ON THE ISSUE OF MUTUAL INFLUENCE OF PROBES IN A MULTIPLE-UNIT (MATRIX) SURFACE EDDY CURRENT PROBE

The distribution of eddy currents induced in metal by a surface multiple-unit eddy current probe (ECP) is investigated. A mathematical formula is derived to calculate the increment in the magnetic moment of the eddy currents within the metal, accounting for the mutual interactions and orientation of the individual eddy current probes within the ECP array. The results indicate that the increment in the magnetic moment of the eddy currents increases monotonically as the spacing between the probes in the ECP array decreases, while the sign of the magnetic moment increment is determined by the phase configuration of the probes in the ECP array. Inphase switching on of eddy current probes in the ECP array reduces the increment of the magnetic moment of eddy currents and diminishes the amplitude of the surface ECP signal. In contrast, when the probes operate in antiphase, the magnetic moment increment increases, leading to an enhanced signal amplitude for the ECP. It is shown that theoretical calculations of the mutual influence between the surface eddy current probes in the multiple-unit ECP are in accordance with experimental observations.