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TDR100

water content = 18%

water content = 37%

FIGURE 8-3. Waveforms collected in a sandy loam using CS610 probe

with RG8 connecting cable. Volumetric water content values are 10,

18, 26, 30 and 37%. Solution electrical conductivity is 10.2 dS m

-1

The combined effect of long cable runs and high soil electrical conductivity

must be considered when TDR measurements are taken.

9. Algorithm Description and Parameter Adjustment

9.1 Introduction

This section presents a general description of the algorithms in the TDR100 for

electrical conductivity and water content measurement.

9.2 Algorithm for Calculation of TDR Probe Rod Apparent

Length

9.2.1 Algorithm Description

Equation [2] of Section 7 shows the relationship between apparent dielectric

constant,

Ka, and apparent TDR probe rod length, La. The equation is

repeated here for convenience. L is the actual rod length.

[2]

Ka is calculated using equation [2] then converted to volumetric water content

using empirical equations such as equations [3] and [4] of Section 7.

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Campbell TDR Specifiche Pagina 36