A transmission line cell for measuring the permittivity of liquids over the frequency range 90 MHz to 2 GHz

Abstract

A coaxial line transmission cell is described which allows accurate permittivity measurements to be made on lossy liquids over the frequency range 90 MHz to 2 GHz. To test the performance of the cell, measurements were made on water, methanol and ethanol at 293K.

Microwave resonant sensor for measurement of ionic concentration in aqueous solutions

“…Transmission methods employ a two-port sample cell, that is loaded with the sample in some way, and use the ratio of the power transmitted by the cell to the power applied to it to infer dielectric properties of the sample [80][81][82]. There have also been various waveguide-based transmission methods for the measurement of complex permittivity discussed in the literature [84][85].…”

Electromagnetic moisture measurement

“…As with the other techniques discussed in the dielectric measurement methods chapter, development specially devoted to electromagnetic moisture determination will be presented below in chapter 5. [175,176]; b) partly filled line section [177,178]; c) line with movable probe for effective length variation of liquid samples [179][180][181]; d) standard setting for both liquids and solids [182]; e) completely filled slotted line [183]; f) slotted line combined with length variation of liquid sample [184]; g) equivalent to f) but partly filled with liquid or solid sample [185]; h) partly filled slotted line [186]; i) convenient setting for reflection coefficient determination, with sample length variation for liquids [187][188][189]. 1, line with ε, sample; 2, feeding line; 3, receiving line; 4, receiving line movable along the direction of wave propagation; 5, movable probe; 6, slotted line; 7, movable shorting plunger; 8, directional coupler.…”

“…Therefore, individual mixture relations are often required in order to correlate the apparent permittivity of building materials with their moisture content. An example is the empirical polynomial = 6644.9 ⋅ w 4 − 7014.9 ⋅ w 3 + 2698.2 ⋅ w 2 − 445.26 ⋅ w + 29.07 (179) which satisfactorily represents the moisture dependent apparent permittivity of gypsum [797]. Another example is the water content of wood for which the following model has been given for the real part of the apparent permittivity [798,799]:…”

Measuring the dielectric properties of materials. Ninety-year development from low-frequency techniques to broadband spectroscopy and high-frequency imaging

“…In particular for the study of high-permittivity samples with reflection factors close to −1, transmission measurements have been considered a superior alternative. A great variety of configurations has been designed [275,281,[300][301][302][303][304][305][306][307][308][309][310][311][312][313][314] of which some popular versions are sketched in figure 16.…”

“…In some correspondence to standing wave and reflection profile determination, techniques using samples of fixed length and transversal dimensions matched to the profile of the measurement line (figure 16(A) [308,311]) have been reported as well as such employing samples which do not completely fill the cross-section of the specimen cell (figure 16(B) [305,309]). In investigations of liquids, measurements at varying sample length have been preferably employed (figure 16(C) [300,301,304,306,310,313,314]).…”