Campbell CS650, CS655 User Manual

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USER MANUAL

CS650 & CS655

Soil Water Content

Reflectometers

Issued: 24.6.15

CSL 912

Guarantee



This equipment is guaranteed against defects in materials and workmanship. This guarantee applies for 24 months from date of delivery. We will repair or replace products which prove to be defective during the guarantee period provided they are returned to us prepaid. The guarantee will not apply to:

Equipment which has been modified or altered in any way without the

written permission of Campbell Scientific Batteries Any product which has been subjected to misuse, neglect, acts of God or

damage in transit.

Campbell Scientific will return guaranteed equipment by surface carrier prepaid. Campbell Scientific will not reimburse the claimant for costs incurred

in removing and/or reinstalling equipment. This guarantee and the Company’s

obligation thereunder is in lieu of all other guarantees, expressed or implied, including those of suitability and fitness for a particular purpose. Campbell Scientific is not liable for consequential damage.

Please inform us before returning equipment and obtain a Repair Reference Number whether the repair is under guarantee or not. Please state the faults as clearly as possible, and if the product is out of the guarantee period it should be accompanied by a purchase order. 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” form will be

issued for completion.

When returning equipment, the Repair Reference Number must be clearly marked on the outside of the package. Complete the “Declaration of Hazardous Material and Decontamination” form and ensure a completed copy is returned with your goods. Please note your Repair may not be processed if you do not include a copy of this form and Campbell Scientific Ltd reserves the right to return goods at the customers’ expense.

Note that goods sent air freight are subject to Customs clearance fees which Campbell Scientific will charge to customers. In many cases, these charges are greater than the cost of the repair.

Campbell Scientific Ltd,

80 Hathern Road,

Shepshed, Loughborough, LE12 9GX, UK

Tel: +44 (0) 1509 601141

Fax: +44 (0) 1509 601091

Email: support@campbellsci.co.uk

www.campbellsci.co.uk

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 in2 (square inch) = 645 mm2

Length: 1 in. (inch) = 25.4 mm

1 ft (foot) = 304.8 mm 1 yard = 0.914 m 1 mile = 1.609 km

Mass: 1 oz. (ounce) = 28.35 g

In addition, while most of the information in the manual is correct for all countries, certain information is specific to the North American market and so may not be applicable to European users.

Differences include the 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 it will be suitable for use in your country.

Reference to some radio transmitters, digital cell phones and aerials may also not be applicable according to your locality.

Some brackets, shields and enclosure options, including wiring, are not sold as standard items in the European market; in some cases alternatives are offered. Details of the alternatives will be covered in separate manuals.

Part numbers prefixed with a “#” symbol are special order parts for use with non-EU variants or for special installations. Please quote the full part number with the # when ordering.

1 lb (pound weight) = 0.454 kg

Pressure: 1 psi (lb/in2) = 68.95 mb

Volume: 1 UK pint = 568.3 ml

1 UK gallon = 4.546 litres 1 US gallon = 3.785 litres

Recycling information

At the end of this product’s life it should not be put in commercial or domestic refuse but sent for recycling. Any batteries contained within the product or used during the products life should be removed from the product and also be sent to an appropriate recycling facility.

Campbell Scientific Ltd can advise on the recycling of the equipment and in some cases arrange collection and the correct disposal of it, although charges may apply for some items or territories.

For further advice or support, please contact Campbell Scientific Ltd, or your local agent.

Campbell Scientific Ltd, 80 Hathern Road, Shepshed, Loughborough, LE12 9GX, UK

Tel: +44 (0) 1509 601141 Fax: +44 (0) 1509 601091

Email: support@campbellsci.co.uk

www.campbellsci.co.uk

Precautions

DANGER — MANY HAZARDS ARE ASSOCIATED WITH INSTALLING, USING, MAINTAINING, AND WORKING ON OR AROUND TRIPODS, TOWERS, AND ANY ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS, CROSSARMS, ENCLOSURES, ANTENNAS, ETC. FAILURE TO PROPERLY AND COM P LE TE LY ASS E M BLE , INSTALL, OPERATE, USE, AND MAINTAIN TRIPODS, TOWERS, AND ATTACHMENTS, AND FAILURE TO HEED WARNINGS, INCREASES THE RISK OF DEATH, ACCIDENT, SERIOUS INJURY, PROPERTY DAMAGE, AND PRODUCT FAILURE. TAKE ALL REASONABLE PRECAUTIONS TO AVOID THESE HAZARDS. CHECK WITH YOUR ORGANIZATION'S SAFETY COORDINATOR (OR POLICY) FOR PROCEDURES AND REQUIRED PROTECTIVE EQUIPMENT PRIOR TO PERFORMING ANY WORK.

Use tripods, towers, and attachments to tripods and towers only for purposes for which they are designed. Do not exceed design limits. Be familiar and comply with all instructions provided in product manuals. Manuals are available at www.campbellsci.eu or by telephoning +44(0) 1509 828 888 (UK). You are responsible for conformance with governing codes a nd regulations, including safety regulations , and the integrity and location o f structures o r land to which towers, tripods, and any attachments are attached. Installation sites should be evaluated and approved by a qualified engineer. If questions or co ncerns arise regarding installation, use, or maintenance of tripods, towers, attachments, or electrical connections, consult with a licensed and qualified engineer or electrician.

General

• Prior to performing site or installation work, obtain required approvals and permits. Comply with all

governing structure-height regulations, such as those of the FAA in the USA.

• Use only qualified personnel for installation, use, and maintenance of tripods and towers, and any

attachments to tripods and towers. The use of licensed and qualified contractors is highly recommended.

• Read all applicable instructions carefully and understand procedures thoroughly before beginning work.

• Wear a hardhat and eye protection, and take other appropriate safety precautions while working on or

around tripods and towers.

• Do not climb tripods or towers at any time, and prohibit climbing by other persons. Take reasonable

precautions to secure tripod and tower sites from trespassers.

• Use only manufacturer recommended parts, materials, and tools.

Utility and Electrical

• You can be killed or sustain serious bodily injury if the tripod, tower, or attachments you are installing,

constructing, using, or maintaining, or a tool, stake, or anchor, come in contact with overhead or underground utility lines.

• Maintain a distance of at least one-and-one-half times structure height, or 20 feet, or the distance

required by applicable law, whichever is greater, between overhead utility lines and the structure (tripod, tower, attachments, or tools).

• Prior to performing site or installation work, inform all utility companies and have all underground utilities

marked.

• Comply with all electrical codes. Electrical equipment and related grounding devices should be installed

by a licensed and qualified electrician.

Elevated Work and Weather

• Exercise extreme caution when performing elevated work.

• Use appropriate equipment and safety practices.

• During installation and maintenance, keep tower and tripod sites clear of un-trained or non-essential

personnel. Take precautions to prevent elevated tools and objects from dropping.

• Do not perform any work in inclement weather, including wind, rain, snow, lightning, etc.

Maintenance

• Periodically (at least yearly) check for wear and damage, including corrosion, stress cracks, frayed cables,

loose cable clamps, cable tightness, etc. and take necessary corrective actions.

• 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, TOWERS, OR ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS, CROSSARMS, ENCLOSURES, ANTENNAS, ETC.

PDF viewers: These page numbers refer to the printed version of this document. Use the PDF reader bookmarks tab for links to specific sections.

1. Introduction ................................................................ 1

2. Cautionary Statements .............................................. 1

3. Initial Inspection ........................................................ 1

4. Quickstart ................................................................... 2

5. Overview ..................................................................... 4

6. Specifications ............................................................ 6

6.1 Electrical Specifications ....................................................................... 7

6.1.1 Current .......................................................................................... 7

6.2 Operational Specifications ................................................................... 8

7. Installation .................................................................. 9

7.1 Orientation and Placement ................................................................... 9

7.2 Proper Insertion .................................................................................. 10

7.3 Datalogger Wiring.............................................................................. 10

7.4 Programming ...................................................................................... 11

8. Operation .................................................................. 12

8.1 A200 and Device Configuration Utility ............................................. 12

8.1.1 Using the A200 ........................................................................... 12

8.1.1.1 Driver Installation ............................................................ 12

8.1.1.2 RS-232 Wiring ................................................................. 12

8.1.1.3 Powering the Sensor ......................................................... 13

8.1.1.4 Determining which COM Port the A200 has been

Assigned ....................................................................... 13

8.1.2 Device Configuration Utility (DevConfig) .................................. 13

8.1.2.1 Settings Editor Tab ........................................................... 15

8.1.2.2 Send OS Tab..................................................................... 16

8.1.2.3 Terminal Tab .................................................................... 17

8.2 SDI-12 Measurements ........................................................................ 19

8.2.1 Use of Multiplexers .................................................................... 19

8.3 Water Content Reflectometer Method for Measuring Volumetric

Water Content ................................................................................. 20

8.3.1 Description of Measurement Method.......................................... 20

8.3.2 The Topp Equation ..................................................................... 20

8.3.3 Electrical Conductivity ............................................................... 21

8.3.3.1 Soil Electrical Conductivity ............................................. 21

8.3.3.2 Temperature Correction of Soil Electrical Conductivity .. 22

8.3.4 Error Sources in Water Content Reflectometer Measurement .... 22

8.3.4.1 Probe-to-Probe Variability Error ...................................... 22

8.3.4.2 Insertion Error .................................................................. 22

8.3.5 Temperature Dependence and Correction ................................ ... 22

8.3.5.1 Accurate Soil Temperature Measurement ........................ 23

8.4 Water Content Reflectometer User-Calibration ................................. 23

8.4.1 Need for Soil Specific Calibration Equation ............................... 23

8.4.2 User-Derived Calibration Equation ............................................ 23

8.4.3 Collecting Laboratory Data for Calibration ................................ 24

8.4.4 Collecting Field Data for Calibration.......................................... 26

8.4.5 Calculations ................................................................................ 27

9. Maintenance and Troubleshooting ......................... 29

10. References ............................................................... 30

Appendices

A. Importing Short Cut Code into a Program

Editor .................................................................... A-1

B. Example Programs ................................................ B-1

B.1 CR1000 Programs ............................................................................ B-1

B.1.1 CR1000 with One CS650 Probe ............................................... B-1

B.1.2 CR1000 with Two CS650 Probes on Same Control Port ......... B-1

B.1.3 CR1000 with 12 CS650 Probes on Multiplexer ........................ B-2

B.2 CR200X with Three CS650 Probes ................................................. B-3

C. Discussion of Soil Water Content ......................... C-1

D. SDI-12 Sensor Support .......................................... D-1

D.1 SDI-12 Command Basics ................................................................. D-1

D.2 Changing the SDI-12 Address Using Terminal Emulator and a

Datalogger .................................................................................... D-3

D.2.1 SDI-12 Transparent Mode ........................................................ D-3

D.2.2 CR200(X) Series Datalogger Example ..................................... D-4

D.2.3 CR1000 Datalogger Example ................................................... D-5

Figures

5-1. CS650 Water Content Reflectometer ................................ ................... 5

6-1. CS650 and CS655 average current drain ............................................. 8

7-1. CS650G Insertion Guide Tool ........................................................... 10

8-1. A200 Sensor-to-PC Interface ............................................................. 12

D-1. SDI-12 transparent mode on CR200(X)-series datalogger using

control port C1/SDI12 and changing SDI-12 address from 0

to 1 ................................................................................................ D-4

D-2. SDI-12 transparent mode on CR1000 datalogger using control

port 1 and changing SD1-12 address from 3 to 1 ......................... D-5

Tables

6-1. Size Specifications ............................................................................... 6

6-2. Relative Dielectric Permittivity Specifications .................................... 8

7-1. CS650 Wiring Code for SDI-12 ......................................................... 11

8-1. CS650 Wiring Code for RS-232 and A200 ........................................ 13

8-2. Real-Time Measurements .................................................................. 16

8-3. CS650 Terminal Commands .............................................................. 18

8-4. CS650 SDI-12 Commands ................................ ................................. 19

9-1. Symptom, Cause, and Solutions ......................................................... 29

B-1. CR1000 Wiring for One Probe Example Program ........................... B-1

B-2. CR1000 Wiring for Two Probe Example Program .......................... B-1

B-3. CR1000 Wiring For Multiplexer Example Program ........................ B-2

B-4. CR200(X) Wiring for Example Program ......................................... B-3

D-1. CS650 SDI-12 Command and Response Set .................................. D-1

iii

NOTE

CS650 and CS655 Water Content Reflectometers

1. Introduction

The CS650 and CS655 are multiparameter smart sensors that use innovative techniques to monitor soil volumetric water content, bulk electrical conductivity, and temperature. They output an SDI-12 signal that many of our dataloggers 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.

This manual provides information only for CRBasic dataloggers. It is also compatible with most of our retired Edlog dataloggers. For Edlog datalogger support, see an older manual at

www.campbellsci.com/old-manuals or contact a Campbell Scientific

application engineer for assistance.

2. Cautionary Statements

 READ AND UNDERSTAND the Precautions section at the front of this

manual.

 Although the CS650 is rugged, it should be handled as precision scientific

instrument.

 External RF sources can affect the probe’s operation. Therefore, the probe

should be located away from significant sources of RF such as ac power lines

and motors.

3. Initial Inspection

 Upon receipt of the CS650, inspect the packaging and contents for damage.

File damage claims with the shipping company.

 The model number and cable length are printed on a label at the connection

end of the cable. Check this information against the shipping documents to

ensure the expected product and cable length are received.

CS650 and CS655 Water Content Reflectometers

4. Quickstart

Short Cut is an easy way to program your datalogger to measure the CS650 and assign datalogger wiring terminals. The following procedures show using Short Cut to program the CS650.

1. Install Short Cut by clicking on the install file icon. Get the install file from

either www.campbellsci.com, the ResourceDVD, or find it in installations of LoggerNet, PC200W, PC400, or RTDAQ software.

2. The Short Cut installation should place a shortcut icon on the desktop of your

computer. To open Short Cut, click on this icon.

3. When Short Cut opens, select New Program.

User Manual

4. Select Datalogger Model and Scan Interval (default of 5 seconds is OK for

most applications). Click Next.

5. Under the Available Sensors and Devices list, select the Sensors |

Meteorological | Soil Moisture | CS650/CS655 Water Content

Reflectometer. Four options are available that monitor different parameters.

In this tutorial, we’ll select CS650/CS655 Water Content Reflectometer

(VWC, EC, T, P, PA, and VR). Click to move the selection to the

Selected device window. The soil temperature defaults to degree C, and the

sensor is measured hourly. These can be changed by clicking the

Temperature or Measure sensor box and selecting one of the other options.

CS650 and CS655 Water Content Reflectometers

6. 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.

5. Overview

7. Select any other sensors you have, then finish the remaining Short Cut steps

to complete the program. The remaining steps are outlined in Short Cut Help, which is accessed by clicking on Help | Contents | Programming Steps.

8. If LoggerNet, PC400, RTDAQ, or PC200W is running on your PC, and the

PC to datalogger connection is active, you can click Finish in Short Cut and you will be prompted to send the program just created to the datalogger.

9. If the sensor is connected to the datalogger, as shown in the wiring diagram in

step 6, check the output of the sensor in the datalogger support software data display to make sure it is making reasonable measurements.

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 communication.

User Manual

Figure 5-1. CS650 Water Content Reflectometer

Volumetric water content information is derived from the probe’s sensitivity to the

dielectric permittivity of the medium surrounding the probe stainless-steel rods. The CS650 is configured as a water content reflectometer, with the two parallel rods forming an open-ended transmission line. A differential oscillator circuit is connected to the rods, with an oscillator state change triggered by the return of a reflected signal from one of the rods. The two-way travel time of the electromagnetic waves that are induced by the oscillator on the rod varies with changing dielectric permittivity. Water is the main contributor to the bulk dielectric permittivity of the soil or porous media, so the travel time of the reflected wave increases with increasing water content and decreases with decreasing water content, hence the name water content reflectometer.

Electrical conductivity is determined by exciting the rods with a known nonpolarizing waveform and measuring the signal attenuation.

Temperature is measured with a thermistor in contact with one of the rods.

It is well known that transmission line oscillators used for water content measurements suffer from unwanted increases in oscillation period as increasing electrical conductivity causes transmission line signal attenuation. The CS650 handles this problem by making an electrical conductivity measurement and then correcting the oscillator period accordingly. On-board processing within the sensor head calculates electrical conductivity from the signal attenuation measurement and combines the result with the oscillation period measurement to calculate the dielectric permittivity of the media and finally applies the Topp equation (Topp et al. 1980) to estimate volumetric water content.

Probe electronics are encapsulated in the rugged epoxy probe head.

A five conductor cable including the drain or shield wire is used to provide power and ground as well as serial communication with the CS650. The CS650 is intended to communicate with SDI-12 recorders, including Campbell Scientific dataloggers. The orange Rx wire can be used to communicate by means of RS232 Tx/Rx. The A200 USB-to-Serial Module allows RS-232 serial communication between a computer and the CS650 by means of Campbell Scientific’s Device Configuration Utility (DevConfig) software.

CS650 and CS655 Water Content Reflectometers

Table 6-1. Size Specifications

CS650

CS655

Rods

300 mm long

3.2 mm diameter 32 mm spacing

120 mm long

3.2 mm diameter 32 mm spacing

Probe Head

L 85 mm W 63 mm D 18 mm

Probe Weight

280 g

240 g

Cable Weight

35 g m-1

The CS650’s cable can terminate in:

 Connector that attaches to a prewired enclosure (option –PW). Refer to

www.campbellsci.com/prewired-enclosures for more information.

Campbell Scientific also offers the CS650-LC, CS655-LC, and CWS655. The CS650-LC and CS655-LC include a connector for attaching the sensor to an ET107 weather station. The CWS655 is a wireless version of our CS655; refer to the Wireless Sensor Network manual for more information.

6. Specifications

Features:

 Larger sample volume reduces error  Measurement corrected for effects of soil texture and electrical

conductivity

 Estimates soil-water content for a wide range of mineral soils  Versatile sensor—measures dielectric permittivity, bulk electrical

conductivity (EC), and soil temperature

 Compatible with Campbell Scientific CRBasic dataloggers: CR6,

CR200(X) series, CR800 series, CR1000, CR3000, and CR5000

Table 6-1 compares the size of the CS650 and CS655 reflectometers.

6.1 Electrical Specifications

Sensor Output:

SDI-12 Serial RS-232

Warmup Time:

3 s

Measurement Time:

3 ms to measure 600 ms to complete SDI-12 command

Power Supply Requirements:

6 Vdc to 18 Vdc Must be able to supply 45 mA @ 12 Vdc

Maximum Cable Length:

610 m (2000 ft) combined length for 1 – 10 sensors connected to the same datalogger control port

Electromagnetic Compatibility:

Œ compliant (EMC compliant performance

criteria available upon request)

Meets EN61326 requirements for protection against electrostatic discharge and surge

External RF sources can affect CS650 measurements. CS650 circuitry should be located away from radio transmitter aerials and cables, or measurements ignored during RF transmissions.

Active (3 ms):

45 mA typical @ 12 Vdc (80 mA @ 6 Vdc, 35 mA @ 18 Vdc)

Quiescent:

135 A @ 12 Vdc

Average Current Drain:

I = 0.09n + [3.5 + 0.024(n-1)]n/s I = average current in milliamps n = number of CS650’s s = number of seconds between measurements (see Figure 6-1)

User Manual

6.1.1 Current

CS650 and CS655 Water Content Reflectometers

Table 6-2. Relative Dielectric Permittivity Specifications

CS650

CS655

Relative Dielectric Permittivity

Range

1 to 81

Accuracy† 1 to 40:

40 to 80:

(2% of reading + 0.6) for solution EC

3 dS/m

1.4 for solution EC 3 dS/m

(3% of reading + 0.8)

for solution EC

8 dS/m

2 for solution EC 2.8 dS/m

Precision‡

<0.02

Figure 6-1. CS650 and CS655 average current drain

Figure 6-1 shows average current drain for different measurement rates and quantities of CS650 probes. If the time between measurements is five minutes or longer, average current drain may be approximated at 0.15 milliamps per sensor.

6.2 Operational Specifications

Table 6-2 provides the operational specifications.

User Manual

Volumetric Water Content using Topp Equation (m3/m3)

Range

5% to 50%

Accuracy†

3% VWC typical in mineral soils where solution EC 3 dS/m

3% VWC typical in mineral soils where solution EC 10 dS/m

Precision‡

<0.05%

Electrical Conductivity

Range Solution EC

0 to 3 dS/m

0 to 8 dS/m

Range Bulk EC

0 to 3 dS/m

0 to 8 dS/m

Accuracy†

(5% of reading + 0.05 dS/m)

Precision‡

0.5% of BEC

Temperature

Soil Measurement Range

–10 to 70 °C

Operational Range

0 to 70 °C

Accuracy†

0.5 C for probe body buried in soil

Precision‡

0.02 °C

Sensing Volume*

7800 cm3

3600 cm3

*Sensing Volume approximately 7.5 cm radius around each probe rod and 4.5 cm beyond the end of the rods

†Accuracy specifications are based on laboratory measurements in a series of solutions with dielectric permittivities ranging from 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.

7. Installation

If you are programming your datalogger with Short Cut, skip Section 7.3, Datalogger Wiring (p. 10), and Section 7.4, Programming (p. 11). Short Cut does this work for you. See Section 4, Quickstart (p. 2), for a Short Cut tutorial.

7.1 Orientation and Placement

The CS650 measures the bulk dielectric permittivity, average volumetric water content, and bulk EC along the length of the rods, which is 30 cm for the CS650 and 12 cm for the CS655. The probe rods may be inserted vertically into the soil surface or buried at any orientation to the surface. The probe may be installed horizontal to the surface to detect the passing of wetting fronts or other vertical water fluxes.

The sensitive volume depends on the surrounding media. In soil, the sensitive volume extends approximately 7.5 cm (3 in) from the rods along their length and

4.5 cm (1.8 in) beyond the end of the rods. Consequently, if the probe is buried horizontally closer than 7.5 cm from the soil surface, it will include air above the surface in its measurements and underestimate soil water content.

CS650 and CS655 Water Content Reflectometers

The thermistor used to measure temperature is in contact with one of the stainless steel rods at the base of the epoxy probe body. Because of the low thermal conductivity of stainless steel, the thermistor does not measure the average temperature along the rod, but instead provides a point measurement of the temperature within the epoxy. For a valid soil temperature reading, the probe body must be in thermal equilibrium with the soil. If the probe is installed vertically with the epoxy probe body above the surface, then the probe body must be shielded from solar radiation and in direct contact with the soil or media of interest.

7.2 Proper Insertion

The method used for probe installation can affect the accuracy of the measurement. The probe rods should be kept as close to parallel as possible when installed to maintain the design wave guide geometry. The probe is more sensitive to permittivity close to the rods so probes inserted in a manner which generates air voids around the rods will have reduced measurement accuracy. In most soils, the soil structure will recover from the disturbance during probe insertion.

In some applications, installation can be improved by using the CS650G insertion guide tool (Figure 7-1). The CS650G is inserted into the soil and then removed. This makes proper installation of the water content reflectometer easier in dense or rocky soils.

Figure 7-1. CS650G Insertion Guide Tool

7.3 Datalogger Wiring

Our dataloggers typically use SDI-12 to measure the sensor because RS-232 communication requires more control ports per CS650 and RS-232 programming is more complicated than SDI-12 programming. SDI-12 communication also allows up to ten probes to be given different addresses and then share a single control port.

User Manual

Table 7-1. CS650 Wiring Code for SDI-12

Colour

Function

Datalogger Connection

Green

SDI-12 Data

SDI-12 Input, Control Port,

or U* configured for SDI-12

measurement

Red

SDI-12 Power

12 V

Black

SDI-12 Reference

Clear

Shield

Orange

Not Used

NOTE

Table 7-1 shows the SDI-12 wiring for the CS650 water content reflectometer. SDI-12 data is transmitted to a CRBasic datalogger odd numbered control port or U terminal. Wiring information for RS-232 communications is provided in Section 8.1.1.2, RS-232 Wiring (p. 12).

The orange Rx wire is only used for RS-232 Tx/Rx communication, and should be grounded when using SDI-12.

7.4 Programming

Short Cut is the best source for up-to-date datalogger programming code. Programming code is needed,

If your data acquisition requirements are simple, you can probably create and maintain a datalogger program exclusively with Short Cut. If your data acquisition needs are more complex, the files that Short Cut creates are a great source for programming code to start a new program or add to an existing custom program.

Short Cut cannot edit programs after they are imported and edited in CRBasic Editor.

A Short Cut tutorial is available in Section 4, Quickstart (p. 2). If you wish to import Short Cut code into CRBasic Editor to create or add to a customized program, follow the procedure in Appendix A, Importing Short Cut Code into a Program Editor (p. A-1). Programming basics for CRBasic dataloggers are provided here. Complete program examples for select CRBasic dataloggers can be found in Appendix B, Example Programs (p. B-1). Programming basics and programming examples for Edlog dataloggers are provided at

www.campbellsci.com\old-manuals.

 when creating a program for a new datalogger installation

 when adding sensors to an existing datalogger program

The SDI12Recorder() measurement instruction programs CRBasic dataloggers (CR6, CR200(X)-series, CR800-series, CR1000, CR3000, and CR5000) to measure the sensor. This instruction sends a request to the sensor to make a measurement and then retrieves the measurement from the sensor. See Section

8.2, SDI-12 Measurements (p. 19), for more information.

When using a CR200(X), the SDI12Recorder() instruction has the following syntax:

CS650 and CS655 Water Content Reflectometers

NOTE

SDI12Recorder(Destination,OutString,Multiplier,Offset)

For the other CRBasic dataloggers, the SDI12Recorder() instruction has the following syntax:

SDI12Recorder(Destination, SDIPort, SDIAddress, “SDICommand”, Multiplier, Offset)

8. Operation

8.1 A200 and Device Configuration Utility

The A200 Sensor-to-PC Interface allows communication between a CS650 and a PC, allowing sensor settings to be changed through Device Configuration Utility (DevConfig) software.

8.1.1 Using the A200

8.1.1.1 Driver Installation

If the A200 has not been previously plugged into your PC and your PC operating system is not Windows 7, the A200 driver needs to be loaded onto your PC.

8.1.1.2 RS-232 Wiring

Drivers should be loaded before plugging the A200 into the PC.

The A200 drivers can be downloaded, at no charge, from:

www.campbellsci.com/downloads.

One end of the A200 has a terminal block while the other end has a type B female USB port. The terminal block provides 12V, G, Tx, and Rx terminals for connecting the sensor (see Figure 8-1 and Table 8-1).

Figure 8-1. A200 Sensor-to-PC Interface

A data cable, pn #17648, ships with the A200. This cable has a USB type-A male

connector that attaches to a PC’s USB port, and a type B male connector that

attaches to the A200’s USB port.

Table 8-1. CS650 Wiring Code

for RS-232 and A200

Colour

Function

A200 Terminal

Orange

RxD

Green

TxD

Red

Power

+12 Vdc

Black

Reference

Clear

Shield

8.1.1.3 Powering the Sensor

The A200 provides power to the sensor when it is connected to a PC’s USB port.

An internal DC/DC converter boosts the 5 Vdc supply from the USB connection to a 12 Vdc output that is required to power the sensor.

8.1.1.4 Determining which COM Port the A200 has been Assigned

When the A200 driver is loaded, the A200 is assigned a COM port number. This COM port number is needed when using DevConfig. Often, the assigned COM port will be the next port number that is free. However, if other devices have been installed in the past (some of which may no longer be plugged in), the A200 may be assigned a higher COM port number.

User Manual

To check which COM port has been assigned to the A200, you can monitor the appearance of a new COM port in the list of COM ports offered in your software package such as LoggerNet before and after the installation, or look in the Windows Device Manager list under the ports section (access via the control panel).

8.1.2 Device Configuration Utility (DevConfig)

DevConfig may be downloaded from the Campbell Scientific website,

www.campbellsci.com/downloads.

Connect the CS650 to the A200 as shown in Table 8-1. Connect the PC to the A200 USB port with the supplied USB cable.

Launch DevConfig and select CS650 Series from the Device Type menu on the left. Select 9600 from the Baud Rate drop-down menu.

CS650 and CS655 Water Content Reflectometers

Select the appropriate PC serial port from the list of available COM ports shown when the browse button on the lower left is selected (see Section 8.1.1.4, Determining which COM Port the A200 has been Assigned (p. 13)).

Select Ok and then Connect to begin communication with the CS650.

8.1.2.1 Settings Editor Tab

The Settings Editor tab shows settings stored in the CS650 firmware. Settings that may be modified include User Name, SDI-12 Address, and RS-232 Baud

Rate. Attempts to change any of the other settings will result in a “Commit failed. Unrecognized error condition” error message. DevConfig polls the CS650 every

two seconds while connected and the results are displayed in the Real-Time Measurements field (Table 8-2). This is useful for verifying probe performance.

User Manual

Default communication 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 firmware. A configuration summary is then shown. The summary may be printed or saved electronically for future reference.

CS650 and CS655 Water Content Reflectometers

Table 8-2. Real-Time Measurements

Measurement Field Name

Meaning

VWC

Volumetric Water Content

EC (dS/m)

Bulk Electrical Conductivity

TS (°C)

Soil Temperature

Bulk Dielectric Permittivity

PA (S)

Period Average

Voltage Ratio

8.1.2.2 Send OS Tab

The Send OS tab is used to update the firmware in the CS650. The firmware is available at www.campbellsci.com/downloads. The file to send will have a filename extension of .a43, such as CS65X.Std.00.36.a43. Sending a new operating system will not affect any of the user-modified settings or probe specific multiplier and offset settings.

User Manual

To download a new operating system, follow the Operating System Download Procedure listed on the Send OS tab.

8.1.2.3 Terminal Tab

The Terminal tab may be used to send serial commands directly to the CS650. See Table 8-3 for a list of serial interface commands.

To send a command from the Terminal tab, left click in the field to get a flashing black cursor, then press <Enter> several times until the CS650> prompt is shown. At the prompt, type in the command then <Enter>.

CS650 and CS655 Water Content Reflectometers

Table 8-3. CS650 Terminal Commands

Command

Values Returned

Units

1) Volumetric Water Content, 

2) Electrical Conductivity, 

3) Temperature

m3/m3 dS/m °C

1) Permittivity, 

2) Electrical Conductivity, 

3) Temperature

dS/m °C

1) Period, 

2) Voltage Ratio, 

3) Temperature

Sec

°C

1) Volumetric Water Content, 

2) Electrical Conductivity, 

3) Temperature

4) Permittivity, 

5) Period, 

6) Voltage Ratio, 

m3/m3 dS/m °C

 Sec

1) Copyright information

2) OS version and Date

3) Product Serial Number

4) Product User Name

5) SDI-12 Address

H or h

Help Menu

8.2 SDI-12 Measurements

Table 8-4. CS650 SDI-12 Commands

SDI-12 command

(“a” is the sensor

address)

Values Returned

Units

aM!

1) Volumetric Water Content, 

2) Electrical Conductivity, 

3) Temperature

m3/m3 dS/m °C

aM1!

1) Permittivity, 

2) Electrical Conductivity, 

3) Temperature

dS/m °C

aM2!

1) Period, 

2) Voltage Ratio, 

3) Temperature

Sec

°C

aM3!

1) Volumetric Water Content, 

2) Electrical Conductivity, 

3) Temperature

4) Permittivity, 

5) Period, 

6) Voltage Ratio, 

m3/m3 dS/m °C

 Sec

aM4! .. aM9!

No Values Returned

Returns the SDI-12 Address

aI!

CampbellSci, OS version, Product Serial Number

NOTE

The CS650 responds to SDI-12 commands M!, M1!, M2!, M3!, ?!, and I!. Table

8-4 shows the values returned for each of these commands.

See Section 7.3, Datalogger Wiring (p. 10), for SDI-12 wiring details.

This section briefly describes using the SDI-12 commands. Additional SDI-12 information is available at Appendix D, SDI-12

Sensor Support (p. D-1), www.sdi-12.org, or

www.youtube.com/user/CampbellScientific.

User Manual

8.2.1 Use of Multiplexers

Up to 10 CS650 probes may be connected to the same datalogger control port as long as each one has a unique SDI-12 address. The CS650 ships with a default SDI-12 address of 0 unless otherwise specified at the time of ordering. The SDI12 address may be changed through DevConfig software (see Section 8.1, A200 and Device Configuration Utility (p. 12)) or with a terminal emulator in SDI-12 transparent mode (see Appendix D, SDI-12 Sensor Support (p. D-1)).

SDI-12 communication is established using the SDI12Recorder() CRBasic instruction. See Appendix D, SDI-12 Sensor Support (p. D-1), for more detail on SDI-12 communication.

Multiplexers such as Campbell Scientific’s AM16/32B may be used to connect up

to 32 CS650 probes to a single control port. When using multiplexers, the simplest configuration is for all probes to have the same SDI-12 address.

CS650 and CS655 Water Content Reflectometers

CAUTION

When multiplexing CS650 probes, the switched 12V channel should be used so that power to the sensor may be turned off under program control before the multiplexer switches to the next channel.

Failure to turn off the switched 12 volt channel before clocking the multiplexer will result in damage to the multiplexer relays.

The proper sequence in the datalogger program for measuring CS650 probes on a multiplexer is:

1. Set RES control port high to enable multiplexer

2. Pulse CLK control port to advance to next multiplexer channel

3. Set switched 12 volt channel high to supply power to CS650

4. Send SDI-12 command(s) to CS650

5. Set switched 12 volt channel low to remove power from CS650

6. Repeat steps 2 through 5 for each CS650 connected to the multiplexer

7. Set RES control port low to disable multiplexer

Program examples in Appendix B, Example Programs (p. B-1), show the commands used in CRBasic.

8.3 Water Content Reflectometer Method for Measuring Volumetric Water Content

8.3.1 Description of Measurement Method

For the water content measurement, a differential emitter-coupled logic (ECL) oscillator on the circuit board is connected to the two parallel stainless steel rods. The differentially driven rods form an open-ended transmission line in which the wave propagation velocity is dependent upon the dielectric permittivity of the media surrounding the rods. An ECL oscillator state change is triggered by the return of a reflected signal from the end of one of the rods.

The fundamental principle for CS650 water content measurement is that the velocity of electromagnetic wave propagation along the probe rods is dependent on the dielectric permittivity of the material surrounding the rods. As water content increases, the propagation velocity decreases because of increasing dielectric permittivity. Therefore, the two-way travel time of the rod signal is dependent upon water content, hence the name water content reflectometer. Digital circuitry scales the high-speed oscillator output to an appropriate frequency for measurement by an on-board microprocessor. Increases in oscillation period resulting from signal attenuation are corrected using an electrical conductivity measurement. A calibration equation converts period and electrical conductivity to bulk dielectric permittivity. The Topp equation is used to convert from permittivity to volumetric water content.

8.3.2 The Topp Equation

The relationship between dielectric permittivity and volumetric water content in mineral soils has been described by Topp et al. (1980) in an empirical fashion using a 3rd degree polynomial. With v the volumetric water content and Ka the bulk dielectric permittivity of the soil, the equation presented by Topp et al. is

User Manual

   

bulk solution

 

v solid



v = -5.3*10-2 + 2.92*10-2Ka – 5.5*10-4K

It has been shown in numerous research efforts that this equation works well in most mineral soils, so a soil specific calibration of the CS650 probe is usually not necessary. If a soil specific calibration is desired, the user can generate an equation relating Ka to v following the methods described in Section 8.4, Water Content Reflectometer User-Calibration (p. 23).

8.3.3 Electrical Conductivity

8.3.3.1 Soil Electrical Conductivity

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 CS650 is predominantly affected by changing dielectric permittivity due to changing water content, but it is also affected by electrical conductivity. Free ions in soil solution provide electrical conduction paths which result in attenuation of the signal applied to the waveguides. This attenuation both reduces the amplitude of the high-frequency signal on the probe rods and reduces the bandwidth. The attenuation reduces oscillation frequency at a given water content because it takes a longer time to reach the oscillator trip threshold.

It is important to distinguish between soil bulk electrical conductivity and soil solution electrical conductivity. Soil solution electrical conductivity refers to the conductivity of the solution phase of soil. Soil solution electrical conductivity,



the solution from the solid and then measuring the electrical conductivity of the extracted solution.

can be determined in the laboratory using extraction methods to separate

solution

+ 4.3*10-6K

The relationship between solution and bulk electrical conductivity can be described by (Rhoades et al., 1976)

with  solution; 

being the electrical conductivity of the bulk soil; 

bulk

, the solid constituents; v, the volumetric water content; and, a

solid

solution

, the soil

soil-specific transmission coefficient intended to account for the tortuosity of the flow path as water content changes. See Rhoades et al., 1989 for a form of this equation which accounts for mobile and immobile water. This publication also discusses soil properties related to CS650 operation such as clay content and compaction. The above equation is presented here to show the relationship between soil solution electrical conductivity and soil bulk electrical conductivity.

Most expressions of soil electrical conductivity are given in terms of solution conductivity or electrical conductivity from extract since it is constant for a soil. Bulk electrical conductivity increases with water content so comparison of the electrical conductivity of different soils must be at the same water content.

The calibration equation in the CS650 firmware corrects the oscillation frequency for the effects of 

10 dS m-1 for the CS655. This is equivalent to  dS m-1 and 2.7 dS m-1 respectively. If 

up to 3 dS m-1 for the CS650 and up to

solution

bulk

exceeds these limits, the CS650 probe

bulk

values of approximately 0.8

will return 99999 for dielectric permittivity and volumetric water content. The measured period average and voltage ratio values will continue to be reported even if the bulk EC is outside the operational range of the probe.

CS650 and CS655 Water Content Reflectometers

8.3.3.2 Temperature Correction of Soil Electrical Conductivity

The EC value reported by the CS650 is bulk electrical conductivity. This value is temperature dependent, changing by 2% per degree Celsius. To compensate for the effect of temperature, EC readings may be converted to a standard temperature, such as 25 °C using the following equation:

where EC25 is the  temperature T

(°C).

soil

EC25 = ECT / (1 + 0.02*(T

value at 25 °C and ECT is the 

bulk

soil

-25)

bulk

value at soil

8.3.4 Error Sources in Water Content Reflectometer Measurement

8.3.4.1 Probe-to-Probe Variability Error

All manufactured CS650s/CS655s are checked in standard media to develop a probe specific span and offset value for electrical conductivity and dielectric permittivity measurements. These probe specific values are written to the probe’s firmware and minimize probe-to-probe variability.

8.3.4.2 Insertion Error

The method used for probe insertion can affect the accuracy of the measurement. The probe rods should be kept as close to parallel as possible when inserted to maintain the design wave guide geometry. The sensitivity of this measurement is greater in the regions closest to the rod surface than at distances away from the surface. Probes inserted in a manner that generates air voids around the rods will indicate lower water content than actual. In some applications, installation can be improved by using insertion guides or a pilot tool. Campbell Scientific offers the CS650G insertion tool.

8.3.5 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 probe electronics and the effect of temperature on the dielectric permittivity of the soil.

The effect of temperature on probe electronics is minimal with period average readings varying by less than 0.5% of the 20 °C reading over the range of 10 to 30 °C and less than 2% of the 20 °C reading over the range of –10 to 70 °C.

The larger error is caused by the change in dielectric permittivity of soil with temperature. This is mostly due to the high temperature dependence of the permittivity of water, which varies from a value of 88 at 0 °C to 64 at 70 °C. Since water is the major contributor to bulk dielectric permittivity of soil, temperature related changes to the permittivity of water will lead to overestimation of volumetric water content at temperatures below 20 °C and underestimation of volumetric water content at temperatures above 20 °C.

The Topp equation does not account for soil temperature. The effect of temperature on the soil permittivity is related to soil specific properties such as porosity and the permittivity of the soil solid phase with temperature. Consequently, a general equation that corrects volumetric water content for temperature for all soils is not available.

A temperature correction equation that works well in quartz sand is given by:



=  - 0.0044*T3 + 0.0014*T2 + 0.0029*T – 0.0002*T + 2.4*3 – 1.6*2 +

Corr

0.32* – 0.046

User Manual

where 

is the temperature corrected volumetric water content, T is soil

Corr

temperature in °C, and  is the volumetric water content value at soil temperature T.

8.3.5.1 Accurate Soil Temperature Measurement

The thermistor used for measuring soil temperature is located in the probe head and is in contact with one of the stainless steel rods. In order to make an accurate soil temperature measurement, the probe head should be buried in the soil so that it is insulated from diurnal temperature fluctuations.

8.4 Water Content Reflectometer User-Calibration

8.4.1 Need for Soil Specific Calibration Equation

While the Topp equation has been determined to work well in a wide range of mineral soils, there are soils for which a user-derived calibration will optimize accuracy of the volumetric water content measurement. The Topp equation underestimates the water content of some organic, volcanic, and fine textured soils. Additionally, porous media with porosity greater than 0.5 or bulk density greater than 1.55 g cm–3 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 probe is expected to measure.

8.4.2 User-Derived Calibration Equation

The relationship between soil permittivity and volumetric water content may be described by a quadratic equation or a 3rd order polynomial. In many applications, a linear equation similar to Ledieu et al (1986) gives required accuracy.

Quadratic form:

v(Ka) = C0 + C1*Ka + C2*K

with v the volumetric water content, Ka the bulk dielectric permittivity of the soil, and Cn , the calibration coefficient.

3rd degree polynomial form:

v(Ka) = C0 + C1*Ka + C2*K

with v the volumetric water content, Ka the bulk dielectric permittivity of the soil, and Cn , the calibration coefficient.

Linear form:

with v the volumetric water content, Ka the bulk dielectric permittivity of the soil, and Cn , the calibration coefficient.

v(Ka) = C0 + C1*K

+ C3*K

0.5

Two data points from careful measurements can be enough to derive a linear calibration. A minimum of three data points are needed for a quadratic calibration. With three evenly spaced water contents covering the expected range, the middle water content data point will indicate whether a linear or polynomial calibration equation is needed.

CS650 and CS655 Water Content Reflectometers

A minimum of four data points are required for derivation of a 3rd degree polynomial. Data points should be spaced as evenly as practical over the expected range of water content and include the wettest and driest expected values.

8.4.3 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, the probe response to changing water content can be described by a linear or polynomial function as described in Section 8.4.2, User-Derived Calibration Equation (p. 23).

Required equipment:

 CS650 connected to datalogger programmed to measure permittivity  Cylindrical sampling devices to determine sample volume for bulk

density, such as copper tubing with diameter of  2.5 cm (1 in) and length at about 5 cm (2 ins).

 Containers and scale to measure soil sample mass  Oven to dry samples (microwave oven can also be used)

The calibration coefficients are derived from a curve fit of known water content and probe permittivity output. The number of data sets needed to derive a calibration depends on the form of the calibration equation. At least three data sets should be generated to determine whether the linear form is valid. If a polynomial is to be used, four data sets will determine whether the function is a quadratic or third order polynomial. Accuracy requirements may require additional data sets. Consider the expected range of soil water content and include data sets from the highest and lowest expected water contents.

The measurement sensitive volume around the probe rods must be completely occupied by the calibration soil. Only soil should be in the region within 10 cm (4 in) of the rod surface. The probe rods can be buried in a tray of soil that is dry or nearly dry. The soil will be homogeneous around the probe rods if it is poured around the rods while dry. Also, a 20 cm diameter PVC pipe with length about 35 cm can be closed at one end and used as the container.

It is important that the bulk density of the soil used for calibration be similar to the bulk density of the undisturbed soil. Using dry soil without compaction will give a typical bulk density, 1.1 to 1.4 g cm–3. This is especially important when bulk density is greater than 1.55 g cm–3. Compaction of the calibration soil to similar bulk density at the field site is necessary for an accurate calibration.

The typically used method for packing a container of soil to uniform bulk density is to roughly separate the soil into three or more equal portions and add one portion to the container with compaction. Evenly place the first loose soil layer in the bottom of the container. Compact by tamping the surface to a level in the container that is correct for the target bulk density. Repeat for the remaining layers. Prior to placing successive layers, scarify (loosen) the top of the existing compacted layer.

The container to hold the soil during calibration should be non-metal and large enough that the rods of the probe are no closer than about 10 cm from any container surface.

Pack the container as uniformly as possible in bulk density with relatively dry soil (volumetric water content <10%).

User Manual



wet dry

dry

m m







bulk

dry

cylinder

volume



Probe rods can be buried in a tray or inserted into a column. When using a column, insert the rods carefully through surface until rods are completely surrounded by soil. Movement of rods from side-to-side during insertion can form air voids around rod surface and lead to measurement error.

Collect the probe permittivity output. Repeat previous step and this step three or four times.

Determine volumetric water content by subsampling soil column after removing probe or using mass of column. If subsampling is used, remove soil from column and remix with samples used for water content measurement. Repack column.

Water can then be added to the top of the container. It must be allowed to equilibrate. Cover the container during equilibration to prevent evaporation. 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 CS650 permittivity output. When permittivity is constant, equilibration is achieved. Collect a set of calibration data values and repeat the water addition procedure again if needed.

With soil at equilibrium, record the CS650 permittivity.

Take subsamples of the soil using containers of known volume. This is necessary for measurement of bulk density. Copper tubing of diameter  2.5 cm (1 in) and length about 5 cm (2 ins) works well. The tubes can be pressed into the soil surface.

It is good to take replicate samples. Three carefully handled samples will provide good results.

The sample tubes should be pushed evenly into the soil. Remove the tube and sample and gently trim the ends of excess soil. Remove excess soil from outside of tube.

Remove all the soil from tube to a tray or container of known mass that can be put in oven or microwave. Weigh and record the wet soil mass.

Water is removed from the sample by heating with oven or microwave. Oven drying requires 24 hours at 105 °C. Microwave drying typically takes 20 minutes depending on microwave power and sample water content. ASTM Method D4643-93 requires heating in microwave for 3 minutes, cooling in desiccator then weighing and repeating this process until measured mass is constant.

Gravimetric water content is calculated after the container mass is accounted for.

For the bulk density

the dry mass of the sample is divided by the sample tube volume.

The volumetric water content is the product of the gravimetric water content and the bulk density

CS650 and CS655 Water Content Reflectometers

  

v g bulk

 *

The average water content for the replicates and the recorded CS650 permittivity are one datum pair to be used for the calibration curve fit.

8.4.4 Collecting Field Data for Calibration

Required equipment:

 CS650 connected to datalogger programmed to measure probe

permittivity

 Cylindrical sampling devices to determine sample volume for bulk

density, such as copper tubing with diameter of  2.5 cm (1 in) and length about 5 cm (2 ins).

 Containers and scale to measure soil sample mass  Oven to dry samples (microwave oven can also be used)

Data needed for CS650 calibration are the CS650 permittivity output and an independently determined volumetric water content. From this data, the probe response to changing water content can be described by a function as described in Section 8.4.2, User-Derived Calibration Equation (p. 23).

Collecting measurements of CS650 permittivity and core samples from the location where the probe is to be used will provide the best on-site soil-specific calibration. However, intentionally changing water content in soil profiles can be difficult.

A vertical face of soil can be formed with a shovel. If the CS650 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. After adding water, monitor the CS650 permittivity to determine if the soil around the rods is at equilibrium.

With soil at equilibrium, record the CS650 permittivity.

Soil hydraulic properties are spatially variable. Obtaining measurements that are representative of the soil on a large scale requires multiple readings and sampling. The average of several core samples should be used to calculate volumetric water content. Likewise, the CS650 should be inserted at least 3 times into the soil recording the permittivitys following each insertion and using the average.

Remove the CS650 and take core samples of the soil where the probe rods were inserted. This is necessary for measurement of bulk density. Copper tubing of diameter  2.5 cm (1 in) and length about 5 cm (2 ins) works well. The tubes can be pressed into the soil surface.

It is good to take replicate samples at locations around the soil surface. Three carefully handled samples will provide good results.

User Manual



wet dry

dry

m m







bulk

dry

cylinder

volume



  

v g bulk

 *

volume

h

 



 



* *

The sample tubes should be pushed evenly into the soil surface. Remove the tube and sample and gently trim the ends of excess soil. Remove excess soil from outside of tube.

Remove all the soil from tube to a tray or container of known mass that can be put in oven or microwave. Weigh and record the wet soil mass. If samples must be stored prior to weighing, seal the container with tape or inside a plastic bag to prevent water loss and store away from direct sunlight.

Gravimetric water content is calculated after the container mass is accounted for.

For the bulk density,

8.4.5 Calculations

the dry mass of the sample is divided by the sample tube volume.

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.

The empty cylinders used for core sampling should be clean and both empty mass and volume are measured and recorded. For a cylinder, the volume is

where d is the inside diameter of the cylinder and h is the height of the cylinder.

During soil sampling it is important that the cores be completely filled with soil but not extend beyond the ends of the cylinder.

Once soil core samples are obtained, place the soil-filled cylinder in a small tray of known empty mass. This tray will hold the core sample during drying in an oven.

To obtain m

, subtract the cylinder empty mass and the container empty mass

wet

from the mass of the soil filled cylinder in the tray. Remove all the soil from the cylinder and place this soil in the tray. Dry the samples using oven or microwave methods as described above.

CS650 and CS655 Water Content Reflectometers



wet dry

dry

m m







bulk

dry

cylinder

volume



  

v g bulk

 *

To obtain m for m

dry

, weigh the tray containing the soil after drying. Subtract tray mass

dry

. Calculate gravimetric water content, g, using

To obtain soil bulk density, use

Volumetric water content is calculated using

9. Maintenance and Troubleshooting

Table 9-1. Symptom, Cause, and Solutions

Symptom

Possible Cause

Solution

All CS650 output values read 0

No SDI12Recorder instruction in datalogger program

Conditional statement that triggers reading is not evaluating as true

Add SDI12Recorder instruction to datalogger program

Check logic of conditional statement that triggers readings

First value reads NAN and all other values read 0* or never change from one measurement to another

CS650 SDI-12 address does not match address specified in datalogger program

Change probe address or modify program so that they match

(*or all values read NAN if the program examples in this manual are followed)

CS650 green wire not attached to SDI port specified in datalogger program

Connect wire to correct control port or modify program to match wiring

CS650 not being powered

Make sure red wire is connected to 12V or SW12V and black wire to G.

If using SW12 to power sensor, make sure red wire is connected and datalogger program switches SW12 on.

VWC reading is 9999999

Soil bulk permittivity is

outside probe’s

operational range

Modify program to collect permittivity value and try soil specific calibration

EC reading is 9999999

Soil bulk electrical conductivity is outside

probe’s operational

range

If using CS650, try CS655

Readings erratic,

including NAN’s and

9999999’s

Multiple probes with same SDI-12 address sharing same control port

Give probes unique addresses or put on separate control ports

The CS650 does not require periodic maintenance. Table 9-1 provides troubleshooting information.

User Manual

CS650 and CS655 Water Content Reflectometers

10. References

Ledieu, J., P. De Ridder, P. De Clerck, and S. Dautrebande. 1986. “A method of

measuring soil moisture by time-domain reflectometry,” J. Hydrol. 88:319-

328.

Rhoades, J.D., P.A.C. Raats, and R.J. Prather. 1976. Effects of liquid-phase

electrical conductivity, water content and surface conductivity on bulk soil electrical conductivity. Soil Sci. Soc. Am. J., 40: 651-653.

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.

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.

NOTE

Appendix A. Importing Short Cut Code into a Program Editor

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 program editor. These files normally reside in the C:\campbellsci\SCWin folder and have the following extensions:

 .DEF (wiring and memory usage information)  .CR6 (CR6 datalogger code)  .CR2 (CR200(X) datalogger code)  .CR1 (CR1000 datalogger code)  .CR8 (CR800 or CR850 datalogger code)  .CR3 (CR3000 datalogger code)  .CR5 (CR5000 datalogger code)

Use the following procedure to import Short Cut code into CRBasic Editor (CR200(X), CR1000, CR800, CR3000, CR5000 dataloggers).

1. Create the Short Cut program following the procedure in Section 4, Quickstart (p. 2). Finish the program and exit Short Cut. Make note of the file name used when saving the Short Cut program.

2. Open CRBasic Editor.

3. Click File | Open. Assuming the default paths were used when Short Cut was installed, navigate to C:\CampbellSci\SCWin folder. The file of interest has a

“.CR6”, “.CR2”, “.CR1”, “.CR8”, “.CR3, or “.CR5” extension, for CR6,

CR200(X), CR1000, CR800, CR3000, or CR5000 dataloggers, respectively. Select the file and click Open.

4. Immediately save the file in a folder different from \Campbellsci\SCWin, or save the file with a different file name.

Once the file is edited with CRBasic Editor, Short Cut can no longer be used to edit the datalogger program. Change the name of the program file or move it, or Short Cut may overwrite it next time it is used.

5. The program can now be edited, saved, and sent to the datalogger.

6. Import wiring information to the program by opening the associated .DEF file. Copy and paste the section beginning with heading “-Wiring for CRXXX–” into the CRBasic program, usually at the head of the file. After pasting, edit the information such that a ' character (single quotation mark) begins each line. This character instructs the datalogger compiler to ignore the line when compiling the datalogger code.

A-1

Appendix A. Importing Short Cut Code

A-2

Table B-1. CR1000 Wiring for One Probe Example Program

CR1000

CS650

12V

Red

Green

Black, Orange, Clear

Table B-2. CR1000 Wiring for Two Probe Example Program

CR1000

CS650’s (wiring same for both)

12V

Red

Green

Black, Orange, Clear

Appendix B. Example Programs

B.1 CR1000 Programs

B.1.1 CR1000 with One CS650 Probe

This CRBasic example program measures one CS650 probe on a CR1000 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.

Public CS650(6) 'Assign aliases to the public array Alias CS650(1)=VWC: Alias CS650(2)=EC: Alias CS650(3)=TSoil Alias CS650(4)=Perm: Alias CS650(5)=PerAvg: Alias CS650(6)=VoltR Units VWC = m^3/m^3: Units EC = dS/m: Units TSoil = deg C DataTable (DatoutCS650,1,-1) DataInterval (0,60,Min,2) Average (3,CS650(1),FP2,False) Sample(3,CS650(4),IEEE4) EndTable BeginProg Scan (15,Min,0,0) SDI12Recorder (CS650(1),1,0,"M3!",1.0,0) CallTable DatoutCS650 'Call Data Table NextScan EndProg

B.1.2 CR1000 with Two CS650 Probes on Same Control Port

This CRBasic example program measures two CS650 probes on a CR1000 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 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. Assignment of aliases and units is not shown in this example.

B-1

Appendix B. Example Programs

Table B-3. CR1000 Wiring For Multiplexer Example Program

CR1000

AM16/32B (2x32 mode)

CS650

12V

G GND

RES

CLK

SW12

COM ODD H

COM ODD L

COM Ground

High Channels 1H – 12H

Red

Low Channels 1L – 12L

Green

Ground Channels to Left of

Low Channels

Black, Orange, Clear

Public CS650(6) Public CS650_2(6) DataTable (DatoutCS650,1,-1) DataInterval (0,60,Min,2) Average (3,CS650(1),FP2,False) Sample(3,CS650(4),IEEE4) Average (3,CS650_2(1),FP2,False) Sample(3,CS650_2(4),IEEE4) EndTable BeginProg Scan (15,Min,0,0) SDI12Recorder (CS650(1),1,0,"M3!",1.0,0) SDI12Recorder (CS650_2(1),1,1,"M3!",1.0,0) CallTable DatoutCS650 'Call Data Table NextScan EndProg

B.1.3 CR1000 with 12 CS650 Probes on Multiplexer

This CRBasic example program measures 12 CS650 probes 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 probes are addressed with SDI-12 address of 0. In this example, the probes are powered through the switched 12V channel and require 3 seconds warm-up time per probe. Total time to measure all 12 probes is more than 36 seconds. Alternately, all of the red wires for the probes could be connected to a bus separate from the multiplexer with the bus connected to 12V for continuous power. This would decrease measurement time. Wiring for the example is shown in Table B-3. Assignment of aliases and units is not shown in this example.

B-2

Appendix B. Example Programs

Table B-4. CR200(X) Wiring for Example Program

CR200(X)

CS650’s (Wiring same for all)

SW Battery

Red

C1/SDI-12

Green

G channels

Black, Orange, Clear

Dim 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(2,1) 'Turn AM16/32 Multiplexer On Delay(0,150,mSec) LCount=1 SubScan(0,uSec,12) PulsePort(3,10000) 'Switch to next AM16/32 channel SW12 (1 ) 'Apply power to CS650 Delay (0,3,Sec) 'Wait three seconds for probe to warm up SDI12Recorder (CS650(LCount,1),1,0,"M!",1.0,0) LCount=LCount+1 SW12 (0) 'Remove power from CS650 NextSubScan PortSet(2,0) 'Turn AM16/32 Multiplexer Off Delay(0,150,mSec) CallTable DatoutCS650 'Call Data Table NextScan EndProg

B.2 CR200X with Three CS650 Probes

This CRBasic example program measures three CS650 probe on a CR200X every 15 minutes, storing hourly averages of volumetric water content, electrical conductivity, soil temperature, permittivity, period average, and voltage ratio. The CS650s have SDI-12 addresses of 0, 1, and 2, respectively. Sensors are powered with the SWBatt channel, which requires a 3 second warm-up time. Alternately, the red wires may be connected to Battery + for continuous power which would reduce measurement time. Wiring for the example is shown in Table B-4. Assignment of aliases and units is not shown in this example.

Public CS650(18)

DataTable (CS650,1,-1) DataInterval (0,60,Min) Average (18,CS650(),False) EndTable

BeginProg Scan (15,Min)

SWBatt (1 ) 'Apply power to CS650's Delay (3,sec) 'Warm-up time of 3 seconds

B-3

Appendix B. Example Programs

'CS650 #1 SDI12Recorder (CS650(1),"0M3!",1,0)

'CS650 #2 SDI12Recorder (CS650(7),"1M3!",1,0)

'CS650 #3 SDI12Recorder (CS650(13),"2M3!",1,0)

SWBatt (0 ) 'Remove power from CS650's CallTable CS650 'Call Data Table NextScan EndProg

B-4



water

soil

wet dry

dry

m m

 







 



water

soil

water

soil

g soil

water

volume

  



bulk

dry

sample

volume







 1

bulk

solid

Appendix C. 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. It is measured by weighing a soil sample (m

sample to remove the water, then weighing the dried soil (m

Volumetric water content (v) is the volume of liquid water per volume of soil. Volume is the ratio of mass to density (b) which gives:

), drying the

wet

dry

The density of water is close to 1 and often ignored.

Soil bulk density (

) is used for 

bulk

and is the ratio of soil dry mass to sample

soil

volume.

Another useful property, soil porosity (), is related to soil bulk density as shown by the following expression.

The term 

is the density of the soil solid fraction and is approximately 2.65 g

solid

cm–3.

C-1

Discussion of Soil Water Content

C-2

Table D-1. CS650 SDI-12 Command and Response Set

Name

Command

Response

Acknowledge Active

a<CR><LF>

Send Identification

aI!

allccccccccmmmmmmvvvxxx...xx<CR> <LF>

Change Address

aAb!

b<CR><LF>

Address Query

a<CR><LF>

Start Measurement

aM!

atttn<CR><LF>

Send Data

aD0! aD1!

a<values><CR><LF> a<values><CR><LF>

Additional Measurements

aM1! aM2! aM3!

atttn<CR><LF> atttn<CR><LF> atttn<CR><LF>

Appendix D. SDI-12 Sensor Support

D.1 SDI-12 Command Basics

SDI-12 commands have three components:

Sensor address (a) – a single character, and is the first character of the command. CS650 sensors are usually assigned a default address of zero unless option –VS is selected at the time of ordering. Sensors with the –VS option are addressed with

the last digit of the probe’s serial number. This allows for multiple CS650’s to be

connected to a single control port without requiring the user to change the SDI-12 addresses from zero.

Command body (e.g., M1) – an upper case letter (the “command”) followed by alphanumeric qualifiers.

Command termination (!) – an exclamation mark.

An active sensor responds to each command. Responses have several standard forms and terminate with <CR><LF> (carriage return – line feed).

SDI-12 commands supported by the CS650 are listed in Table D-1. Continuous and concurrent measurements are not supported.

Address Query Command (?!)

Change Address Command (aAb!)

Command ?! requests the address of the connected sensor. The sensor replies to the query with the address, a.

Sensor address is changed with command aAb!, where a is the current address and b is the new address. For example, to change an address from 0 to 2, the command is 0A2!. The sensor responds with the new address b, which in this case is 2.

D-1

Appendix D. SDI-12 Sensor Support

Send Identification Command (aI!)

Sensor identifiers are requested by issuing command aI!. The reply is defined by the sensor manufacturer, but usually includes the sensor address, SDI-12 version, manufacturer’s name, and sensor model information. Serial number or other sensor specific information may also be included.

An example of a response from the aI! command is: 313CampbellCS65X 000Std.00.35=2196405 <CR><LF> where: Address = 3 SDI-12 version =1.3 Manufacturer = Campbell Sensor model = CS65X OS version = 000Std.00.35 Sensor serial number = 2196405

Start Measurement Commands (aM!)

A measurement is initiated with M! commands. The response to each command has the form atttnn, where

a = sensor address ttt = time, in seconds, until measurement data are available nn = the number of values to be returned when one or more subsequent D!

commands are issued.

Start Measurement Command (aMv!)

Qualifier v is a variable between 1 and 3 that requests variant data. Variants include different subsets of the CS650 probe output:

M0! Volumetric Water Content (Bulk Electrical Conductivity

(Temperature (°C)

M1! Permittivity (Bulk Electrical Conductivity (Temperature (°C)

M2! Period (Voltage Ratio (Temperature (°C)

M3! Volumetric Water Content (), Bulk Electrical Conductivity

(Temperature (°C), Permittivity (Period (Voltage Ratio (

D-2

Aborting a Measurement Command

A measurement command (M!) is aborted when any other valid command is sent to the sensor.

Send Data Command (aDv!)

This command requests data from the sensor. It is normally issued automatically by the datalogger after measurement commands aMv!. In transparent mode, the user asserts this command to obtain data. If the expected number of data values are not returned in response to an aD0! command, the data logger issues aD1!. The limiting constraint is that the total number of characters that can be returned

Appendix D. SDI-12 Sensor Support

to an aD0! command is 35 characters. If the number of characters exceed the limit, the remainder of the response are obtained with the subsequent aD1! command.

D.2 Changing the SDI-12 Address Using Terminal

Emulator and a Datalogger

Up to ten CS650’s or other SDI-12 sensors can be connected to a single datalogger control port. Each SDI-12 device on the same control port must have a unique SDI-12 address. The CS650 supports addresses of 0-9, a-z, and A-Z.

The factory-set SDI-12 address for the CS650 is 0 when the probe is ordered with the –DS option or the last digit of its serial number when ordered with the –VS option. The CS650 SDI-12 address is changed by issuing the aAb! command where a is the current address and b is the new address. The current address can be found by issuing the ?! command.

The easiest way to change the address on a CS650 sensor is with DevConfig and an A200 Sensor to PC Interface as described in Section 8.1, A200 and Device Configuration Utility (p. 12). However if an A200 is not available, it is possible to change the address by connecting a single CS650 to an SDI-12 compatible control port on a datalogger and utilizing SDI-12 transparent mode to send commands directly to the sensor.

D.2.1 SDI-12 Transparent Mode

System operators can manually interrogate and enter settings in probes using transparent mode. Transparent mode is useful in troubleshooting SDI-12 systems because it allows direct communication with probes. Datalogger security may need to be unlocked before transparent mode can be activated.

Transparent mode is entered while the PC is in telecommunications with the datalogger through a terminal emulator program. It is easily accessed through Campbell Scientific datalogger support software, but is also accessible with terminal emulator programs such as Windows HyperTerminal. Datalogger keyboards and displays cannot be used.

The terminal emulator is accessed by navigating to the Datalogger menu in PC200W, the Tools menu in PC400, or the Datalogger menu in the Connect screen of LoggerNet.

The following examples show how to use LoggerNet software to enter transparent mode and change the SDI-12 address of a CS650 sensor. The same steps are used to enter transparent mode with PC200W and PC400 software after accessing the terminal emulator as previously described.

D-3

Appendix D. SDI-12 Sensor Support

D.2.2 CR200(X) Series Datalogger Example

1. Connect a single CS650 to the datalogger as follows:

2. In the LoggerNet Connect screen navigate to the Datalogger menu and select

3. Click on the Open Terminal button.

4. Press the <enter> key until the datalogger responds with the “CR2XX>”

5. To query the CS650 for its current SDI-12 address, key in ?! <enter> and the

 Green to Control Port C1/SDI12  Black, Orange, Clear to G  Red to Battery +

Terminal Emulator. The “Terminal Emulator” window will open. In the Select Device menu, located in the lower left-hand side of the window, select the CR200Series station.

prompt. At the “CR2XX>” prompt, make sure the All Caps Mode box is checked and enter the command SDI12 <enter>. The response “SDI12>” indicates that the CS650 is ready to accept SDI-12 commands.

CS650 will respond with its SDI-12 address. If no characters are typed within 60 seconds, then the mode is exited. In that case, simply enter the command SDI12 again and press <enter>.

D-4

Figure D-1. SDI-12 transparent mode on CR200(X)-series datalogger using

control port C1/SDI12 and changing SDI-12 address from 0 to 1

6. To change the SDI-12 address, key in aAb!<enter> where a is the current

address from the above step and b is the new address. The CS650 will change its address and the datalogger will respond with the new address. To exit SDI-12 transparent mode select the Close Terminal button.

D.2.3 CR1000 Datalogger Example

1. Connect a single CS650 to the datalogger as follows:

 Green to Control Port C1  Black, Orange, Clear to G  Red to 12V

2. In the LoggerNet Connect screen navigate to the Datalogger menu and select Terminal Emulator. The “Terminal Emulator” window will open. In the Select Device menu, located in the lower left-hand side of the window, select the CR1000 station.

3. Click on the Open Terminal button.

4. Press the <enter> key until the datalogger responds with the “CR1000>” prompt. At the “CR1000>” prompt, make sure the All Caps Mode box is checked and enter the command SDI12 <enter>. At the “Enter Cx Port 1, 3,

5, or 7” prompt, key in the control port number where the CS650 green lead is connected and <enter>. The response “Entering SDI12 Terminal” indicates

that the CS650 is ready to accept SDI-12 commands.

Appendix D. SDI-12 Sensor Support

5. To query the CS650 for its current SDI-12 address, key in ?! <enter> and the CS650 will respond with its SDI-12 address. If no characters are typed within 60 seconds, then the mode is exited. In that case, simply enter the command SDI12 again, press <enter>, and key in the correct control port number when prompted.

Figure D-2. SDI-12 transparent mode on CR1000 datalogger using control

port 1 and changing SD1-12 address from 3 to 1

6. To change the SDI-12 address, key in aAb!<enter> where a is the current address from the above step and b is the new address. The CS650 will change its address and the datalogger will respond with the new address. To exit SDI-12 transparent mode, press the Esc key or wait for the 60 second timeout, then select the Close Terminal button.

D-5

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Campbell CS650, CS655 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Guarantee

PLEASE READ FIRST

Precautions

Contents

1. Introduction

2. Cautionary Statements

3. Initial Inspection

4. Quickstart

5. Overview

6. Specifications

6.1 Electrical Specifications

6.1.1 Current

6.2 Operational Specifications

7. Installation

7.1 Orientation and Placement

7.2 Proper Insertion

7.3 Datalogger Wiring

7.4 Programming

8. Operation

8.1 A200 and Device Configuration Utility

8.1.1 Using the A200

8.1.2 Device Configuration Utility (DevConfig)

8.2 SDI-12 Measurements

8.2.1 Use of Multiplexers

8.3 Water Content Reflectometer Method for Measuring Volumetric Water Content

8.3.1 Description of Measurement Method

8.3.2 The Topp Equation

8.3.3 Electrical Conductivity

8.3.4 Error Sources in Water Content Reflectometer Measurement

8.3.5 Temperature Dependence and Correction

8.4 Water Content Reflectometer User-Calibration

8.4.1 Need for Soil Specific Calibration Equation

8.4.2 User-Derived Calibration Equation

8.4.3 Collecting Laboratory Data for Calibration

8.4.4 Collecting Field Data for Calibration

8.4.5 Calculations

9. Maintenance and Troubleshooting

10. References

Appendix A. Importing Short Cut Code into a Program Editor

Appendix B. Example Programs

B.1 CR1000 Programs

B.1.1 CR1000 with One CS650 Probe

B.1.2 CR1000 with Two CS650 Probes on Same Control Port

B.1.3 CR1000 with 12 CS650 Probes on Multiplexer

B.2 CR200X with Three CS650 Probes

Appendix C. Discussion of Soil Water Content

Appendix D. SDI-12 Sensor Support

D.1 SDI-12 Command Basics

D.2.1 SDI-12 Transparent Mode

D.2.2 CR200(X) Series Datalogger Example

D.2.3 CR1000 Datalogger Example

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