| 摘要 |
The device described includes at least one core (3, 4) of a highly-permeable material, a coil (5, 6) to magnetize this core by means of an alternating current source (I) connected to the coil, and at least one measuring coil (7, 8), in which a voltage is induced corresponding to the resulting magnetic field created in the core by the application of the alternating current and by the external magnetic field which is to be measured. The measurement of very small magnetic fields and of relative field variations is made by an integrator device (9) connected downstream of the measuring coil, a device to subtract the direct current from the alternating current in the voltage measurement (Uai) (low-pass filter 13, differential amplifier 10) and a device for recording the maximum values of successive half-waves of the output signal (Ux) of the subtraction device (13, 10). |
