Proximity sensors shed their wires

A radio-based proximity sensing system which could reduce substantially the amount of wiring needed in manufacturing plants was previewed at the recent Hanover Fair. As well as cutting installation and maintenance costs, the system, developed by ABB Stotz-Kontact, is also predicted to reduce wiring faults, and to improve safety and reliability.

The new system is expected to be particularly attractive for car plants, where manufacturing cells can contain 50 proximity switches - and, in some cases, more than 200. Each of these conventional sensors has to be fitted with signal and power supply cabling which is costly to install, service and modify.

The new sensors - which ABB claims are a world first - draw their power from a surrounding magnetic field and transmit their signals via radio in the 2.4GHz band. The only cabling needed is a loop to produce the energising field. Each sensor draws just 6mW of power.

Up to 60 of the sensors can be linked to a control system via a receiver module. Each sensor reports its status and its correct operation twice a second. ABB says this will result in "previously unknown" levels of reliability and will open new possibilities in mechanical engineering.