[en] The invention deals with magnetic measurings and it can be used in mass-spectrometry for precise measuring the square of induction of constant and slowly varying magnetic fields. A digital gauge of the square of magnetic induction containing cascadly connected two Hall transducers, current source, keys voltage-digital converter phase-sensitive elements, control unit and digital detection device is close to the suggested one in technical essence. The purpose of the invention is the increase of measuring fast response. Use of the suggested devise permits to build precise digital gauges of induction square of spacefully non-uniform direct and alternating magnetic fields at the increased fast response of the gauges