ATS665LSG

TRUE ZERO-SPEED GEAR TOOTH SENSOR

Final Version, Rev 1.0; DSD; 01Aug03

Page 11

SENSOR/TARGET EVALUATION

In order to establish the proper operating specification for a particular sensor/target system, a systematic evaluation of the

magnetic circuit should be performed. The first step is the generation of a magnetic map of the target. By using a

calibrated device, a magnetic signature of the system is made. The following is a map of the 60-0 reference target. Flux

density shown is the differential of the magnetic fields sensed at the two Hall elements.

-300

-250

-200

-150

-100

-50

0

50

100

150

200

250

300

0

5

10

15

20

25

30

35

Position [º]

0.94mm

1.19mm

1.44mm

1.69mm

1.94mm

2.19mm

2.44mm

2.69mm

2.94mm

3.19mm

A single curve is distilled from this map data that describes the peak-peak magnetic field versus air gap. Knowing the

minimum amount of magnetic flux density that guarantees operation of the sensor, one can determine the maximum

operational air gap of the sensor/target system. Referring to the chart below, a minimum required peak-peak signal of 60G

corresponds to a maximum air gap of approximately 2.5 mm.

ATS665LSG 60-0 TARGET MAP

0

100

200

300

400

500

600

700

0.511.522.533

Air Gap [mm]

.5

Worcester, Massachusetts 01615-0036 (508) 853-5000

Copyright © 1993, 1995 Allegro MicroSystems, Inc.

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