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Fig. 8. Frequency dispersion of the real part, ε’, of the complex dielectric constant and the loss angle, δ, for the electrolyte for its various electrical conductivities, EC w The time-domain reflectometry as applied to the measurement of water content and salinity of porous materials implements the property described above. 3.4.2. Summary 1. The lower electric conductivity of the electrolyte present in the soil, the lower is the lower frequency limit, where the electrolyte behaves as pure water (dielectric, insulator), which enables the dielectric measurement of soil water content without the influence if its electric conductivity. 2. If the electrical conductivity of the soil electrolyte does not exceed the value of 1 [Sm -1 ], using the sufficiently high, but not higher than 10 10 Hz, frequency of the applied electric field, the ion conduction is dominated by orientation polarization of soil water particles. 29
4. THE INFLUENCE OF SOIL ELECTRICAL CONDUCTIVITY ON THE SOIL WATER CONTENT VALUES MEASURED BY TDR METHOD Topp et al. [90] did not find the influence of soil salinity, or soil electrical conductivity, EC a , on the the electromagnetic wave velocity of propagation for mineral soils wetted with NaCl and CaSO 4 solutions of conductivity values practically found for soil solutions. However they found the increase of TDR measured water content, θ TDR , measurement error for high saline soils. The explained is as a result of high attenuation of the TDR pulse and the problems with finding the correct reflection point. Dalton et al. [19] measured simultaneously water content and electrical conductivity in the range 0.03 ÷ 0.14 [Sm -1 ] of saturated soil samples (θ = 0.34 ± 0.01) using the TDR method. They found that TDR determined soil water content is not influenced by the soil electrical conductivity. In the electromagnetic field of high frequency the soil electric conductivity does seem to influence the velocity of EM propagation. Fig. 8 shows that in the defined frequency range the loss angle decreases to the values close to zero. This means that for the frequencies in this range the imaginary part of the complex dielectric permittivity (6) is negligible. Consequently for the TDR measurement technique of soil content determination based on the measurement of the electromagnetic wave propagation velocity in the soil can be simplified from Eq. (4) to Eq. (2). The following chapter will practically verify these conclusions. 4.1. Material and method The soil material consisted of two soils (Table 4) and their mixtures prepared in the proportion, so as to have the density of soil samples equally distributed in the range 1.23 – 1.91 [gcm -3 ]. Table 4. The parameters of the soils used for the preparation of soil mixtures. 30
Page 2 and 3: TDR METHOD FOR THE MEASUREMENT OF W
Page 4 and 5: PREFACE The importance of water for
Page 6 and 7: CONTENTS 1. Status of water as an s
Page 8 and 9: 12.2. New prototype version of FOM/
Page 10 and 11: that stimulate the phenomena and pr
Page 12 and 13: The solution to the problem of elec
Page 14 and 15: 3. ELECTRICAL MEASUREMENTS METHODS
Page 16 and 17: v = c 1 2L = = ( θ ) n ∆t ε (2)
Page 18 and 19: The TDR probe consists of two waveg
Page 20 and 21: ε a =1 and φ=0.5 the Eq. (10) has
Page 22 and 23: The experiment description is given
Page 24 and 25: Results obtained with the discussed
Page 26 and 27: Notice that at C s = 0, ie when dis
Page 28 and 29: water orientation polarization [s],
Page 32 and 33: The measurements were performed in
Page 34 and 35: 5. EVALUATION OF DIELECTRIC MIXING
Page 36 and 37: ε α = ∑V α iε i (29) i where
Page 38 and 39: where SAND and CLAY are percents of
Page 40 and 41: Below the transition value, the soi
Page 42 and 43: To verify the observations concerni
Page 44 and 45: 6. TEMPERATURE EFFECT ON SOIL DIELE
Page 46 and 47: chamber and the freezer, only one w
Page 48 and 49: The user interface on the main comp
Page 50 and 51: soil sample volumetric water conten
Page 52 and 53: close vicinity of the analyzed obje
Page 54 and 55: process of measurement is non-destr
Page 56 and 57: dielectric permittivity change caus
Page 58 and 59: The values of the refractive index
Page 60 and 61: The relative, ∆n/∆T, and absolu
Page 62 and 63: Fig. 25. The temperature effect on
Page 64 and 65: The temperature effect of TDR soil
Page 66 and 67: The purpose of the above discussion
Page 68 and 69: ( ,25 + T )( 45 + T ) 49 9 f rel =
Page 70 and 71: 8. THE ACCURACY OF SOIL WATER CONTE
Page 72 and 73: gravimetric method and the soil ref
Page 74 and 75: where: a 0 ÷ a 6 are coefficients
Page 76 and 77: values of p F calculated for the re
Page 78 and 79: eason of this is the fact that wate
Page 80 and 81:
9 ∆θ = 0,2 ⋅10 ⋅ ∆t = 0.00
Page 82 and 83:
values of θ rel for lower values o
Page 84 and 85:
9. COMPARISON OF OPEN-ENDED COAX AN
Page 86 and 87:
ε" = EC ε d " + (82) 2π fε wher
Page 88 and 89:
dielectric permittivity, the dielec
Page 90 and 91:
The applied lumped capacitance mode
Page 92 and 93:
stainless steel wires soldered to t
Page 94 and 95:
ε’ Open Coax and ε b-TDR , exce
Page 96 and 97:
− − The difference of the imagi
Page 98 and 99:
Integrated Circuit) recently introd
Page 100 and 101:
10.2. Electromechanical microwave s
Page 102 and 103:
RF1. Two PIN diodes in series in ea
Page 104 and 105:
The significant aspect of the proto
Page 106 and 107:
visible for lower values of soil el
Page 108 and 109:
In the TDR method the signal propag
Page 110 and 111:
description of functional and techn
Page 112 and 113:
MASTER modules are wireless transce
Page 114 and 115:
time the Real Time Clock module wak
Page 116 and 117:
ase station distinguishes A SLAVE d
Page 118 and 119:
sensor, format the data received fr
Page 120 and 121:
12. SOIL WATER STATUS MONITORING DE
Page 122 and 123:
D-LOG/mpts is a moisture/pressure/t
Page 124 and 125:
For compatibility reasons it uses t
Page 126 and 127:
D-LOG/mts (Fig. 59) is a TDR (Time-
Page 128 and 129:
12.4. FP/m, FP/mts - Field Probe fo
Page 130 and 131:
inside of a separate polyethylene b
Page 132 and 133:
differential water capacity and the
Page 134 and 135:
− maximum number of LP/p probes t
Page 136 and 137:
12.7. LP/t - Laboratory Probe for s
Page 138 and 139:
From the collected data set, after
Page 140 and 141:
25. de Loor G.P.: Dielectric proper
Page 142 and 143:
TDR. Symposium on Time Domain Refle
Page 144 and 145:
100. Whalley W.R.: Considerations o
Page 146 and 147:
Fig. 14. Fig. 15. Fig. 16. Fig. 17.
Page 148 and 149:
Fig. 38. The three-rod TDR probe -
Page 150 and 151:
Fig. 67. A set of LP/ms and LP/p LO
Page 152:
Table 17. An example of the executa
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