an electric field, a force is exerted on the silicon crystals, causing the spring to slightly compress or extend.

An additional grid located above the movable silicon grid is lined up so precisely that the grid openings on one grid are concealed by the other. When an electric field is present, the movable structure moves slightly out of perfect alignment with the fixed grid, allowing light to pass through the openings. This light is measured, from which the strength of the electric field can be calculated by an appropriately calibrated device.

Precision measurement

The prototype so far been used to measure electric fields of up to one kilohertz. “Using our prototype, we have been able to reliably measure weak fields of less than 200 volts per metre,” said 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.”

“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.”

Schematics of the sensor: the moveable and the fixed grid

26 January 2018

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Ben has worked as a journalist and editor, covering technology, engineering and industry for the last 20 years. Initially writing about subjects from nuclear submarines to autonomous cars to future design and manufacturing technologies, he was editor of a leading UK-based engineering magazine before becoming editor of Aerospace Testing in 2017.

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