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Hollow-Shaft Encoders


POSITAL will soon be rolling out a new family of absolute rotary encoder components for servomotors, stepper motors, robot joints and anywhere else a hollow center design is needed to achieve an optimal mechanical layout. Both single and multi-turn variants will be available. For multi-turn models, the rotation counter is self-powered, using POSITAL’s Wiegand energy-harvesting technology. This eliminates the need for backup batteries and lowers maintenance costs.

These new products make use of a capacitive measurement system. Each encoder has two principle components, a stator and rotor, both with specially shaped areas of conductive material on their surfaces. These function as capacitor plates. As the rotor turns, the conductive areas on the rotor and stator change their relative positions, causing changes to capacitive coupling across the system. This causes changes to the amplitude and phase angle of a high-frequency electrical signal generated by exciter circuits in the stator and transmitted through the capacitor system. Special processors capture and decode these signal variations and determines the rotor’s angular position to a high level of precision.

The new POSITAL hollow shaft kit encoders offer excellent accuracy (+/- 0.02 °) and dynamic response (up to 6000 RPM), making them suitable for use in critical motion control systems. However, what makes them especially useful in many applications is their shape. Both stator and rotor elements are in the form of thin disks with large central openings. This makes them an ideal choice in space-limited situations, such as servomotors, stepper motors or the joints in robotic arms, where it is desirable to have an embedded position sensor fitting around a central shaft, structural component or cable cluster.

POSITAL hollow shaft kit encoders will be available in two sizes, with 30 mm or 50 mm internal diameters. Non-proprietary SSI and BiSS C communications interfaces are supported.



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