Accurate measurement of electric fields is very important for many applications, such as weather forecasting, process control of industrial equipment, or safety issues for high-voltage cable workers. However, from a technical point of view, accurate electric field measurement is not easy.
According to reports, a research team from the Vienna University of Technology (TU Wien) has developed a silicon-based MEMS electric field measurement sensor that has exceeded the design principles used in other current measurement devices. In cooperation with the Institute of Integrated Sensor Systems at Danube University Krems, the main design advantage of this sensor is that it does not interfere with the electric field being measured. The research results were published in the recently published Nature Electronics magazine.
Measurement principle of MEMS electric field sensor
“The equipment currently used to measure electric field strength has some significant drawbacks,†explains Andreas Kainz of the TU Wien Institute for Sensors and Actuators Systems. “These devices contain live parts. These conductive metal components can have a significant effect on measurement. The measured electric field; if the equipment needs to be grounded to provide a reference for measurement, this effect will be further amplified.†Therefore, such electric field measurement equipment is often relatively impractical and difficult to transport.
The MEMS sensor developed by TU Wien is made of silicon and is based on a very simple principle: a miniature spring, and a micro-grid-like silicon structure fixed to the spring for measuring micrometer-level movement. When the silicon structure is in an electric field, a certain force is exerted on the silicon crystal to make the spring slightly stretch or compress.
a. Measurement principle of this MEMS electric field sensor: A mass (m) is suspended on an elastic member (rigidity k), and the elastic member is fixed to a conductive fixing frame. When placed in an electric field (E), electrostatic induction generates a force (F es ) on the mass. The mass will produce a certain displacement (δx) under this force, and then use the optical principle to measure the displacement; b. The cross-sectional view of the device shows the light emitted by the LED, which can pass through the grid-like silicon structure and holes The gap between them is projected onto the photodiode below. The movement of the mass changes the gap between the opaque area and the hole, thus changing the amount of light that the LED's emitted light can reach the photodetector. c. The MEMS electric field 3D view of the sensor; d. SEM image of this MEMS electric field sensor
How to measure the subtle displacement of the mass, the researchers designed an optical solution: a layer of mesh structure was placed on top of the movable mesh silicon structure, and the holes of the upper and lower two layers of the mesh structure were precisely arranged. The apertures and the lower opaque areas are precisely aligned, that is, the LED light cannot penetrate the two silicon structures when the underlying mesh silicon structure is not displaced. When the sensor is placed in an electric field, the underlying reticular silicon structure is displaced by the electrostatic force so that there is a gap between the upper and lower two layers of the reticular structure, and the LED light can pass through the gap to reach the lower photoelectric detection. On the device. By measuring the amount of incoming light, the strength of this electric field can be calculated using a suitable calibration device.
The accuracy of the prototype device is exciting
This MEMS electric field sensor cannot measure the direction of the electric field, but it can accurately measure the electric field strength. It can measure the electric field strength from low frequency to up to 1 KHz. “Using our prototype sensors, we can reliably measure weak electric fields of less than 200 volts/meter,†Andreas Kainz said. “This means that our system is already comparable to existing products, and our sensors are smaller. In addition, this MEMS sensor still has a lot of room for improvement. Other measurement methods are already mature solutions. Our MEMS electric field sensor has just been designed. In the future, it will certainly be improved. â€
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