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AS5215

Datasheet - Detailed Descr i pti on

7.1.3 Axial Distance (Airgap)

Figure 7. Sinusoidal Magnetic Field Generated by the Rotating Magnet

The recommended magnetic field, measured at the chip surface on a radius equal to the Hall sensor array radius (typ 1mm) should be within a

certain range. This range lies between 45 and 75mT or between 20 and 80mT, depending on the encoder product.

Linear position sensors are more sensitive as they use weaker magnets. The allowed magnetic range lies typically between 5 and 60mT.

7.1.4 Angle Error vs. Radial and Axial Misalignment

The angle error is the deviation of the actual angle vs. the angle measured by the encoder. There are several factors in the chip itself that

contribute to this error, mainly offset and gain matching of the amplifiers in the analog signal path. On the other hand, there is the nonlinearity of

the signals coming from the Hall sensors, caused by misalignment of the magnet and imperfections in the magnetic material.

Ideally, the Hall sensor signals should be sinusoidal, with equal peak amplitude of each signal. This can be maintained, as long as all Hall

elements are within the linear range of the magnetic field Bz (see Figure 5).

7.1.5 Mounting the Magnet

Generally, for on-axis rotation angle measurement, the magnet must be mounted centered over the IC package. However, the material of the

shaft into which the magnet is mounted, is also of big importance.

Magnetic materials in the vicinity of the magnet will distort or weaken the magnetic field being picked up by the Hall elements and cause

additional errors in the angular output of the sensor.

Figure 8. Magnetic Field Lines in Air

Figure 8 shows the ideal case with the magnet in air. No magnetic materials are anywhere nearby.

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360º

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