Campbell CS616, Instruction Manual

Page: 6 / 54

Table of Contents
7.3 Calibration Equations ........................................................................ 29
7.4 Operating Range................................................................................ 31
7.4.1 Soil Electrical Conductivity ....................................................... 31
7.4.2 Soil Organic Matter, Clay Content and Soil Bulk Density......... 32
7.5 Error Sources in Water Content Reflectometer Measurement .......... 32
7.5.1 Probe-to-Probe Variability Error................................................ 32
7.5.2 Insertion Error ............................................................................ 32
7.5.3 Signal Attenuation Error ............................................................ 32
7.6 Temperature Dependence and Correction ......................................... 33
8. Water Content Reflectometer User-Calibration......34
8.1 Signal Attenuation in Conductive Soils and Need for Site-
Specific Calibration ....................................................................... 34
8.2 The User-Derived Calibration Equation............................................ 35
8.3 Collecting Laboratory Data for Calibration....................................... 35
8.4 Collecting Field Data for Calibration ................................................ 38
8.5 Calculations....................................................................................... 40
9. Maintenance ..............................................................41
10. References.................................................................41
Appendix
A. Discussion of Soil Water Content .........................A-1
Figures
6-1. CS616 Water Content Reflectometer .................................................. 5
6-2. CS625 Water Content Reflectometer .................................................. 6
7-1. CS616 and CS625 linear and quadratic calibrations derived from
loam soil......................................................................................... 27
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
. ...................................................................................... 28
7-3. Difference in % volumetric water content between linear and
quadratic forms of calibrations ...................................................... 30
7-4. Percent volumetric water content error corrected for by
temperature correction equation..................................................... 34
Tables
6-1. CS616/625 wiring code. ...................................................................... 5
6-2. CS625 Sample Programs................................................................... 12
6-3. CS616 Sample Edlog Programs ........................................................ 17
7-1. Standard calibration coefficients for linear and quadratic forms....... 29
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................................................ 30
ii