Figure 9.

Cross sections in the dimensionless plane $x^{*}=2x/D$ $y^{*}=2y/D$ of the spatial distribution of sensor sensitivity in medium. Distribution is deduced from the expression of electrical field for the electrode design in Figure 8. Each contour corresponds to points in which sensitivity normalized by its maximum value has a value $\eta$, with $\eta =0.40$ (filled with magenta color), $\eta =0.25$ (purple) and $\eta =0.10$ (blue), respectively. The distribution depends on the sensor geometry factor $\alpha =\mathsf{\Phi }/D$, where D is the electrode spacing and $\mathsf{\Phi }$ their diameter. Distributions are reported for (a) $\alpha =0.12$; (b) $\alpha =0.25$; (c) $\alpha =0.50$.