GEOMAGNETIC SENSOR

PROBLEM TO BE SOLVED: To reduce output errors caused by phase shift of synchronous detection by preventing time required up to magnetic saturation of a magnetic substance core from being changed even when temperature is changed.SOLUTION: A geomagnetic sensor having a sensor part 10 obtained by winding an excitation coil 12 and a detection coil 13 around a magnetic substance core 11 and constituted so as to synchronously detect an output obtained by removing a DC component from a detection output obtained by the detection coil 13 by a signal having a frequency twice an excitation frequency for exciting the excitation coil 12, integrate the detected output, and negatively feed back the integrated output to the detection coil 13 includes: an oscillation circuit 70 for outputting an excitation frequency signal, a signal having a frequency twice the excitation frequency and a signal obtained by shifting the phase of the twice frequency signal by 90 degrees; a phase difference detection part 50 for detecting and outputting a phase difference between the output obtained by removing the DC component and the signal whose phase is shifted from the signal having the frequency twice the excitation frequency by 90 degrees; an integrator 60 for integrating the output of the phase difference detection part 50; and an excitation control part 33 for controlling an excitation current flowing into the excitation coil 12 by an output from the integrator 60.