A novel method of determining the permittivity of liquids

A novel method to measure the permittivity of liquids is used in a microwave gauging system, developed for detection of liquid levels in tanks. The system is described as a frequency stepped continuous wave (FSCW) radar for precision liquid level detection. Usually a radar system is only employed to find the surface of the liquid. With the microwave measurement system described here one can detect a second level which may be the tank bottom or an impurity level, for example. To monitor the permittivity of the liquid with the same measurement system a novel algorithm is derived. Measured uncertainties of ±0.2 mm have been achieved for the multi-level range detection performed in the frequency range from 2 to 3 GHz. From these measured data the error of the calculated permittivity was about 2%. By using this technique to determine the permittivity of the liquid it is possible to reduce the complexity of the measurement system