Decagon Devices EC-20 User manual

EC-20, EC-10, EC-5
Soil Moisture Sensors
User’s Manual
Version 10

Decagon Devices, Inc.
2365 NE Hopkins Court
Pullman WA 99163 USA
Trademarks:
“ECH2O” is a registered trademark
of Decagon, Devices, Inc All rights reserved..
©2001-2010 Decagon Devices, Inc.
All rights reserved.

EC-20, EC-10 and EC-5 User’s Manual
Table of Contents
i
Contents
1. Introduction . . . . . . . . . . . . . . . . .1
Welcome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . 1
Contact Information . . . . . . . . . . . . . . . . . . . 2
Warranty Information . . . . . . . . . . . . . . . . . 3
Seller’s Liability . . . . . . . . . . . . . . . . . . . . . . . 3
2. About the EC-20, EC-10, EC-5 . .4
The EC-10 and EC-20 . . . . . . . . . . . . . . . . . . 4
The EC-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Sensor Features . . . . . . . . . . . . . . . . . . . . . . . 5
Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . 5
3.5mm Plug Wiring . . . . . . . . . . . . . . . . . . 5
Wiring to Non-Decagon Dataloggers . . . . 6
Extended cable lengths . . . . . . . . . . . . . . . . . 7
3. Installing the Sensors . . . . . . . . . .8
Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Orientation . . . . . . . . . . . . . . . . . . . . . . . . 10
Removing the Sensor . . . . . . . . . . . . . . . . 10
4. Collecting Data . . . . . . . . . . . . . .11
Datalogger Requirements . . . . . . . . . . . . . . 11
Connecting to a Datalogger . . . . . . . . . . . . . 12
Sample Program . . . . . . . . . . . . . . . . . . . . . 12
SCWin (Short Cut) Directions . . . . . . . . . . 14
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . 15

EC-20, EC-10 and EC-5 User’s Manual
Table of Contents
ii
Sensor Calibration Values . . . . . . . . . . . . 16
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . 20
Declaration of Conformity . . . . . . 21
Index . . . . . . . . . . . . . . . . . . . . . . . 23

EC-20, EC-10 and EC-5 User’s Manual
1. Introduction
1
1. Introduction
Welcome
Welcome to the EC-20, EC-10 and EC-5 sensors for
measuring soil water content. These innovative sensors
will enable you to monitor soil moisture accurately and
affordably.
Specifications
Measurement Time: 10ms (milliseconds)
Accuracy:
EC-10 and EC-20:
± .04 m3/m3(±4%) < 0.5 dS/m
With soil-specific calibration: ±.02 m3/m3(±2%)
EC-5:
at least 0.03 m3/m3all soils, up to 8 dS/m
With soil-specific calibration: ±.02 m3/m3(±2%)
Resolution:
EC-10 and EC-20: 0.002m3/m3
EC-5: 0.001 m3/m3VWC in mineral soils, 0.25% in
growing media
Power:
Requirements:
EC-10 & EC-20: 2.5VDC @ 2mA to 5VDC @ 7mA
EC-5: 2.5VDC - 3.6VDC @ 10mA
Output: 10-40% of excitation voltage (250-1000mV at
2500mV excitation)

EC-20, EC-10 and EC-5 User’s Manual
1. Introduction
2
Operating Environment:
EC-10 and EC-20: 0 to 50°C
EC-5: -40 to +60 °C
Range of Measurement:
EC-10 and EC-20: 0 to 40% VWC
EC-5: 0 to saturation
Sensor dimensions:
EC-20: 25.4cm x 3.17cm x .15cm
EC-10: 14.5cm x 3.17cm x .15cm
EC-5: 8.9cm x 1.8cm x 0.7cm
Cable length: 5m standard, custom lengths or extension
cables are available
Connector types: 3.5 mm plug or stripped and tinned
lead wires
Datalogger Compatibility (not exclusive):
Decagon: Em5b, Em50 (and radio-enabled versions)
Campbell Scientific: CR10X, 21X, 23X, CR1000,
CR3000, etc.
Contact Information
To contact Decagon for questions or customer support:
•E-mail us at: [email protected]
[email protected]
•Fax us at: 1-[phone]
•Call us at: 1-800-755-2751 in US and Canada only
or 1-509-332-2756 International.

EC-20, EC-10 and EC-5 User’s Manual
1. Introduction
3
Warranty Information
The EC-20, EC-10 and EC-5 have a 30-day satisfaction
guarantee and a one-year warranty.
Seller’s Liability
Seller warrants new equipment of its own manufacture
against defective workmanship and materials for a
period of one year from date of receipt of equipment
(the results of ordinary wear and tear, neglect, misuse,
accident and excessive deterioration due to corrosion
from any cause are not to be considered a defect); but
Seller’s liability for defective parts shall in no event
exceed the furnishing of replacement parts F.O.B. the
factory where originally manufactured. Material and
equipment covered hereby which is not manufactured
by Seller shall be covered only by the warranty of its
manufacturer. Seller shall not be liable to Buyer for loss,
damage or injuries to persons (including death), or to
property or things of whatsoever kind (including, but
not without limitation, loss of anticipated profits), occa-
sioned by or arising out of the installation, operation,
use, misuse, nonuse, repair, or replacement of said
material and equipment, or out of the use of any method
or process for which the same may be employed. The
use of this equipment constitutes Buyer’s acceptance of
the terms set forth in this warranty. There are no under-
standings, representations, or warranties of any kind,
express, implied, statutory or otherwise (including, but
without limitation, the implied warranties of merchant-
ability and fitness for a particular purpose), not
expressly set forth herein.

EC-20, EC-10 and EC-5 User’s Manual
2. About the EC-20, EC-10, EC-5
4
2. About the EC-20, EC-10, EC-5
The EC-10 and EC-20
The EC-10 and EC-20 measure the dielectric constant of
the soil in order to find its volumetric water content.
Since the dielectric constant of water is much higher
than that of air or soil minerals, the dielectric constant of
the soil is a sensitive measure of water content. The EC-
10 and EC-20 have a very low power requirement and
high resolution. This gives you the ability to make as
many measurements as you want (even hourly) over a
long period of time (like a growing season, for exam-
ple), with minimal battery usage.
The EC-5
The EC-5 varies from its EC-10 and EC-20 cousins.
Although the principles of measurement are the same,
its two-prong design and higher measurement frequency
allows the EC-5 to measure VWC from 0 to 100%
(VWC of saturated soils is generally 40-60% depending
on the soil type) and allows accurate measurement of all
soils and soilless medias and a much wider range of
salinities.

EC-20, EC-10 and EC-5 User’s Manual
2. About the EC-20, EC-10, EC-5
5
Sensor Features
Fig.1: EC-20 diagram Fig. 2: EC-5 diagram
Wiring Diagrams
3.5mm Plug Wiring
The EC-20, EC-10 and EC-5 come with a 3.5mm “ste-
reo plug” connector. This allows for rapid connection
directly to Decagon’s Em50 and Em5 logger and the
Circuitry
Sensor

EC-20, EC-10 and EC-5 User’s Manual
2. About the EC-20, EC-10, EC-5
6
ECH2O Check. Below is a diagram showing the wiring
configuration for this connector.
Fig. 2: 3.5mm “Stereo Plug” wiring configuration
Wiring to Non-Decagon Dataloggers
Models with stripped and tinned leads are pre-config-
ured for connecting to non-Decagon dataloggers. Sim-
ply wire the lead into the datalogger as described in
“Connecting to a Datalogger” in Chapter 4.
If your model uses the standard 3.5mm plug, you have
two choices when attaching the sensor to non-Decagon
dataloggers. First, you can clip off the plug on the sen-
sor cable, strip and tin the wires, and wire it directly into
the datalogger. This has the advantage of creating a
direct connection with no chance of the sensor becom-
ing un-plugged; however, it then cannot be used in the
future with a Decagon Em50 or Em5 logger. The other
choice is to obtain an adapter cable from Decagon. The
3-wire sensor adapter cable has a connector for the sen-
sor jack on one end, and three wires on the other end for
connection to a datalogger (this type of wire is often
referred to as a “pigtail” adapter). Both the sensor wire
and adapter cable wire have the same wire output
Analog
out
Ground
Excitation

EC-20, EC-10 and EC-5 User’s Manual
2. About the EC-20, EC-10, EC-5
7
(shown in Fig. 3); the white wire is excitation, red is
output, and the bare wire is ground.
Fig. 3: 3-wire cable wiring configuration
Extended cable lengths
Decagon supplies 50-foot (15.25m) and 10-foot (3m)
extension cables for use with the EC-20, EC-10 and EC-
5 with the 3.5 mm connector . You can safely connect
up to 4 of the 50-foot cables without signal attenuation.
For most applications, you will want to seal the connec-
tions from the elements to maintain a good connection
and to prevent corrosion. It is imperative that these
connections are checked before the sensor is buried.
Please see the Decagon web-site (www.decagon.com)
for an application note detailing some preferred meth-
ods for waterproofing these connections
However, if possible, Decagon recommends that you
purchase customized cable lengths if your project
requires longer cable leads. Custom cable lengths may
be requested with a 3.5mm connector or stripped &
tinned end.
Analog out (Red)
Ground (Bare)
Excitation (White)
Sensor cable

EC-20, EC-10 and EC-5 User’s Manual
3. Installing the Sensors
8
3. Installing the Sensors
When selecting a site for installation, it is important to
remember that the soil adjacent to the sensor surface has
the strongest influence on the sensor reading and that
the sensor measures the volumetric water content.
Therefore any air gaps or excessive soil compaction
around the sensor can profoundly influence the read-
ings. Also, do not install the sensors adjacent to large
metal objects such as metal poles or stakes. This can
attenuate the sensor’s electromagnetic field and
adversely affect output readings. Because the EC-5 has
gaps between its prongs, it is also important to consider
the size of the media you are inserting the sensor into. It
is possible to get sticks, bark, roots or other material
stuck between the sensor prongs, which will adversely
affect readings. Finally, be careful when inserting the
sensors into dense soil, as the prongs will break if exces-
sive sideways force is used when pushing them in.
Procedure
When installing the EC-20, EC-10 and EC-5, it is best to
maximize contact between the sensor and the soil. There
are two methods to accomplish this.
For the EC-10/EC-20:
1. Use Decagon’s Installation Kit to install the sensor.
This kit has a custom-shaped blade to make the
insertion in the soil, then another tool to place the
sensor into the insertion. For deeper installations,

EC-20, EC-10 and EC-5 User’s Manual
3. Installing the Sensors
9
use an augur to reach the desired depth, then use the
Installation Kit with extension rods to install the
sensor.
2. Use a thin implement like a trenching shovel, gar-
dening spade, or flat bar to make a pilot hole in the
soil. Then insert the sensor into the hole, making
sure the entire length of the sensor is covered.
Finally, insert the shovel again into the soil a few
inches away from the sensor, and gently force soil
toward the sensor to provide good contact between
the sensor and the soil. For deeper installation, exca-
vate down to the level you wish to measure, then
install the sensor as described.
For the EC-5:
1. The EC-5 sensor was designed for easy installation
into the soil. After digging a hole to the desired
depth, push the prongs on the sensor into undis-
turbed soil at the bottom of the hole or into the side-
wall of the hole. Make sure that the prongs are
buried completely up to the black overmolding, as
shown below.

EC-20, EC-10 and EC-5 User’s Manual
3. Installing the Sensors
10
The sensor may be difficult to insert into extremely
compact or dry soil. If you have difficulty inserting
the sensor, try loosening the soil somewhat or wet-
ting the soil. Never pound it in!
2. Carefully backfill the hole to match the bulk density
of the surrounding soil. Be careful not to bend the
black overmolding connecting the sensor to the
cable.
Orientation
The sensor can be oriented in any direction. However,
orienting the flat side perpendicular to the surface of the
soil will minimize effects on downward water move-
ment.
Removing the Sensor
When removing the sensor from the soil, do not pull it
out of the soil by the cable! Doing so may break inter-
nal connections and make the sensor unusable.

EC-20, EC-10 and EC-5 User’s Manual
4. Collecting Data
11
4. Collecting Data
Datalogger Requirements
The EC-20, EC-10 and EC-5 sensors are designed to
work most efficiently with Decagon’s 5-channel Em5b,
Em50, ProCheck or ECH2O Check handheld readout.
All Decagon readout devices use either a 3.0V or 5V
excitation.
The sensors however, may be adapted for use with other
dataloggers, such as those from Campbell Scientific,
Inc., for example. The EC-10 and EC-20 sensors require
an excitation voltage in the range of 2 to 5 volts. The
EC-5 requires an excitation voltage in the range of 2 to
3.6 volts. The sensors produce an output voltage that
depends on the dielectric constant of the medium sur-
rounding the sensor, and ranges between 10 and 50% of
the excitation voltage. Any datalogger which can pro-
duce a 2.5 to 5V (2.5 to 3.6V for EC-5) excitation with
approximately 10 millisecond duration and read a volt-
level signal with 12-bit or better resolution should be
compatible with the EC-20, EC-10 and EC-5 sensors.
For the EC-10 and EC-20 sensors, the current require-
ment at 2.5V is around 2mA, and at 5V it is 7-8mA. For
the EC-5, it is 10mA at 2.5V.
NOTE: EC-20, EC-10 and EC-5 are intended only for
use with dataloggers and readout devices which can
provide short excitation pulses, leaving the sensors
turned off most of the time. Continuous excitation not

EC-20, EC-10 and EC-5 User’s Manual
4. Collecting Data
12
only wastes battery power, but may, under certain cir-
cumstances, cause the sensor to exceed government
specified limits on electromagnetic emissions.
Connecting to a Datalogger
Connect the wires to the datalogger as shown, with the
supply wire connected to the excitation, the analog out
wire to an analog input, and the bare ground wire to
ground:
Fig. 5: Datalogger configuration
Sample Program
The following program is an example that can be used
with Campbell Scientific’s CR10X datalogger and our
EC-20, EC-10 & EC-5 sensors at a 2500mV excitation:
;{CR10X}
; Example ECH2O Datalogger Program for CR10X
; Wiring:
Exc. HLG
Supply Analog
out Ground
Datalogger
Analog
In

EC-20, EC-10 and EC-5 User’s Manual
4. Collecting Data
13
; White: Excitation Channel 1
; Red: Input Single Ended Channel 1
; Black: Ground
*Table 1 Program
01: 1 Execution Interval (seconds)
; Factory calibration equations for ECH2O
; probes convert mV output of ECH2O to
; volumetric water content (VWC, m3/m3)
; EC-20: VWC = 0.00069 * mV - 0.29
; EC-10: VWC = 0.00093 * mV - 0.376
; EC-5: VWC = 0.00119 * mV - 0.400
; The multiplier and offset in this
; example are for the EC-5
1: Excite-Delay (SE) (P4)
1: 1 Reps
2: 5 2500 mV Slow Range
3: 1 SE Channel
4: 1 Excite all reps w/Exchan 1
5: 1 Delay (0.01 sec units)
6: 2500 mV Excitation
7: 1 Loc [ Probe_VWC ]
8: .00119 Multiplier
9: -.4 Offset
*Table 2 Program
02: 0.0000 Execution Interval (seconds)
*Table 3 Subroutines
End Program

EC-20, EC-10 and EC-5 User’s Manual
4. Collecting Data
14
SCWin (Short Cut) Directions
Following are instructions for using our SCWin (Short
Cut) program to read EC-5, EC-10 and EC-20 soil mois-
ture sensors.
1. Download EchoCSI.zip from http://www.deca-
gon.com/appnotes/EchoCSIappnote.pdf.
2. Unzip the folder EchoCSI.zip.
3. Locate the file containing SCWin.exe. It should be
in C:\Program Files\Campbellsci\SCWin. Place the
following files from the unzipped EchoCSI.zip
folder into the folder with SCWin.exe:
AM1632Z.MUX
AM416Z.MUX
EC10.SCS
EC101632.SCS
EC10416.SCS
EC20.SCS
EC201632.SCS
EC20416.SCS
EC5.SCS
EC5632.SCS
EC5416.SCS
SCWIN-DECAGON.CNT
SCWIN-DECAGON.HLP
Note: If you are not able to find this directory path,
search for the folder that contains SCWIN.exe and place
the files into that folder.
4. Open up SCWin.exe (Short Cut). If you are using a
V.3 copy of LoggerNet, there is a tab for SCWin
(Short Cut) on the tool bar.

EC-20, EC-10 and EC-5 User’s Manual
4. Collecting Data
15
5. Select “New” to start a new program to read the EC-
20, EC-10 and EC-5.
a. Select the datalogger you will be using to read the
sensors.
b. Select the measurement interval (a shorter mea-
surement interval, i.e. 1 sec., is sometimes desirable
when testing the sensor).
6. Click on Sensors (this should open a new page with
a file tree on it).
7. Under the “Sensors” file tree, double-click on
“Meteorological” and then select “Soil Moisture.”
8. ECHO Probe EC-10 and ECHO Probe EC-20
should appear on the tree along with other soil mois-
ture sensors.
a. If they don’t appear, check to make sure you have
pasted the files above into the correct location.
Calibration
Decagon’s ECH2O Utility, ECH2O Utility Mobile, and
DataTrac automatically apply factory calibrations to the
sensors’ output data. However, this general calibration
may not be applicable for all sensors and all soil types.
While the factory calibrations for the EC-5 is appropri-
ate for almost all soil types, the standard calibrations for
the EC-20 and EC-10 sensors do not perform in soils
with high sand or salt content. Therefore, for added
accuracy we encourage our customers to perform soil-
specific calibrations.
The calibration equation that you will use depends on
where you will be using it. If you will be using it with

EC-20, EC-10 and EC-5 User’s Manual
4. Collecting Data
16
sensors connected to a non-Decagon datalogger you will
need to use the 2500 mV calibration. If you use any
Decagon software (DataTrac, ECH2O Utility, etc.) or
the user calibration menu in the ECH2O Check, you will
need to use the RAW calibration. The difference
between the two is the slope constant. To increase the
resolution of the sensor output, Decagon uses all avail-
able increments of the 12-bit number (value of 4096)
where the measurement is stored. Thus, the output of the
sensors read by the ECH2O Check and Decagon loggers
must be multiplied by 0.61 AND the 2500 mV slope to
give the right value.
Sensor Calibration Values
Following is a list of the both the millivolt and RAW
calibration values for the EC-20, EC-10 and EC-5,
where is the volumetric water content, mV is the milli-
volt output of the sensor, and where xis the RAW sen-
sor output.
EC-20:
mV: (m3/m3) = 0.000695mV - 0.29
RAW: (m3/m3) =0.000424 x - 0.29
EC-10:
mV: (m3/m3) = 0.000936mV - 0.376
RAW: (m3/m3) = 0.000571 x - 0.376
EC-5:
The EC-5 is much less sensitive to variation in texture
and electrical conductivity because it runs at a much
higher measurement frequency. Therefore, its general
calibration equation should apply for all mineral soils up