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

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In the TDR method the signal propagates through the switch twice (to the probe and back to the generator) and therefore it is attenuated two times. The implemented prototype switch does not introduce the decrease of frequency band, which would be distinguished from the increase of rise and fall times of the pulses. 10.6. Summary The tested prototype RF SP16T switch has frequency parameters good enough for application in reflectometric soil water content meters. However the attenuation of the signals caused by their insertion loss and energy loss caused by the discontinuity of impedances introduced by them in the 50 Ω transmission lines may produce measurement errors. It seems that the connection of “tree” and “star” topologies would give better results. The presented RF MMIC prototype SP8T switch is integrated in one small enclosure, which introduces smaller insertion loss. Return loss caused by discontinuity of impedances can be easier solved by careful design of the strip lines of the mounting PC board. As compared to the other switches used in the reflectometric technique they have lower power consumption and contain built-in convenient decoder for control signals. The integrated construction with eight channels available additionally increases the competitiveness of the applied microwave MMIC switch. 107
11. TDR SOIL WATER CONTENT, SALINITY AND TEMPERATURE MONITORING SYSTEM – DESCRIPTION OF THE PROTOTYPE Selective measurements, without destructive interference to the measurement process and measured medium from unpredictable reasons are easy for interpretation but practically hard to accomplish. The unwanted sources of error when identified can be eliminated by application of a physically good model of the observed process or by empirical correction based on reference measurements. A lot of measurement errors happen during the wire-transmission of an analog signal from the sensor equipped by an appropriate transducer, converting the usually non-electrical signal to its electrical representation, to the measuring unit. To avoid wire-transmission errors modern measurement systems combine the measuring unit with the sensor-transducer element in the form of a smart transducer or smart sensor. Smart sensors are equipped with microcontrollers or digital signal processors capable to convert the measured signal to the digital form, performing individual calibrations and necessary corrections. Thus most of the data processing is completed at the sensor and the command and data communication with it usually performed in wireless way. The main reasons for the development of automatic measurements systems are: the requirement objective readouts, without the unwanted interference from error sources including the influence of an experiment operator and economical reasons. The integral part of such a system is a data logger for autonomic data collection and storing. The recent development of telecommunication and associated electronics gives the new tools and means for the idea of automatic measurement of environmental physical and chemical properties, especially low power converters of non-electrical signals to easy for processing electrical signal, powerful microcontrollers integrated with analog-to-digital and digital-to-analog converters, timers, digital interfaces and abundant non-volatile memory. The presented study shows the potential of the MIDL (Multi Interface Data Logger) data logger (Fig. 51), its functional features and the function in the automatic measurement system of physical and chemical parameters of soil and ground. The system has been developed in the Institute of Agrophysics in Lublin, Poland, as the direct answer for the need to collect data from ion-selective electrodes that measure the concentration of selected ions in the soil (Research Project 2 P04G 032 26 financed by the State Committee for Scientific Research). Also, the measurement devices developed, produced by the Institute of Agrophysics and used by a number of scientific soil laboratories [29] need a modern and hardware as well as software compatible data logger. The detailed 108
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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
Page 58 and 59: The values of the refractive index
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 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
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