Fig. 8
Self-noise level of the induction coil. The induction coil sensor noise level is measured in a magnetically shield room using a dynamic signal analyzer Agilent 35670A. The noise level is approximately 1 pT/√Hz at 1 Hz. There is 1/f noise in the 1000 to 0.1-Hz frequency band, and in the nearby band of 1000-Hz frequency, the noise level is flat. Peaks at 50 Hz and its harmonics are clearly observed because of the ambient 50-Hz noise. This is because the magnetically shield room was not very “clear”