In this paper an easy way to calibrate and adjust the output response of a multi-sensor probe for non-destructive testing on conductive material is proposed in order to perform the calibration, a simple coil is used, considered as a reference magnetic field generator thanking to a preliminary characterization carried out by using a simulation software. An FFT based algorithm was then used for probe adjustment. The calibration and adjustment apparatus can be easily integrated in the realized multi-sensor probe, so realizing a self-calibrating NDT instrument. The realized probe has then been tested on specimen with known cracks and the experimental results have been compared with the theoretical ones showing a very good agreement.