User Manual for the
Contents
1. Spare parts and accessories for sensors or other products not manufactured by Delta T may have to be obtained from our supplier and a certain amount of additional delay is inevitable No goods or equipment should be returned to Delta T without first obtaining the agreement of Delta T or our distributor On receipt at Delta T the goods will be inspected and the user informed of the likely cost and delay We normally expect to complete repairs within a few working days of receiving the equipment However if the equipment has to be forwarded to our original supplier for specialist repairs or recalibration additional delays of a few weeks may be expected Technical Support Technical Support is available on Delta T products and systems Users in countries that have a Delta T Distributor or Technical Representative should contact them in the first instance Technical Support questions received by Delta T will be handled by our Tech Support team Your initial enquiry will be acknowledged immediately with a T number and an estimate of time for a detailed reply Make sure to quote our T number subsequently so that we can easily trace any earlier correspondence In your enquiry always quote instrument serial numbers software version numbers and the approximate date and source of purchase where these are relevant Contact details Tech Support Team Delta T Devices Ltd 128 Low Road Burwell Cambridge CB5 OE U K email tech su2. User Manual for the SM200 Soil Moisture Sensor eo O D a a o 2 3 SM200 UM 1 1 Delta T Devices Ltd Notices Copyright All parts of the SM200 design and documentation are the exclusive right of Delta T Devices and covered under copyright law 2006 Patent s pending CE conformity The SM200 product is CE compliant conforming to EN61326 1997 Design changes Delta T Devices Ltd reserves the right to change the designs and specifications of its products at any time without prior notice User Manual Version SM200 UM 1 1 May 2006 Delta T Devices Ltd Tel 44 1638 742922 128 Low Road Burwell Fax 44 1638 743155 Cambridge CB5 0EJ email sales delta t co uk UK web www delta t co uk Contents Introduction Description Parts list Care and Safety How the SM200 works Operation Cable attachment Installation Logger connections and configuration GP1 DL6 DL2e Other data loggers HH2 moisture meter Calibration Soil calibration Sensor calibration Soil moisture reading Troubleshooting Technical Reference Specifications Definitions References Technical Support Soil specific Calibration Laboratory calibration for non clay soils Laboratory calibration for clay soils Index SM200 User Manual 1 1 21 21 25 27 28 30 31 33 36 Operation 3 Introduction Description The SM200 measures soil moisture content at a single location sampling 0 5 litres of soil or other gr
3. 18 D Data logger 13 19 20 DL2e 12 19 20 DL6 11 20 GP1 10 20 other 13 Definitions 25 Dielectric performance 18 refractive index 15 16 30 E Extension cables 8 G GP1 10 20 H HH2 5 14 15 20 SM200 User Manual 1 1 I Installation buried 9 insertion rod 5 8 9 surface 9 Meter 20 Moisture content 4 7 27 30 P Patent 2 Permittivity 7 15 27 R Range 21 References 27 Rods 4 6 7 9 S Sales code 5 Salinity 21 26 Servicing 29 Soil clay 16 17 25 30 31 33 mineral 15 17 19 31 32 34 organic 15 17 19 25 32 stony 9 Specifications 2 21 Technical support 28 29 Troubleshooting 20 W Wiring 10 Index 36
4. Colour wiring terminal Power V Red 63 NO Signal White 58 58 Ground Shield and 61 For configuration details see the DL2e User Documentation SM200 User Manual 1 1 Index 12 Other data loggers The SM200 should be connected as a single ended powered sensor Configure the logger input as a voltage sensor approximately O0 to 1 0 volts corresponding to 0 to 60 water content see next section The SM200 has been optimised for a 1 second warm up period It is recommended that the sensor is not powered continuously Configure the logger to convert the SM200 readings into soil moisture using the polynomial or linearisation tables see Calibration SM200 User Manual 1 1 Operation 13 HH2 moisture meter Connect the SM200 to the HH2 meter Press Esc to turn the meter on and if necessary press again until the HH2 displays the start up screen Read Set the meter to read from an SM200 store A Press Set and scroll down to the salvi Device option Press again and scroll down to select SM200 DELTA T DEVICES CAMBRIDGE ENGLAND Press Set to confirm this choice If you intend to store readings it may be helpful to define each reading by setting a plot label and sample number accessed by pressing Set Jand scrolling to the Data option Press to take a reading it takes about 2 seconds You can choose different units from the Display option Press Store to save or Esc to
5. content of the wet soil 6 can be calculated from the weight of water lost during drying W Wo and its volume Ls Calculate 6 Re insert the SM200 into the dry sample and record this 6 W W L 743 3 627 2 463 5 0 25 SM200 User Manual 1 1 Index 32 Ow 0 25 Calculate a In the wet soil V Vy 0 350 Volts and substituting gives Je 3 88 Finally a Je fe 0 3 88 1 73 0 25 0 8 60 a 8 60 Laboratory calibration for clay soils This technique is adapted to avoid the near impossibility of inserting the SM200 into completely dry clay soil It requires taking measurements at 2 significantly different but still damp moisture levels Equipment you will need SM200 and meter Soil corer Heat resistant beaker gt 500ml Weighing balance accurate to lt 1g Temperature controlled oven Process Notes and example Collect a wet sample of the clay soil 25 to 30 water content would be ideal This sample needs to be unchanged from its in situ density to be gt 500ml to have the correct dimensions to fit the beaker and to be generally uniform in water content This is most easily done with soil corer Measure the volume occupied by the sample L 463 5ml Weigh the wet sample including the beaker Wu 743 3g SM200 User Manual 1 1 Soil specific Calibration 33 Insert SM200 into the wet sample and record its output in Volts Vw 0 349V Dry th
6. g cm g cm Organic 40 C gt 7 c 02 0 7 SM200 User Manual 1 1 Soil specific Calibration 25 Salinity The preferred SI units for ionic conductivity are mS m where S is Siemens the unit of electric conductance ohm The following conversions apply 1mS m 0 01 dS m 0 01 mS cm 10 uS cm Soil salinity is also partitioned into the following descriptive categories non saline 0 200 mS m_ slightly saline 200 400 mS m moderately saline 400 800 mS m_ strongly saline 800 1600 mS m extremely saline gt 1600 mS m SM200 User Manual 1 1 Index 26 References 1 Gaskin G J and J D Miller 1996 Measurement of soil water content using a simplified impedance measuring technique J Agr Engng Res 63 153 160 J Topp G C J L Davis and A P Annan 1980 Electromagnetic determination of soil water content Water Resour Res 16 3 574 582 3 Whalley W R 1993 Considerations on the use of time domain reflectometry TDR for measuring soil moisture content Journal of Soil Sci 44 1 9 4 White l J H Knight S J Zegelin and Topp G C 1994 Comments on Considerations on the use of time domain reflectometry TDR for measuring soil water content by W R Whalley Journal of Soil Sci 45 503 508 S Roth C H M A Malicki and R Plagge 1992 Empirical evaluation of the relationship between soil dielectric constant and volumetric water content as the basis for cali
7. sample needs to be unchanged from its in situ density to be gt 0 5 litre to have the correct dimensions to fit the beaker and to be generally uniform in water content For cohesive soils this is most easily done with a soil corer Sandy soils can be poured into the beaker but you should take the subsequent measurements immediately as the water will quickly begin to drain to the bottom of the beaker Compressible soils and composts often require measurement of the in situ density and then need to be carefully reconstituted at that density within the beaker Measure the volume occupied by the sample L 463 5ml Weigh the sample including the beaker Wu 743 3g SM200 User Manual 1 1 Soil specific Calibration 31 Insert SM200 into the sample and record its output in Volts Vy 0 350V Dry the sample thoroughly With mineral soils this is usually achieved by keeping it in the oven at 105 C for several hours or days the time required depends on the sample size and porosity For organic soils and composts it s usual to air dry the sample to avoid burning off any volatile factions Weigh the dry sample in the beaker Wro 627 29 reading Vo 0 051V For the SM200 Je 1 0416 103V 38 725V7 60 88 17 46 0327 13 530 In the dry soil V Vo 0 051 Volts and substituting this value into the above equation gives A i 7 Since o 0 this is the value needed for ao Ap 1 73 The water
8. where one or the other effect dominates the SM200 will appear to have a significant temperature response This illustration is based on the model in reference 7 Illustrating temperature dependence of SM200 readings in clay soil 0 5 O 0 4 D Q 0 3 oO P ED O 0 2 E Q 0 1 w 0 2 Soil moisture content m m o 0 10 20 30 40 50 Soil temperature C Note ice has a quite different refractive index from water so SM200 readings cannot be interpreted reliably when inserted into soil below 0 C SM200 User Manual 1 1 Index 22 Sampling Volume The SM200 is most sensitive to signals very close to the two rods but a small proportion of the signal reaches up to 50mm from the rods For best accuracy we recommend taking readings in at least 0 5 litres of soil preferably 1 0 litre SM200s may interact if they are placed too close together they should be separated by at least 100mm The sensitivity field for an SM200 inserted in water has been tested as shown in this figure the vertical scale is in arbitrary units 5M200 field of sensitivity surrounding the rods Distance parallel to plane of rods from a centre line between the rods mm SM200 User Manual 1 1 Soil specific Calibration 23 Electromagnetic Compatibility EMC General information SM200 is a Class A product intended for operation in non residential environments Only use cables a
9. Combining the Soil calibrations and Sensor calibration steps the conversion equation becomes o I1 0 16 103V 38 7257 60 881V 46 032V 13 536 a a where a and q are the calibration coefficients For a generalised mineral soil this becomes 0 0 071 1 917V 4 61V 7 248V gt 5 48V 1 611V mineral And for a generalised organic soil 0 0 039 2 0917 5 029V 7 9077 5 978V 1 758V organic Linearisation table conversion Alternatively the conversion from SM200 reading Volts to soil moisture 0 m m or vol can be accomplished by a linearisation table The following table lists the values used for the DL2e data logger Soil Mineral Organic Soil Mineral Organic moisture soil soil moisture soil soil vol Volts Volts vol Volts Volts 4 2 090 2 090 52 0 826 0 678 0 0 041 0 019 56 0 901 0 747 4 0 068 0 041 60 0 975 0 816 8 0 099 0 066 64 1 043 0 884 12 0 135 0 094 68 1 103 0 952 16 0 178 0 126 72 1 156 1 017 20 0 230 0 164 76 1 199 1 076 24 0 292 0 209 80 1 237 1 127 28 0 365 0 262 84 1 269 1174 32 0 443 0 324 88 1 297 1 210 36 0 523 0 393 92 1 322 1 244 40 0 601 0 466 96 1 347 1 278 44 0 676 0 538 100 1 800 1 800 48 0 751 0 609 104 2 090 2 090 SM200 User Manual 1 1 Soil specific Calibration 19 Troubleshooting Always try to identify which part of the measurement system is the source of the difficulty For the SM200 this may fall into one of the follo
10. area is likely to cause harmful interference in which case the user will be required to correct the interference at his her own expense Modifications not expressly approved by the manufacturer could void the user s authority to operate the equipment under FCC rules SM200 User Manual 1 1 Index 24 Definitions Volumetric Soil Moisture Content is defined as 0 Vy where V is the volume of water contained in the sample r Vs and V is the total volume of the soil sample The preferred units for this ratio are m m though vol is frequently used Soil Moisture Content varies from approx 0 02 m m for sandy soils at the permanent wilting point through approx 0 4 m m for clay soils at their field capacity up to values as high as 0 85 m m in saturated peat soils Gravimetric Soil Moisture Content is defined as M Where M is the mass of water in the sample Os M 99 and M is the total mass of the dry sample S To convert from volumetric to gravimetric water content use the equation 9 g x2r where p is the density of water 1g cm g U x _ M Ps and p is the bulk density of the sample 7 S Organic and Mineral soil definitions The general calibrations have been optimised to cover a wide range of soil types based on the following definitions optimised for p setor bulk use fo around density bulk Soil type organic ve organic _ range densities contents 3 Z content
11. brating soil moisture measurements Journal of Soil Sci 43 1 13 6 Knight J H 1992 Sensitivity of Time Domain Reflectometry measurements to lateral variations in soil water content Water Resour Res 28 2345 2352 T Or D and J M Wraith 1999 Temperature effects on soil bulk dielectric permittivity measured by time domain reflectrometry A physical model Water Resour Res 35 371 383 SM200 User Manual 1 1 Soil specific Calibration 27 Technical Support Terms and Conditions of Sale Our Conditions of Sale ref COND 1 00 set out Delta T s legal obligations on these matters The following paragraphs summarise Delta T s position but reference should always be made to the exact terms of our Conditions of Sale which will prevail over the following explanation Delta T warrants that the goods will be free from defects arising out of the materials used or poor workmanship for a period of twelve months from the date of delivery Delta T shall be under no liability in respect of any defect arising from fair wear and tear and the warranty does not cover damage through misuse or inexpert servicing or other circumstances beyond our control If the buyer experiences problems with the goods they shall notify Delta T or Delta T s local distributor as soon as they become aware of such problem Delta T may rectify the problem by supplying replacement parts free of charge or by repairing the goods free of charge at D
12. discard the reading Remove the SM200 and move to a new location If you have saved data connect your HH2 to a PC and run HH2Read to retrieve the readings Refer to the HH2 User Manual for further details SM200 User Manual 1 1 Index 14 Calibration The SM200 is provided with general calibrations for mineral and organic soils which can be used to convert the output from the sensor directly into soil moisture when used with Delta T loggers and the HH2 moisture meter This section explains how these calibrations work how to adapt them for other soils and how to provide calibrations for other data loggers The SM200 measures volumetric soil moisture 6 by detecting the dielectric properties of the damp soil the permittivity or more conveniently the refractive index which is closely equivalent to The SM200 response is best understood in these stages 1 Soil calibration 2 Sensor calibration 0 gt Ve V gt ve Soil calibrations SM200 dielectric performance Ve o Fu 3 Soil moisture reading SM200 soil moisture reading SM200 User Manual 1 1 Soil specific Calibration 15 Soil calibration Damp soil is essentially a mixture of soil particles air and water and together these raat determine its dielectric properties including the refractive index Ve The refractive index of the mixture is approximated simply by adding the contributions from the
13. e sample until still moist 15 water content Gentle warming can be used to accelerate the process but take care not to over dry in places and allow time for the water content to equilibrate throughout the sample before taking a reading Reweigh Wn 693 2g Re measure with the SM200 Vin 0 180V Dry the sample thoroughly With mineral soils this is usually achieved by keeping it in the oven at 105 C for several hours or days the time required depends on the sample size and porosity Weigh the dry sample in the beaker Wo 627 2g SM200 User Manual 1 1 Index 34 Calculations Substituting in the SM200 equation Je 1 0 16 103V 38 725V 60 881V 46 032V 13 536V provides two dielectric values Ve and Vsem at two known water contents and 0 For the wet soil Substituting Vw 0 349 gives Je 3 88 a a 0 w for 0 743 3 627 2 463 5 0 25 For the moist soil Substituting Vm 0 180 gives E 2 95 a a 0 For 6 693 2 627 2 463 5 0 14 Calculate a Then a Je Je a 6 8 56 ad 8 56 Calculate a and a J 4 E 2173 do 1 73 SM200 User Manual 1 1 Soil specific Calibration 35 Index A Accuracy 21 Auger 5 9 C Calibration check 20 generalised 19 sensor 15 18 19 soil 15 16 19 soil specific 30 Care and safety 6 Certification emc 24 Connections 10 Conversions linearisation table 13 17 18 19 polynomial 13 17
14. ection Soil specific calibration Instead of adopting these general calibrations you may wish to determine specific calibration values of and a for your soil This procedure is fairly straightforward if you can get access to standard laboratory equipment and is described in detail in Appendix A Soil specific calibration can significantly improve the accuracy of individual readings but make less of an improvement to readings where installation and sampling errors are high SM200 User Manual 1 1 Soil specific Calibration 17 Sensor calibration Each SM200 is individually adjusted to provide consistent dielectric performance SM200 dielectric performance 8 0 E Soil refractive index V2 N O O 2 0 0 2 0 4 0 6 0 8 1 12 SM200 output Volts This response can be approximated either by a polynomial or by a linearisation table Polynomial use for SM200 readings from 0 to 1 1 Volts JE 1 0 16 103V 38 72V 60 88 1V 46 032V 13 536V where V is the SM200 output in Volts Linearisation table use for SM200 readings from 0 to 1 2 Volts V Ve V Ve V Ve V Ve 0 000 1 011 0 150 2 129 0 400 4 102 1 100 7 290 0 030 1 453 0 180 2 956 0 600 4 956 1 150 7 610 0 060 1 842 0 220 3 218 0 820 5 939 1 200 7 982 0 090 2 179 0 260 3 446 0 960 6 571 1 220 8 205 0 120 2 473 0 310 3 701 1 040 6 960 1 800 9 000 SM200 User Manual 1 1 Index 18 Soil moisture reading Polynomial conversion
15. elta T s premises in the UK during the warranty period If Delta T requires that goods under warranty be returned to them from overseas for repair Delta T shall not be liable for the cost of carriage or for customs clearance in respect of such goods However we much prefer to have such returns discussed with us in advance and we may at our discretion waive these charges Delta T shall not be liable to supply products free of charge or repair any goods where the products or goods in question have been discontinued or have become obsolete although Delta T will endeavour to remedy the buyer s problem Delta T shall not be liable to the buyer for any consequential loss damage or compensation whatsoever whether caused by the negligence of the Delta T our employees or distributors or otherwise which arise from the supply of the goods and or services or their use or resale by the buyer Delta T shall not be liable to the buyer by reason of any delay or failure to perform our obligations in relation to the goods and or services if the delay or failure was due to any cause beyond the Delta T s reasonable control SM200 User Manual 1 1 Index 28 Service and Spares Users in countries that have a Delta T Distributor or Technical Representative should contact them in the first instance Spare parts for our own instruments can be supplied from our works These can normally be despatched within a few working days of receiving an order
16. g in a stable voltage output that acts aS a simple sensitive measure of soil moisture content SM200 User Manual 1 1 Operation 7 Operation Cable attachment 7 Signal HH2 Extension cable cables 1 1m 5m 5m 10m 25m If you plan to install the SM200 at depth using the insertion rod pass the connector through the rod before attaching the cable Take care when attaching cables to ensure that the connectors are clean undamaged and properly aligned before pushing the parts together Screw together firmly to ensure the connection is water tight Extension cables can be joined up to a recommended maximum of Som Cable functions The SM200 is a single ended sensor The cables are assigned as follows Function Name Colour Power to sensor Power V Red Sensor output Signal White Power V i Ground Shield Sensor output silver SM200 User Manual 1 1 Operation 8 Installation Surface installation and spot measurements Clear away any stones Pre form holes in very hard soils before insertion Push the SM200 into the soil until the rods are fully inserted Ensure good soil contact Ifyou feel strong resistance when inserting the SM200 you have probably hit a stone Stop and re insert at a new location Installing at depth Auger a 45mm diameter hole 10 to vertical is recommended Fit insertion rod to SM200 remember to pass the cable through the inser
17. individual components ref 4 For a particular soil the contribution from the soil particles can be assumed to be constant so the refractive index measured by the SM200 is only affected by changes to the water content 8 This relationship simplifies to Ve a a 0 where the coefficients a and a conveniently parameterise the dielectric properties of soils Soil calibrations oO D Soil refractive index Ve N gt Offset ao 2 0 0 0 2 0 4 0 6 0 8 Soil moisture m m Note that Ay JEay son S USUally between 1 3 to 2 3 a corresponds approximately to 1 and usually takes a value about 8 0 Real soil values for a and a can vary significantly from these guidelines when they are affected by other factors in particular bound water in clay soils may result in higher values of d4 SM200 User Manual 1 1 Index 16 General soil calibrations Most soils can be characterised simply by choosing one of the two general calibrations we supply one for mineral soils predominantly sand silt and clay and one for organic soils with a high organic matter content a a General soil calibrations Mineral Organic Soil refractive index Ve 0 0 0 2 0 4 0 6 0 8 Soil Moisture m m These values have been used to generate the polynomial conversions and linearisation tables in the Soil moisture reading s
18. m up recommended requirement 15mA typical 200ms minimum Output signal 0 to 1 0V Nominal 0 to 60 vol SLE SUT hE IP68 Sensor buriable sealed to IP68 sealing Operating range 20to 60 C Readings in frozen soil are not meaningful Accuracy figures apply to calibration soils and over 0 to 60 C Percentages quoted as vol are volumetric water content Conductivity response M200 conductivity response at different water contents m 100 water 85 m 45 22 Typical artificial substrate conditions SM200 output Volts 0 100 200 300 400 500 600 Conductivity ECp mS m SM200 User Manual 1 1 Soil specific Calibration 21 Temperature response The SM200 temperature response in any particular soil will depend on a combination of effects The SM200 electronics has a very low temperature sensitivity and makes a negligible contribution to the overall sensitivity The refractive index of water ve see Calibration section reduces as the temperature increases This produces a negative temperature response particularly in soils or substrates with high water content Water that is bound to the surface of soil particles has a much lower refractive index than free water The percentage of bound water decreases with temperature and this produces a positive temperature response particularly in clay soils at lower water contents The last two effects partially offset each other but in soil conditions
19. nd accessories authorised by Delta T Sensor cables from other sources for example can adversely affect product performance and affect quality of results If possible route cables along the soil surface or bury them this also reduces possible trip hazard and animal damage Do not modify the product or its supplied accessories Regulatory information Europe SM200 has been assessed for CE compliance under the European Union EMC directive 89 336 EEC and conforms to the appropriate standards EN61326 1997 providing the product is used as described in this manual Use of non Delta T cables and accessories may invalidate this FCC compliance USA This device complies with part 15 of the FCC Rules Operation is subject to the following conditions 1 This device may not cause harmful interference 2 This device must accept any interference received including interference that may cause undesired operation Note This equipment has been tested and found to comply with the limits for a Class A digital device pursuant to part 15 of the FCC rules These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment This equipment generates uses and can radiate radio frequency energy and if not installed and used in accordance with the instruction manual may cause harmful interference to radio communications Operation of this equipment in a residential
20. on Care must be the probe always store and transport the taken and handling SM200 in this protective tube precautions followed CAUTION Avoid touching the rods or SHARP PINS exposing them to other sources of static damage Keep the SM200 in its protective tube when not in use Handle with care Take care when attaching cables to ensure that the connectors are clean undamaged and properly aligned before pushing the parts together Screw together firmly to ensure the connection is water tight If the connector is damaged apply a light smearing of silicon grease to maintain sealing Do not pull the SM200 out of the soil by its cable If you feel strong resistance when inserting the SM200 into soil it is likely you have encountered a stone Stop pushing and re insert at a new location SM200 User Manual 1 1 Index 6 How the SM200 works aVAVAVAY Vout When power is applied to the SM200 it creates a 1OOMHz waveform similar to FM radio The waveform is applied to a pair of stainless steel rods which transmit an electromagnetic field into the soil The water content of the soil surrounding the rods dominates its permittivity A measure of a material s response to polarisation in an electromagnetic field Water has a permittivity 81 compared to soil 4 and air z 1 The permittivity of the soil has a strong influence on the applied field which is detected by the SM200 resultin
21. owing medium It consists of a sealed plastic body 40mm diameter attached to two sensing rods The probe is fitted with a waterproof connector that is easily connected to extension cables When taking a reading the probe rods are inserted directly into the soil The output from an SM200 is a simple analogue dc voltage This output can be converted into soil moisture using the IP68 CONNECTOR 3 12mm supplied general soil calibrations or the aA probe can be calibrated for specific soils DIA Features 3 scientific accuracy Low salinity sensitivity Excellent temperature stability Minimal soil disturbance Easy installation at depth in augered holes 51mm IP68 connector Rugged weatherproof and buriable 22mm SM200 User Manual 1 1 Index 4 Parts list You consignment may have the following parts SM200 soil moisture sensor fitted with M8 connector in protective packing tube supplied Quick Start Guide with SM200 1 1m cable for connecting SMCI SM200 to HH2 using 25 way HH2 D connector 5m cable connects SM200 to SM2C w 05 data loggers Terminates in bare wires EXT M8 05 5 10 and 25m extension EXT M8 10 cables Terminates in IP68 in EXT M8 25 line connector ML2 AG1 45mm spiral auger 1 2m long SL SM200 User Manual 1 1 Introduction 5 Care and Safety The rods of the SM200 are sharp in order to ease To prevent personal injury and damage to inserti
22. pport delta t co uk Web site www delta t co uk Tel 44 0 1638 742922 Fax 44 0 1638 743155 SM200 User Manual 1 1 Soil specific Calibration 29 Soil specific Calibration This note provides details of 2 techniques for generating soil specific calibrations 1 Laboratory calibration for substrates and non clay soils 2 Laboratory calibration for clay soils We use the term substrate to refer to any artificial growing medium Underlying principle Soil moisture content 8 is proportional to the refractive index of the soil Ve as measured by the SM200 see Calibration section Dielectric property of soil compared to moisture content 6 00 5 00 400 3 00 0 10 0 20 0 30 moisture content m m The goal of calibration is to generate two coefficients ao 44 which can be used in a linear equation to convert probe readings into soil moisture Ve a a x0 SM200 User Manual 1 1 Index 30 Laboratory calibration for non clay soils This is the easiest technique but it s not suitable for soils that shrink or become very hard when dry Equipment you will need Process SM200 and meter Soil corer if doing a calibration for a cohesive soil rather than sand ora substrate Heat resistant beaker gt 0 5 litre Weighing balance accurate to lt 1g Temperature controlled oven for mineral soils or substrates Notes and example Collect a damp sample of the soil or substrate This
23. tion rod and fit the connector first Push the SM200 into the soil until rods are fully inserted Ensure good soil contact Backfill around the insertion rod Alternatively Dig a trench and install horizontally see diagram SM200 User Manual 1 1 Operation 9 Logger connections and configuration GP1 2 SM200s can be connected to each GP1 as shown in the photo The diagram and table illustrate the connections for Channel 1 SM200 wiring Colour Power V Signal Ground Red White Shield 1 F GP1 terminal F CH1 PWR CH1 CH1 GND and CH1 Configure the GP1 by choosing SM200 from the sensor menu in DeltaLINK PC or Pocket DeltaLINK For configuration details see the GP1 Quick Start Guide SM200 User Manual 1 1 Index 10 DL6 eae Up to 6 SM200s can be connected to each DL6 These details illustrate connection to Channel1 SM200 DL6 a Colour f wiring terminal Power V Red V Signal White IN IN Ground Shield and 0V Configure the DL6 by choosing SM200 from the sensor menu in DeltaLINK PC or Pocket DeltaLINK For configuration details refer to the DL6 Quick Start Guide SM200 User Manual 1 1 Operation 11 tt e Up to 60 SM200s can be connected to each DL2e These details illustrate connection to Channel 58 using the LAC1 input card configured in 15 channel mode and warm up channel 63 SM200 DL2e eae
24. wing areas The measurement device What equipment is being used to read the probe output e A Delta T HH2 Moisture Meter e A Delta T data logger such as the GP1 DL6 or DL2e Consult the user manuals or the on line help for these devices and their related software Try alternative types of equipment if you have them available Check that you are using an appropriate soil calibration and the correct conversion method see Calibration section The SM200 itself Try to isolate the problem into one of the following areas e The SM200 or the connecting cable Then try to narrow down the area further e Mechanical problems faults or damage e Electrical or electronic problems or faults Functional check The following two simple checks can be used to establish whether your SM200 is functioning within expected bounds Air reading Hold the SM200 away from other objects and take a reading using an HH2 meter or other meter or logger The reading should be 0 12mV when used with a 5m cable Finger reading Hold the SM200 with your fingers wrapped closely but carefully around the two metal rods and take a reading using an HH2 meter or other meter or logger The reading should be between 500 to 750mV SM200 User Manual 1 1 Index 20 Technical Reference Specifications Range and Notes Accuracy 0 to 50 vol sam 50 to 500 mS m o o Salinity errors 3 5 vol 0 to 40 vol over 0 5 to 5 dS m Power 5 to 14V 1 second war
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