Sensors last a lifetime

Nov. 6, 2003
Advances in controls and networks combined with components that pack more punch have opened the door to more-precise, durable, and economical pneumatic systems.
Magnetoresistive sensors are said to outperform Hall-effect sensors and reed switches. A wide range of configurations permit mounting to most any pneumatic cylinder.

Thanks to the reliability and robustness of magnetoresistive technology, Balluff, Florence, Ky., has extended lifetime warranty coverage to its entire BMF cylinder sensor product line, designed to handle virtually any pneumatic end-of-stroke application.

Magnetoresistive technology is inherently more suited for rugged factory applications than unprotected Hall-effect sensors and wear-prone mechanical reed switches, according to Balluff product manager Henry Menke. "In fact, it's difficult to damage our BMF sensors electronically in normal hard use, because their outputs are protected against short circuits, polarity reversal, and transient spikes."

Pneumatic cylinders are typically made of aluminum, so magnetic-field sensors indicate end of stroke from outside the cylinder tube using an internal magnet installed on the piston at the factory. The magnet lets an externally mounted magnetic-field sensor detect piston motion. Compared to Hall-effect and reed switches, magnetoresistive sensors are said to be more sensitive and accurate, and offer superior speed, temperature stability, and noise immunity. Moreover, the sensors can operate with magnets installed either parallel or perpendicular to their axis. Other magnetoresistive benefits include high repeatability, low hysteresis, and universal compatibility with reed and Hall-effect magnets.

Balluff's BMF family includes six designs that offer wide-ranging mounting flexibility. These include a unit designed to use a wide selection of interchangeable brackets to fit virtually any cylinder type, as well as designs for ultracompact short-stroke cylinders; flush mounting in narrow channels; quick flush mounting in T-channels; tie-rod installations; and installations requiring heavy-duty operating characteristics.

Cylinder-mounting configurations include T-slots, C-slots, all types of round mounting systems, duo-rail, trapezoidal rails, and dovetail slots. Each BMF sensor includes connector choices and output options to meet customer requirements.

About the Author

Kenneth Korane

Ken Korane holds a B.S. Mechanical Engineering from The Ohio State University. In addition to serving as an editor at Machine Design until August 2015, his prior work experience includes product engineer at Parker Hannifin Corp. and mechanical design engineer at Euclid Inc. 

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