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Campbell CS650 Product Manual

Water content reflectometers
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PRODUCT MANUAL
CS650
and CS655
Water Content Reflectometers
Revision: 07/2025
Copyright © 2011 – 2025
Campbell Scientific, Inc.

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  • Page 1 PRODUCT MANUAL CS650 and CS655 Water Content Reflectometers Revision: 07/2025 Copyright © 2011 – 2025 Campbell Scientific, Inc.

  • Page 2: Please Read First

    U.S. standard external power supply details where some information (for example the AC transformer input voltage) will not be applicable for British/European use. Please note, however, that when a power supply adapter is ordered from Campbell Scientific it will be suitable for use in your country.

  • Page 3: Table Of Contents

    Table of contents 1. Introduction 2. Precautions 3. Initial inspection 4. QuickStart 5. Overview 6. Specifications 6.1 Electrical specifications 6.2 Operational specifications 7. Installation 7.1 Orientation and placement 7.2 Proper insertion 7.3 Data logger wiring 7.4 Programming 8. Operation 8.1 A200 and Device Configuration Utility 8.1.1 Determining which COM port the A200 has been assigned 8.1.2 Device Configuration Utility 8.1.2.1 Settings Editor tab...
  • Page 4 8.6.1 User-derived calibration equation 8.6.2 Collecting laboratory data for calibration 8.6.3 Collecting field data for calibration 8.6.4 Calculations 9. Maintenance and troubleshooting 10. References Appendix A. Importing Short Cut code into CRBasic Editor Appendix B. Example programs Appendix C. Discussion of soil water content Appendix D.

  • Page 5: Introduction

    SDI-12 signal that many Campbell Scientific data loggers can measure. The CS650 has 30 cm length rods, whereas the CS655 has 12 cm length rods. This manual uses CS650 to reference model numbers CS650 and CS655. Unless specifically stated otherwise, information in the manual applies equally to both models.

  • Page 6: Quickstart

    1. Open Short Cut and click Create New Program. 2. Double-click the data logger model. 3. In the Available Sensors and Devices box, type CS650. You can also locate the sensor in the Sensors > Meteorological > Soil Moisture > CS650/CS655 Water Content Reflectometer folder.
  • Page 7 4. Repeat step three for other sensors you want to measure. 5. In Output Setup, type the scan rate. If you chose to measure the CS650 hourly rather than every scan, this scan interval must be evenly divisible into an hour. Type a meaningful table name and type the Data Output Storage Interval.

  • Page 8: Overview

    LoggerNet, RTDAQ, or PC400 to make sure it is making reasonable measurements. 5. Overview The CS650 measures volumetric water content, electrical conductivity, dielectric permittivity, and temperature of soils or other porous media. These values are reported through SDI-12 communications.
  • Page 9 Volumetric water content (VWC) is derived from the sensor sensitivity to the dielectric permittivity of the medium surrounding the sensor stainless-steel rods. The CS650 functions as a water content reflectometer, with the two parallel rods forming an open-ended transmission line.

  • Page 10: Specifications

    A five-conductor cable, including the drain or shield wire, provides power, ground, and communications for the CS650. The CS650 is intended to communicate with SDI-12 recorders, including Campbell Scientific data loggers. Alternatively, the orange wire can be used for RS-232 communication.

  • Page 11: Electrical Specifications

    610 m (2000 ft) combined length for up to 25 sensors connected to the same data logger control or U terminal Electromagnetic: External radio frequency (RF) sources can affect CS650 measurements. CS650 circuitry should be located away from radio transmitter aerials and cables or measurements should be discarded during RF transmissions.

  • Page 12: Operational Specifications

    Figure 6-1. CS650 and CS655 average current drain Figure 6-1 (p. 8) shows average current drain for different measurement rates and quantities of CS650 sensors. If the time between measurements is five minutes or longer, average current drain is approximately 0.15 milliamps per sensor. 6.2 Operational specifications Table 6-2 (p.
  • Page 13 1 to 81 and solution electrical conductivities ranging from 0 to 3 dS/m. ‡Precision describes the repeatability of a measurement. It is determined for the CS650 by taking repeated measurements in the same material. The precision of the CS650 is better than 0.05 % volumetric water content and 0.01 dS/m electrical conductivity.

  • Page 14: Installation

    The CS650 measures the bulk dielectric permittivity, average volumetric water content, and bulk electrical conductivity (EC) along the length of the rods, which is 30 cm for the CS650 and 12 cm for the CS655. The sensor rods can insert vertically into the soil surface or be buried at any orientation to the surface.

  • Page 15: Data Logger Wiring

    SDI-12 programming. Table 7-1 (p. 12) shows the SDI-12 wiring for the CS650 water content reflectometer. SDI-12 data is transmitted to a CRBasic data logger odd numbered control or U terminal. Wiring information for RS-232 communications is provided in A200 and Device Configuration Utility (p.

  • Page 16: Programming

    For the CR6 and CR1000X data loggers, triggering conflicts may occur when a companion terminal is used for a triggering instruction, such as TimerInput(), PulseCount(), or WaitDigTrig(). For example, if the CS650 is connected to C3 on a CR1000X, C4 cannot be used in the TimerInput(), PulseCount(), or WaitDigTrig() instructions.

  • Page 17: Operation

    8.6 Water content reflectometer user-calibration 8.1 A200 and Device Configuration Utility The A200 Sensor-to-Computer Interface allows communications between a CS650 and a computer to change sensor settings through Device Configuration Utility software. Device Configuration Utility is included in installations of LoggerNet, RTDAQ, and PC400. It can also be downloaded separately using this link: www.campbellsci.com/devconfig...
  • Page 18 A data cable that ships with the A200 has a USB type-A male connector for attaching to a computer USB port and a type B male connector for attaching to the A200 USB port. Table 8-1: CS650 wiring code for RS-232 and A200 Color...

  • Page 19: Determining Which Com Port The A200 Has Been Assigned

    (p. 14). Connect the computer to the A200 USB port with the supplied USB cable. Launch Device Configuration Utility and search for CS650 Series from the Device Type list on the left. Select 9600 from the Baud Rate list. Browse for and select the Communications Port used for your device (see...

  • Page 20: Settings Editor Tab

    Default communications settings are 9600 baud, no parity, 1 stop bit, 8 data bits, and no error checking. After any changes to CS650 settings, select Apply to write the changes to the CS650 operating system. A configuration summary is then shown. The summary may be printed or saved electronically for future reference.
  • Page 21 CS650 and CS655 Water Content Reflectometers...

  • Page 22: Send Os Tab

    PA (μS) Period average Voltage ratio 8.1.2.2 Send OS tab The Send OS tab is used to update the operating system in the CS650. The operating system is available at www.campbellsci.com/downloads . The file to send has a filename extension of .a43, such as CS65X.Std.02.a43.

  • Page 23: Sdi-12 Measurements

    8.2 SDI-12 measurements The CS650 responds to SDI-12 commands M!, M1!, M2!, M3!, M4!, ?!, and I!. Table 8-3 (p. 19) shows the values returned for each of these commands. Establish SDI-12 communications using the SDI12Recorder() CRBasic instruction. See Data logger wiring (p.

  • Page 24: M3! And M4! Commands

    CS650 sensors can connect to the same data logger control or U terminal. Each must have a unique SDI-12 address. Valid addresses are 0 through 9, A through Z, and a through z. The CS650 ships with a default SDI-12 address of 0 unless otherwise specified at the time of ordering.
  • Page 25 The Topp et al (1980) equation used by the CS650 to estimate volumetric water content works well for most mineral soils up to a maximum water content of about 0.45. If the CS650 estimates the soil permittivity to be more than 42, which calculates to a volumetric water content of 0.52, then the M3! command reports 9999999 or NAN for volumetric water content.

  • Page 26: Use Of Multiplexers

    8.4 Use of multiplexers Multiplexers such as Campbell Scientific AM16/32B can connect up to 32 CS650 sensors to a single control or U terminal. When using multiplexers, the simplest configuration is for all sensors to have the same SDI-12 address.

  • Page 27: Topp Equation

    + 4.3•10 Research has shown this equation works well in most mineral soils, so a soil specific calibration of the CS650 sensor is usually not necessary. For a soil specific calibration, you can generate an equation relating K to θ...

  • Page 28: Temperature Correction Of Soil Electrical Conductivity

    The calibration equation in the CS650 operating system corrects the oscillation frequency for the effects of σ up to 3 dS/m for the CS650 and up to 10 dS/m for the CS655. This is equivalent solution to σ...

  • Page 29: Error Sources In Water Content Reflectometer Measurement

    8.5.5 Temperature dependence and correction The two temperature dependent sources of error in CS650 water content measurements are the effect of temperature on the operation of the sensor electronics and the effect of temperature on the dielectric permittivity of the soil.

  • Page 30: Water Content Reflectometer User-Calibration

    1.55 g cm may require a media-specific calibration equation. In these cases, the user may develop a calibration equation to convert CS650 permittivity to volumetric water content over the range of water contents the sensor is expected to measure. 8.6.1 User-derived calibration equation A quadratic equation or third order polynomial can describe the relationship between soil permittivity and volumetric water content.

  • Page 31: Collecting Laboratory Data For Calibration

    8.6.2 Collecting laboratory data for calibration Water content reflectometer data needed for CS650 calibration are the CS650 permittivity reading and an independently determined volumetric water content. From this data, a linear or polynomial function can describe the sensor response to changing water content. For more...
  • Page 32 Repeat steps b through d for each of the remaining soil layers. 3. Carefully insert CS650 rods through the soil surface until the rods are completely surrounded by soil. Avoid moving the rods from side to side because this can form air voids around the rods.

  • Page 33: Collecting Field Data For Calibration

    The volumetric water content is the product of the gravimetric water content and the bulk density The average water content for the replicates and the recorded CS650 permittivity are one datum pair to be used for the calibration curve fit.
  • Page 34 The following is the procedure for obtaining samples. 1. Use a shovel to form a vertical face of soil. 2. If using the CS650 within about 0.5 meters of the surface, insert the sensor into the face. 3. Add water to the surface using percolation.
  • Page 35 The volumetric water content is the product of the gravimetric water content and the bulk density The average water content for the replicates and the recorded CS650 period are one datum pair to be used for the calibration curve fit.

  • Page 36: Calculations

    Calculate gravimetric water content, θ , using To obtain soil bulk density, use Volumetric water content is calculated using 9. Maintenance and troubleshooting The CS650 does not require periodic maintenance. Table 9-1 (p. 33) provides troubleshooting information. CS650 and CS655 Water Content Reflectometers...
  • Page 37 Table 9-1: Symptom, cause, and solutions Symptom Possible cause Solution All CS650 output values read 0 No SDI12Recorder instruction Add SDI12Recorder instruction in data logger program to data logger program Conditional statement that Check logic of conditional triggers reading is not...

  • Page 38: References

    New formulations and calibrations. Soil Sci. Soc. Am. J., 53:433-439. Topp, G.C., J.L. Davis & A.P. Annan. 1980. “Electromagnetic determination of soil water content: measurements in coaxial transmission lines,” Water Resources Research, v. 16, No. 3:574-582. CS650 and CS655 Water Content Reflectometers...

  • Page 39: Appendix A. Importing Short Cut Code Into Crbasic Editor

    Block. This adds an apostrophe (') to the beginning of each of the highlighted lines, which instructs the data logger compiler to ignore those lines when compiling. The Comment Block feature is demonstrated at about 5:10 in the CRBasic | Features video CS650 and CS655 Water Content Reflectometers...

  • Page 40: Appendix B. Example Programs

    (p. 36) measures one CS650 sensor on a CR1000X every 15 minutes, storing hourly averages of volumetric water content, electrical conductivity, and soil temperature and samples of permittivity, period average and voltage ratio. The CS650 has an SDI-12 address of 0. Wiring for the example is shown in Table B-1 (p.
  • Page 41 The first CS650 has an SDI-12 address of 0 and the second has an address of 1. Wiring for the example is shown in Table B-2 (p.
  • Page 42 CRBasic Example 3 (p. 39) measures 12 CS650 sensors on a AM16/32B multiplexer every 15 minutes, storing hourly averages of volumetric water content, electrical conductivity, soil temperature, permittivity, period average, and voltage ratio. All sensors are addressed with SDI- 12 address of 0. In this example, the sensors are powered through the switched 12V terminal and require 3 seconds warm-up time per sensor.
  • Page 43 CRBasic Example 3: CR1000X with 12 CS650 sensors on multiplexer LCount Public CS650(12,6) DataTable (DatoutCS650,1,-1) DataInterval (0,60,Min,2) Average (72,CS650(),IEEE4,False) EndTable BeginProg Scan (15,Min,0,0) PortSet(C2,1)  'Turn AM16/32 Multiplexer On Delay(0,150,mSec)     LCount=1 SubScan(0,uSec,12) PulsePort(C3,10000)  'Switch to next AM16/32 terminal SW12 (SW12_1,1)  'Apply power to CS650 Delay (0,3,Sec)  'Wait three seconds for sensor to warm up...

  • Page 44: Appendix C. Discussion Of Soil Water Content

    Another useful property, soil porosity (ε), is related to soil bulk density, as shown by the following expression. –3 The term ρ is the density of the soil solid fraction and is approximately 2.65 g cm solid CS650 and CS655 Water Content Reflectometers...

  • Page 45: Appendix D. Sdi-12 Sensor Support

    SDI-12 (Serial Data Interface at 1200 baud) is a protocol developed to simplify sensor and data logger compatibility. Only three wires are necessary — serial data, ground, and 12 V. With unique addresses, multiple SDI-12 sensors can connect to a single SDI-12 terminal on a Campbell Scientific data logger.

  • Page 46: Acknowledge Active Command (A!)

    Table D-1: Campbell Scientific sensor SDI-12 command and response set Response Name Command Address Query a<CR><LF> aAb! Change Address b<CR><LF> Start Measurement atttn<CR><LF> aM1!...aM9! a<values><CR><LF> or aD0!...aD9! Send Data a<values><CRC><CR><LF> Information on each of these commands is given in the following sections.

  • Page 47: Start Verification Command (Av!)

    D commands. n = the number of values returned when one or more subsequent D commands are issued. For the aM! command, n is an integer from 0 to 9. CS650 and CS655 Water Content Reflectometers...

  • Page 48: Stopping A Measurement Command

    D command that follows an M! or MC! command. A sensor may return up to 75 characters of data in response to a D command that follows a C! or CC! command. Data values are separated by plus or minus signs. CS650 and CS655 Water Content Reflectometers...

  • Page 49: Sdi-12 Transparent Mode

    The following examples show how to enter transparent mode and change the SDI-12 address of an SDI-12 sensor. The steps listed are used with most Campbell Scientific data loggers. This example was done with a CR1000X, but the steps are only slightly different for CR6, CR3000, CR800-series, CR300-series, and CR1000 data loggers.
  • Page 50 4. Select the correct Communication Port and click Connect. 5. Click the Terminal tab. 6. Select All Caps Mode. 7. Press Enter until the data logger responds with the data logger (CR1000X>) prompt. 8. Type SDI12 and press Enter. CS650 and CS655 Water Content Reflectometers...

  • Page 51: References

    CR1000X. D.3 References SDI-12 Support Group. SDI-12: A Serial-Digital Interface Standard for Microprocessor-Based Sensors – Version 1.4. River Heights, UT: SDI-12 Support Group, 2017. https://sdi- 12.org/specification CS650 and CS655 Water Content Reflectometers...

  • Page 52: Appendix E. Faqs

    3 dS/m and are reported as NAN or 9999999. Because EC is part of the permittivity equation, an EC reading of NAN leads to a permittivity reading of NAN as well. Thus, the CS650 cannot provide good readings in sea water.
  • Page 53 Can the CS650 and the CS655 measure water content in greenhouse pots? Yes, but the pots would have to be large. The CS650 and CS655 can detect water as far away as 10 cm (4 in.) from the rods. If the pot has a diameter smaller than 20 cm (8 in.), the sensor could potentially detect the air around the pot, which would underestimate the water content.
  • Page 54 The permittivity of saturated sediments in a stream bed is expected to read somewhere between 25 and 42, while the permittivity of water is close to 80. A CS650 or CS655 installed in saturated sediments could be used to monitor sediment erosion. If the...
  • Page 55 SDI-12 communications terminal. If the -VS option is not selected when ordering, the CS650 or CS655 will ship with its SDI- 12 address set to 0 (the default -DS option). The address can be changed to a non-zero value using the A200 Sensor to PC Interface or by connecting the sensor to an SDI-12 communications terminal and sending the aAb! Command.
  • Page 56 How close to each other can multiple CS650 or CS655 sensors be installed? CS650 and CS655 sensors are read one at a time using SDI-12 commands. Consequently, they are never active at the same time and do not interfere with each other electrically.
  • Page 57 In this type of soil, the standard equations in the firmware will overestimate water content. When using a CS650 or a CS655 in artificial or organic soil, it is best to perform a soil- specific calibration. A linear or quadratic equation that relates period average to volumetric water content will work well.
  • Page 58 12 cm long rods of the CS655 are preferable to the 30 cm long rods of the CS650. With the CS650 and the CS655, where is the electrical conductivity measurement made? The bulk electrical conductivity (EC) measurement is made along the sensor rods, and it is an average reading of EC over that distance at whatever depth the rods are placed.
  • Page 59 How are the CS650 and the CS655 different? The CS650 has rods that are 30 cm long, and the CS655 has rods that are 12 cm long. The difference in rod length causes some changes in specifications. For example, the CS650 is slightly more accurate in its permittivity and water content readings, but the CS655 works over a larger range of electrical conductivity.
  • Page 60 How important is it to install the CS650 or CS655 with the rods exactly parallel? The CS650 and CS655 work best when the rods are inserted into the soil as parallel to each other as possible. To make parallel pilot holes before installation, use the...
  • Page 61 3 to 6. When liquid water freezes, its dielectric permittivity drops to 3.8, essentially making it look like soil particles to the sensor. A CS650 or CS655 installed in soil that freezes would show a rapid decline in its volumetric water content reading with corresponding temperature readings that are below 0°C.
  • Page 62 How close to the soil surface can a CS650 or a CS655 be installed? Both the CS650 and the CS655 can detect water as far away as 10 cm in wet sand. That distance decreases as the soil dries down to approximately 4 cm in dry sand. In practice, a...
  • Page 63 1995. There are CS615-L and CS616 sensors in many locations that have been in continuous use for more than ten years with no reported problems. If a CS650 or CS655 remains undamaged by external forces such as lightning, harsh chemicals, or animal actions, the sensor is expected to continue working for decades.
  • Page 64 62 sensors if each one had a unique address. In the specifications for the CS650 and the CS655, a limit is stated of 10 sensors per universal terminal or control port because the -VS option gives the sensor an SDI-12 address that matches the last digit of its serial number.

  • Page 65: Limited Warranty

    2. The defect cannot be the result of misuse. 3. The defect must have occurred within a specified period of time; and 4. The determination must be made by a qualified technician at a Campbell Scientific Service Center/ repair facility.
  • Page 66 Campbell Scientific’s Terms, the provisions of Campbell Scientific’s Terms shall prevail. Furthermore, Campbell Scientific’s Terms are hereby incorporated by reference into this Warranty. To view Terms and conditions that apply to Campbell Scientific, Logan, UT, USA, see Terms and Conditions ...
  • Page 67 Please state the faults as clearly as possible. 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, when equipment is returned to Campbell Scientific, Logan, UT, USA, it is mandatory that a “Declaration of Hazardous Material and...
  • Page 68 Comply with all electrical codes. Electrical equipment and related grounding devices should be installed by a licensed and qualified electrician. Only use power sources approved for use in the country of installation to power Campbell Scientific devices. Elevated Work and Weather Exercise extreme caution when performing elevated work.
  • Page 69 Periodically (at least yearly) check electrical ground connections. WHILE EVERY ATTEMPT IS MADE TO EMBODY THE HIGHEST DEGREE OF SAFETY IN ALL CAMPBELL SCIENTIFIC PRODUCTS, THE CUSTOMER ASSUMES ALL RISK FROM ANY INJURY RESULTING FROM IMPROPER INSTALLATION, USE, OR MAINTENANCE OF TRIPODS,...
  • Page 70 Campbell Scientific Regional Offices Australia France Spain Location: Garbutt, QLD Australia Location: Montrouge, France Location: Barcelona, Spain Phone: 61.7.4401.7700 Phone: 0033.0.1.56.45.15.20 Phone: 34.93.2323938 Email: info@campbellsci.com.au Email: info@campbellsci.fr Email: info@campbellsci.es Website: www.campbellsci.com.au Website: www.campbellsci.fr Website: www.campbellsci.es Brazil Germany Thailand Location: São Paulo, SP Brazil...

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