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Sensor detects metal in plastics with micrometre accuracy

06 May, 2020

A German start-up has developed a sensor that, it claims, can detect metallic structures embedded in plastics or other electrically non-conductive materials precisely “for the first time”. The sensor, based on a radar technology, is claimed to measure, with micrometre accuracy, the distances to objects made of steel, copper or other metals, embedded in plastics, cardboard, rubber and other substances. It can also detect objects behind electrically non-conductive materials.

The sensor’s developer, OndoSense, was founded in 2018 by Mathias Klenner and Axel Hülsmann, two radar and high-frequency experts from the Fraunhofer Institute for Applied Solid State Physics. Klenner, who is the company’s managing director, says that ability to detect metallic objects precisely “opens up new, highly attractive industrial areas of application in quality control”.

The networkable technology can be used for non-destructive inspection of hard-to-access components or products in quality or assembly operations. This includes spotting components hidden inside products made of composite materials. It can also analyse items made of GRP (glass-fibre-reinforced plastics) for defects such as air pockets.

OndoSense says its technology can detect metallic items hidden in non-conductive materials with micrometre accuracy

Another application is to find items hidden in pharmaceutical or food products – such as metal chips in chocolate bars.

With the help of a €150,000 grant from the German government, OndoSense is now developing the technology further to identify and classify the embedded materials based on their relative permittivity. When measuring distances of objects in variable materials – such as different polymers – the system will calibrate itself automatically to the new material.

“If you want to measure distances in the micrometre range, the material properties have a high impact on measuring precision,” explains OndoSense’s technical director, Axel Hülsmann. “We offer a sensor that is consistently offering customers a highly reliable result, even when measuring in different materials. In future, this will be automated and there will be no need for additional calibration.”

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