iC-MH8
12 BIT ANGULAR HALL ENCODER
Rev A0.9, Page 16/25
Vsin
be set more accurately by varying GAINF. Variations in
the gain factor, as shown in Figure 12, have no effect
on the Lissajous curve, enabling the angle information
for the interpolator to be maintained.
VOSS
a
Vsin
GAING
GAINF
Vcos
a
C141107-3
Vcos
Figure 13: Effect of the sine offset setting
Vsin
VOSC
C141107-2
Figure 12: Effect of gain settings GAING and
GAINF
a
Deviations of the observed Lissajous curve from the
ideal circle can be corrected by varying the ampli-
tude offset (register VOSS, VOSC) and amplitude ratio
(register GCC). Changes in these parameters are de-
scribed in the following figures 13 to 15. Each of these
settings has a different effect on the interpolated angle
value. A change in the sine offset thus has a maximum
effect on the angle value at 0° and 180°, with no al-
terations whatsoever taking place at angles of 90° and
270°. When varying the cosine offset exactly the oppo-
site can be achieved as these angle pairs can be set
independent of one another. Setting the cosine/sine
amplitude ratio does not change these angles (0°, 90°,
180° and 270°); however, in-between values of 45°,
135°, 225° and 315° can still be influenced by this pa-
rameter.
Vcos
C141107-4
Figure 14: Effect of the cosine offset setting
Vsin
GCC
a
Once calibration has been carried out a signal such as
the one illustrated in Figure 11 should be available.
Vcos
In the final stage of the process the amplitude control
can be switched back on (ENAC =1) to enable devi-
ations in the signal amplitude caused by variations in
the magnetic field due to changes in distance and tem-
perature to be automatically controlled.
C141107-5
Figure 15: Effect of the amplitude ratio
ICHAUS [ IC-HAUS GMBH ]
