Magnetic field fluctuations seen by the orthogonally oriented Hall sensors. The sensors generate proportional (sinusoidal) voltages from which processing circuits extract the angle and direction of the rotating position marker producing the field. (Select for full image)

Most rotary position sensors have some effect on the motion they aim to measure. They also tend to complicate design, requiring shaft-to-shaft connections and special mounting considerations, while introducing wear.

A new feedback mechanism addresses these limitations by placing nothing more than a thin magnetic disc on the end of a rotating shaft. As the disc spins, it produces a fluctuating magnetic field that's transduced by an equally small chip — a magnetic pickup incorporating a pair of Hall-effect devices — mounted on a stationary surface. By processing the sinusoidal output voltages (one from each Hall element), the device can track shaft angle as well as direction of rotation.

The system is currently configured to work with shafts from 13 to 48 mm in diameter, and is rated IP69K against liquids and contaminants. It operates from -40° to 125° C, measuring rotary position out to 14 bits, repeatable to within 0.1°. Output options include analog, incremental, SPI, and PWM, with redundant-output versions available.

VITAL STATS

On display: Vert-X E series angle sensors

Key feature: Magnetic sensing mechanism

What it means to you: Tiny sensor measures shaft angle and direction over a full 360° range with up to 14 bits of resolution without requiring a mechanical linkage to and from the machine.

What else: Eliminate torsion and vibration-induced wear associated with mechanical linkages and sensor loads; solve contamination and barrier challenges by enclosing or sealing sensitive processes and load axes; increase safety or simplify system control using programmable angle limits to locally control motion axes.

A low-inertia magnet fastened to a rotating shaft produces a fluctuating magnetic field that’s converted (by a Hall sensing circuit) to a rotary position feedback signal. By normalizing the X and Y field components, the circuit compensates for misalignment, axial play, and field variations caused by temperature changes and aging.

Innovator: Novotechnik U.S. Inc.
Southborough, Mass.

Follow-up: www.novotechnik.com or (508) 485-2244