The present invention relates to a field-sensor device comprising a reference field sensor providing a reference sensor signal in response to a field, a calibrated field sensor providing a calibrated sensor signal in response to the field, a reference circuit connected to the reference field sensor and adapted to receive a reference signal, and an adjustable circuit connected to the calibrated field sensor and adapted to receive a calibrated signal. When the adjustable circuit is adjusted with the calibrated signal, said calibrated signal being different from the reference signal, the calibrated field sensor provides a calibrated sensor signal substantially equal to the reference sensor signal. The field sensor device is arranged to be exposed, when in a calibration mode, to a uniform calibration field and, when in operational mode, to an operational field being a field gradient.