Abstract: An improved ring core second harmonic flux gate magnetometer is constructed as a module for use as a ferrous metal detector. Pairs of modules may also be used as gradiometers. Various uses and winding arrangements on the ring cores are disclosed.

Abstract: A passive ferromagnetic detection station in which the position of the ferromagnetic object carried by a person may be indicated. A plurality of gradiometers mounted at predetermined vertical positions along two vertical members are used to sense any disturbances in the earth's magnetic field. Each gradiometer has a predetermined pattern or area of sensitivity to magnetic fields in which it senses disturbances in the earth's magnetic field. In a preferred embodiment the sensitivity patterns may overlap in predetermined areas. The outputs of the gradiometers are individually processed and converted to digital signals. The digital signals may be used to control a visual display device.