New Ferroprobe Excitation Method and Modulator Variant for its Implementation

A new method of ferroprobe excitation was developed. The method consists in simultaneous influence of bias longitudinal constant magnetic field and exciting longitudinal alternating field on its modulator magnetic core. This simultaneously initiates two physical processes on the frequency of the electro mechanic resonance in the magnetic core, particularly, magnetic modulation transformation of magnetic core magnetic permeability and eddy current excitation in its surface layer. Due to the electrodynamic interaction of eddy currents with the bias constant magnetic field, acoustic field is excited in the magnetic core in the form of radial longitudinal waves. These waves go through further acoustic modulation transformation of magnetic core magnetic permeability. A modulator was proposed to implement the new bifactor method of ferroprobe excitation. It consists of a core-type magnetic circuit designed as two cores joined with a permanent magnet and a feed-through measuring coil. This coil consists, in its turn, of two sections symmetrically spaced-apart in relation to the permanent magnet. Exciting cylindrical electrodes with long slots are installed on the inner surface of these sections. Together with the low wire layer in the corresponding winding sections, they form structural coupling capacitors through which alternating voltage is supplied to the winding. When the modulator works as part of a ferroprobe operating in the magnetic field meter mode, winding sections have opposite connection, when the ferroprobe operates in the gradiometer mode, feed-through coil winding sections must have series connection. The developed method makes it possible to improve the measuring accuracy, sensitivity and interference resistance.