New slant on old technology

A team of researchers led by Dr. Paul Robertson at Cambridge University’s Engineering Department are working on a new slant to an old sensing technology.

Flux-gate magnetic sensors have been around for many decades and are still used today for tasks such as geological surveys, aerospace instruments and even detecting submarines, as submarines disturb the Earth’s magnetic field around them.

These devices are usually quite large and are assembled from coils wound on to magnetic cores.

Dr. Robertson and his team, though, have developed new techniques to micro-fabricate flux-gate magnetic sensors, producing tiny versions of these sensors which are extremely sensitive, contained in a miniature package and able to work over a wide frequency range

These properties allow the sensors to be used in a range of new applications including the measurement of electrical currents in circuits and the evaluation of the magnetic properties of materials – both of which can be achieved in a non-destructive manner.

One example of this is a magnetic microscope, in which the magnetic sensor is scanned over the surface of an item and the measured magnetic field is displayed as an image on a computer screen.

Currently, magnetic microscopes are commercially available which use highly cooled superconducting sensors, but the new sensors operate at room temperature – resulting in a much lower system cost.

Possible uses for such an instrument include surface defect detection in components and the development of ticketing, security cards, anti-counterfeiting devices and security features on bank notes, as all of these contain magnetic recording material.

The picture below shows an image of current flow around a PCB track, scanned with a system built in at the University.

Dr. Robertson and his team are currently developing the sensor technology with a local Cambridge company for use in a new product – a novel type of current probe for use by electronics engineers. The project is now in the production engineering phase.