Machine Design
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Hall Sensor Measures 360 Deg. of Rotation

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Fig. 1Engineers who want to measure and control rotating antennas, fluid flow direction, or a robotic arm joint can now use a Two-Pi hallpot angle sensor from Elweco Inc., Painesville, Ohio, to measure the angular rotation of a shaft or joint. The sensor can measure angles up to 360 deg. and motion at up to 5,000 rpm, and the response is linear with the rotation. The sensor generates two simultaneous linear responses with opposite slopes, thus letting engineers choose the preferred direction of rotation and then use either slope. The device relies on non-contacting magnetic Hall effect sensors, so there are no moving parts to wear out.

The sensors do not require any additional hardware to obtain or decode the linear measurement or control signals, which means software is also unnecessary. Because the sensor supplies signals for two slopes, engineers can insert the device directly in the system and have the desired slope—again, without adding hardware.

Fig. 2This graph shows the two simultaneous signals generated by the device as the sensor perceives rotation. With a positive and negative slope for either direction of rotation available, users can choose the slope best suited to their applications.

The sensor uses two ABEC Class-5 ball bearings on each rotor shaft for the servo-mount design, and anodized aluminum bearings are used on the threaded journal potentiometer-mount types. The sensor comes in three different mounting configurations in standard sizes and shapes, so no special mounting hardware is required for adding it into most new or existing systems.

The device is powered by 4.5 to 5.5 Vdc at 12 ma, and unregulated power supplies are acceptable. The output signals range from 300 to 2,700 mV. It works in temperatures from −20° to 85°C and relative humidity from 0 to 95%.

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This file type includes high resolution graphics and schematics when applicable.
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