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Product category: Rotary Position, Tilt and Angular Sensors
News Release from: Renishaw | Subject: Magnetic rotary encoders
Edited by the Engineeringtalk Editorial Team on 11 July 2005

Magnetic rotary encoders cover many
applications

The rugged noncontact design of Renishaw's magnetic encoders makes them suitable for a diverse range of demanding applications.

Motion control feedback is now widely used in many diverse applications Requirements vary from high accuracy, low speed to low accuracy and high speed

Renishaw designs and manufactures a range of high performance noncontact optical encoders.

In rotary applications such as C axis positioning and rotary tables, arc second accuracy performance is offered by Renishaw's RESR angle encoder.

In addition to Renishaw's high specification optical product range, a new range of magnetic rotary encoders has now been introduced.

The RM and RE range incorporates compact, noncontact, magnetic sensing technology, which is suited to applications where optical angle encoders cannot be used due to demanding environmental conditions.

The resolution and accuracy of these magnetic rotary encoders make them suitable for totally different applications to Renishaw's existing RESR angle encoder.

The main benefit of Renishaw's magnetic rotary encoders, compared with other similar resolution/accuracy offerings available, is the robust noncontact design.

Additional benefits include low inertia of moving parts, reliable operation within external magnetic fields, variety of output formats, 5 and 24V power supply options, multiple package designs and competitive pricing, thanks to the simple design of the product.

Simple construction, innovative design and solid-state electronics, means that the RM and RE packaged range of magnetic encoders has many advantages over traditional optical rotary glass encoders.

These include: a compact noncontact design; the ability to withstand high levels of shock, vibration and acceleration; low inertia with only one small moving part; a zero-wear design; high immunity to dirt, dust and cutting fluids; operation up to +125C; reliable position sensing up to 30,000rev/min; and low unit cost and minimal cost of integration.

At the heart of every Renishaw magnetic rotary encoder are two core components - a small diametrically polarised magnet and a custom Hall sensor ASIC.

The custom ASIC detects the change in magnetic flux as the magnet rotates above it.

The encoder ASIC contains an array of Hall effect sensors arranged to generate a voltage when exposed to a magnetic flux field.

As the N and S poles pass over them, they experience changes in the flux field and generate changing voltages.

The sensors only respond to the component of the magnetic field that is perpendicular to the surface of the chip.

Through smart design, the ASIC is able to achieve cancellation of 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 magnet.

Signals coming out of the sensors are then interpolated by electronics to give the required resolution and required output format.

Output formats include absolute, incremental and analogue.

Designers who require the smallest possible encoder can incorporate the ASIC and magnet within their own designs, or purchase a modular solution.

Packaged versions are also available in noncontact (RM) or traditional bearing/shaft (RE) format, fully sealed to IP68.

The RM and RE encoders are available in either 22 or 36mm diameter bodies with multiple industry standard mounting options.

Chips, modules and packaged products all offer easy integration with a range of industry standard output formats including absolute, incremental, analogue, linear voltage and linear current.

Resolutions are available from 7bit (128 counts per revolution incremental) to 12bit (4096 counts per revolution incremental).

Supply voltage is either 5 or 24V depending on the encoder/output format.

The rugged noncontact design of Renishaw's magnetic encoders makes them suitable for a diverse range of demanding applications: in motors for reliable high speed feedback control; in pumps, actuators and valves to provide reliable long term position information; in marine applications for both instrumentation and feedback control in harsh environments; in medical applications for reliable feedback in "washdown" environments; and in packaging and print machinery to provide reliable feedback information in industrial environments. Request a free brochure from Renishaw ...

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