Campbell Scientific CS616 and CS625 Water Content Reflectometers - Manual (Page 6)

Table of Contents
7.4 Operating Range ................................................................................ 29
7.4.1 Soil Electrical Conductivity ....................................................... 29
7.4.2 Soil Organic Matter, Clay Content and Soil Bulk Density ......... 29
7.5 Error Sources in Water Content Reflectometer Measurement .......... 30
7.5.1 Probe-to-Probe Variability Error ................................................ 30
7.5.2 Insertion Error ............................................................................ 30
7.5.3 Signal Attenuation Error ............................................................ 30
7.6 Temperature Dependence and Correction ......................................... 31
8. Water Content Reflectometer User-Calibration ...... 32
8.1 Signal Attenuation in Conductive Soils and Need for Site-Specific
Calibration ..................................................................................... 32
8.2 The User-Derived Calibration Equation ............................................ 33
8.3 Collecting Laboratory Data for Calibration ....................................... 34
8.4 Collecting Field Data for Calibration ................................................ 36
8.5 Calculations ....................................................................................... 38
9. Maintenance .............................................................. 39
10. References ................................................................. 39
Appendix
A.
Discussion of Soil Water Content ......................... A-1
Figures
6-1. CS616 Water Content Reflectometer .................................................. 5
6-2. CS625 Water Content Reflectometer .................................................. 5
7-1. CS616 and CS625 linear and quadratic calibrations derived from
loam soil ......................................................................................... 25
7-2. CS616 and CS625 response for low EC loam with bulk density
1.4 g cm -3 , a low EC sandy clay loam with bulk density 1.6 g
cm -3 , and a high EC sandy clay loam with bulk density 1.6 g
cm -3 . ............................................................................................... 26
7-3. Difference in % volumetric water content between linear and
quadratic forms of calibrations ...................................................... 28
7-4. Percent volumetric water content error corrected for by
temperature correction equation ..................................................... 32
Tables
6-1. CS616/625 wiring code. ......................................................................... 5
6-2. CS625 Sample Programs ...................................................................... 11
6-3. CS616 Sample Edlog Programs ............................................................ 16
7-1. Standard calibration coefficients for linear and quadratic forms. ......... 27
7-2. Calibration coefficients for sandy clay loam with bulk density 1.6 g
cm -3 and electrical conductivity at saturation 0.4 dS m -1 for both
linear and quadratic forms. ............................................................ 28
7-3. Calibration coefficients for sandy clay loam with bulk density 1.6 g
cm -3 and electrical conductivity at saturation 0.75 dS m -1 for
both linear and quadratic forms. .................................................... 28
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