Equivalent Input Magnetic Noise Analysis for the Induction Magnetometer of 0.1 mHz to 1 Hz

Induction magnetometer (IM) is the transducer for measuring the magnetic field's variations, which is widely used in space research, geophysical exploration, and so on. Among all kinds of IMs, IMs of 0.1 mHz to 1 Hz with negative feedback flux and chopper stabilized amplifiers are especially popular used for the magnetotelluric method in geophysical explorations. In this paper, the equivalent input magnetic noise (EIMN) of IMs of 0.1 mHz to 1 Hz is discussed and modeled. Seven main noise sources are described, numerical evaluated, and experimental modeled separately. At last, an experimental IM is built and its EIMN is measured low to 0.1 mHz to confirm the theoretical model.