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Fig. 38. The three-rod TDR probe – A, and an Open-Ended Coax probe – B, used in the measurement of dielectric permittivity of soils. ...........91 Fig. 39. Frequency change of real and imaginary parts of the complex dielectric permittivity of methanol for Cole-Cole modelled data and measured using open-ended coaxial probe ...................................92 Fig. 40. Comparison of real, ε’, and imaginary, ε”, parts of the complex dielectric permittivity for the selected soils, calculated from the TDR and Open-Ended Coax probe measurements. ε b-TDR is the bulk dielectric constant measured by TDR..........................................93 Fig. 41. TDR meter output – probe in air .........................................................97 Fig. 42. Examples of electromagnetic microwave switches .............................99 Fig. 43. Construction of SPDT switches build on PIN diodes: A – typical connections, B – serial connection of the diodes in a single channel increase isolation of the switch ............................................100 Fig. 44. Scheme of connections of the tested prototype SP16T switches.......101 Fig. 45. Insertion loss and isolation between channels related to frequency for the MMIC device HMC253QS24 implemented in the prototype TDR switch .......................................................................102 Fig. 46. Prototype one-to-eight microwave switch for the application in TDR soil water content meter............................................................103 Fig. 47. Input pulse and output pulses from the tested SP16T switches.........104 Fig. 48. The reflected signal attenuation introduced by the prototype reed relay and MMIC GaAs switches when the TDR probe was inserted into dry (left picture) and wet (right picture) sand...............104 Fig. 49. Reflections observed from the tested SP16T switches and TDR probe in wet sand...............................................................................105 Fig. 50. Reflectograms presenting reflections of the needle pulse from the TDR probe rods with the application of the prototype MMIC switch (right column) and without it (left column). Left axis represents voltage in mV, θ is the water content of the measured soil samples .......................................................................................106 Fig. 51. Multi Interface Data Logger (in the middle between TDR soil water content, salinity and temperature meters)) in the configuration for the measurement of 16 TDR FP/mts probes..........109 Fig. 52. Example setup of devices for soil and ground physico-chemical parameter monitoring system using wireless communication...........110 Fig. 53. Direct connection of SLAVE modules to Internet network ..............112 Fig. 54. Simplified functional diagram of the MIDL setup in SLAVE configuration .....................................................................................113 147
Fig. 55. Simplified functional diagram of the MIDL setup in MASTER configuration .....................................................................................114 Fig. 56. Serial RS232C port terminal window with the MIDL system initial tests..........................................................................................115 Fig. 57. Portable TDR meter, FOM/mts, for the measurement of soil water content using TDR technique as well as soil apparent electrical conductivity and temperature ............................................................121 Fig. 58. Prototype of a handheld soil water content, salinity and temperature meter constructed with the application of modern components........................................................................................123 Fig. 59. An example of the D-LOG/10/mts-controlled stand incorporating six D-MUX/10/mts 2-nd level multiplexers. Maximum amount of the controlled FP/mts (or FP/m) probes is 60. For clarity only a single D-MUX was linked with the D-LOG and a single probe was connected to each D-MUX when taking the picture ..................124 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) ................125 Fig. 61. FP/m, FP/mts - Field Probe for water content, temperature and salinity of soil developed in the IAPAS, Lublin................................127 Fig. 62. The principle of installation of the FP-type probes. In order to minimize disturbances in the soil structure the probes are inserted into the soil via pilot holes, circularly distributed over the soil surface. The holes run slantwise and converge along a chosen vertical line. The cables are buried below the soil surface to protect them against the UV sun radiation as well as against rodents. ..............................................................................................127 Fig. 63. A near-surface probe FP/mts/ns ........................................................129 Fig. 64. Approximate region of influence of the FP probe, defined as a solid beyond of that changes in water content do not markedly affect readings of water content ........................................................130 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......................................................................................131 Fig. 66. LP/ms - Laboratory miniProbe for soil water content and salinity measurement......................................................................................133 148
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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
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ε" = EC ε d " + (82) 2π fε wher
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dielectric permittivity, the dielec
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The applied lumped capacitance mode
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stainless steel wires soldered to t
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ε’ Open Coax and ε b-TDR , exce
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− − 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 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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