A magnetometric device for evaluating a physical parameter (D, K), comprising a circuit (1) which is sensitive to a magnetic field, a measurement circuit (2) and a magnetic field generator (3), the sensitive circuit (1) being subjected to a magnetic field which varies with the physical parameter to be measured and having an electrical characteristic which is evaluated by the measurement circuit and which varies as a function of the magnetic field. The field generator (3) is designed to reverse the polarity of the applied magnetic field, the evaluation of the physical parameter thus being able to be corrected of the parasitic influence of the terrestrial magnetic field.