ECH
Soil Moisture Sensor
O EA-10
2
Integrator’s Guide
EA-10 Soil Moisture Sensor Integrator’s Guide
Contents
Contents
1. Introduction . . . . . . . . . . . . . . 1
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . 2
Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . 2
Seller’s Liability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Installing the EA-10. . . . . . . .4
Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Turf Installation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical Connection . . . . . . . . . . . . . . . . . . . . . . . . 5
Extension Cables. . . . . . . . . . . . . . . . . . . . . . . . . 6
Hardware Requirements . . . . . . . . . . . . . . . . . . . . . . 6
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. How the EA-10 Works . . . . . 8
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Functional Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Further Reading . . . . . . . . . . . 10
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EA-10 Soil Moisture Sensor Integrator’s Guide
1. Introduction
1. Introduction
Thank you for using the ECH2O EA-10 Dielectric
Soil Moisture sensor. The EA-10 sensor has a standard 2-wire, 4-20 mA analog interface for use with
industrial data acquisition and control systems. The
EA-10 has a very low power requirement and high resolution. This gives you the ability to make as many
measurements as you want over a long period of time
(i.e. a growing season), with minimal battery usage.
This guide covers the basics of integrating the EA-10
into an existing ECH2O system.
Specifications
Model: ECH2O EA-10 Dielectric Soil Moisture
Sensor.
Electrical specs:
Interface: 4-20 mA, 2-wire analog transmitter
Red: (+) supply; White: (-) supply; Shield: NC
Supply voltage: line powered 7-32 Volt; DC
Overvoltage and reverse polarity protected
Sensor specs:
Measurement type: Volumetric Water Content (VWC)
Measurement range: typical 0 to 40 percent VWC
Measurement resolution: depends on acquisition hardware
Measurement accuracy: ± 2% with soil specific calibra-
tion; accuracy at standard factory calibration varies
depending on soil type
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EA-10 Soil Moisture Sensor Integrator’s Guide
1. Introduction
Measurement output: current linearly related to VWC.
Active sensor length: 10 cm
Minimum measurement time: 10 ms
Soils: all types; coarse sand to clay
Operating environment:
Temperature: -40 to +60 °C.
Humidity: 0-100%
Physical properties:
Dimensions: 14.5cm x 3.17cm x 0.15 cm
Cable: 3 m 26 AWG tinned, bare wire
Calibration:
Percent Volumetric Water Content = 4.25 x Current - 34.2.
Functional testing:
Sensor output in air: 4.3 - 4.9 mA
Sensor output in distilled water: 17.6 - 18.2 mA.
Contact Information
If you need to contact Decagon:
• E-mail us at support@decagon.com
• Send us a fax at (509) 332-5158
• Call us at: (US and Canada only) 1-800-755-2751,
or 509-332-2756.
Warranty Information
The EA-10 has a 30-day satisfaction guarantee and a
one-year warranty.
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EA-10 Soil Moisture Sensor Integrator’s Guide
1. Introduction
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),
occasioned 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 understandings, representations, or
warranties of any kind, express, implied, statutory or
otherwise (including, but without limitation, the
implied warranties of merchantability and fitness for a
particular purpose), not expressly set forth herein.
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EA-10 Soil Moisture Sensor Integrator’s Guide
2. Installing the EA-10
2. Installing the EA-10
The EA-10 monitors the water content of the soil in
which it is placed by measuring the dielectric constant
of the soil and water surrounding the probe. While the
probe measures just the soil which is adjacent to it, its
reading is most useful if that measurement represents
the general soil conditions in which the probe is
placed. For that to happen, the monitoring site must
be carefully sel-ected, and the probe must be properly
installed.
Procedure
When installing the ECH2O probe, it is best to maximize contact between the probe and the soil. There
are two methods to accomplish this.
1. Use Decagon’s Probe Installation Kit to install the
probe. This kit has a custom-shaped blade to make
the insertion in the soil, then another tool to place
the probe into the insertion. For deeper installa-
tions, use an augur to reach the desired depth,
then use the Installation kit with extension rods to
install the probe.
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 probe into the hole, making
sure the entire length of the probe is covered.
Finally, insert the shovel again into the soil a few
inches away from the probe, and gently force soil
toward the probe to provide good contact
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EA-10 Soil Moisture Sensor Integrator’s Guide
2. Installing the EA-10
between the probe and the soil. For deeper instal-
lation, excavate down to the level you wish to mea-
sure, then install the probe as described.
When selecting a site for installation, it is important to
remember that the soil adjacent to the probe surface
has the strongest influence on the probe reading and
that the probe measures the volumetric water content.
Therefore any air gaps or excessive soil compaction
around the probe can profoundly influence the readings. Also, do not install the probes adjacent to large
metal objects such as metal poles or stakes. This can
attenuate the probe’s electromagnetic field and
adversely affect output readings.
Turf Installation
When installing the EA-10, the installation procedure
is almost the same, except that the probe must be
placed at a 45° angle to the ground, instead of straight
down.
Orientation
The probe can be oriented in any direction. However,
orienting the flat side perpendicular to the surface of
the soil will minimize effects on downward water
movement.
Removing the Probe
When removing the probe from the soil, do not
pull it out of the soil by the cable! Doing so may
break internal connections and make the probe unuable.
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EA-10 Soil Moisture Sensor Integrator’s Guide
2. Installing the EA-10
ground level
(2.54 cm)
1.0"
45°
EA-10 turf placement
Electrical Connection
The EA-10 is a 2 wire, 4 - 20 mA transmitter. When
connected to a 7 - 32 volt source (line power), the current is linearly proportional to the water content of the
soil. Below is an EA-10 wiring diagram:
Analog out (Red)
Sensor cable
Ground (Bare)
Excitation (White)
The red wire connects to the positive supply and the
white wire to the negative supply. The shield (bare
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EA-10 Soil Moisture Sensor Integrator’s Guide
2. Installing the EA-10
wire) can be connected to a shield terminal, if available, or left open. The probe is electrically floating,
and the shield is not electrically connected to the
probe circuitry. Extension wire can be used to connect
the EA-10 to the 4-20 mA receiver. The extension
wire should be a 2 conductor shielded, direct burial
cable.
NOTE: It is essential that sensor wire connections be watertight! Use wire nuts with grease or
silicon gel caps for all splices.
Extension Cables
Decagon supplies bulk cable for use as extension
cables with the EA-10. For most applications, we recommend sealing the connections from the elements to
maintain a good connection and to prevent corrosion.
Decagon supples 2 conductor shielded cable, and this
is the best type to use if you supply your own cable.
Hardware Requirements
The EA-10 is designed to work with industrial control
and acquisition devices. The EA-10 is loop powered,
drawing its operational power from the current used
to measure volumetric water content. Any device
capable of producing a 7 - 32 mA loop voltage should
be compatible with the EA-10. The EA-10 is also
reverse-polarity protected. If it is installed in the
wrong direction, it will not operate, but will be protected from electrical overload.
NOTE: The EA-10 is intended for use with industrial control and acquisition devices which can
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EA-10 Soil Moisture Sensor Integrator’s Guide
2. Installing the EA-10
provide a short pulse, leaving the probes turned
off most of the time. Continuous power may
cause the probe to exceed government FCC limits
on electromagnetic emissions.
Troubleshooting
If you encounter problems with the EA-10, they will
usually be in the form of negative or erroneous VWC
readings. The most common solution to this problem
is to make sure that you have adequate probe-to-soil
contact. When inserted, the EA-10 should be completely covered up to the black overmolding. Doing
this should remedy any reading errors. If it does not,
please contact Decagon for assistance.
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EA-10 Soil Moisture Sensor Integrator’s Guide
3. How the EA-10 Works
3. How the EA-10 Works
In essence, the EA-10 monitors the water budget of
the soil in which it is placed. It senses water addition
and water loss. If the soil is too wet, irrigation can be
stopped. If the soil becomes too dry, additional irrigation time can be programmed.
Proper monitoring of the water budget requires that
the moisture sensor be located in the active root zone
of relatively homogeneous vegetation, and in welldrained soil of above-average moisture holding capacity. Avoid locations where water can run-on or pool,
and locations with poor vegetative cover, or where
vegetation tends to water stress because of poor moisture holding capacity of the soil or shallow root zone.
Vegetation in non-monitored zones will use water at a
rate proportional to water use in the monitored zone.
Water application rates in these zones must therefore
be proportional for the entire system to remain properly irrigated. If trees use 30% more water than turf,
and turf is being monitored, then the tree zone needs
to be irrigated for 30% more time than the monitored
turf to maintain adequate soil moisture.
Since dielectric probes (such as the EA-10) measure
the moisture in the immediate vicinity of the probe, it
is essential that the probe be installed so that the entire
length of the probe is in intimate contact with the soil
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EA-10 Soil Moisture Sensor Integrator’s Guide
3. How the EA-10 Works
(no air gaps). The soil must therefore be packed tightly
around the entire probe length during installation. The
probe is installed with the blade perpendicular to the
surface to interfere as little as possible with water
movement through the soil.
Calibration
The probe reading is converted to volumetric water
content using the following equation:
Volumetric Water Content = 0.0425 x Current - 0.342
Water content is in m3 m-3, and current is in milliamps. For water content in terms of percent of total
volume, use the following equation:
Volume percent = 4.25 x Current - 34.2.
These calibrations are for typical soils with mid range
texture, and are accurate enough for most irrigation
scheduling purposes. For greater accuracy, a soil specific calibration should be undertaken, as outlined on
the Decagon website.
Functional Testing
ECH2O EA-10 sensors are tested to perform correctly in the following conditions:
Sensor output in air: 4.3 - 4.9 mA
Sensor output in distilled water: 17.6 - 18.2 mA
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EA-10 Soil Moisture Sensor Integrator’s Guide
Further Reading
Further Reading
ECH
O Probes Soil-Specific Calibration
2
http://www.decagon.com/appnotes/echocal.pdf
ECH
O Dielectric Probes vs. Time Domain
2
Reflectometers (TDR)
http://www.decagon.com/appnotes/echovstdr.pdf
ECH
O Probe insertion guide
2
http://www.decagon.com/appnotesprobeinsert2.pdf
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EA-10 Soil Moisture Sensor Integrator’s Guide
Index
Index
C
calibration 9
contact information 2
E
e-mail address 2
F
functional testing 9
I
installation
electrical connection 5
hardware requirements 6
procedure 4
S
seller’s liability 2
specifications 1
T
troubleshooting 7
W
warranty 2
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