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Campbell TDR100 Instruction Manual

Other manuals for TDR100: Instruction Manual
Manual is about: REFLECTOMETER

Summary of TDR100

  • Page 1

    Instruction manual tdr100 revision: 5/15 c o p y r i g h t © 2 0 0 0 - 2 0 1 5 c a m p b e l l s c i e n t i f i c , i n c ..

  • Page 3: Limited Warranty

    Limited warranty “products manufactured by csi are warranted by csi to be free from defects in materials and workmanship under normal use and service for twelve months from the date of shipment unless otherwise specified in the corresponding product manual. (product manuals are available for review ...

  • Page 4: Assistance

    Assistance products may not be returned without prior authorization. The following contact information is for us and international customers residing in countries served by campbell scientific, inc. Directly. Affiliate companies handle repairs for customers within their territories. Please visit www...

  • Page 5: Precautions

    Precautions danger — many hazards are associated with installing, using, maintaining, and working on or around tripods, towers, and any attachments to tripods and towers such as sensors, crossarms, enclosures, antennas, etc. Failure to properly and completely assemble, install, operate, use, and mai...

  • Page 7: Table Of Contents

    I table of contents pdf viewers: these page numbers refer to the printed version of this document. Use the pdf reader bookmarks tab for links to specific sections. 1. Introduction ................................................................. 1 2. Cautionary statements ..............................

  • Page 8

    Table of contents ii 7.2.6.2 sdm cable and cable length considerations ................ 15 7.2.7 enctdr100 .............................................................................. 15 7.2.7.1 mounting equipment in enctdr100 ............................ 15 7.2.8 soil probes ........................

  • Page 9

    Table of contents iii 8-1. Waveforms collected in a sandy loam using cs610 probe with rg8 connecting cable. Volumetric water content is 24% and bulk electrical conductivity is 0.3 ds m –1 . ...................................... 21 8-2. Waveforms collected in a sandy loam using cs610 probe with rg8 ...

  • Page 10

    Table of contents iv.

  • Page 11: Tdr100

    1 tdr100 1. Introduction this document presents operating instructions for the tdr100 and associated equipment and discusses time domain reflectometry (tdr) principles. Section 4.1 , getting started with tdr100 using pc-tdr (p. 2) , describes a simple start- up configuration to quickly and easily di...

  • Page 12: 4.  Quickstart

    Tdr100 2 3.1 tdr100 packing list the following are included with a tdr100. 1. Tdr100 time domain reflectometer 2. Pc-tdr software and instruction manual on resource dvd 3. A 6 foot long, 9-conductor cable for connection between the serial port of a computer and the rs-232 port of the tdr100 4. Short...

  • Page 13

    Tdr100 3 run of the windows system and type d:/disk1/setup.Exe or use the browse button to access the cd-rom drive and select the setup executable file in the disk1 folder. • the pc-tdr installation utility is activated. Follow the prompts to complete the installation. • if the installation disk is ...

  • Page 14

    Tdr100 4 for example, if the actual length of a cable having a v p of 0.78 is 5 m and the selected v p is 1.0, the apparent distance to the end of the cable is 5 x (1.0/0.78) = 6.41 m. Typical cable v p ’s range from 0.67 to 0.9. Campbell scientific tdr probes use rg-58 with a v p of 0.80, rg-8 with...

  • Page 15: 5.  Overview

    Tdr100 5 figure 4-2. Waveform of cs610 in water after changing start and length parameters to display relevant portion of reflected signal 4.3 more information information on pc-tdr is available from the help menu or by pressing f1. Using f1 gives specific help associated with the position of the cu...

  • Page 16: 6.  System Specifications

    Tdr100 6 complete tdr system that includes a compatible datalogger, tdr100, sdmx50 series or sdm8x50 multiplexers, 12 v power supply, weatherproof enclosure, and solar panel is recommended. A single tdr probe can be connected directly to the tdr100 or multiple probes connected via coaxial multiplexe...

  • Page 17

    Tdr100 7 6.2 electromagnetic compatibility the tdr100 is Πcompliant with performance criteria available upon request. Rf emissions are below en55022 limit. The tdr100 meets en61326 requirements for protection against electrostatic discharge and surge except for electrostatic discharge on the center...

  • Page 18: 7.  Installation

    Tdr100 8 6.3.2 electrical input power: 12 vdc quiescent current drain: current drain during switching: ~90 ma (all multiplexers of the same level switch simultaneously for less than 1 s. See figure 7-2 .) relay contact life expectancy: 100 x 10 6 operations 7. Installation 7.1 pc-tdr software a disp...

  • Page 20

    Tdr100 10 7.1.3 pc-tdr parameter selection boxes 7.1.3.1 cable the cable propagation velocity, v p , depends on the dielectric constant of the insulating material between the coaxial cable center conductor and outer shield. The value entered in this parameter selection box is the ratio of the actual...

  • Page 21

    Tdr100 11 7.1.3.3 a discussion of start and length parameters only the waveform reflection near the probe is used for water content determination. The reflections for most of the cable between the tdr100 and the tdr probe are not used for tdr100 measurements. The apparent probe length algorithm begi...

  • Page 22

    Tdr100 12 table 7-1. Recommended waveform length values for range of tdr probe rod lengths assuming soil porosity of 0.60 probe rod length (m) recommended waveform length value (m) 0.10 to 0.20 3 0.21 to 0.30 4 0.31 to 0.40 5 0.41 to 0.6 6 0.61 to 0.75 7 0.76 to 1.00 9 use the recommended values lis...

  • Page 23

    Tdr100 13 7.2.2 datalogger campbell scientific cr6, cr800 series, cr1000, and cr3000 dataloggers use the tdr100() crbasic instruction to control the tdr100 measurement sequence and store the resulting data. Pc400 or loggernet (version 3.0 or higher) are used to create and send the crbasic program to...

  • Page 24

    Tdr100 14 campbell scientific recommends using datalogger switched 12 volts to power the tdr100. This will provide power savings and will automatically reset the tdr100 and provide automatic recovery from system malfunctions. This practice can reduce loss of measurement data when a problem exists. T...

  • Page 25

    Tdr100 15 there are a maximum of three multiplexer levels (see figure a-2 ). The level 1 multiplexer has an address value equal to the tdr100 address plus 1. Level 2 multiplexers have an address value equal to the tdr100 address plus 2 and the level 3 multiplexers have an address value equal to the ...

  • Page 26

    Tdr100 16 figure 7-4. Enctdr100 with sdm8x50, ps150, tdr100, and cr1000 7.2.8 soil probes the tdr probes are the sensors of the tdr measurement system and are inserted into the medium to be measured. The probes are a wave guide extension on the end of coaxial cable. Reflections of the applied signal...

  • Page 27

    Tdr100 17 7.2.8.1 determining probe constant, k p , using pc-tdr section 8.1 , tdr principles (p. 19) , presents the principles for tdr measurements of soil electrical conductivity. The result of the measurement must be multiplied by the probe constant (k p ) to give bulk electrical conductivity in ...

  • Page 28

    Tdr100 18 option: the option parameter determines the output of the instruction. Code description 0 measure l a /l (ratio of apparent to physical probe rod length). Dividing l a by the real rod length, l, gives the square root of dielectric constant. The l a /l value is empirically related to volume...

  • Page 29: 8.  Operation

    Tdr100 19 until the probe reflection can be viewed. Subtract about 0.5 meters from the distance associated with the beginning of the probe reflection. Note that the specified cablelength applies to all probes read by this instruction; therefore, all probes must have the same cable lengths. Windowlen...

  • Page 30

    Tdr100 20 the relationship between dielectric constant and volumetric water content has been described by, among others, topp et al. (1980) and ledieu et al. (1986) in an empirical fashion using both polynomial and linear forms. These expressions are presented here since it has been shown in numerou...

  • Page 31

    Tdr100 21 8.2 cable length and soil electrical conductivity effect on water content determination 8.2.1 cable length effect on water content measurement the determination of water content using the tdr system relies on the evaluation of a pulse reflection from the tdr probe. The pulse generated by t...

  • Page 32

    Tdr100 22 minimizing cable lengths should always be considered in the design of a measurement system using tdr. If long cable lengths are necessary, the adverse effects can be minimized by using low attenuation cable such as rg8. Careful probe design ensures correct probe impedance giving robust ref...

  • Page 33

    Tdr100 23 figure 8-3. Waveforms collected in a sandy loam using cs610 probe with rg8 connecting cable. Volumetric water content values are 10, 18, 26, 30 and 37%. Solution electrical conductivity is 10.2 ds m –1 . The combined effect of long cable runs and high soil electrical conductivity must be c...

  • Page 34

    Tdr100 24 conversion uses the number of waveform data points (250 for the waveform in figure 8-4 ) and the width of the waveform window as defined by pc-tdr or datalogger instruction parameters. Figure 8-4. Typical tdr100 waveform showing key features with numbers 1, 2 and 3. The algorithm to calcul...

  • Page 35

    Tdr100 25 > see operating manual for command descriptions press enter for > prompt *************************************** electrical conductivity parameters sec1 xx set ec parameter 1 sec2 xx.Xx set ec parameter 2 sec3 xx.Xx set ec parameter 3 sec4 xx.Xx set ec parameter 4 gecp get ec parameters **...

  • Page 36

    Tdr100 26 3. Calculate the mean and standard deviation of waveform values between parameter 1 and the halfway point. 4. Calculate a threshold value using: threshold = a*(maximum derivative) + b*(mean from step 3) + c*(standard deviation from step 3) the default values for a, b and c are 0, 1 and 2 r...

  • Page 37: 9.  References

    Tdr100 27 figure 8-6. Waveform and derivative values near tdr probe and locations of index for point of maximum derivative and maximum derivative value. The green band represents the results of the search using the threshold value. 9. References bilskie, jim. 1997. “reducing measurement errors of se...

  • Page 38

    Tdr100 28 rhoades, j.D., p.A.C. Raats, and r.J. Prather. 1976. Effects of liquid-phase electrical conductivity, water content and surface conductivity on bulk soil electrical conductivity. Soil sci. Soc. Am. J. 40:651-655..

  • Page 39: Multiplexers

    A-1 appendix a. Sdmx50-series multiplexers a.1 general prior to the sdm8x50, the sdmx50 series multiplexers were used with the tdr100 to measure multiple sensors. The sdmx50sp was identical to the sdm8x50 in form, fit, and function. The sdmx50 came with the multiplexer mounted in a 10” x 12” enclosu...

  • Page 40: A.3  Signal Attenuation

    Appendix a. Sdmx50-series multiplexers a-2 sdmx50sp 50 ohm coaxial multiplexer with strain relief bracket multiplexer circuit board encased in metal housing and a separate strain relief bracket. Both the circuit board and bracket include mounting holes and hardware for attaching them to the backplat...

  • Page 41: A.4  Sdm Communication

    Appendix a. Sdmx50-series multiplexers a-3 100 1 . 10 3 1.4 1.2 1 0.8 0.6 0.4 0.2 0 frequency (mhz) s d m x 50 a tte nu ati on (d bm ) figure a-1. Sdmx50 signal attenuation each of the eight ports can be connected to a probe or another multiplexer (see figure 7-2 ). A.4 sdm communication a.4.1 sdm a...

  • Page 42

    Appendix a. Sdmx50-series multiplexers a-4 figure a-2. Location of address jumpers on sdmx50

  • Page 43

    B-1 appendix b. Example program b.1 cr1000 program example this cr1000 program measures and records analog measurements and volumetric water content. It also captures the tdr probe waveforms. Equipment wiring cr1000 tdr100 sdm8x50 sw12 +12 v 12 v g g g c1 c1 c1 c2 c2 c2 c3 c3 c3 sensor wiring tdr100...

  • Page 44

    Appendix b. Example program b-2 'cr1000 series datalogger 'program: c:\mydoc\cr1000\cr1000-testing\tdr&sdm&f1&wave_cr1k.Cr1 'measure and record analog measurements, volumetric water content, & store waveforms ' 'declare public & dim variables ------------------------------------ public batt_volt pub...

  • Page 45

    Appendix b. Example program b-3 if flag(1)=high then '************************************* sw12 (1) 'turn on 12v power to tdr100 & sdmx50 'note: wire tdr100 & sdm8x50 12v power leads to cr1000 sw12 terminal delay (1,2,sec) 'pause 2 sec to allow power supply voltage to settle ' 'measure la/l on sdmx...

  • Page 46

    Appendix b. Example program b-4 flag(2)=0 'reset state of flag 2 sw12 (0 ) 'switched 12v low endif 'endif ******************************** ' portsconfig (&b00000111,&b00000000) 'configure sdm ports c1,c2,c3 as inputs ' nextscan endprog.

  • Page 48

    Campbell scientific companies campbell scientific, inc. (csi) 815 west 1800 north logan, utah 84321 united states www.Campbellsci.Com • info@campbellsci.Com campbell scientific africa pty. Ltd. (csaf) po box 2450 somerset west 7129 south africa www.Csafrica.Co.Za • cleroux@csafrica.Co.Za campbell sc...