Permittivity measurements on low and medium loss liquids using a terminated coaxial line

A method is given for measuring the complex permittivity of a liquid contained in a short-circuited line. Basically, the technique consists of plotting a standing wave pattern and comparing this with the theoretically predicted waveform. This is an improvement on previous methods in that the dielectric properties of a lossy liquid with poorly defined maxima and minima can be investigated; moreover, a liquid with a low permittivity and a first minimum lying outside the range of measurement can be examined. A method is also given for improving the capabilities of the standard least squares computer analysis when parameter information from the data is low, or when the initial parameter estimates are far away from the correct value.