Related Manuals for Campbell TDR
Summary of Contents for Campbell TDR
- Page 1 CAMPBELL SCIENTIFIC TDR SOIL MOISTURE MEASUREMENT SYSTEM MANUAL REVISION: 2/92 COPYRIGHT (c) 1991, 1992 CAMPBELL SCIENTIFIC, INC.
- Page 2 CONTROL MODULE, and the SDMX50 50 OHM COAX MULTIPLEXER. These products are warranted by CAMPBELL SCIENTIFIC, INC. to be free from defects in materials and workmanship under normal use and service for twelve (12) months from date of shipment unless specified otherwise.
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Page 3: Table Of Contents
....................8 Example 1, Measure and Record Every Hour ................8 Example 2, Hourly Average Using Topp's Calibration............... 9 Example 3, TDR Measurements in Table 2 with Analog Measurements in Table 1 ....10 TABLES SDM Addresses......................... 4 Waveform Resolution Determined by Probe Length ..............7 FIGURES TDR System Components...................... -
Page 4: Introduction
Topp, Davis, and Annan in 1980, the method has proven itself through the work of numerous researchers. Campbell Scientific has developed a system in which the Tektronix 1502B cable tester is coupled with a CR10 or 21X datalogger and multiplexers to provide automated multiple probe TDR soil moisture measurements. -
Page 5: System Components
Datalogger Software - Special PROMS for the CR10 or 21X datalogger include Instruction 100 for controlling the 1502B and multiplexers. 6590 - Transient suppressor attaches to cable from 1502B and is required if ENC TDR is not purchased. Coax cable connects the 1502B and the 3. -
Page 6: Assigning Addresses
There are sixteen possible addresses; a maximum of four are used in a TDR system. The address assigned the SDM1502 determines the addresses that need to be assigned to the multiplexers: The multiplexer... -
Page 7: Installing 1502B In Enc Tdr
TDR SOIL MOISTURE MEASUREMENTS FIGURE 3-3. Mounting 1502B in ENC TDR 3.2 INSTALLING 1502B IN ENC TDR TABLE 3-1. SDM Addresses The 1502B is mounted in the ENC TDR enclosure by removing the handle (the required ADDRESS SDM1502 SDMX50 Allen wrench is included with the ENC TDR) -
Page 8: Ps1502B
TDR SOIL MOISTURE MEASUREMENTS FIGURE 3-4. SDM Wiring 3.3.2 PS1502B The PS1502B has three connections to the datalogger: +12, Ground, and a control input which allows the datalogger to switch the power to the 1502B. In the example program (Section 5), the control input is connected to control port 4. -
Page 9: Grounding
TDR SOIL MOISTURE MEASUREMENTS Options in instruction allow: 3.5 GROUNDING The TDR system should be installed with a finding a soil moisture probe automatically single ground point. A good earth ground or specifying the "distance" to the probe should be established close to the datalogger/1502B. -
Page 10: Calibration For Water Content
TDR SOIL MOISTURE MEASUREMENTS 1990, and calculates 1/V p ; the multiplier and Parameter 4 Cable length: The "length" in offset (parameters 7 and 8) may be used to meters to the probe or 1502B cursor. Enter "0" obtain the result directly in volumetric water and the datalogger will automatically search for content (Section 5). -
Page 11: Programming Examples
6. PROGRAMMING EXAMPLES Cable length (meters) 05: 1008 MMMP--Mux channels & Probes There are several things to keep in mind when Loc [:WATER #1 ] writing a datalogger program to make TDR 0.1138 Mult measurements: -0.1758 Offset 1. Set the control port high that controls the... -
Page 12: Example 2, Hourly Average Using Topp's Calibration
TDR SOIL MOISTURE MEASUREMENTS Sample P100 SDM-1502 Reps Address Loc WATER #1 Moisture Probe length (meters) End Table 1 Cable length (meters) 05: 1008 MMMP--Mux channels & Probes Mode 10 Memory Allocation Loc [:Wv #1 Input Locations Mult Intermediate Locations Offset 6.2 EXAMPLE 2, HOURLY AVERAGE USING... - Page 13 30 minutes and the averages are output every 4 hours. P100 SDM-1502 Address Placing the TDR measurements in Table 2 Moisture allows analog measurements to be made in Probe length (meters) Table 1. The analog measurements will...
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Page 14: Soil Moisture Measurement By Time Domain Reflectometry
TDR SOIL MOISTURE MEASUREMENTS End Table 2 Mode 10 Memory Allocation Input Locations Intermediate Locations LITERATURE CITED Baker, J.M. and R.R. Allmaras. 1990. System for Automating and Multiplexing Soil Moisture Measurement by Time- Domain Reflectometry. Soil Science Society of America Journal 54: 1-6.
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