SBAA449B October   2020  – October 2021 TMAG5110 , TMAG5110-Q1 , TMAG5111 , TMAG5111-Q1

 

  1.   Trademarks
  2. 1Introduction
  3. 2Latch Response of the 2D Hall Effect
  4. 3Two Axis Sensor Consideration
    1. 3.1 Magnet Selection
      1. 3.1.1 Pole Count
      2. 3.1.2 Magnet Strength
    2. 3.2 Sensor Selection
      1. 3.2.1 Axes of Sensitivity
        1. 3.2.1.1 In-Plane Sensor Alignment
        2. 3.2.1.2 Out-Of Plane Sensor Alignment
      2. 3.2.2 Sensor Placement
        1. 3.2.2.1 On-Axis Magnetic Field
        2. 3.2.2.2 In-Plane Magnetic Field
        3. 3.2.2.3 Out-of-Plane Magnetic Field
      3. 3.2.3 Sensitivity Selection
  5. 4Optimizing for Accuracy
    1. 4.1 Optimizing Placement for Accuracy
    2. 4.2 Optimizing a Magnet for Accuracy
  6. 5Application Implementation
  7. 6Summary
  8. 7References
  9. 8Revision History

Out-of-Plane Magnetic Field

Out-of-Plane placement can be the easiest to configure mechanically. There are also measurable magnetic field components in all three directions. This gives the greatest flexibility for tracking magnet rotation.

GUID-63B3ECB2-A8A3-4846-B614-0CD0AA4A4E7E-low.pngFigure 3-22 Sensor Out-of-Plane

There is a significant issue here. The peak amplitudes of each component are so different from each other that there will be noticeable error. If we consider the components which are closest matched, Z and θ, an worst case error of about 1.83° is expected. This error becomes more significant with the sensor placed further from the magnet where the field is weaker.

GUID-20210108-CA0I-JT7P-J7M6-T0CPQFQLNKZX-low.gifFigure 3-23 Out-of-Plane Magnetic Field Components
With placement of the sensor out-of-plane, an additional option exists for magnet selection. While not as common, it is also possible to obtain multi-pole ring magnets with axial polarization, or in the z-direction.

For comparison, observe the change to the peak amplitudes available with this type of magnet. In this case, the same material and dimensions are used, but the polarization is now directed outward from the face of the magnet. This type of polarization will allow for greater air gaps and pole counts for sensors in the out-of-plane alignment. However, they fail to produce adequate inputs when the device is in-plane with the magnet. These are often manufactured as custom magnets, and tend to be less commercially available .

GUID-20210108-CA0I-JZT1-VJXD-6SDGQXQMPT3J-low.gifFigure 3-24 Face Polarized Magnet