**Fig. 12.15.** The lead field current density distribution of a unipolar single-coil magnetometer with a 10 mm coil radius in a cylindrically symmetric volume conductor calculated from Equation 12.42. The dashed lines are the *isosensitivity lines*, joining the points where the lead field current density is 100, 200, 300, 400, and 500 pA/m^{2}, respectively, as indicated by the numbers in italics.