1.2.2.3.1.1.1 Analogue signals errors
This type of error initially appears in the analogue output of the magnetic field sensor on the chip or so-called
sin/cos signals. These distortions come from:
1. Offsets in static positioning of the chip in respect to the ring
2. Imperfect air gap
3. Chip to chip circuitry deviations
These errors are mostly removed after
the encoder calibration procedure.
Some of the error is left and can’t
be fully compensated. The amount of leftover error depends on particular installation conditions and
severely increases with deviation from optimal installation position. Typical leftover narrow-angle error lies in
the range given in
provided that the installation requirements are met.
for calibrating the narrow angle.
Attention
The analogue calibration should be repeated if the mechanical setup was changed.
1.2.2.3.1.1.2 Magnetic ring magnetization errors
One of the main limitations of any encoder is the accuracy of the actuator or position encoding device. It can
be an optical disk, magnetic ring or a capacitive system. Very accurate magnetic rings are expensive and
further accuracy improvements result in exponential production complexity and hence price growth. Thus,
there will always be some magnetization inaccuracies. However, their amplitude is smaller than the Analogue
signal errors.
1.2.2.3.1.2 Wide angle error (installation-dependent non-
linearity)
This type of error is the most dominant and caused by imperfect mechanical assembly. If the magnetic ring
rotates with some axial or radial runout (so-called eccentricity), then this will be reflected in the overall
accuracy. The eccentricity is typically caused by a mismatch between a geometric center of the ring and the
actual rotation center.
The effect of the eccentricity-caused error can be computed based on geometrical properties of the encoder
system after installation.
Err = 3600
where:
Err : amplitude of the eccentricity-caused error [″]
e: eccentricity of the rotational axis (or radial runout of the ring) [mm]
R: sensing radius of the corresponding Circulo encoder [mm]
ecc
ecc
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