The FGM400 is a gradiometer magnetometer that used along with the SBL10 and DBL15 as borehole or diver probe. The FGM400 features same performance and sensitivity than the FGM650 probe.
The FGM400 has a base distance between the Fluxgate sensing elements of 400mm. the sensor is cased into an Aluminum tube, sealed for 100m water depth. The probe connector is a MIL grade one, protected by an screw-on aluminum sealing cap.