Introduction - Philips KMZ51 Application Note

Philips Semiconductors
Electronic Compass Design using
KMZ51 and KMZ52

1. INTRODUCTION

The magnetic compass is a crucial navigation tool in many areas, even in times of the global positioning system
(GPS). Replacing the "old" magnetic needle compass or the gyrocompass by an electronic solution offers
advantages like having a solid-state component without moving parts and the ease of interfacing with other
electronic systems.
For the magnetic field sensors within a compass system, the magnetoresistive (MR) technology is the
preferable solution. Compared to flux-gate sensors, which could be found in most electronic compasses until
now, the MR technology offers a much more cost effective solution, as it requires no coils to be wound and can
be fabricated in an IC-like process. Due to their higher sensitivity, MR sensors are also superior to Hall elements
in this application field.
The intention of this paper is to give a general introduction of electronic compass design with MR sensors and
also to give detailed realization hints. Therefore, the basic characteristics of the earth´s magnetic field are
explained and an overview of the building blocks of an electronic compass is given. Following a description of
Philips´ magnetoresistive sensors for compass applications, the design of each building block is covered in
detail. Here, both hardware and software realisations are shown. Further sections are dedicated to special items
like interference field calibration, true north calibration, tilt compensation and system accuracy. Finally,
examples for complete compass systems are given, consisting of previously described building blocks.
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Application Note
AN00022