SLYA051B October   2020  – May 2024 DRV5055 , DRV5055-Q1 , DRV5057 , DRV5057-Q1 , TMAG5170 , TMAG5170-Q1 , TMAG5170D-Q1 , TMAG5173-Q1 , TMAG5273

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Linear Transit Position Sensing
  6. 3Linear Array Design
  7. 4Absolute Rotational Position
  8. 5Identifying Sources of Error
  9. 6Summary
  10. 7References
  11. 8Revision History

Absolute Rotational Position

This same linear arrangement for this application may be transformed into a rotational measurement as well. For example, now consider a cylindrical magnet with a radius of 1/32” and a thickness of ¼” made of N52 material. The magnet is placed such that there is approximately a 2-mm gap between the magnet and sensor. The magnet rotates about the z axis at 20 mm from center. Again, the selected sensor is DRV5055A1 with a sensitivity of 60 mV/mT.

 DRV5055 Circular ArrayFigure 4-1 DRV5055 Circular Array

In this scenario we find a spacing of about 16° from sensor to sensor provides a continuous gradient output. With six sensors in this format we are able to accurately monitor about 99° (10° to 109°) .

 DRV5055 Circular Array
                OutputFigure 4-2 DRV5055 Circular Array Output

With this implementation of the linear Hall sensor array, we are now able to track movement along a circumference. Typically angle calculations can be done with 2 sensors installed adjacent to a rotating cylindrical magnet. A rotational array configuration allows for flexibility of magnet placement and is useful in cases where it is not practical to place a magnet or sensors on or near the axis of rotation.