Campbell CS650 User manual

CS650 and CS655 Water
Content Reflectometers
Revision: 10/12
Copyright © 2011-2012
Campbell Scientific, Inc.

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Table of Contents
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. Overview......................................................................1
5. Specifications .............................................................3
5.1 Dimensions/Weight..............................................................................3
5.2 Electrical Specifications.......................................................................4
5.2.1 Current..........................................................................................4
5.3 Operational Specifications ...................................................................5
6. Installation...................................................................7
6.1 Orientation and Placement ...................................................................7
6.2 Proper Insertion....................................................................................7
6.3 Wiring ..................................................................................................8
6.3.1 SDI-12 Wiring ..............................................................................8
6.3.2 RS-232 Wiring ..............................................................................9
6.4 A200 and Device Configuration Utility ...............................................9
6.4.1 Using the A200 .............................................................................9
6.4.1.1 Driver Installation ..............................................................9
6.4.1.2 Cabling .............................................................................10
6.4.1.3 Powering the Sensor.........................................................10
6.4.1.4 Determining which COM Port the A200 has been
Assigned .......................................................................10
6.4.2 Device Configuration Utility (DevConfig) .................................11
6.4.2.1 Settings Editor Tab...........................................................13
6.4.2.2 Send OS Tab ....................................................................15
6.4.2.3 Terminal Tab....................................................................16
6.5 SDI-12 Measurements........................................................................17
6.5.1 Use of Multiplexers.....................................................................18
6.6 Program Examples .............................................................................19
6.6.1 CR1000 With a Single CS650 Probe ..........................................19
6.6.2 CR1000 With 2 CS650 Probes on Same Control Port ................20
6.6.3 CR1000 With 12 CS650 Probes on Multiplexer.........................20
6.6.4 CR10X With a Single CS650 Probe ...........................................21
6.6.5 CR10X With 2 CS650 Probes on Same Control Port .................22
6.6.6 CR200X With 3 CS650 Probes...................................................24
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Table of Contents
7. The Water Content Reflectometer Method for
Measuring Volumetric Water Content...................25
7.1 Description of Measurement Method ................................................ 25
7.2 The Topp Equation............................................................................ 25
7.3 Electrical Conductivity...................................................................... 25
7.3.1 Soil Electrical Conductivity ....................................................... 25
7.3.2 Temperature Correction of Soil Electrical Conductivity............ 26
7.4 Error Sources in Water Content Reflectometer Measurement .......... 27
7.4.1 Probe-to-Probe Variability Error................................................ 27
7.4.2 Insertion Error ............................................................................ 27
7.5 Temperature Dependence and Correction ......................................... 27
7.5.1 Accurate Soil Temperature Measurement .................................. 28
8. Water Content Reflectometer User-Calibration......28
8.1 Need for Soil Specific Calibration Equation ..................................... 28
8.2 The User-Derived Calibration Equation............................................ 28
8.3 Collecting Laboratory Data for Calibration....................................... 29
8.4 Collecting Field Data for Calibration ................................................ 31
8.5 Calculations....................................................................................... 33
9. Maintenance ..............................................................33
10. Troubleshooting........................................................34
11. References.................................................................35
Appendices
A. Discussion of Soil Water Content .........................A-1
B. SDI-12 Sensor Support ...........................................B-1
B.1 SDI-12 Command Basics ................................................................ B-1
B.2 Changing the SDI-12 Address Using Terminal Emulator and a
Datalogger.................................................................................... B-3
B.2.1 SDI-12 Transparent Mode........................................................ B-3
B.2.2 CR200(X) Series Datalogger Example .................................... B-4
B.2.3 CR1000 Datalogger Example................................................... B-5
B.2.4 CR10X Datalogger Example.................................................... B-6
B.2.5 CR10X-PB Table-Based Datalogger Example......................... B-7
Figures
4-1. CS650 Water Content Reflectometer .................................................. 2
5-1. CS650 and CS655 average current drain............................................. 5
6-1. CS650G Insertion Guide Tool............................................................. 8
6-2. A200 Sensor-to-PC Interface............................................................. 11
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Table of Contents
B-1. SDI-12 transparent mode on CR200(X)-series datalogger using
control port C1/SDI12 and changing SDI-12 address from
0 to 1.............................................................................................B-4
B-2. SDI-12 transparent mode on CR1000 datalogger using control
port 1 and changing SD1-12 address from 3 to 1 .........................B-5
B-3. SDI-12 transparent mode on CR10X datalogger using control
port 1 and changing SDI-12 address from 0 to 1..........................B-7
B-4. SDI-12 transparent mode on CR10X-PB table-based datalogger
using control port 1 and changing SDI-12 address from 0 to 1 ....B-8
Tables
6-1. CS650 Wiring Code for SDI-12...........................................................8
6-2. CS650 Wiring Code for RS-232 and A200..........................................9
6-3. CS650 Terminal Commands ..............................................................17
6-4. CS650 SDI-12 Commands.................................................................18
6-5. Wiring For Program Example 1 .........................................................19
6-6. Wiring For Program Example 2 .........................................................20
6-7. Wiring For Program Example 3 .........................................................21
6-8. Wiring For Program Example 4 .........................................................22
6-9. Wiring For Program Example 5 .........................................................23
6-10. Wiring For Program Example 6 .........................................................24
B-1. CS650 SDI-12 Command and Response Set....................................B-1
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Table of Contents
iv

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.
NOTE
Before installing the sensor, please study
•Section 2, Cautionary Statements
•Section 3, Initial Inspection
2. Cautionary Statements
•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.
4. 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 communication.
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CS650 and CS655 Water Content Reflectometers
FIGURE 4-1. 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 non-
polarizing 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
2

CS650 and CS655 Water Content Reflectometers
means of RS-232 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 software, DevConfig.
The CS650's cable can terminate in:
•Pigtails that connect directly to a Campbell Scientific datalogger
(option –PT).
•Connector that attaches to a prewired enclosure (option –PW). 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 theWireless Sensor Manual for more information.
5. 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
Compatibility
Dataloggers: CR200(X) series
CR800 series
CR1000
CR3000
CR5000
CR510
CR10(X)
CR23X
5.1 Dimensions/Weight
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
L 85 mm
W 63 mm
D 18 mm
Probe Weight: 280 g 240 g
Cable Weight: 35 g m-1 35 g m-1
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CS650 and CS655 Water Content Reflectometers
5.2 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:
Πcompliant (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.
5.2.1 Current
Active (3 ms): 45 mA typical @ 12 Vdc
(80 mA @ 6 Vdc, 35 mA @ 18 Vdc)
Quiescent: 135 μA @ 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 5-1)
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CS650 and CS655 Water Content Reflectometers
FIGURE 5-1. CS650 and CS655 average current drain
FIGURE 5-1 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.
5.3 Operational Specifications
CS650 CS655
Relative Dielectric
Permittivity
Range: 1 to 81 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 <0.02
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CS650 and CS655 Water Content Reflectometers
CS650 CS655
Volumetric Water
Content using Topp
Equation (m3/m3)
Range: 5% to 50% 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% <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)
±(5% of reading +
0.05 dS/m)
Precision‡: 0.5% of BEC 0.5% of BEC
Temperature
Soil
Measurement
Range:
-10 to + 70°C
-10 to + 70°C
Operational
Range:
0 to + 70°C 0 to + 70°C
Accuracy†: ±0.5°C for probe
body buried in soil
±0.5°C for probe
body buried in soil
Precision‡: ±0.02°C ±0.02°C
Sensing Volume*: 7800 cm33600 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.
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CS650 and CS655 Water Content Reflectometers
6. Installation
6.1 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.
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.
6.2 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. 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.
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CS650 and CS655 Water Content Reflectometers
FIGURE 6-1. CS650G Insertion Guide Tool
6.3 Wiring
CS650 connections to a datalogger are shown below. Dataloggers are divided
into those which are programmed with the CRBasic programming language
and those that are programmed with Edlog. CRBasic dataloggers include the
CR1000, CR3000, CR5000, CR800-series, and CR200X-series. Compatible
Edlog dataloggers include the CR10X, CR23X, and CR510.
6.3.1 SDI-12 Wiring
TABLE 6-1 shows the SDI-12 wiring code for the CS650 water content
reflectometer. SDI-12 data is transmitted to a CRBasic datalogger odd
numbered control port or to any control port of an Edlog datalogger that is
capable of SDI-12 communication. See Section 6.6, Program Examples, for
SDI-12 programming examples.
TABLE 6-1. CS650 Wiring Code for SDI-12
Color Function Datalogger Connection
Green SDI-12 Data SDI-12 Input or Control Port
Red SDI-12 Power 12 Vdc
Black SDI-12 Reference G
Clear Shield G
Orange Not Used G
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CS650 and CS655 Water Content Reflectometers
SDI-12 communication has the advantage that up to ten probes may be given
different addresses and share a single control port. Another advantage is that
the datalogger programming is much simpler for SDI-12 communication than
RS-232.
The orange Rx wire is only used for RS-232 Tx/Rx
communication, and should be grounded when using SDI-12.
NOTE
6.3.2 RS-232 Wiring
TABLE 6-2 shows the wiring code for communicating with a CS650 using
RS-232 serial protocol. Device Configuration Utility software uses RS-232 to
communicate with a CS650 through the A200 USB-to-Serial Module. See
Section 6.4, A200 and Device Configuration Utility, for details.
RS-232 communication is not recommended for use with Campbell Scientific
dataloggers because it requires two control ports per CS650 and the
programming is more complicated than for SDI-12 communication.
For RS-232 serial communication with devices other than Campbell Scientific
dataloggers, use the wiring information in TABLE 6-2. Factory default
communication settings are 9600 baud, no parity, 1 stop bit, 8 data bits, and no
error checking.
See TABLE 6-3 for a list of serial commands for the CS650.
TABLE 6-2. CS650 Wiring Code
for RS-232 and A200
Color Function A200 Terminal
Orange RxD Rx
Green TxD Tx
Red Power +12 Vdc
Black Reference G
Clear Shield G
6.4 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.
6.4.1 Using the A200
6.4.1.1 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.
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CS650 and CS655 Water Content Reflectometers
Drivers should be loaded before plugging the A200 into the PC.
NOTE
The A200 drivers can be downloaded, at no charge, from:
www.campbellsci.com/downloads.
6.4.1.2 Cabling
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 6-2 and TABLE 6-2).
A data cable, part number 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.
6.4.1.3 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.
6.4.1.4 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 the Device Configuration Utility.
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.
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 (e.g., LoggerNet) before and after the installation, or look in
the Windows Device Manager list under the ports section (access via the
control panel).
10

CS650 and CS655 Water Content Reflectometers
FIGURE 6-2. A200 Sensor-to-PC Interface
6.4.2 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 6-2. 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.
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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
6.4.1.4, Determining which COM Port the A200 has been Assigned).
Select Ok and then Connect to begin communication with the CS650.
12