AS5030 8-bit Programmable Magnetic Rotary Encoder

Rev. 1.8

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Page 24 of 33

The resolution of the encoder determines the smallest step size. The angle error caused by quantization cannot get better than

± ½ LSB. As shown in Figure 28, a higher resolution system (right picture) has a smaller quantization error, as the step size is

smaller.

For the AS5030, the quantization error is ± ½ LSB = ± 0.7°

INL including quantization error

-1,5

-1

-0,5

0

0,5

1

1,5

0

45

90

135

180

225

270

315

360

Angle steps

INL

Average (16x)

Figure 29: Typical INL error over 360°

Figure 29 shows a typical example of an error curve over a full turn of 360° at a given X-Y displacement. The curve includes the

quantization error, transition noise and the system error. The total error is ~2.2° peak/peak (± 1.1°).

The sawtooth-like quantization error (see also Figure 28) can be reduced by averaging, provided that the magnet is in constant

motion and there are an adequate number of samples available. The solid bold line in Figure 29 shows the moving average of

16 samples. The INL (intrinsic non-linearity) is reduced to from ~± 1.1° down to ~± 0.3°. The averaging however, also increases

the total propagation delay, therefore it may be considered for low speeds only or adaptive; depending on speed (see also: 0,

Position Error over speed ).