Abstract: The author designed a new kind of compass which has the features of greater accuracy, low cost and greater portability. When the magnetic material gets saturated, the inductance’s self-induced coefficient is inversely proportional to the magnetic field’s intensity which is proportional to the surge frequency in RL surge oscillator circuits. The magnetic azimuth angle which is displayed on the LCD is calculated based on the frequency of the RL surging circuits detected by MCU. The errors caused by the apparatus itself are modified by the positive and inverse charging and discharging of RL circuits, and those caused by the outside are modified by the software. This compass adopts digital processing techniques, and it is anti-jamming, precise, dependable, and flexible. Test results have proved that the electromagnetic compass can reach a high accuracy. The error is less than 1 degree. Thus it can meet the requirements of actual application.

Key words: magnetic field, electronic magnetic compass, MCU, PNI, surge frequency