Fig. 11. (a) Calculated sensor capacitances C_{model with FEP}() and C_{model without FEP}() for the case where the access tube is coated (hollow circles) and not coated (solid squares) with the 0.5 mm thick the FEP shrink fit with permittivity _FEP = 2. (b) Normalized sensor readings N_{model with FEP}() and N_{model without FEP}() derived from C_{model, with FEP}() and C_model, _{without FEP}() using Eq. [11] for the case with (hollow circles) and without (solid squares) the shrink fit on the access tube.