Philips KMZ51 Application Note page 2

Philips Semiconductors
Electronic Compass Design using
KMZ51 and KMZ52
The KMZ51 and KMZ52 from Philips Semiconductors are magnetic field sensors, dedicated to compass
applications. Both sensors rely on the magnetoresistive effect and provide the required sensitivity and linearity
to measure the weak magnetic field of the earth. While the KMZ51 is a single axis field sensor, the KMZ52
comprises a two-dimensional field sensor, as it is required for a compass, within one package. Both devices are
equipped with integrated set/reset and compensation coils. These coils allow to apply the flipping technique for
offset cancellation and the electro-magnetic feedback technique for elimination of the sensitivity drift with
temperature.
Besides the sensor elements, a signal conditioning unit and a direction determination unit are required to build
up an electronic compass. The main functions of the signal conditioning unit are amplification of the sensor
signals and offset compensation. For high resolution systems, also the temperature drift of sensitivity should be
compensated. Both compensation techniques can be implemented simply by controlling the integrated set/reset
and compensation coils of the KMZ51/KMZ52. In the direction determination unit, the azimuth is derived as the
desired compass output quantity.
The given paper shows how to realize signal conditioning and direction determination in conjunction with KMZ51
or KMZ52. Also calibration techniques with respect to interference fields, declination and tilt are pointed out.
Finally, system accuracy is covered and examples for complete compass systems are given.
Abstract
2
Application Note
AN00022