Miniature Three-Axis Induction Magnetometer for Borehole Logging

A miniature three-axis induction magnetometer (IM) for borehole logging was designed, manufactured, and tested. The form of the IM is a cube with 12 coils at edges, which are embedded in a ring cylinder. Thus, the 12 coils are placed along the x, y, and z axes. Each axis consists of four coils that are connected in series. The length, inner diameter, and outer diameter of the ring cylinder are 40, 43, and 64 mm, respectively. The mass of the IM is 450 g. The working frequency bandwidth is set within 1 Hz-10 kHz. The equivalent induction magnetic noise level of the IM is less than 10 pT/√Hz at 100 Hz for three axes. The features and the noise performances of the IM show the potential for its use in borehole logging.