Campbell TDR100 Manuel d'instructions télécharger pdf (Page 23)

TDR100

FIGURE 5-4. Location of Address Jumpers on SDMX50

5.8 Soil Probes

The TDR probes are the sensors of the TDR measurement system and are

inserted into the medium to be measured. The probes are a wave guide

extension on the end of coaxial cable. Reflections of the applied signal along

the waveguide will occur where there are impedance changes. The impedance

value is related to the geometrical configuration of the probe (size and spacing

of rods) and also is inversely related to the dielectric constant of the

surrounding material. A change in volumetric water content of the medium

surrounding the probe causes a change in the dielectric constant. This is seen

as a change in probe impedance which affects the shape of the reflection. The

shape of the reflection contains information used to determine water content.

Both volumetric water content and electrical conductivity can be measured

using fixed spacing 2-rod designs and 3-rod designs (CS605 and CS610).

Campbell Scientific TDR Probes

CS605 CS610

General Description 3-rod probe

no balun required

stainless steel rods

3-rod probe

no balun required

stainless steel rods

Dimensions Rods:

30 cm length

0.476 cm diameter

Probe head

cable-to-rod 10.8 cm

width 7.0 cm

thickness 1.9 cm

Rods

30 cm length

0.476 cm diameter

Probe head

cable-to-rod 10.8 cm

width 7.0 cm

thickness 1.9 cm

Cable type RG58 RG8 low loss

Cable length user-specified length user-specified length

Probe offset factor 0.085 m 0.085 m

Probe constant for

electrical

conductivity (Kp)

*see Section 5.8.1

1.74 1.74

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 55 56

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Campbell TDR100 Manuel d'instructions Page 23

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