TLE4923 Datasheet, PDF (10/18 Pages) Siemens Semiconductor Group – Dynamic Differential Hall Effect Sensor IC

TLE 4923
Application Notes
Two possible applications are shown in Figure 10 and Figure 11 (Toothed and Magnet
Wheel).
Two-wire application is shown in Figure 12.
Gear Tooth Sensing
In the case of ferromagnetic toothed wheel applications the IC has to be biased by the
south or north pole of a permanent magnet (e.g. SmCo₅ (Vacuumschmelze VX170) with
the dimensions 8 mm × 5 mm × 3 mm) which should cover both Hall probes.
The maximum air gap depends on:
– the magnetic field strength (magnet used; pre-induction) and
– the tooth wheel that is used (dimensions, material, etc.; resulting differential field).
a centered distance
of Hall probes
b Hall probes to
IC surface
L IC surface to
tooth wheel
a = 2.5 mm
b = 0.3 mm
Figure 8 Sensor Spacing
b
L
N
S
a
AEA01259
T
d
AEA01260
DIN
d
diameter (mm)
z
number of teeth
m module m = d/z (mm)
T
pitch T = π × m (mm)
Conversion DIN – ASA
m = 25.4 mm/p
T = 25.4 mm CP
ASA
p
PD
CP
diameter pitch p = z/d (inch)
pitch diameter PD = z/p (inch)
circular pitch CP = 1 inch × π/p
Figure 9 Tooth Wheel Dimensions
Semiconductor Group
10
1998-04-29