IC-MA_14 Datasheet, PDF (9/19 Pages) IC-Haus GmbH – 8-BIT ANGULAR HALL SENSOR / ENCODER

iC-MA
8-BIT ANGULAR HALL SENSOR / ENCODER
THE SENSOR PRINCIPLE
Rev C1, Page 9/19
S
N
cal, diametrically magnetized permanent magnet (with
a diameter D of 4 mm and length L of 4 mm, for exam-
ple) provides optimal sensor signals. Magnetic materi-
als such as neodymium iron boron (NdFeB) or samar-
ium cobalt (SmCo) are very well suited to the sensor
and not readily influenced by external magnetic distur-
bance fields. The L/D ratio of a magnet magnetized
to saturation point has a bearing on the resulting field
strength and should lie within the region of 0.3 to 2.
zy
B
+B_z
x
-B_z
Figure 3: The principle of magnetic field measure-
ment using a Hall sensor
In conjunction with a permanent magnet iC-MA can be
used to create a complete encoder system. A cylindri-
iC-MA has four Hall sensors which are used to deter-
mine angles and to convert the magnetic field into a
measurable Hall voltage. Only the z component of the
magnetic field is assessed where the line of magnetic
flux must pass through two facing Hall sensors in the
opposite direction. An example line of magnetic flux
is given in Figure 4. The Hall sensors have been ar-
ranged in such a way that the assembly of the mag-
net with iC-MA is extremely tolerant. Two Hall sen-
sors combined generate a differential Hall signal. If
the magnet is rotated along its longitudinal axis sine
and cosine output voltages are created which can be
used to determine angles.
DEFINITION OF THE ANGLE OF ROTATION AND THE DIRECTION OF ROTATION
The arrangement of permanent magnet and iC-MA il-
lustrated in Figure 4, where the diametrically magne-
tized magnet is placed vertical to the chip’s surface, is
used to determine both the angle ω and direction of ro-
tation. An angle of 0 ° lies along the diagonal. Rotating
the magnet clockwise as shown in Figure 4 increases
the angular position and hence the output signal.
N
S
N
S
0°
Figure 4: Definition of the angle and direction of ro-
tation