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Delta-T Devices SWT5 User Manual

Tensiometer
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User Manual for the

Tensiometer

types SWT5 & SWT5x
SWT5-UM-2
Delta-T Devices Ltd

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Summary of Contents for Delta-T Devices SWT5

  • Page 1: User Manual For The

    User Manual for the Tensiometer types SWT5 & SWT5x SWT5-UM-2 Delta-T Devices Ltd...

  • Page 2: Notices

    All rights reserved. Under the copyright laws, this manual may not be copied, in whole or in part, without the written consent of Delta-T Devices Ltd. and UMS GmbH. Under the law, copying includes translation into another language. Copyright © 2009 Delta-T Devices Limited ©...

  • Page 3: Table Of Contents

    3.1.4 Ideal conditions for installation 3.1.5 Documentation 3.1.6 Selecting the installation angle Installation procedure Offset correction for non horizontal installations Connecting SWT5 and SWT5x 3.4.1 Spot readings with the SWT-MR (Infield7) 3.4.2 Cables 3.4.3 General requirements 3.4.4 Connection to a data logger 3.4.5...
  • Page 4 4.1.2 Refilling SWT5 in lab and field Testing 4.2.1 Calibration 4.2.2 Check the Offset Cleaning Storage Protecting the measuring site Theft and vandalism Cable protection Frost Useful notes Maximum measuring range and data interpretation Temperature influences Vapor pressure influence Osmotic effect...

  • Page 5: Introduction

    Ceramic cup: Do not touch the cup with your fingers. Grease, sweat or soap residues will influence the ceramic's hydrophilic performance. Do not twist the SWT5 shaft against the sensor body! Introduction  5 SWT5 User Manual v2...

  • Page 6: Unpacking

    1.2 Unpacking An SWT5 or SWT5x delivery includes:  Tensiometer, calibrated and filled, with 4-pin plug M12/IP67 with plug cap  This manual  Rubber protection cap, half filled with water, for keeping the ceramic moist and clean See also “Accessories” on page 41.

  • Page 7: Foreword

    See Terms and Conditions of Sale on page 46. 1.5 Durability The nominal lifespan for outdoor usage is 10 years, but protection against UV-radiation and frost as well as proper and careful usage substantially extends the lifespan. Introduction  7 SWT5 User Manual v2...

  • Page 8: Swt5 And Swt5X

    The atmospheric reference pressure is provided through a membrane on the cable, a unique patented method. The SWT5 Miniature Tensiometer is specially designed for point measurements, e. g. in soil columns, pots or laboratory lysimeters, or when the measurement of a minimal span is desired.

  • Page 9: Typical Applications

    -450 kPa, but this is an exception and cannot be guaranteed. The SWT5x is identical with the SWT5 but has a different ceramic. The extended measuring range is made possible by an effect called boiling retardation, which requires a special ceramic with smaller pores and an absolutely gas-free filling process.

  • Page 10: Specific Notes

     It does not make sense to refill a Tensiometer while the soil is dryer than -90 kPa (-900 hPa) for the SWT5 or - 160 kPa ( -1600 hPa) for the SWT5x.  The use of a quartz clay slurry is only recommended in clayey soils and only if the drilled diameter is larger than the shaft diameter (5 mm).

  • Page 11: Quick Start

    The procedure is the same for SWT5 and SWT5x. In very soft soils the SWT5 can be inserted directly without drilling a hole. As the shaft is fragile, no force should be applied. For hard soils a special auger kit for is available in the SWT5-FRK2 field refill kit, When the SWT5 auger is used, slurrying is unnecessary.
  • Page 12 Acrylic glass shaft Shafts are available with lengths from 2 to 20 cm High grade porous ceramic cup Filled with degassed water. wassergefüllt, mit Befüllröhrchen. 12  Introduction SWT5 User Manual v2...

  • Page 13: Sensor Description

    The white membrane on the cable must always be in contact with air during a measurement and should never be submersed under water. Sensor Description  13 SWT5 User Manual v2...

  • Page 14: The Ceramic Tip

    Compared to conventional porous ceramic the cup is much more durable. The bubble point of a SWT5 cup is about 200 kPa (20 bar, 2,000 hPa), and for a SWT5x it is about 500 kPa (50 bar, 5,000 hPa).

  • Page 15: Installation

    To obtain a differential description of the soil water situation at least 2 Tensiometers are recommended per horizon, one in the upper and one in the lower level. The maximum recommendable cable lengths for SWT5 and SWT5x are 20 meters. ...

  • Page 16: Ideal Conditions For Installation

    If the ceramic cup is positioned higher than the sensor body the first bubble that appears inside the shaft will block the water exchange and stop the Tensiometer working. 16  Installation SWT5 User Manual v2...

  • Page 17: Installation Procedure

    2. If the hole’s diameter is larger than 5 mm mix a slurry of water and ground-up soil material. 3. Connect the SWT5 to a readout device, for example a data logger for continuous measurements or the SWT-MR (INFIELD7) handheld device for spot readings.

  • Page 18: Offset Correction For Non Horizontal Installations

    The pressure transducer is calibrated without a cup. Thus, no compensation is required for horizontal installations. If a SWT5 or SWT5x is installed in a non horizontal position, the vertical water column draws on the pressure sensor and causes an offset shift.

  • Page 19: Connecting Swt5 And Swt5X

    3.4 Connecting SWT5 and SWT5x 3.4.1 Spot readings with the SWT-MR (Infield7) SWT5 and SWT5x are fitted with a 4-pin plug. The plug can be connected directly to the handheld measuring device for taking spot readings of the soil water tension. This displays and stores the soil water tension readings.

  • Page 20: Connection To A Data Logger

    3.4.5 TVB1 and TVB-M Tensiometer power supplies These power supplies are designed for Tensiometers SWT3, SWT4, SWT4R and SWT5. They offers a stabilized 10,6 V power supply, supplying -5 V and +5,6 V for powering up to 30 tensiometers. These provide tensiometer output signals of <1V, which is suitable for many loggers, The TVB1 fits inside a DL2e logger terminal compartment.

  • Page 21: Delta-T Tensiometer Loggers

    Up to 60 SWT tensiometers may be connected to a single DL2e. Each group of 15 Tensiometers require one LAC1 input card. In addition, each group of 30 require one TVB1 voltage regulator. Installation  21 SWT5 User Manual v2...

  • Page 22: Service And Maintenance

    95 kPa). By diffusion and slight leakage the reading will slowly drop within months. If the soil dries out and reaches the bubble point (-200 kPa for SWT5; -500 kPa for SWT5x), the tension will decrease rapidly as air will enter the cup.

  • Page 23: Refilling Swt5 In Lab And Field

    4.1.2 Refilling SWT5 in lab and field This chapter describes the refilling of SWT5 or SWT5x using the SWT5-FRK2 kit The procedure has 5 steps: 1. Check the SWT5 Tensiometer 2. Degas cup and shaft 3. Degas sensor 4. Reassemble 5.
  • Page 24 Check the SWT5 1. First, check if the SWT5 3. Now wave the SWT5 tip requires refilling: connect it to an around in the air. If the tension SWT-MR (Infield7) or a increases to -80 kPa within 10 voltmeter and power supply.
  • Page 25 Turn the still evacuated syringe to collect all bubbles. Hold the syringe upright, unblock the tube and remove all air. Repeat this procedure until no more bubbles appear. Take care to avoid bubbles. Service and maintenance  25 SWT5 User Manual v2...
  • Page 26 Remove all air from the syringe. wards and tap on it to loosen all bubbles. 6. Put the tube back on the syringe. Leave no air gaps inside the tube around the ceramic. 26  Service and maintenance SWT5 User Manual v2...
  • Page 27 Release the spacers and allow water to flow into the shaft. Carefully remove the tube from the syringe nozzle and remove all air from the syringe (see 6). Service and maintenance  27 SWT5 User Manual v2...
  • Page 28 1. Now take the syringe with the 2. Hold the syringe upwards attached sensor body adapter. and remove all air. Pull up the syringe, but not so far that the spacers snap in. 28  Service and maintenance SWT5 User Manual v2...
  • Page 29 7. Squeeze the tube to remove any air inside while reattaching the syringe. 2. Pull up the syringe a few times. Hold the syringe downwards so bubbles are collected inside the syringe. Service and maintenance  29 SWT5 User Manual v2...
  • Page 30 Press in the spacers and slowly release the piston. When removing the syringe from the sensor body take care to avoid damaging the pressure transducer! 30  Service and maintenance SWT5 User Manual v2...
  • Page 31 ... 4. Reattach the sensor body and draw up the syringe again. Tap on the sensor body to release any bubble. Let the piston release slowly. Service and maintenance  31 SWT5 User Manual v2...
  • Page 32 The reading should rise to -80 reading should be between kPa within 10 seconds. - 3 hPa and + 3 hPa If this is the case, the SWT5 is (= -0.3 kPa to +0.3 kPa). filled perfectly. 32  Service and maintenance...
  • Page 33 It should take one day for the Tensiometer to return to it’s initial value. Service and maintenance  33 SWT5 User Manual v2...

  • Page 34: Testing

    0 kPa. There are two ways to check the offset. 1. Connect the Tensiometer to a readout device. Place the SWT5 in a beaker and fill the beaker with de-ionized water up to the centre of the sensor body (see 3.4.) Wait until the reading is stable.

  • Page 35: Cleaning

    (grain size 150...240). Storage If the SWT5 or SWT5x is not be used for a year or more then empty shaft and sensor body to avoid algae growth. Store both in a dry place. 5 Protecting the measuring site 5.1 Theft and vandalism...

  • Page 36: Useful Notes

    If the soil dries to -15,000 hPa, the ceramic’s bubble point is reached. The water in the ceramic cup will run out quickly and the reading of the air-filled cup will go to zero (Fig. 6.1, day 16 to 19). 36  Useful notes SWT5 User Manual v2...
  • Page 37 Soil water tension normally change only slowly. An erratic signal curve with many discontinuities could indicate, for example loose contacts, moisture in defective cables or plugs, poor power supply or a data logger malfunction. Useful notes  37 SWT5 User Manual v2...

  • Page 38: Temperature Influences

    Thus, an influence of osmosis on the measurements is negligible because ion concentration differences are equalized quickly. If the SWT5 cup is dipped into a saturated NaCl solution the reading will be 1 kPa for a short moment, then it will drop to 0 kPa again.

  • Page 39: Appendix

    5 ... 15 VDC, stabilized Current consumption 1,3 mA at 10,6 V (TV-batt) Environmental (chemical) pH range pH 3 ... pH 10 Limited to substances that do not harm silicon, flour silicon, EPDM, PMMA and polyetherimid. Appendix  39 SWT5 User Manual v2...

  • Page 40: Wiring Configuration

    8.2 Wiring configuration Configuration of SWT5 and SWT5x Tensiometer plug and the 4-wire connecting cables type SWTCC: Pin and wiring configuration for connecting cable type Signal Wire Function brown Supply plus blue Supply minus A-OUT+ white Signal plus A-OUT- black Signal minus 40 ...

  • Page 41: Accessories

    Plastic protection tubes Please contact Delta-T Thermal insulation tubes Please contact Delta-T Plastic protection tubes for cables are available with several diameters, including dividable slotted tubes for easy re-fitting. Contact Delta-T for details. Appendix  41 SWT5 User Manual v2...

  • Page 42: Handheld Measuring Device

    A USB converter is available for data collection from the SWT-MR to a PC via PC or laptop. It includes Windows PC software TensioVIEW. Item Delta-T no, SWT-MR-USB USB PC adapter for SWT-MR 42  Appendix SWT5 User Manual v2...

  • Page 43: Tensiometer Loggers

    Each group of 15 Tensiometers require one LAC1 input card and one TVB1 voltage regulator. Item Delta-T no. Contact Delta-T 6-channel modified DL6 logger 2-channel GP1 logger Contact Delta-T Contact Delta-T 60 channel DL2e logger Appendix  43 SWT5 User Manual v2...

  • Page 44: Voltage Regulators

    8.3.4 Voltage regulators Tensiometer stablised power supply unit for SWT3, SWT4, SWT5, suited in DL2e-logger extension frame (left), or as an open module (right). The regulated power supply itself can power up to 60 tensiometer. Each TVB1 logger frame has supply terminals for 15 Tensiometers.

  • Page 45: Units For Soil Water And Matrix Potentials

    8.4 Units for soil water and matrix potentials Appendix  45 SWT5 User Manual v2...

  • Page 46: Technical Support

    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 Delta-T’s reasonable control. 46  Technical Support SWT5 User Manual v2...

  • Page 47: Service And Spares

    Contact Details Tel: +44 (0) 1638 742922 Tech Support Team Fax: +44 (0) 1638 743155 Delta-T Devices Ltd email: tech.support@delta-t.co.uk 130 Low Road, Burwell, email: repairs@delta-t.co.uk Cambridge CB25 0EJ, U.K. web: www.delta-t.co.uk Technical Support  47 SWT5 User Manual v2...

  • Page 48: Index

    Offset · 34 Degas the cup · 25 Degas the sensor body · 28 offset correction · 19 Offset correction · 18 Description · 13 Osmotic effect · 38 DL2e Logger · 21 SWT5 User Manual v2 IndexIndex IndexIndexIndexIndexIndexIndexIndex  48...
  • Page 49 Service · 22, 47 Wiring · 40 Slurry · 10 Soil columns · 8 soils · 8 Spares · 47 specifications · 39 Zero offset · 32 Spot readings · 19 Storage · 35 Index  49 SWT5 User Manual v2...

This manual is also suitable for:

Swt5x

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