Gradiometer coil system and diagnostic device

[0001] Provided is a gradiometer coil system (100; 302; 304; 306) for measuring a magnetic field emanating from a specimen located within the coil system (100; 302; 304; 306). The system comprises at least one receiving coil section (102; 202; 302a), which is sensitive to the mag netic field. Additionally, the system includes at least one compensation coil section (104a, ..., 104d; 204a, ..., 204d; 302b) connected in series with the receiving coil section (102; 202; 302a). The compensation coil section (104a, ..., 104d; 204a, ..., 204d; 302b) is arranged to compensate for external magnetic fields affecting the receiving coil section (102; 202; 302a). Furthermore, the area enclosed by the compensation coil section (104a, ..., 104d; 204a, ..., 204d; 302b) is smaller than the area enclosed by the receiving coil section (102; 202; 302a).