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Campbell Scientific CS616 CS616 and CS625 Water Content Reflectometers - Page 34

for both linear and quadratic forms.

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CS616 and CS625 Water Content Reflectometers FIGURE 7-3. Difference in % volumetric water content between linear and quadratic forms of calibrations The linear and quadratic coefficients for the sandy clay loam data in FIGURE 7-3 follow and can be used in similar soils. TABLE 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. Linear C0 -0.6200 C1 0.0329 C0 0.0950 Quadratic C1 -0.0211 C2 0.0010 TABLE 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. Linear C0 -0.4470 C1 0.0254 C0 -0.0180 Quadratic C1 -0.0070 C2 0.0006 28

Section	Page
Revision and Copyright Information	1
Warranty	3
Assistance	4
Table of Contents	5
1. Introduction	7
2. Cautionary Statements	7
3. Initial Inspection	7
4. Overview	7
5. Specifications	8
5.1 Dimensions	9
5.2 Weight	9
5.3 Electrical Specifications	9
5.4 Operational Details	10
6. Installation	10
6.1 Orientation	10
6.2 Potential Problems with Improper Insertion	10
6.3 Wiring	11
6.4 Datalogger Instructions and Programming	12
6.4.1 Measuring the CS616 Using CRBasic	12
6.4.1.1 CS616 Sample CRBasic Program 1	13
6.4.1.2 CS616 Sample CRBasic Program 2	15
6.4.2 Measuring CS625 Output Using CR200(X) PeriodAvg Instruction	16
6.4.3 Sample Programs for CS625	17
6.4.3.1 CS625 Sample Program 1	17
6.4.3.2 CS625 Sample Program 2	18
6.4.4 Measuring CS616 Using Edlog	19
6.4.4.1 Using Edlog Instruction 138	19
6.4.4.2 Using Edlog Instruction 27 (Period Averaging)	20
6.4.5 Sample Edlog Programs for CS616	22
6.4.5.1 CS616 Sample Edlog Program 1	22
6.4.5.2 CS616 Sample Edlog Program 2	23
6.4.5.3 CS616 Sample Edlog Program 3	24
6.4.5.4 CS616 Sample Edlog Program 4	25
6.4.5.5 CS616 Sample Edlog Program 5	27
7. The Water Content Reflectometer Method for Measuring Volumetric Water Content	30
7.1 Description of Measurement Method	30
7.2 Response Curves	30
7.3 Calibration Equations	33
7.4 Operating Range	35
7.4.1 Soil Electrical Conductivity	35
7.4.2 Soil Organic Matter, Clay Content and Soil Bulk Density	35
7.5 Error Sources in Water Content Reflectometer Measurement	36
7.5.1 Probe-to-Probe Variability Error	36
7.5.2 Insertion Error	36
7.5.3 Signal Attenuation Error	36
7.6 Temperature Dependence and Correction	37
8. Water Content Reflectometer User-Calibration	38
8.1 Signal Attenuation in Conductive Soils and Need for Site-Specific Calibration	38
8.2 The User-Derived Calibration Equation	39
8.3 Collecting Laboratory Data for Calibration	40
8.4 Collecting Field Data for Calibration	42
8.5 Calculations	44
9. Maintenance	45
10. References	45
Appendix A. Discussion of Soil Water Content	47