ekS - Instytut Agrofizyki im. Bohdana DobrzaÅskiego PAN w Lublinie ...

More documents

Recommendations

Info

The values of the refractive index of the tested mineral soils were determined by the laboratory TDR meter [29], and a field TDR meter FOM/mts was used for the measurement of n in the peat soil. The measured values of water content, θ, were recalculated to the desired values of the refractive index, n, on the base of the applied calibration function θ=f(n) [29]. The field measurements were performed in spring on the non tilled saturated soil. The TDR probes were installed below the ground water level (22 – 36 cm), ie at the depth of 60 cm. During the measurement period the soil temperature increased almost two t<strong>im</strong>es, from 6,3°C do 11,7 °C, in continuous saturated conditions (the ground water level did not drop below 60 cm). Therefore, it can be assumed that the observed changes of the EM velocity of propagation, and the values of the refractive index, n, of the soil resulted only from the change of the soil temperature. Table 7. No. Localization Selected physical parameters of the tested soils Soil type (FAO) Depth [cm] Wytyczno Gleyic 1 (sand) Podzol 30 - 40 1.53 ÷ 1.64 Tarnawatka Eutric 2 (silt) Regosol 20 - 30 1.30 ÷ 1.62 2.7 11.8 0.1 Eutric 3 Kępa (clay) Fluvisol 15 - 25 1.08 ÷ 1.40 2.66 Rhinluch Eutric 4 Germany Histosol 20 - 30 0.12 1.4 - 51.4 ρ [g⋅cm -3 ] ρ s [g×cm -3 ] CEC C [%] 2.61 1.4 0.4 24 1.2 A two-rod TDR sensors, LP/m from Easy Test, Ltd. [29], with the rods of 0.8 mm in diameter, 53 length and 5 mm distance between the rods, were applied for the TDR laboratory measurements. The soil samples were stored in PVC cylinders of 10 cm in diameter and 5 cm height. The temperature of the soil samples was measured by thermocouples. A TDR probe was installed horizontally in each cylinder with a soil sample, at the middle of its height. A thermocouple was installed at the same level. Containers with soil samples and the probes were sealed to avoid evaporation of water during the measurement process (about 3 hours), placed in a microwave for homogenous heating and then the velocity of EM propagation in the heated soil sample were measured. 57
7.4. Results and discussion Due to the well known temperature effect of n(T ) (CRC [17]) and the need to verify the measurement instrumentation and the correction formulas (43) and (46), the measurements were performed also on pure water. The calibration formula (47) used in TDR soil water content meters from Easy Test, Ltd. [29] was applied to calculate to evaluate the temperature effect, n T , for pure water. Substituting θ = θT and n = n T we have: θ = 0,175⋅ n − 0,57 (47) nT = 3 ,25 + 5, 7⋅θ (48) T where θ T i n T are temperature dependent result of soil water content measurement with the TDR meter and the temperature dependent soil refractive index, respectively. The conditions necessary to meet for the non-temperature effect water content measurement are: dn / dT ≈ ∆ n / ∆T = 0 and n(20° C) = 8,95 ±E n , where E n represents the absolute measurement error of n. The results of the correction formulas are presented in Fig. 23 and Table 8. They show that the corrections according to (43) and (46) almost meet the discussed conditions. Fig. 23. The effect of the applied temperature corrections for TDR measurement in water: (43) – for the measured refractive index, n (part A), and (46) – for the calculated volumetric water content, θ TDR (part B) 58
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 30 and 31: Fig. 8. Frequency dispersion of the
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 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
show all

ekS - Instytut Agrofizyki im. Bohdana DobrzaÅskiego PAN w Lublinie ...

Create successful ePaper yourself

Delete template?

Save as template?

ekS - Instytut Agrofizyki im. Bohdana DobrzaÅskiego PAN w Lublinie ...