OnAxis Magnetic Rotary Encoders Win at Motor Positioning and Speed Control with Low Cost, Simple Mounting, High Reliability, and Performance


Non-contact solid-state RLS encoders provide frictionless, zero-wear, "fit and forget" reliability

December 2007 - OnAxis(TM) magnetic encoders bring high performance, robust armored construction, simple mounting system, small size and low purchase price to demanding motor control, shaft position and velocity measurement applications for OEM manufacturers. Part of Renishaw's family of high-performance, industrial-strength encoders, the solid-state On-Axis units feature a Hall sensor ASIC epoxy-embedded inside a rugged metal housing to deliver high IP ratings, extreme temperature range (-40°C to 125°C), and superior resistance to shock, vibration, G forces and pressures. The hard-body sealed encoders also deliver high EMC immunity when shielded according to installation instructions. Non-contact, frictionless, zero-wear operation delivers "fit and forget" reliability. Designed for easy integration on electric motors and other shaft-drive devices, the encoder ASIC/metal case can be mounted to motor backs, fit into a cast or machined hole, and simply fastened down with two screws. Actuator magnets can be mounted onto or inset into the shaft. No adjustment is needed after mounting.

OnAxis magnetic encoders are available in analog, incremental and absolute formats with resolutions up to 13 bit (8192 counts per revolution), speeds to over 30,000 rpm, measurement accuracies to 0.5°, and 5V or 24V power supply. Units are fully sealed to IP68 and RoHS compliant. Versions can ordered for immersion applications (pumps, gearboxes, etc.

Breakthroughs in simplicity, the OnAxis encoders have at their heart just two core components - a small diametrically polarized magnet and a custom Hall sensor ASIC which contains a circular array of Hall effect sensors that generate a voltage when exposed to a magnetic flux field. The ASIC detects the change in magnetic flux as the magnet rotates above it. Sine and cosine voltage outputs from the sensor array vary with magnetic position and are converted to absolute angle position by a fast flash interpolator. The absolute angle position value is output through a parallel binary interface or a serial SSI interface. Relative changes of angle position are output through A QUAD B encoder signals.

Through creative design, the ASIC is able cancel magnetic interference, enabling it to operate in areas of high external magnetic fields and cope with imperfections in the shape of the flux field of the actuating magnetic.

Manufactured by Renishaw's encoder partner, RLS Slovenia, the ultra-compact, fully-sealed, non-optical encodes provide versatile, low-cost solutions to rotary positioning across a vast range of applications and industries - motor control, instrumentation, metalworking, marine, medical, automotive, aerospace, robotics, vision systems, industrial automation, packaging, printing and converting, agriculture and oilfield machinery, lift equipment and elevators, power tools and fluid control.
As with all Renishaw's products, a worldwide application support network and local inventory stocking bring added confidence to system developers.

For more information on Renishaw miniature magnetic sensors/encoders, contact Howard Salt, business manager-encoder systems, Renishaw, Inc., 5277 Trillium Boulevard, Hoffman Estates, IL 60192. Phone 847-286-9953; fax 847-286-9974. Email: howard.salt@renishaw.com

For a detailed look at other productivity enhancements for metrology, linear and rotary position feedback, and machine tool calibration, visit Renishaw's web site at: www.renishaw.com

Inquiries should be directed to: Susan Wilm, marketing assistant, Renishaw Inc., 5277 Trillium Blvd., Hoffman Estates, IL 60192.

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