SM300 user manual
Contents
1. Make sure to quote the reference 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 Technical Support Tel 44 1638 742922 Delta T Devices Ltd 130 Low Road Fax 44 1638 743155 Burwell E mail tech support delta t co uk Cambridge CB25 0EJ sales delta t co uk England UK Web www delta t co uk SM300 User Manual 1 1 Technical Support 34 Appendix 1 Soil specific Calibration This note provides details of 2 techniques for generating soil specific calibrations Laboratory calibration for substrates and non clay soils 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 Vs as measured by the SM300 see Calibration section Dielectric property of soil compared to moisture content 6 00 5 00 400 3 00 2 00 1 00 0 00 0 10 0 20 0 30 moisture content m m The goal of calibration is to generate two coefficients dao a1 which can be used in a linear equation to convert probe readings into soil moisture Ve a a x0 SM300 User Manual 1 1 Appendix 1 35 Laboratory calibration for non clay soils This is the easiest technique but it2. Warning Do not touch the pins 24 Index 47
3. 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 where one or the other effect dominates the SM300 will appear to have a significant temperature response This illustration is based on the model in reference 7 see page 32 Illustrating temperature dependence of SM300 readings in a clay soil 6 0 4 a 0 3 a 0 2 9 0 1 bound water J m u E p eD 0 c O cD pe 0 we e O W p am eD Pas Q Q lt x 20 30 Soil temperature C Note ice has a quite different refractive index from water so SM300 soil moisture readings cannot be interpreted reliably when inserted into soil below 0 SM300 User Manual 1 1 Technical Reference 27 Sampling Volume _ on e 2 tq e A i e 2 Lu SM300 User Manual 1 1 The SM300 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 Minimum soil sample size Ful
4. 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 5 Roth C H M A Malicki and R Plagge 1992 l Empirical evaluation of the relationship between soil dielectric constant and volumetric water content as the basis for calibrating 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 7 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 SM300 User Manual 1 1 References 32 Technical Support Terms and Conditions of Sale Our Conditions of Sale ref COND 1 07 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 throu
5. Using the DeltaLINK logger software configure channel 1 or 2 as sensor type SM300 and channel 3 or 4 as an SM300 Temperature sensor see also GP1 Quick Start Guide and the DeltaLINK on line Help t You need the PC logger software DeltaLINK version 2 4 or later A free upgrade can be obtained from www delta t co uk or from the Software and Manuals CD Issue 3 SM300 User Manual 1 1 Operation 12 DL6 6 SM300s can be connected to a DL6 Each soil moisture sensor is wired as a differential powered sensor A DL6 logger can only read one SM300 temperature sensor These details illustrate connection to channels 6 amp 7 SM300 wiring Colour DL6 terminal Power OV brown OV Power V white V Signal HI blue IN Signal LO black IN Temperature grey RES IN Cable shield green 7777 In DeltaLINK configure channel 6 as type SM300 and channel 7 as a tyoe SM300 Temperature sensor See also the DL6 Quick Start Guide and the DeltaLINK online Help You need the PC logger software DeltaLINK version 2 4 or later A free upgrade can be obtained from www delta t co uk or from the Software and manuals CD Issue 3 SM300 User Manual 1 1 Operation 13 DL2e Up to 60 SM300s can be connected to a DL2e logger if not using the temperature sensor channel Up to 30 SM300s can be connected if also reading the temperature sensor Each moisture sensor is connected as a differential powered sensor These details illustrate
6. connection to Channels 57 and 58 using a LAC1 input card configured in 15 channel mode and warm up channel 63 SM300 wiring Colour DL2e terminal Power OV brown CH62 or 61 Power V white CH63 NO Signal HI blue CH58 Signal LO black CH58 Temperature grey CH57 and CH57 Cable shield green CH61 or 62 Configure the chosen DL2e logger channels by selecting the appropriate S3M and S30 sensor types for mineral and organic soils and S3T for the temperature sensor type listed in the Ls2Win sensor library See the DL2e User Manual and the Ls2Win online help gt You need a PC running Ls2Win version 1 0 SR6 or later A free upgrade can be obtained from www delta t co uk or from the Software and manuals CD Issue 3 SM300 User Manual 1 1 Operation 14 Other data loggers The SM300 soil moisture output should be connected as a differential powered sensor Configure the logger to convert the SM300 readings from milliVolts into soil moisture units by using either Polynomial conversion on page 21 or Linearisation table conversion on page 22 Note Output signals in the range 0 to 1 0 volts from the SM300 corresponding to 0 to 60 water content in mineral soils see Linearisation table conversion on page 22 Note The SM300 has been optimised for warm up of 0 5 to 1 second duration lt is recommended that the sensor is not powered continuously The temperature sensor output should be read as a resistance and t
7. s not suitable for soils that shrink or become very hard when dry Equipment you will need Process SM300 and meter Soil corer if doing a calibration for a cohesive soil rather than sand or a 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 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 Wy 743 3g SM300 User Manual 1 1 Appendix 1 36 Insert SM300 into the sample and record its output in Volts V 0 350 V 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
8. 6 Parts list Your shipment may include the following SM300 sensor with Quick Start Guide 1 5m cable connects SMSC d HH2 to HH2 meter via 25 way D connector 5m cable with SMSC sw 05 100 mm flying leads for GP1 or DL6 logger 5m cable with 200mm flying leads for DL2e logger SMSC Iw 05 aii EXT 5W 05 5 10 and 25m FS EXT 5W 10 extension cables J Dz EXT 5W 25 IP68 M12 connectors ML EX50 50 and 100cm ML EX100 Extension Tube 45mm spiral auger 1 2m long SM300 User Manual 1 1 Introduction 7 Care and Safety The rods of the SM300 are sharp in To prevent personal injury and damage to order to ease insertion Care must the probe always store and transport the SM300 in this protective tube be taken and handling precautions followed CAUTION Avoid touching the rods or exposing SHARP PINS them to other sources of static damage particularly when powered up Keep the SM300 in its protective tube when not in use Take care when attaching cables to ensure that the connectors are clean undamaged and properly aligned before pushing the parts together Do not pull the SM300 out of the soil by its cable If you feel strong resistance when inserting the SM300 into soil it is likely you have encountered a stone Stop pushing and re insert ata new location Do not touch the pins particularly when the sensor is attached to a cable An electrostatic discharge from your b
9. User Manual for the SM300 Soil Moisture Sensor SM300 UM 1 1 AT Delta T Devices Ltd Notices Copyright All parts of the SM300 design and documentation are the exclusive right of Delta T Devices and covered under copyright law 2010 Delta T Devices Ltd Patent s pending EMC Compliance See page 29 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 SM300 UM 1 1 Juneay 2010 Delta T Devices Ltd 130 Low Road Burwell Cambridge CB25 OE UK Tel 44 1638 742922 Fax 44 1638 743155 email sales delta t co uk web www delta t co uk Contents Introduction Description Features Dimensions Parts list Care and Safety How the SM300 works Operation Cable Connections Installation Logger connections and configuration GP1 DL6 DL2e Other data loggers HH2 Meter Calibration Soil calibration sensor calibration Soil moisture reading Troubleshooting Technical Reference Specifications Volumetric water content Temperature SM300 User Manual 1 1 o1 Ol 16 17 18 20 21 23 25 25 25 25 3 SM300 must be fully buried to accurately measure soil temperature Definitions References Technical Support Appendix 1 Soil specific Calibration Laboratory calibration for non clay soils Laboratory calibration for clay soils Appendix 2 The SM300 Temperat
10. ad to retrieve the readings See also Support for the SM300 Soil Moisture Sensor with an HH2 and HH2 User Manual and HH2 User Manual Addendum to V4 SM300 Note the HH2 does not display or store SM300 temperature readings Note For an upgrade contact Delta T SM300 User Manual 1 1 Operation 16 Calibration The SM300 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 SM300 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 Ve The SM300 response is best understood in these stages 1 Soil calibration 2 Sensor calibration 0 ve V gt ve Soil calibrations SM300 dielectric performance 0 6 8 vol SM300 output V V 60 0 6 SM300 output V SM300 User Manual 1 1 Operation 17 Soil calibration Damp soil is essentially a mixture of soil particles air and water and together these components determine its dielectric properties including the refractive index Vs The refractive index of the mixture is approximated simply by adding the contributions from t
11. attached to a cable A typical electrostatic discharge from your body can create a temporary 10mV offset in sensor readings lasting for up to one hour Mid range reading dip rod tips in water If you wish to take a quick reading to check the sensor is working you can dip the sensor into water With the pins half immersed in tap water an HH2 set to read an SM300 with soil type set to Organic should give a reading in the range 80 to 100 vol SM300 User Manual 1 1 Troubleshooting 24 Technical Reference Specifications Volumetric water content Accuracy 2 5 vol over 0 to 50 vol and 0 60 C Measurement range O to 100 vol with reduced accuracy Salinity error see p 26 lt 3 5 vol over 50 to 1000 mS m and 0 40 vol Output Signal 0 1V differential 0 to 60 vol nominal Output compatible with GP1 DL6 DL2e HH2 SM300 must be fully buried to accurately measure Temperature soil temperature Sensor accuracy 0 5 C over 0 40 C not including logger or cabling error Output Resistance 5 8kQ to 28kQ Output compatible with GP1 DL6 DL2e Cabling error contribution Negligible for GP1 amp DL6 any cable length to temperature readings Negligible for DL2e with 5m cable Maximum cable length 100m GP1 amp DL6 data loggers 100m DL2e water content measurement 25m DL2e temperature measurement Power requirement 5 14VDC 18mA for 0 5 to 1s Operating range Environment Sample volume Dime
12. ay fall into one of the following areas The measurement device What equipment is being used to read the probe output A Delta T HH2 Moisture Meter Note the HH2 does not measure SM300 temperature A Delta T data logger such as the GP1 DL6 or DL2e Check Versions Check you have the correct versions HH2 Meter Firmware version 2 5 and PC software HH2read version 5 or later are recommended GP1 amp DL6 Loggers DeltaLINK version 2 4 or later is required DL2e Logger Ls2Win 1 0 SR6 is required 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 SM300 itself Try to isolate the problem into one of the following areas The SM300 or the connecting cable Then try to narrow down the area further Mechanical problems faults or damage Electrical or electronic problems or faults SM300 User Manual 1 1 Troubleshooting 23 Functional check The following two simple checks can be used to establish whether your SM300 is functioning within expected bounds Air reading Hold the SM300 away from other objects and take a reading using an HH2 meter or voltmeter or logger The reading should be 0 4mV when used with a 5m cable Warning Do not touch the pins Do not touch the pins when the sensor is
13. composts it s usual to air dry the sample to avoid burning off any volatile factions Weigh the dry sample in the beaker Mo 627 2g reading Vo 0 051 V For the SM300 In the dry soil V Vo 0 051 Volts Substitute this into the equation Ve 1 0 14 868V 33 56V2 51 223V 36 283V 9 715V Calculate ao gives Je 1 68 Since o 0 this is the value needed for ao Re insert the SM300 into the dry sample and record this Ao 1 68 SM300 User Manual 1 1 Appendix 1 37 Calculate 6 The water content of the wet soil 6w can be calculated from the weight of water lost during drying Ww Wo and its volume Ls 0 W W L 743 3 627 2 463 5 0 25 6 0 25 Calculate a In the wet soil V V 0 350 Volts and substituting gives Je 3 79 Finally a Je fe 0 0 3 79 1 68 0 25 0 8 44 ad 8 44 Result Ao 1 68 ad 8 44 In this example this soil is now calibrated You can now use these two numbers in place of the standard mineral or organic calibration factors to convert SM300 readings into volumetric water content using Je d a x0 See also page Underlying principle on page 35 SM300 User Manual 1 1 Appendix 1 38 Laboratory calibration for clay soils This technique is adapted to avoid the near impossibility of inserting the SM300 into completely dry clay soil It requires taking measurements at 2 significantly different but still damp moisture
14. ding section 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 1 on page 34 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 SM300 User Manual 1 1 Operation 19 Sensor calibration Each SM300 is individually adjusted to provide consistent dielectric performance SM300 dielectric performance w Ea x c3 S oD 2 pe Q S Ge e9 Sun i N 0 4 0 6 0 8 SM300 output Volts This response can be approximated either by a polynomial below or by a linearisation table see next page Polynomial for use over the full range of SM300 readings Ve 1 0 14 868V 33 56V 51 223V 36 283V 9 715V where V is the SM300 output in Volts SM300 User Manual 1 1 Operation 20 Linearisation table for use over the full range of SM300 readings V VE V Ve V Ve V VE V VE 0 000 1 000 0 300 3 556 0 600 4 956 0 900 6 471 1 200 7 961 0 075 1 963 0 375 3 913 0 675 5 327 0 975 6 841 1 275 8 411 0 150 2 641 0 450 4 254 0 750 5 708 1 050 7 205 1 350 8 971 0 225 3 149 0 525 4 598 0 825 6 092 1 125 7 571 1 425 9 724 Soil moisture
15. e SM300 equation Ve 1 0 14 868V 33 56V 51 223V3 36 283V 9 715V provides two dielectric values Vew and Vem at two known water contents 6w and On Substituting Vw 0 349 gives 2 2 0 e a for 6 743 3 627 2 463 5 0 25 Substituting Vm 0 180 gives alEm 2 0I 4 4 G For 693 2 627 2 463 5 0 14 Then a Je Je 6 0 8 69 a 8 69 and a Je 4 6 1 61 do 1 61 a 8 69 do 1 61 In this example this soil is now calibrated You can now use these two numbers in place of the standard mineral or organic calibration factors to convert SM300 readings into volumetric water content using Je a a x0 See also page Underlying principle on page 35 SM300 User Manual 1 1 41 Appendix 2 The SM300 Temperature Sensor Soil moisture content is used with the measurement of soil temperature in several major application areas including the following Global warming and climate studies Soils contain more than four times as much carbon as the CO2 in the atmosphere and each year they release about ten times as much carbon through soil respiration as the combined release through burning fossil fuels Soil respiration rates are particularly sensitive to changes in both temperature and the moisture content of the soil Soils also have a significant interaction with climate as they store and release heat soil temperature provides a measure of the energy partit
16. gh misuse or inexpert servicing or other circumstances beyond their 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 replacing faulty parts free of charge or by repairing the goods free of charge at Delta 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 Delta T requires that such returns are discussed with them in advance and may at their 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 their 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 their obligations in relation to the goods and or services if the delay or failure was due to any cause beyond the De
17. he 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 SM300 is only affected by changes to the water content This relationship simplifies to Ve a a 0 where the coefficients a and a conveniently parameterise the dielectric properties of soils Soil calibrations E9 ro En fo 25 Slope a1 D fo Ww gt Ee x lt v 5 v 2 40 Q Sas q o Sa O A Offset ao 0 2 0 4 0 6 Soil moisture m m Note that do Ear soi 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 may result in higher values of a4 SM300 User Manual 1 1 Operation 18 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 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 rea
18. he logger configured with a look up table to covert the measured resistance to temperature See SM300 Temperature Measurement on page 43 and Resistance to Temperature Lookup Table on page 45 SM300 User Manual 1 1 Operation 15 HH2 Meter This assumes you have version 2 5 or later for both the PC software HH2Read and the HH2 firmware see foot of page Connect the SM300 to the HH2 meter zng DELTA T DEVICES CAMBRIDGE ENGLAND Press Esc to turn the meter on and if necessary press again until the HH2 displays the start up screen Set the meter to read from an SMS300 Press and scroll down to the Device option Press Set again and scroll down to select SM300 Press Set to confirm this choice Make sure the HH2 is correctly configured for your soil type At the start up screen press Set and scroll down to the Soil Type option Press Set again and scroll down to the appropriate soil type use Mineral for sand silt or clay soils or Organic for peaty soils Press Set to confirm this choice Choose the units you want for displaying readings At the start up screen press Set and scroll down to the Display option Press Set again and scroll down to select units Press Set to confirm this choice Press to take a reading Press to save or Esc to discard the reading Remove the SM300 from the soil and move to a new location If you have saved data connect your HH2 to a PC and run HH2Re
19. he bulk density of the sample Ps V S SM300 User Manual 1 1 Technical Reference 30 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 use for bulk use for organic j density bulk contents range densities g cm g cm Note C denotes percentage Carbon and is a measure of organic content 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 can be classified using the following descriptive categories non slightly moderately saline saline saline Classification of salinity See also http www land vic gov au DP Vro vrosite nsf pages water_ spotting soil salting class ranges s1 SM300 User Manual 1 1 Technical Reference 31 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 2 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
20. ication emc 29 Civil engineering 42 climate 42 Conductivity response 26 Connections 12 contamination 42 Conversions linearisation table 19 20 polynomial 19 20 Copyright 2 D Data logger 15 22 23 24 DL2e 22 23 DL6 23 GP1 13 23 SM300 User Manual 1 1 other 15 Definitions 30 Description 5 Dielectric performance 20 refractive index 17 18 35 Dimensions 6 DL6 13 EMC 2EG29 9 Extension cables 10 FCC compliance 29 Features 5 G Global warming 42 GP1 12 13 23 H HH2 7 16 17 23 24 hydrogeology 42 Installation buried 11 insertion rod 11 surface 11 Index 46 L Linearisation table 21 volts to vol 15 22 M M12 5w 05 43 Meter 23 Moisture content 5 9 32 35 O Organic and Mineral 31 p Parts 7 Patent 2 Permittivity 9 17 32 Polynomial conversion 21 R References 32 Regulatory information 29 Rods 8 9 11 Sales code 7 Salinity 31 SM300 User Manual 1 1 Sampling Volume 28 Servicing 34 Soil clay 18 19 30 35 36 39 mineral 17 19 21 36 37 40 organic 17 19 21 31 37 stony 11 soil calibrations 19 Specifications 2 25 T Technical support 33 34 Temperature cable length correction 15 43 Temperature response of soil moisture readings 27 Temperature sensor cable length correction 44 Temperature Sensor Lookup Table 45 Troubleshooting 23 V Volumetric Soil Moisture 30 W
21. ioning which in turn is strongly influenced by the effect of soil moisture on thermal conductivity Civil engineering Most civil engineering projects depend critically on the mechanical properties of soils Those properties are effected by many different parameters but moisture content and temperature are the two variables that are most likely to change over time so may be measured together in order to assess their impact Soil contamination and hydrogeology Soil moisture is the main determinant for the movement of contaminants and solutes through soils but temperature also has a significant influence so they are often measured together Agriculture Temperature may be measured alongside soil water content for studies of evapotranspiration soil water balance and irrigation Soil strength and seedling emergence depend on soil moisture and temperature and both need to be taken into account when deciding when to sow SM300 User Manual 1 1 Appendix 2 42 SM300 Temperature Measurement The SM300 Temperature sensor uses a thermistor with a 10K resistance at 25 C However A This sensor has a different response curve from the more widely used 10K3A1B type The response curve is given in the Resistance to Temperature Lookup Table on page 45 B The Thermistor circuit shares the Power OV wire If the thermistor is measured when the SM300 is powered the measured resistance measurement may need to be corrected for 18 mA SM300 s
22. l accuracy requires a soil volume of one litre but the additional error from taking a reading in a 0 5 litre sample is negligeable SM300s may interact if they are placed too close together they should be separated by at least 100mm If the SM300 is inserted too close to the wall of a plant pot the sensing field can see outside the pot This behaviour is shown in the graph below For best results keep a gap of at least 25mm 1 inch between the body of the sensor and the wall of the plant pot SM300 Error close to wall of plant pot live pin nearest to pot wall Gap between SM300 body and wall of pot mm Technical Reference 28 Electromagnetic Compatibility EMC General information SM300 is a Class A product intended for operation in non residential environments Only use cables and accessories authorised by Delta T sensor cables from other sources for example may 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 see also SM300 EMC Guidance on the Software and Manuals CD Issue 3 Regulatory information Europe This device conforms to the essential requirements of the EMC directive 2004 108 EC based on the following test standards EN61326 1 2006 Electrical requirement for measurement control and laboratory
23. levels Equipment you will need SM300 and meter Soil corer Heat resistant beaker gt 500ml Weighing balance accurate to lt 19 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 Wy 743 3g SM300 User Manual 1 1 Appendix 1 39 Insert SM300 into the wet sample and record its output in Volts Vw 0 349 V Dry the 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 Win 693 2g Re measure with the SM300 Vm 0 180 V Dry the sample thoroughly With clay 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 SM300 User Manual 1 1 Appendix 1 40 Calculations For the wet soil For the moist soil Calculate a Calculate ao Result Substituting in th
24. lta T s reasonable control SM300 User Manual 1 1 Technical Support 33 Service Repairs 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 and can normally be despatched within a few working days of receiving an order Spare parts and accessories for 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 return authorisation from Delta T or our distributor On receipt of the goods at Delta T you will be given a reference number Always refer to this reference number in any subsequent correspondence The goods will be inspected and you will be informed of the likely cost and delay We normally expect to complete repairs within one or two weeks 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 For contact details see below Technical Support Users in countries that have a Delta T distributor or technical representative should contact them in the first instance Technical Support is available on Delta T products and systems Your initial enquiry will be acknowledged immediately with a reference number
25. nsions Weight 77 gm without cable 4 In water no soil present the reading may not be 100 vol It depends on a0 and a1 but can still be used as a quick check that the unit is working See page 24 5 See Appendix 2 on page 42 6 Note The DL6 has only one temperature channel The DL6 error contribution to SM300 temperature measurement is negligible compared to the accuracy of the SM300 temperature sensor itself The two only become comparable below 15C 7 DL2e logger users can apply a correction in the Ls2Win logging software for cable lengths gt 5m SM300 User Manual 1 1 Technical Reference 25 Conductivity response This chart shows how salinity affects the output of the soil moisture sensor at various soil moisture levels SM300 conductivity response at different water contents 100 water e 60 o 45 e 38 o 30 e 20 gt Q gt e O O fas N 200 300 400 Conductivity EC mS m t slightly moderately saline saline Classification of salinity SM300 User Manual 1 1 Technical Reference 26 Temperature response of soil moisture readings The effect of temperature on the SM300 soil moisture readings in any particular soil will depend on a combination of effects The SM300 soil moisture electronics has very low temperature sensitivity and makes a negligible contribution to the overall sensitivity The refractive index of water Ve
26. o a recommended maximum of 100m see Specifications on page 25 SM300 User Manual 1 1 Operation 10 Installation Surface installation and spot measurements Clear away any stones Pre form holes in very hard soils before insertion Push the SM300 into the soil until the rods are fully inserted Ensure good soil contact If you feel strong resistance when inserting the SM300 you have probably hit a stone Stop and re insert at a new location Note The SM300 is not suitable for soil surface temperature measurements For soil temperature near the surface dig a trench and install horizontally as shown below Cover both SM300 and the first 30cm of cable with at least 5cm of soil Installing at depth Make a 45mm diameter hole preferably at about 10 to the vertical using the SM AUG 100 auger Connect an extension tube e g ML EX50 Push the SM300 into the soil until rods are fully inserted Ensure good soil contact Alternatively Dig a trench and install horizontally SM300 User Manual 1 1 Operation 11 Logger connections and configuration GP1 Two SM300s can connect to each GP1 Each soil moisture sensor is wired as a differential powered sensor These details illustrate connection to Channels 1 and 3 SM300 wiring Colour GP1 terminal Power OV brown ND Power V white CH1 PWR Signal HI blue CH1 Signal LO black CH1 Temperature grey Temp3 IN Cable shield green CH1 GND
27. ody can typically cause a temporary 10mV offset in sensor readings for up to one hour At worse it may permanently damage the sensor SM300 User Manual 1 1 Introduction 8 How the SM300 works amp Shy YK When power is applied to the SM300 It creates a 100MHz 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 1 The permittivity of the soil has a strong influence on the applied field V which is detected by the SM300 resulting in a stable out voltage output that actS as a simple sensitive measure of soil moisture content SM300 User Manual 1 1 Introduction 9 Operation Cable Connections brown Power OV white Power V blue Signal HI black Signal LO grey Temperature Cable shield HH2 Extension Logger cable cables cables 5m with 5m 1 5m 100 or 200 10m mm bare 25m leads 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 t
28. ogger uses voltage or current excitation for resistance measurement Voltage Excited You need to know the excitation voltage Vref reference resistance Rref The correct resistance is given by the equation R a0 a1 Rmeas Where a0 Ic Rc Rref Vref al 1 lc Rc Vref Ic 18 mA SM300 sensor supply current For Delta T EXT 5W xx series cables Rc 0 066 Q m For the SMSC Iw 05 5m logger cable Re 0 33 Q Current Excited You need to know the excitation current lex The corrected resistance is given by the equation using terms defined above R Rmeas Ic Rc lex Effect of Temperature on Water Permittivity See Temperature response of soil moisture readings on page 27 SM300 User Manual 1 1 Appendix 2 44 Resistance to Temperature Lookup Table degrees C Kohms 4 SM300 Resistance to Temperature Conversion Chart Temperature degrees C Note This table has been optimised for use as a look up table To minimise linear interpolation errors the data points fall either side of the manufacturers specified sensor response curve This helps optimise the overall accuracy of readings SM300 User Manual 1 1 Appendix 2 45 Index A Agriculture 42 Air reading 24 Auger 7 C Cable Connections 10 Cable length correction 43 Calibration check 24 generalised 21 sensor 20 21 soil 18 21 Soil 35 soil specific 35 Care and safety 8 Care and Safety 8 Certif
29. reading Polynomial conversion Combining the Soil calibrations and Sensor calibration steps the conversion equation becomes 1 0 14 868V 33 56V2 51 223V 36 283V 9 715V gt Ao A1 where a and a are the calibration coefficients For a generalised mineral soil this becomes O mineral 0 071 1 77V 3 995V2 6 098V 4 319V 1 157V And for a generalised organic soil 9 organic 0 039 1 931V 4 358V 6 652V3 4 712V 1 262V SM300 User Manual 1 1 Operation 21 Linearisation table conversion The conversion from SM300 reading Volts to soil moisture 0 m m or vol can be accomplished by a look up 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 0 801 0 670 0 0 044 0 021 56 0 867 0 731 4 0 074 0 045 60 0 934 0 791 8 0 108 0 072 64 1 003 0 852 12 0 147 0 102 68 1 072 0 913 16 0 193 0 137 72 1 140 0 976 20 0 248 0 178 76 1 204 1 039 24 0 313 0 226 80 1 260 1 102 28 0 384 0 281 84 1 309 1 163 32 0 457 0 343 88 1 351 1 220 36 0 530 0 410 92 1 388 1 270 40 0 600 0 477 96 A9 1 314 44 0 669 0 544 100 1 447 I 33 48 0 735 0 608 104 2 090 2 090 SM300 User Manual 1 1 Operation 22 Troubleshooting Always try to identify which part of the measurement system is the source of the difficulty For the SM300 this m
30. upply current GP1 and DL6 loggers The SM300 Temperature sensor type in DeltaLINK performs the supply current correction DL2e Logger The linearization table for the S3T sensor code SM300 Temperature provides supply current correction for the SMSC Iw 05 5m logger cable ONLY Extension cables and other cable lengths Create your own custom sensor type s and linearization tables as described in Ls2Win Help topic How to Add or modify a sensor type in the sensor library Enter corrected resistance values R for each linearization table point R R5 0 059 x Lex kQ See footnote or R R5 0 9 x Re 0 297 KQ where R5 value supplied in the table for the SM300 Temp 5m sensor type Lex length of extension cable excluding the 5m of SMSC Iw 05 cable Rc total cable resistance including resistance of SMSC Iw 05 cable if fitted Note This equation only applies to Delta T SM300 cables SM300 User Manual 1 1 Appendix 2 43 Other loggers If your logger can be programmed so that the soil moisture and temperature readings can be taken sequentially i e the sensor is not powered during the temperature reading then the temperature can be obtained directly from the response curve on page 45 Otherwise correct the resistance reading before applying the response curve You need to know the resistance of the Power OV wire in the SM300 cable Rc and establish whether your l
31. ure Sensor SM300 Temperature Measurement Effect of Temperature on Water Permittivity Resistance to Temperature Lookup Table Index SM300 User Manual 1 1 25 30 32 33 35 35 36 39 42 42 43 44 45 46 Introduction Description The SM300 measures soil moisture content and temperature lts sealed plastic body is attached to two sensing rods which insert directly into the soil for taking readings A waterproof plug connects to a choice of signal cables Both extension cables and extension tubes can be used The soil moisture output signal is a differential analogue DC voltage This is converted to soil moisture by a data logger or meter using the supplied general soil calibrations lt can also be calibrated for specific soils Features Soil moisture accurate to 2 5 Soil temperature to 0 5 C over 0 40 C Low salinity sensitivity Excellent stability Minimal soil disturbance Easy installation at depth in augered holes Waterproof connector to IP68 l Rugged weatherproof and can be buried Good electrical immunity Choice of cabling system options Cable connector cylindrical profile and extension tube design simplifies removal for servicing See also Specifications on page 25 SM300 User Manual 1 1 Introduction 5 Dimensions Cable connector sealed to IP68 M12 5 pin male Thread inch BSP for connecting to Extension Tube s SM300 User Manual 1 1 Introduction
32. use EMC requirements Group 1 Class A equipment emissions section only EN61326 1 2006 Electrical requirement for measurement control and laboratory use EMC requirements Basic Immunity immunity section only FCC compliance USA This device conforms to Part 18 of FCC rules Industrial Scientific amp Medical Equipment Note with reference to FCC Part 18 115 Elimination and investigation of harmful interference a The operator of the ISM equipment that causes harmful interference to radio services shall promptly take appropriate measures to correct the problem SM300 User Manual 1 1 Technical Reference 29 Definitions Volumetric Soil Moisture Content is defined as V where V is the volume of water contained in the O y sample S 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 0 g g and M is the total mass of the dry sample S To convert from volumetric to gravimetric water content use the equation 5 where p is the density of water 1g cm 0 0 x M Ps and p is t
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