Fig. 5. Effective dielectric constant in ethanol where a torus is dangling, as a function of the distance between the central electrode tip and the top surface of the torus. Negative values correspond with the tip above the torus. The torus section is a square of 9 mm². Torus outside diameters of (a) 20, (b) 26, and (c) 32 mm, respectively. For the 32-mm torus diameter, the probe annular electrode may be inserted inside the torus. Circles correspond with measured values. Lines correspond with simulations assuming for the torus material (polyvinyl chloride)