A major component of the MRI machine is the magnet, which guarantees the polarization field Bo. The homogeneity of Bo is an important property for obtaining good quality images. The calibration and measurement of this parameter during the assembly process of the equipment is essential to ensure a proper operation. In this paper is described a hardware capable of making measurements of a magnetic field in a fast, comfortable, dynamic form and very low cost compared to the price of commercially available magnetometers. The proposed hardware is based on measurements of the magnetic field flux in certain samples, of chemical composition and magnetic properties well known, that originate the phenomenon of nuclear magnetic resonance. With the measurements obtained are created homogeneity maps in certain regions of interest allowing the characterization of the magnet.