group of Cambridge scientists claims to have developed the world's thinnest position encoder. The 50-micron thick devices--half as thick as a sheet of paper--are based on the phenomenon of mutual inductance between a target and an antenna, discovered by Michael Faraday in the 19th century.

Faraday's phenomenon has been adapted for the 21st century by a start-up company called Zettlex, which has combined it with modern manufacturing techniques, digital electronics and software, to produce a patented electromagnetic resonance technology.

The company is marketing the sensors as an inexpensive replacement for conventional non-contact displacement encoders, especially in applications where cost, space, dirt or weight issues mean that traditional sensors cannot be used. They could also be used as the basis for rotary control knobs or as linear encoders in tough environments.

"We hope the market will find the slim, lightweight form of the sensor attractive," says Dr. Darran Kreit, Zettlex's chief technologist, "but I suspect the slim price tags will be the key to our success."

The technology is based on simple, flexible printed circuit boards which, when conformally coated, need no mechanical housing. They can be sealed to IP 68 and operate from -40°C to +125°C.

The PCBs can be extended to carry power and signals, avoiding the need for cables and connectors. By applying a contact adhesive to one side of the PCB, mechanical fixings can also be avoided when connecting to control panels.

The encoders are available in rotary, linear, two-dimensional and three-dimensional forms, in a variety of sizes. Linear versions span lengths from 1-2850mm.