Campbell CS616 User Manual
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Campbell CS616 User Manual

Water content reflectometers
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Download this manual See also: Instruction Manual
CS616 & CS625
Water Content
Reflectometers
Issued: 11.8.15
Copyright © 2002-2015 Campbell Scientific, Inc.
Printed under licence by Campbell Scientific Ltd.
CSL 467

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Summary of Contents for Campbell CS616

  • Page 1 CS616 & CS625 Water Content Reflectometers Issued: 11.8.15 Copyright © 2002-2015 Campbell Scientific, Inc. Printed under licence by Campbell Scientific Ltd. CSL 467...
  • Page 3 Quotations for repairs can be given on request. It is the policy of Campbell Scientific to protect the health of its employees and provide a safe working environment, in support of this policy a “Declaration of Hazardous Material and Decontamination”...

  • Page 5: About This Manual

    PLEASE READ FIRST About this manual Please note that this manual was originally produced by Campbell Scientific Inc. primarily for the North American market. Some spellings, weights and measures may reflect this origin. Some useful conversion factors: Area: 1 in...

  • Page 7: Table Of Contents

    Orientation ................... 7 Potential Problems with Improper Insertion ........7 Wiring ....................7 Datalogger Programming ..............8 7.4.1 CS616 CRBasic Programming............8 7.4.2 CS625 CRBasic Programming............9 8. Operation ..............10 Water Content Reflectometer Method for Measuring Volumetric Water Content ................. 10 8.1.1...
  • Page 8 B. Importing Short Cut Code ........B-1 C. Example Programs ..........C-1 CS616 Programs ................C-1 C.1.1 CR1000 Program for Measuring Eight CS616 Probes ..... C-1 C.1.2 CR1000/Multiplexer Program for Measuring 48 CS616 Probes ..................C-3 CS625 Programs ................C-5 C.2.1 CR200(X) Program for Measuring Four CS625 Probes ...

  • Page 9: Introduction

    CS616 and CS625 Water Content Reflectometers Introduction The CS616 Water Content Reflectometer is an improved version of the CS615 Water Content Reflectometer. The CS625 is a modified CS616 for use with the CR200(X)-series dataloggers. The difference between the CS616 and the CS625 is the output voltage level.

  • Page 10: Quickstart

    CS616 and CS625 Water Content Reflectometers Quickstart Short Cut is an easy way to program your datalogger to measure the CS616 or CS625 probe and assign datalogger wiring terminals. The following procedure shows using Short Cut to program the CS616. The procedure for the CS625 is similar.
  • Page 11 Select Datalogger Model and Scan Interval (default of 5 seconds is OK for most applications). Click Next. Under the Available Sensors and Devices list, select the Sensors | Soil Moisture folder. Select CS616 Water Content Reflectometer. Click to move the selection to the Selected device window. It defaults to measuring the sensor hourly.

  • Page 12: Overview

    CS616 and CS625 Water Content Reflectometers After selecting the sensor, click at the left of the screen on Wiring Diagram to see how the sensor is to be wired to the datalogger. The wiring diagram can be printed out now or after more sensors are added.

  • Page 13: Specifications

    A calibration equation converts period to volumetric water content. The CS616/CS625’s cable can terminate in:  Pigtails that connect directly to a Campbell Scientific datalogger (option –PT).  Connector that attaches to a prewired enclosure (option –PW).

  • Page 14: Electrical Specifications

    CS625 is typically used to measure soil volumetric water content. Precision describes the repeatability of a measurement. It is determined for the CS616 and CS625 by taking repeated measurements in the same material. The precision of the CS616/CS625 is better than 0.1 % volumetric water content.

  • Page 15: Installation

    User Manual Installation Orientation The probe rods can be inserted vertically into the soil surface or buried at any orientation to the surface. A probe inserted vertically into a soil surface will give an indication of the water content in the upper 30 cm of soil.

  • Page 16: Datalogger Programming

    7.4.1 CS616 CRBasic Programming The output of the CS616 is a square wave with amplitude of 0.7 Vdc and a frequency that is dependent on the dielectric constant of the material surrounding the probe rods. The CRBasic instruction CS616() is used by the CR6, CR800, CR850, CR1000, CR3000, and CR5000 dataloggers to measure the CS616 output period.

  • Page 17: Cs625 Crbasic Programming

    CS616 sensor. MeasPerPort: The MeasPerPort parameter is the number of control ports to be used to control the CS616 sensor(s). If Reps is set to 4, MeasPerPort = 4 will result in the same port being used for all measurements.

  • Page 18: Operation

    The fundamental principle for CS616/CS625 operation is that an electromagnetic pulse will propagate along the probe rods at a velocity that is dependent on the dielectric permittivity of the material surrounding the line.

  • Page 19: Cs616 And Cs625 Linear And Quadratic Calibrations Derived From Loam Soil

    Output period (microseconds) cali brati on data li near fi t quadrati c fi t Figure 8-1. CS616 and CS625 linear and quadratic calibrations derived from loam soil Figure compares the CS616 response in the Figure loam soil to a higher density sandy clay loam for two different electrical conductivities.

  • Page 20: Calibration Equations

    CS616 and CS625 Water Content Reflectometers Figure 8-2. CS616 response for different soil types The compacted soil response shows the effect of compaction and high clay content. The signal attenuation caused by compaction or high clay content causes an offset in the response as shown by the near-parallel curves at water contents above 10%.

  • Page 21: Linear Versus Quadratic Calibration Differences

    Figure shows the difference between the linear and the quadratic calibration forms over the typical range. A CS616/CS625 output period of 16 microseconds is about 1.2% VWC and 32 microseconds is 44.9%. The linear calibration is within ± 2.7% VWC of the quadratic. The linear calibration underestimates water content at the wet and dry ends of the range and overestimates it by up to about 2.6 % VWC at about 20% VWC.

  • Page 22: Operating Range

    The quality of soil water measurements which apply electromagnetic fields to wave guides is affected by soil electrical conductivity. The propagation of electromagnetic fields in the configuration of the CS616/CS625 is predominantly affected by changing dielectric constant due to changing water content, but it is also affected by electrical conductivity.

  • Page 23: Soil Organic Matter, Clay Content, And Soil Bulk Density

    Discussion of the effects of soil electrical conductivity on CS616/CS625 performance will be on a soil solution or extract basis unless stated otherwise. –1...

  • Page 24: Signal Attenuation Error

    The propagation of electromagnetic energy along the probe rods depends on the dielectric properties of the medium. When the reflection of the applied signal from the end of the rods is detected by the CS616/CS625 circuit, another pulse is applied. The time between pulses depends on the propagation time, and the associated period is empirically related to volumetric water content.

  • Page 25: Water Content Reflectometer User-Calibration

    User Manual W ater Content Error w i th Temperature Soil Temperature (C) W ater Content = 30% W ater Content = 12% Figure 8-4. Percent volumetric water content error adjusted with temperature correction equation Water Content Reflectometer User-Calibration 8.2.1 Signal Attenuation in Conductive Soils and Need for Site- Specific Calibration A shift in water content reflectometer response results if the applied signal is attenuated significantly.

  • Page 26: User-Derived Calibration Equation

    8.2.3 Collecting Laboratory Data for Calibration Water content reflectometer data needed for CS616/CS625 calibration are the CS616/CS625 output period (microseconds) and an independently determined volumetric water content. From this data, the probe’s response...
  • Page 27 , the intercept; and C , the slope. Required equipment: 1. CS616/CS625 connected to datalogger programmed to measure output period 2. Cylindrical sampling devices to determine sample volume for bulk density; for example, copper tubing of diameter  1 inch and length about 2 inches 3.
  • Page 28 The time required for equilibration depends on the amount of water added and the hydraulic properties of the soil. Equilibration can be verified by frequently observing the CS616/CS625 period output. When period is constant, equilibration is achieved. Collect a set of calibration data values and repeat the water addition procedure again if needed.

  • Page 29: Collecting Field Data For Calibration

      bulk The average water content for the replicates and the recorded CS616/CS625 period are one datum pair to be used for the calibration curve fit. 8.2.4 Collecting Field Data for Calibration Required equipment 1. CS616/CS625 connected to datalogger programmed to measure probe output period 2.
  • Page 30 However, intentionally changing water content in soil profiles can be difficult. A vertical face of soil can be formed with a shovel. If the CS616/CS625 is to be used within about 0.5 metres of the surface, the probe can be inserted into the face and water added to the surface with percolation.

  • Page 31: Calculations

      bulk The average water content for the replicates and the recorded CS616 period are one datum pair to be used for the calibration curve fit. 8.2.5 Calculations The empty cylinders used for core sampling should be clean; both empty weight and volume are measured and recorded.
  • Page 32 CS616 and CS625 Water Content Reflectometers Rhoades, J.D., N.A. Manteghi, P.J. Shouse, W.J. Alves. 1989. Soil electrical conductivity and soil salinity: New formulations and calibrations. Soil Sci. Soc. Am. J., 53:433-439.
  • Page 33 Appendix A. Discussion of Soil Water Content The water content reflectometer measures volumetric water content. Soil water content is expressed on a gravimetric and a volumetric basis. To obtain the independently determined volumetric water content, gravimetric water content must first be measured. Gravimetric water content (g) is the mass of water per mass of dry soil.

  • Page 35: Importing Short Cut Code

    Appendix B. Importing Short Cut Code This tutorial shows:  How to import a Short Cut program into a program editor for additional refinement  How to import a wiring diagram from Short Cut into the comments of a custom program Short Cut creates files that can be imported into either CRBasic Editor.

  • Page 37: Example Programs

    C.1 CS616 Programs C.1.1 CR1000 Program for Measuring Eight CS616 Probes The following CR1000 program uses the CS616() instruction to measure eight CS616 probes connected to the CR1000 datalogger (Table C-1). Although this example is for the CR1000, other CRBasic dataloggers are programmed similarly.
  • Page 38 '+++++++++++++++++++++++++++ If Flag (1) = high Then 'measure 8ea CS616 probes on CR1000 CS616 (Period(1),4,9,7,4,1.0,0) 'measure 4ea CS616 probes, enable w/ C7 CS616 (Period(5),4,13,8,4,1.0,0) 'measure 4ea CS616 probes, enable w/ C8 For I=1 to 8 'convert CS616 period to Volumetric Water Content...

  • Page 39: Cr1000/Multiplexer Program For Measuring 48 Cs616

    C.1.2 CR1000/Multiplexer Program for Measuring 48 CS616 Probes The following CR1000 program uses the AM16/32-series multiplexer to measure 48 CS616 probes connected in the 4x16 configuration; wiring is provided in Table C-2). The program also measures datalogger battery voltage and temperature.
  • Page 40 'Set flag 1 High every 30 min (Note: User can manually set flag 1 high/low) If IfTime (0,30,min) Then flag (1) = high '+++++++++++++++++++++++++++ If Flag (1) = high Then 'measure 48ea CS616 probes on AM16/32 in (4x16) mode PortSet (4,1) 'Set Mux Reset line High 'Set sub scan loop counter...

  • Page 41: Cs625 Programs

    Appendix C. Example Programs C.2 CS625 Programs C.2.1 CR200(X) Program for Measuring Four CS625 Probes This CR200X program measures volumetric water content with four CS625 probes; Table provides wiring. The average hourly readings are saved in final storage every 4 hours. Table C-3.

  • Page 42: Cr200(X) Program With Temperature Correction

    Appendix C. Example Programs C.2.2 CR200(X) Program with Temperature Correction This CR200X program measures temperature with 109 probe and uses the 109 temperature to correct the period for one CS625. The standard calibration equation is used to convert temperature-corrected period to volumetric water content.
  • Page 43 Appendix C. Example Programs 'CR200(X) program to read one 109 temperature probe and 1 CS625. 'Use temperature to correct CS625 period. 'Standard calibration is used to convert CS625 output 'period to volumetric water content. 'Sensors are read hourly and average water content and 'temperature are written to storage every 4 hours.
  • Page 44 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 sales@csafrica.co.za Campbell Scientific Australia Pty. Ltd. (CSA)

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Cs625

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