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12.7. LP/t - Laboratory Probe for soil temperature LP/t is a laboratory probe for monitoring instantaneous profiles of soil temperature in soil columns or in undisturbed soil cores (Fig. 68). Thin-wall halfrigid polyethylene body of the probe provides ult<strong>im</strong>ate low heat conductivity, thus allowing avoiding the parasite “thermal bridge” effects. Several LP/t probes can be inserted through the wall of the soil column or the sampling cylinder, thus allowing for vertical recording of the instantaneous profiles of temperature. Such an array, when combined with miniprobes for soil moisture/salinity and also probes for matrix potential, makes it possible to collect a set of corresponding temperature data from non-isothermal transition of drying or wetting front, from which readings of bulk electric conductivity as well as matrix potential can be temperature corrected. Also heat transport coefficients (thermal conductivity, thermal diffusivity, specific heat) can be determined if a heat flux meter is installed in the column under investigation. The wall of the cylinder containing a soil core is provided with tapped holes (8 mm diameter). A guide is screwed into the hole prior to the probe installation. This guide helps to avoid air gap around the probe, which otherwise might result while installing. LP/t is pushed into the soil core and fixed with a screwed gland. Fig. 68. LP/t - Laboratory Probe for soil temperature measurement 135
12.8. LP/p - Laboratory miniProbe for soil water capillary pressure LP/p (Fig. 69) is a laboratory miniprobe designed for monitoring instantaneous profiles of soil water capillary pressure (matrix potential, suction force) in soil columns or in undisturbed soil cores sampled with standard sampling equipment. The wall of a cylinder containing the soil core is provided with tapped holes (8 mm diameter). A guide is screwed into the hole prior to the probe installation. This guide helps to avoid air gaps between the ceramic suction cup and the soil, which otherwise might result while inserting the probe into the soil. LP/p is pushed into the soil core and fixed with a clamp nut. Several LP/p can be inserted through the wall of a soil column or a steel sampling cylinder, thus allowing for vertical scanning of the instantaneous water potential profiles. Such an array, when combined with s<strong>im</strong>ilarly installed miniprobes for soil moisture (see 12.6), makes it possible to collect a set of corresponding water content and matrix potential data from drying or wetting front transition (Fig. 70). Fig. 69. LP/p - Laboratory miniProbe for soil water capillary pressure 136
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TDR METHOD FOR THE MEASUREMENT OF W
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PREFACE The importance of water for
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CONTENTS 1. Status of water as an s
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12.2. New prototype version of FOM/
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that stimulate the phenomena and pr
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The solution to the problem of elec
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3. ELECTRICAL MEASUREMENTS METHODS
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v = c 1 2L = = ( θ ) n ∆t ε (2)
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The TDR probe consists of two waveg
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ε a =1 and φ=0.5 the Eq. (10) has
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The experiment description is given
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Results obtained with the discussed
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Notice that at C s = 0, ie when dis
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water orientation polarization [s],
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Fig. 8. Frequency dispersion of the
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The measurements were performed in
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5. EVALUATION OF DIELECTRIC MIXING
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ε α = ∑V α iε i (29) i where
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where SAND and CLAY are percents of
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Below the transition value, the soi
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To verify the observations concerni
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6. TEMPERATURE EFFECT ON SOIL DIELE
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chamber and the freezer, only one w
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The user interface on the main comp
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soil sample volumetric water conten
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close vicinity of the analyzed obje
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process of measurement is non-destr
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dielectric permittivity change caus
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The values of the refractive index
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The relative, ∆n/∆T, and absolu
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Fig. 25. The temperature effect on
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The temperature effect of TDR soil
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The purpose of the above discussion
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( ,25 + T )( 45 + T ) 49 9 f rel =
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8. THE ACCURACY OF SOIL WATER CONTE
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gravimetric method and the soil ref
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where: a 0 ÷ a 6 are coefficients
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values of p F calculated for the re
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eason of this is the fact that wate
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9 ∆θ = 0,2 ⋅10 ⋅ ∆t = 0.00
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values of θ rel for lower values o
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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 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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