Low Cost 360° Tilt Compensated Electronic Compass

Abstract

Compasses are the traditional way to estimate the north direction. Less known is the fact, that the earth magnetic field in middle Europe has a field strength of approximately 41µT in the downward direction and only 18µT in the northward direction. Thus compasses are sensitive toward tilt angles out of the horizontal directions. Traditionally the magnetised needle is swimming on fluid or mounted with a cardan bearing. For electronic compasses this should be avoided. Additional tilt sensors are required to measure and compensate the resulting tilt. This leads to increased expenses for the system. Now, using low g accelerometers and CMOS integrated fluxgate magnetometers, a low cost micro controller system is presented, that has a size of only 105mm x 60mm x 30mm including display and batteries and a weight below 100g. This system enables a full 360° tilt compensation, a resolution significantly better than 1° and a refresh rate of 10 to 50 Hz, depending on the filter algorithm. It is a suitable addition for GPS based navigation systems and gives the possibility to compensate the influence of the operation surroundings on the earth magnetic field.