IC-MU_17 Datasheet, PDF (13/66 Pages) IC-Haus GmbH – MAGNETIC OFF-AXIS POSITION ENCODER - POLE WIDTH 1.28MM

iC-MU MAGNETIC OFF-AXIS
POSITION ENCODER - POLE WIDTH 1.28MM
PRINCIPLE OF MEASUREMENT
Rev D1, Page 13/66
An absolute position measuring system consists of a
magnetized code carrier and an iC-MU which integrates
Hall sensors for signal scanning, signal conditioning,
and interpolation in one single device. iC-MU can be
used in rotative and linear measurement systems.
1
MASTER 16
2
15
3
14
4
13
5
12
6
11
7
10
8
NONIUS
9
TOLtang
CHIP CENTER
POLEDISK CENTER
AXIS CENTER
TOLrad
WOBrad
Figure 7: Rotative position measurement system
Figure 9: Definition of system measurements
Figure 8: Linear position measurement system
Rotative measuring system
The magnetic code carrier consists of two magnetic
encoder tracks. The outer track comprises an even
number of alternately magnetized poles and is used for
high-precision position definition. This is thus called the
master track. The second inside track has one pole pair
less than the outer track and is thus referred to as the
nonius track. This track is used to calculate an absolute
position within one revolution of the pole disc. To this
end, the difference in angle between the two tracks is
calculated.
Number of pole pairs
Master track diameter
Chip center to axis center
Nonius track diameter
Master track pole width
Nonius track pole width
16 32 64
[mm] 13.04 26.08 52.15
[mm] 4.72 11.24 24.28
[mm] 5.84 18.88 44.95
[mm] 1.28 1.28 1.28
[mm] 0.61 0.96 1.12
Table 6: Pole disc dimensions in mm for rotative sys-
tems
The Hall sensors of iC-MU span one pole pair of the
code carrier. The pole width of the master track is de-
fined by the distance of the Hall sensors and is 1.28 mm.
The position of the sensors on the upper chip edge has
been optimized for 32 pole pairs. Accordingly, the Hall
sensors generate a periodic sine and cosine signal with
a cycle length of 2.56 mm. The scan diameter can be
computed from the number of pole pairs. The diameter
of the pole disc although depends on other mechanical
requirements and should be approx. 3 mm greater than
the scan diameter. A specific diameter for the master
and nonius tracks is derived depending on the number
of configured pole pairs.
The distance between the hall sensors of the nonius
track and the master track is stipulated as being 3.6 mm
by the evaluation device. The scan diameters of the
nonius track can be seen in Table 6.
Linear measuring system
With a linear nonius system the pole width of the mas-
ter track is also 1.28 mm. The pole width of the nonius
track is defined by the number of pole pairs with
p_nonius
=
1.28
mm
∗
number
number
of
of
poles_master
poles_nonius
Number of pole pairs
16 32 64
Master track pole width [mm] 1.28 1.28 1.28
Nonius track pole width [mm] 1.365 1.321 1.300
Table 7: Linear scales, pole widths in mm