Drives and Controls Magazine

Tiny balls will sense temperature and other variables without wires

01 August, 2000

Tiny balls will sense temperature and other variables without wires

Miniature wireless sensors that will measure variables such as temperature, humidity, pressure and flow, are being developed jointly by a Japanese and a US company. The sensors will consist of integrated circuits and micro electromechanical systems (Mems) etched onto the surface of silicon spheres just 1mm in diameter.

The developers, the Yamatake Corporation and Ball Semiconductor, say that the manufacturing process is much simpler than that used to etch circuits onto flat wafers with the result that the sensors will be much cheaper.

Initially, the developers are working on temperature sensors that will combine a temperature sensing circuit, a control logic circuit, a wireless transmission circuit, and a coil, onto the surface of a spherical semiconductor. The temperature data gathered by the sensor will be transmitted to an external transceiver which will also power the sensor using radio waves picked up by the coil.

The developers plan to produce a prototype by the last quarter of this year which will be capable of making measurements in the range 0-50°C with an accuracy of ±0.1°C. In a second phase of the development programme, they hope to extend the range down to -55°C and up to +125°C, and to improve the accuracy to ±0.01°C.

The developers believe that the ball sensors will revolutionise sensing technology. As well as being cheap, the sensors will be small enough to be placed next to a target, improving the accuracy of readings. They say that the cost of putting the ball semiconductors into production will be about a tenth as much as setting up a plant to produce wafer semiconductors, allowing smaller players to enter the market.

Yamatake and Ball Semiconductor predict that their technology will open up many "previously undreamed of" applications. But they admit that before the ball sensors can be sold, improvements will be needed in areas such as packing density and power consumption.