Scientists in Hong Kong have developed wireless current sensors which are capable of running on the electromagnetic energy of the very systems they monitor.

Unlike conventional current monitoring devices, such as Hall sensors and reluctance coils, the tiny sensor chips developed by scientists from the Hong Kong Polytechnic University do not require external power supplies or signal conditioners to operate.

This dispenses with the need for power cords or other active components, a feature which, in tandem with the tiny dimensions of chips – which measure a mere millimetre in thickness, means they can be deployed on sites where it would be impossible to make recourse to conventional sensors.


Surface mount and through-hole type magnetoelectric sensors.

The wireless chip can operate in just about any location, including hard-to-access areas such as high rise buildings, railway lines, tunnels and underground facilities, where the cords of traditional sensors would rule out their usage.

These features radically enhance the ability of engineers to monitor the functioning of modern electrical assets and power grids, in order to detect faults or malfunctions in advance.

According to Professor Derek Siu-wing Or, who led the team of scientists from Hong Kong Polytechnic’s Department of Electrical Engineering in the development of the device, the sensors represent a major step towards “energy-harvesting smart wireless sensors.”

Their ability to harvest the electromagnetic energy produced by the very systems and equipment they monitor enables them to function independently of external power sources, as well as run microcontrollers and wireless transmitters by storing up harvested electricity.

Or said the key to the sensor chip’s unique capabilities is the use of an advanced “magnetoelectric smart material,” a rare earth multiferroic which can directly detect the magnetic fields produced by electrical currents, before converting these fields in a linear fashion into electrical voltage signals.

In addition to their modest size and ability to be deployed just about anywhere, Or said the sensors are capable of producing strong, clear output voltage signals which are 2,000 times greater than those emitted by conventional current sensors.

The passive and self-sufficient nature of the sensors also enables them to monitor the functioning of electrical equipment constantly and in real time.

The Hong Kong Polytechnic team is currently working to further refine the technology, with Or hoping to increase the ability of the sensors to harvest electricity and heighten their sensitivity and accuracy of measurement.

The smart wireless sensors have already been deployed on the electrical traction systems of trains in Hong Kong and Singapore in order to monitor traction conditions and look for electrical faults which could disrupt the operation of services.

Germany electrical engineering company E-T-A Elektrotechnische Apparate GmbH, which provided support for Or’s research via a EUR500,000 fund, also plans to incorporate Or’s device into its next generation electrical circuit protection products, in order to improve their safety and efficiency.