Modeling of the process for measurement of interface position between two media in a tank by using radiofrequency method

The article describes modeling of the process for measurement of interface position between two media, in particular two immiscible liquids with different density, one over the other, contained in a tank using radiofrequency method. In this case it is provided invariance of measurement results to electrical parameters of both media. Independent sections of transmission lines with end horizontal sections are used as sensors. To provide invariance to electrical parameters of the lower medium there are used natural resonance frequencies of the two sections of a transmission line or phase shifts of electromagnetic waves with fixed frequency excited and received at the section inputs and reflected from section ends. Functional conversion of informative parameters helps to determine interface position between two media in the tank. In the modeled measurement process in order to provide invariance to electrical parameters of two liquids there are placed vertically three sections of a coaxial or two-wire transmission line. Due to the availability of horizontal end sections at all three transmission line sections, there is no uncertainty of measurement results when measuring the interface position at its zero-, or close to zero, readings in the course of functional processing of resonance frequencies of the three transmission line sections. These sections may be done identical with equal end horizontal parts of a fixed length but with different reactive loads at the ends of horizontal parts. Between parallel outer conductors of coaxial line sections up to the ends of their horizontal parts, electromagnetic oscillations are excited as in a two-conductor line section having end reactive load that is different from the end reactive loads of coaxial line sec-tions. This provides the difference of three dependencies of corresponding resonance frequencies on coordinate of interface position between two media. Determination of interface position in the modeled measurement process on the base of this method is characterized by higher measurement accuracy, easy realization of radiofrequency devices and is free from shortcomings of other radiofrequency methods.