Abstract: Gradient meter to measure the spatial derivatives.DELTA.Hi/.DELTA.j (i=x, y, z ; j=x, y, z)of a magnetic field.This gradient meter comprises two magnetic sonds (7a, 7b) with thin layer, of which the geometric axes of the counterreaction windings are aligned in the direction of axis i, said sonds being spaced from each other along the axis j, the counterreaction current of the first sond being injected in the second sond, the counterreaction current of said second sond being then representative of the value.DELTA.Hi/.DELTA.jto be measured.

Abstract: Each end of the rods surrounding the positioning sensor is provided with a coil, through which passes a current, whose intensity is automatically regulated as a function of the sensor readings in order to make the gradient of the magnetic field due to the rods and to the field itself zero within the sensor area.

Abstract: This invention relates to methods of measuring magnetic fields and a magnetometer for performing the method.According to the method an alternating magnetic field is applied to a thin magnetic film along its axis of difficult magnetization.The alternating magnetic field applied to the film has an amplitude which is less than the anisotropy field of the film, the direction of magnetization of the film then undergoing an oscillation without reversal.An electrical signal representing variations per unit of time of the magnetic induction in the film is withdrawn and analyzed and to effect the analysis the component of the magnetic field is measured at any of the odd harmonic frequencies of the electrical signal. The electrical signal is obtained by collecting the voltage at the terminals of a conducted loop surrounding the film and having its axis directed along the easy axis of the film.