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D-LOG/mts (Fig. 59) is a TDR (Time-Domain Reflectometry) technology based, computer aided instrument, designed for periodic recording of instantaneous profiles of soil water content, temperature and salinity (bulk electrical conductivity) in chosen time intervals. It is suitable for long-term lysimeter-based investigations and also for field experiments, when monitoring of water, solute and heat transport is required. Fig. 60. Example of an arrangement of the D-LOG/mts system able to scan 60 FP/m(ts) probes. All cables are laid about 30 cm beneath the soil surface to protect them against static electricity, UV radiation and rodents as well. FP/mts feeder cables (6 m) The example of an arrangement of the D-LOG/mts system able to scan 60 FP/m(ts) probes is presented in Fig. 60. D-LOG is equipped with a built-in local computer having an RS232C serial port. It serves for: • controlling pulse circuitry action 125
• recording voltage-versus-time traces • calculating pulse attenuation and velocity of propagation • calculating the soil dielectric constant, water content and electrical conductivity • communicating with a master PC via the RS232C serial port D-LOG uses probes type of FP/mts for water content, temperature and bulk electrical conductivity. Also FP/m probes can be applied if only water content is of concern. To calculate water content a factory-installed conversion equation can be used and/or a user-determined calibration function can be applied as well. To switch between FP/mts or FP/m probes D-LOG is provided with an inherent 1-st level switch and optional amount of standing alone 2-nd level switches (D-MUX/n/...), as shown in figures. Each 2-nd level switch contains a water content, temperature and salinity control circuitry and also a single-pole-nthrow microwave switch, where 2
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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
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 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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