TLE 4923

Semiconductor Group

10

1998-04-29

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. SmCo

the dimensions 8 mm

× 5mm × 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).

Figure 8

Sensor Spacing

Figure 9

Tooth Wheel Dimensions

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

b

L

a

N

S

AEA01259

d

T

AEA01260

Conversion DIN – ASA

m = 25.4 mm/p

T = 25.4 mm CP

DIN

d

diameter (mm)

z

number of teeth

m

module

T

pitch

ASA

p

diameter pitch

p

=

PD

pitch diameter PD =

CP

circular pitch

CP = 1 inch

× π/p