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Precision Rotary Encoders with a Magnetic Heart

Precision Rotary Encoders with a Magnetic Heart

A new generation of magnetic rotary encoders from POSITAL-FRABA combine the ruggedness and simplicity of magnetic measurement devices with the accuracy and dynamic response of optical encoders.

Motion-control or industrial automation system designers who need to measure the rotation of shafts or other mechanical components can typically choose from two types of rotary encoders. Encoders based on optical measurement techniques will provide high levels of precision and dynamic response, but are relatively bulky and expensive. Moreover, optical encoders tend to be unreliable in damp or dusty conditions. Magnetic encoders are usually more compact and rugged, but until now have offered lower levels of precision and dynamic response.

POSITAL-FRABA eliminated the need for compromise with a new generation of magnetic absolute encoders that are accurate and fast enough for precision positioning tasks. They are also compact and tough enough for the most challenging environmental conditions.

At the heart of POSITAL’s IXARC encoders are four Hall-effect magnetic sensors that track the rotation of a set of permanent magnets attached to the device’s shaft. These sensors produce analog signals that are digitized and filtered by advanced signal-processing software running on a powerful 32-bit microprocessor. This system can deliver accuracies of ±0.2° for speeds of up to 12,000 PRM.

For absolute encoders with multi-turn ranges, a POSITAL-developed Wiegand wire system captures electrical energy from the rotary motion of the magnet. This energy-harvesting system powers a rotation counter so that every complete revolution of the device’s shaft is reliably recorded—regardless of whether or not control system power is available. This means that there is never a need to re-zero the control system by moving all of the mechanical components back to a known reference position after a power outage. And, since the revolution counters are self-powered, neither backup batteries nor complex mechanical gear-train systems often found in multi-turn optical encoders are required.

The electronic components are all mounted on a 35-mm-diameter printed circuit board (PCB). This compact unit can be fitted into a wide range of housings. As a result, the POSITAL engineering team is able to offer an enormous variety of mechanical variants with different housing types, flange configurations, shaft diameters and types, connector types, etc. To see the full range of possibilities, check out POSITAL’s Product Finder at

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