How the Faraday Cage effect may finally have been overcome

Written by: Paul Fanning | Published:

The 'Faraday Cage' effect has long been an apparently insurmountable fact of engineering. The fact that a metallic enclosure prevents the entry or escape of an electromagnetic field has been both a boon and an obstacle to engineers since the effect was first observed in 1836 by the eponymous Sir Michael.

Since that time, the effect has become one of the better known aspects of physics, becoming a staple of science lessons, as well as appearing in film plots and other aspects of the media. Today, it is probably most commonly understood as the reason why it is impossible to get a mobile phone signal in a steel lift.

However, engineers at The Technology Partnership (TTP) now appear to have developed a way to break through the Faraday Cage. Part of the TTP Group, 300-strong TTP is a leading product development company based in the Melbourn Science Park in Hertfordshire. The technology the company has developed is called 'Fluxor'.

Of course, as previously mentioned, the Faraday Cage effect does have useful applications, from preventing leakage from microwave ovens to lightning strike protection and screening data cables. However TTP's new patent-pending Fluxor technology will have major benefits for power and data transfer through metal shielding. TTP is already using the technology for monitoring fluid levels in steel pipes, taking readings from medical implants and measuring data from inside F1 engines.

TTP's Fluxor method creates a 'window' for electromagnetic transmission of power and data by applying a strong DC magnetic field, which lines up the magnetic dipoles in the material to 'saturate' a small area of the metal screen. This reduces the permeability and increases penetration to make it possible to transfer electromagnetic power and signals. Experiments conducted by TTP using steels from 5-15mm thick show that the optimum operating frequency range is in the region of 400-500Hz.

In a typical operating scenario, a portable interrogator unit with a permanent magnet or electromagnet could be placed on top of a fixed sensor through a metal wall. A Fluxor window is opened to transmit power to energise the sensor and transmit a signal back – all without the need for physical openings in the enclosure.

"The ability to overcome the shielding characteristics of a Faraday Cage opens up many exciting opportunities, combined with new battery-free, ultra-low power wireless sensor technology also being pioneered at TTP," says Dr Allan Carmichael from TTP. "We see these developments as major enablers for delivering the Internet of Things that will allow billions of devices to communicate and interact with each other. We are currently working with a number of customers on use cases that exploit the Fluxor technology and expect to see practical applications deployed in the next few years."


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