A Method for Determination of Alcohol Content in Dielectric Liquids by a Longitudinal-Slot Waveguide
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A Method for Determination of Alcohol Content in Dielectric Liquids by a Longitudinal-Slot Waveguide Viatcheslav Viatcheslavovich Meriakri & Roberto Olmi & Ivan P. Nikitin & Evgenii E. Chigryai & Nikolai A. Fedoseev
Received: 12 November 2009 / Accepted: 5 January 2010 / Published online: 30 January 2010 # Springer Science+Business Media, LLC 2010
Abstract A new method is proposed to determine the content of alcohol in dielectric liquids. The method is based on measuring the attenuation of a wave propagating in a rectangular waveguide with a longitudinal slot in its narrow wall, immersed in a liquid under test. The propagation constant of the H10 mode in such a waveguide is calculated numerically for various parameters of the medium and the waveguide. It is shown that the attenuation of the wave depends on the parameters of the dielectric medium outside the waveguide. Experiment is carried out on two different types of waveguide at frequencies from 29 to 37 GHz with a solution of ethyl alcohol in water as the external medium. The results of the measurements show that the method can be used for the on-line measurement of alcohol concentration during fermentation. Keywords Longitudinal-slot waveguide . Dielectric media . Water solutions
1 Introduction The concentration of ethyl alcohol is one of the main parameters indicating the process of fermentation in the production of alcoholic beverages. There have been a number of publications devoted to the determination of alcohol content in liquids that apply electromagnetic waves as the means for on-line measurement (see, for example, [1–3]). The spectrum of electromagnetic waves used ranges from microwaves [3] to infrared band [1, 2]. The accuracy of alcohol content determination ensured by these methods is about 0.1 vol.%. There also exist other methods (see, for example, [4–6]) that provide higher accuracy; however, these methods involve more sophisticated and expensive equipment. V. V. Meriakri (*) : I. P. Nikitin : E. E. Chigryai : N. A. Fedoseev Kotel’nikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Fryazino, Moscow region 141190, Russia e-mail: [email protected] R. Olmi Institute of Applied Physics “N. Carrara,” National Research Council, Florence, Italy e-mail: [email protected]
J Infrared Milli Terahz Waves (2010) 31:608–613
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In the present paper, we propose a simple method for the determination of alcohol content in liquids that is based on the measurement of a single parameter—attenuation of a wave traveling through a rectangular waveguide with a longitudinal slot. The use of electromagnetic waves of the millimeter-wave band allows one to make the device compact; another advantage is the simplicity of the measurement method, which means that the device can be operated by untrained personnel. The accuracy of the device is about 0.3 vol.%, which is on the same order of magnitude as that of [1, 2].
2 Theory A waveguide with a longitudinal slot is well known as a leaky-wave antenna (see, for example, [7, 8]). The op
