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differential water capacity and the unsaturated water diffusivity as well as the solute transport data. Also the heat flow parameters (thermal conductivity, thermal diffusivity, specific heat) can be determined if a temperature gradient is applied and a heat flux meter is installed in the soil column. Fig. 65. Example of structure of a LOM/4/mpts based stand for recording instantaneous profiles of soil water content, capillary pressure of soil water, temperature and salinity (apparent electrical conductivity) from soil column(s), with application of a single MUX/8/mpts. Probes are switched in two levels. For instance the LOM above is provided with a 3-pole-4-throw first level multiplexer (FLM) to switch between 1 to 4 131
second level multiplexers (SLMs). To switch between the probes 3-pole-8-throw multiplexers can be applied as the SLMs, as shown in the picture. For such configuration up to 32 LP/ms, 32 LP/t and 32 LP/p probes can be switched. Other options are also possible. The TDR LP/ms probes for water content and salinity use special microwave switches. Remaining probes (LP/p, LP/t) are switched using common solid-state switches and/or reed relays. Characteristics of LOM/mpts meter: • Pulse: sin -like needle pulse having rise-time of about 250 ps. • Range: − apparent electrical conductivity, EC a : 0.000 ≤ EC a ≤ 1 S/m − dielectric constant, ε: 2 ≤ ε ≤ 90 (at EC a < 0.3 S/m) − volumetric water content, θ: 0 ≤ θ ≤ 100 % (at EC a < 0.3 S/m) − matrix potential, ψ : 0 ≤ ψ ≤ 950 mbar − temperature, T: -20 ≤ T ≤ +60 °C • Accuracy: − dielectric constant absolute error: displayed value ±2 − water content absolute error: displayed water content ±2 % or less if contribution of solid matter is accounted for − el. conductivity relative error: ±5 % of displayed value − matric potential absolute error: displayed value ±8 mbar − temperature absolute error: ±0.2 °C • Resolution: − dielectric constant: 0.1 − water content: 0.1 − el. conductivity: 0.001 S/m − matric potential: 1 mbar − temperature: 0.01 °C • Time of test: − dielectric constant: 6 s for first reading then about 3 s for each next single reading − water content: 6 s for first reading then about 3 s for each next single reading − electrical conductivity: 8 s for each single reading − matric potential: 1.5 s for each single reading − temperature: 3 s for each single reading • LOM switching capability: − maximum number of SLMs to control: 15 • SLM switching capability: − maximum number of LP/ms probes to switch: 8 132
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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
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 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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