Automatic Determination of the Complex Permittivity of Liquids of Low Dielectric Loss

At frequencies of about 10 GHz, the complex relative permittivity of liquids of low loss is determined by an automatic precision method based on the computer-controlled measurement of the microwave power at the lower exit of a liquid-filled, inclined, standard waveguide and on a computer curve-fitting procedure. For the real part of the permittivity, a relative uncertainty of ±0.0007 is achieved. For the loss tangent, the uncertainty is |δtan Δ| ≦ 11 × 10-6.