SBAA463A january   2021  – april 2023 TMAG5170 , TMAG5170-Q1 , TMAG5170D-Q1 , TMAG5173-Q1 , TMAG5273

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
    1. 1.1 Angle Measurement With One-Dimensional Sensors
    2. 1.2 Challenges of Angular Measurements
  4. 2Benefit of Multi-Axis Sensors
    1. 2.1 Simplified Mechanical Placement
    2. 2.2 Sensitivity Matching
    3. 2.3 CORDIC Angle Estimations
    4. 2.4 Tamper and Stray Field Detection
  5. 3Angular Measurement Considerations
    1. 3.1 Sensor Alignment
    2. 3.2 Sensor Calibration
    3. 3.3 Input Referred Noise
    4. 3.4 Impact of Sample Rate
  6. 4Practical Application
    1. 4.1 Push-Button Knob
      1. 4.1.1 Evaluating Design Constraints
      2. 4.1.2 Magnet Selection
      3. 4.1.3 Prototyping and Verification
    2. 4.2 Off-Axis Design
      1. 4.2.1 Sensitivity Gain Correction
      2. 4.2.2 Accuracy Verification
  7. 5Summary
  8. 6References
  9. 7Revision History

Sensitivity Gain Correction

Efforts with simulation software helped find an off-axis placement which resulted with a peak input in the Z-direction of approximately 45 mT. The same placement results in a peak magnitude of about 32 mT in the X-direction.

GUID-20201229-CA0I-KFMN-J1BT-723BHBNS1SMD-low.gif Figure 4-5 Simulated Off-Axis Configuration

This configuration was then matched in a physical setup and the outputs of a single rotation were captured. Here we see fairly close behavior between the X and Z components in the simulation and the captured results.

GUID-20201229-CA0I-LJNF-TCLM-DWZHKRZ5MXQD-low.gif Figure 4-6 Initial Off-Axis Measured Data

To properly configure TMAG5170 for angular measurements it was necessary to attenuate the Z component to match the X component following the procedure detailed in Sensor Calibration. Based on measurements of peak input values, a scaling factor of 67.3% was determined to be required to match peak amplitudes.