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Campbell Scientific TDR100 TDR100 Time Domain Reflectometry Systems - Page 24

Datalogger Instructions for TDR Measurements

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TDR100 Campbell Scientific TDR Probes General Description Dimensions Cable type Cable length Probe offset factor Probe constant for electrical conductivity (Kp) *see Section 5.8.1 CS605 3-rod probe no balun required stainless steel rods Rods: 30 cm length 0.476 cm diameter Probe head: cable-to-rod 10.8 cm width 7.0 cm thickness 1.9 cm RG58 user-specified length 0.085 m 1.74 CS610 3-rod probe no balun required stainless steel rods Rods: 30 cm length 0.476 cm diameter Probe head: cable-to-rod 10.8 cm width 7.0 cm thickness 1.9 cm RG8 low loss user-specified length 0.085 m 1.74 5.8.1 Determining Probe Constant, Kp, using PCTDR Section 6.2.6 presents the principles for TDR measurements of soil electrical conductivity. The result of the measurement must be multiplied by the probe constant (Kp) to give bulk electrical conductivity in S/m (Siemens/meter). The Kp value can be measured using PCTDR. The method requires submersion of the TDR probe rods in de-ionized water of known temperature. See PCTDR HELP for simple instructions. 6. Datalogger Instructions for TDR Measurements 6.1 CR800, CR850, CR1000, or CR3000 Datalogger Instruction "TDR100" The TDR100 instruction is used to measure one or more time domain reflectivity (TDR) probes attached to a TDR100 device. Syntax TDR100 ( Dest, SDMAddress, Option, Mux/ProbeSelect, WaveAvg, Vp, Points, CableLength, WindowLength, ProbeLength, ProbeOffset, Mult, Offset Remarks This instruction can be used to measure one TDR probe connected to the TDR100 directly or multiple TDR probes connected to one or more SDMX50 multiplexers. Dest: The Dest parameter is a variable or variable array in which to store the results of the measurement. The variable must be dimensioned to accommodate all of the values returned by the instruction, which is determined by the Option parameter. 18

Section	Page
Revision and Copyright Information	1
Warranty and Assistance	2
Table of Contents	3
TDR100	7
1. Introduction	7
1.1 TDR100 Packing List	7
1.2 ENCTDR100 Packing List	7
2. System Specifications	8
2.1 General	8
2.2 Power Consumption	8
2.2.1 TDR100	8
2.2.2 SDMX50	8
2.3 TDR100 Performance Specifications	8
2.4. Electromagnetic Compatibility	9
3. Getting Started with TDR100 using PCTDR	9
3.1 Discussion of Distances and Propagation Velocity (Vp) when using TDR100	10
3.2 PCTDR Help	12
4. PCTDR Software	12
4.1 General	13
4.2 PCTDR Help	13
4.3 Menu Selections	14
4.3.1 File Menu	14
4.3.2 Settings Menu	14
4.3.3 Options Menu	14
4.4 PCTDR Parameter Selection Boxes	14
4.4.1 Cable	14
4.4.2 Waveform	15
4.4.2.1 A Discussion of Start and Length Parameters	15
5. System Components: Datalogger Control	17
5.1 General	17
5.2 Datalogger	17
5.3 TDR100	18
5.4 SDMX50	18
5.5 Power Supply	19
5.5.1 Grounding	19
5.6 SDM Communication	20
5.6.1 SDM Addressing for TDR100 System	20
5.6.2 SDM Cable and Cable Length Considerations	22
5.7 ENCTDR100	22
5.7.1 Mounting Equipment in ENCTDR100	22
5.8 Soil Probes	23
Campbell Scientific TDR Probes	24
5.8.1 Determining Probe Constant, Kp, using PCTDR	24
6. Datalogger Instructions for TDR Measurements	24
6.1 CR800, CR850, CR1000, or CR3000 Datalogger Instruction “TDR100”	24
6.2 CR10X and CR23X Datalogger Instruction 119	26
6.3 Discussion of TDR Instruction Parameters (Instruction 119)	27
6.3.1 Parameter 1: SDM Address	27
6.3.2 Parameter 2: Output Option	27
6.3.2.1 Enter 0: Measure La/L	27
6.3.2.2 Enter 1: Collect Waveform	28
6.3.2.3 Enter 2: Collect Waveform and First Derivative	28
6.3.2.4 Enter 3: Measure Bulk Electrical Conductivity	28
6.3.3 Parameter 3: Multiplexer and Probe Selection	28
Example 2	29
6.3.4 Parameter 4: Waveform Averaging	29
6.3.5 Parameter 5: Relative Propagation Velocity	29
6.3.6 Parameter 6: Points	29
6.3.7 Parameter 7: Cable Length (meters)	29
6.3.8 Parameter 8: Window Length (meters)	30
6.3.9 Parameter 9: Probe Length (meters)	30
6.3.10 Parameter 10: Probe Offset (meters)	30
6.3.11 Parameter 11: Input Location	30
6.3.11.1 Reflection Waveform Values to Input Storage	30
6.3.12 Parameter 12: Multiplier	31
6.3.13 Parameter 13: Offset	31
6.3.13.1 Probe Constant for Electrical Conductivity Measurement	31
7. TDR Principles	32
8. Cable Length and Soil Electrical Conductivity Effect on Water Content Determination	34
8.1 Cable Length Effect on Water Content Measurement	34
8.2 Soil Electrical Conductivity Effect on Water Content Measurement	35
9. Algorithm Description and Parameter Adjustment	36
9.1 Introduction	36
9.2 Algorithm for Calculation of TDR Probe Rod Apparent Length	36
9.2.1 Algorithm Description	36
9.2.1.1 Waveform Evaluation	37
9.2.2 Algorithm Parameter Adjustment for Special Conditions	38
9.2.2.1 Terminal Emulator Commands for Apparent Length Algorithm	38
9.3 Algorithm for Calculation of Bulk Electrical Conductivity	39
9.3.1 Algorithm Description	39
9.3.2 Algorithm Parameter Adjustment for Special Conditions	39
10. Programming Examples	41
10.1 CR1000 Program Example	41
Example 1, Measure and Record; Analog Measurements, Volumetric Water Content, and Capture TDR Probe Waveforms	41
10.2 CR10X/CR23X Program Examples	44
Example 1, Measure and Record; Analog Measurements and Volumetric Water Content	44
Example 2, Measure and Record; Analog Measurements, Volumetric Water Content, Electrical Conductivity, and Capture a Waveform	46
Example 3, Measure and Record; Volumetric Water Content and Analog Measurements	50
Example 4, Measure and Record; Analog Measurements and Volumetric Water Content	52
Example 5, Trouble Shooting Program for SDMX50 Multiplexer, Datalogger Control Ports, and Analog Measurements	56
11. References	57