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

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