AS5040

Data Sheet

www.austriamicrosystems.com

Revision 2.10

27 - 33

Figure 25: Example of Linearity Error over 360°

Transition Noise

Transition noise is defined as the jitter in the transition between two steps.

Due to the nature of the measurement principle (Hall sensors + Preamplifier + ADC), there is always a certain degree

of noise involved.

This transition noise voltage results in an angular transition noise at the outputs. It is specified as 0.12 degrees rms (1

sigma)

This is the repeatability of an indicated angle at a given mechanical position.

The transition noise has different implications on the type of output that is used:

Absolute output; SSI interface:

The transition noise of the absolute output can be reduced by the user by applying an averaging of readings.

An averaging of 4 readings will reduce the transition noise by 6dB or 50%, e.g. from 0.12°rms to 0.06°rms (1

sigma).

PWM interface:

If the PWM interface is used as an analog output by adding a low pass filter, the transition noise can be

reduced by lowering the cutoff frequency of the filter.

If the PWM interface is used as a digital interface with a counter at the receiving side, the transition noise

may again be reduced by averaging of readings.

Incremental mode:

In incremental mode, the transition noise influences the period, width and phase shift of the output signals A,

B and Index. However, the algorithm used to generate the incremental outputs guarantees no missing or

additional pulses even at high speeds (up to 30,000 rpm and higher)

3 sigma represents 99.73% of readings.

linearity error with centered magnet [degrees]

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

1

55

109 163 217 271 325 379 433 487 541 595 649 703 757 811 865 919 973

transition noise

Errmax

Errmi