Texas Instruments TIDA-060040, Manual

Page: 7 / 33

Air Gap Distance (mm)
Mag
netic Flux
Den
sity (m
T)
0 3 6 9 12 15 18 21 24
0
60
120
180
240
300
360
420
480
540
600
660
720
780
Figure 2-5. In-Plane Magnitude vs Airgap Distance
The subsequent plots depict the magnetic field vector components at a few select locations to demonstrate the
nature of the magnetic field. In each case the sensor location is perfectly aligned with the center of the magnet,
and therefore there is no Z component in the vector.
2-mm Airgap Magnetic Field Inputs is an example of a sensor placed too close to the magnet source. The input
on the (X-axis) has a peak value of nearly 150 mT while the (Y-axis) input has a peak value over 300 mT, which
exceeds the linear input range for
TMAG5170 .
Angle (deg)
Mag
netic Flux
Den
sity (m
T)
0 45 90 135 180 225 270 315 360
-400
-350
-300
-250
-200
-150
-100
-50
0
50
100
150
200
250
300
350
400
450
Bx
By
Figure 2-6. 2-mm Airgap Magnetic Field Inputs
Additionally, there is some minor harmonic distortion to the sinusoidal inputs. Ultimately any distortion to the
magnetic field inputs results in some periodic angle error. For all magnets, the sinusoidal nature typically
improves with range.
5.9-mm Airgap Magnetic Field Inputs shows a case where the field is too far from the sensor. While the X and Y
components have an ideal sinusoidal form, the 4.5 mT peak input signal is too small to be used in high-precision
applications. With such a small input signal, the output noise could cause significant errors in angle calculations.
www.ti.com System Overview
TIDUC07 – MARCH 2022
Submit Document Feedback
Absolute Angle Encoder Reference Design With Hall-Effect Sensors for
Precise Motor Position Control
7
Copyright © 2022 Texas Instruments Incorporated