The 16453A is designed for accurate dielectric constant and loss tangent measurements on the E4991A/4291A/B. It employs the parallel plate method, which sandwiches the material between two electrodes to form a capacitor. The E4991A/4291A/B measures the capacitance created from the fixure, and option 002 firmware calculates the relative complex permittivity as described in the 16451B. Adjustment to insure parallel electrodes is required when using the 16451B. This adjustment is not required with the 16453A because the fixure has a flexible electrode that adjusts automatically to the material surface.