10458-01 EA-10 manual · EA-10 Soil Moisture Sensor Integrator’s Guide 1. Introduction 1 1. Introduction Thank you for using the ECH 2O EA-10 Dielectric Soil Moisture sensor. The

ECH2O EA-10Soil Moisture Sensor

Integrator’s Guide

EA-10 Soil Moisture Sensor Integrator’s GuideContents

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Contents

1. Introduction . . . . . . . . . . . . . . 1Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . 2Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . 2Seller’s Liability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Installing the EA-10. . . . . . . . 4Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Turf Installation . . . . . . . . . . . . . . . . . . . . . . . . . . 5Electrical Connection . . . . . . . . . . . . . . . . . . . . . . . . 5

Extension Cables. . . . . . . . . . . . . . . . . . . . . . . . . 6Hardware Requirements . . . . . . . . . . . . . . . . . . . . . . 6Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3. How the EA-10 Works . . . . . 8Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Functional Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Further Reading . . . . . . . . . . . 10

EA-10 Soil Moisture Sensor Integrator’s Guide1. Introduction

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1. Introduction

Thank you for using the ECH2O EA-10 DielectricSoil Moisture sensor. The EA-10 sensor has a stan-dard 2-wire, 4-20 mA analog interface for use withindustrial data acquisition and control systems. TheEA-10 has a very low power requirement and high res-olution. This gives you the ability to make as manymeasurements 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-10into an existing ECH2O system.

SpecificationsModel: ECH2O EA-10 Dielectric Soil Moisture Sensor.

Electrical specs:Interface: 4-20 mA, 2-wire analog transmitter

Red: (+) supply; White: (-) supply; Shield: NCSupply voltage: line powered 7-32 Volt; DCOvervoltage and reverse polarity protected

Sensor specs:Measurement type: Volumetric Water Content (VWC)Measurement range: typical 0 to 40 percent VWCMeasurement resolution: depends on acquisition hardwareMeasurement accuracy: ± 2% with soil specific calibra-tion; accuracy at standard factory calibration variesdepending on soil type


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Measurement output: current linearly related to VWC.Active sensor length: 10 cmMinimum 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 cmCable: 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 mASensor output in distilled water: 17.6 - 18.2 mA.

Contact InformationIf you need to contact Decagon:• E-mail us at [email protected]• Send us a fax at (509) 332-5158• Call us at: (US and Canada only) 1-800-755-2751,

or 509-332-2756.

Warranty InformationThe EA-10 has a 30-day satisfaction guarantee and aone-year warranty.


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Seller’s LiabilitySeller warrants new equipment of its own manufactureagainst defective workmanship and materials for aperiod of one year from date of receipt of equipment(the results of ordinary wear and tear, neglect, misuse,accident and excessive deterioration due to corrosionfrom any cause are not to be considered a defect); butSeller’s liability for defective parts shall in no eventexceed the furnishing of replacement parts F.O.B. thefactory where originally manufactured. Material andequipment covered hereby which is not manufacturedby Seller shall be covered only by the warranty of itsmanufacturer. Seller shall not be liable to Buyer forloss, 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, opera-tion, use, misuse, nonuse, repair, or replacement ofsaid material and equipment, or out of the use of anymethod or process for which the same may beemployed. The use of this equipment constitutesBuyer’s acceptance of the terms set forth in this war-ranty. There are no understandings, representations, orwarranties of any kind, express, implied, statutory orotherwise (including, but without limitation, theimplied warranties of merchantability and fitness for aparticular purpose), not expressly set forth herein.

EA-10 Soil Moisture Sensor Integrator’s Guide2. Installing the EA-10

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2. Installing the EA-10

The EA-10 monitors the water content of the soil inwhich it is placed by measuring the dielectric constantof the soil and water surrounding the probe. While theprobe measures just the soil which is adjacent to it, itsreading is most useful if that measurement representsthe general soil conditions in which the probe isplaced. For that to happen, the monitoring site mustbe carefully sel-ected, and the probe must be properlyinstalled.

Procedure When installing the ECH2O probe, it is best to maxi-mize contact between the probe and the soil. Thereare two methods to accomplish this.1. Use Decagon’s Probe Installation Kit to install the

probe. This kit has a custom-shaped blade to makethe insertion in the soil, then another tool to placethe probe into the insertion. For deeper installa-tions, use an augur to reach the desired depth,then use the Installation kit with extension rods toinstall the probe.

2. Use a thin implement like a trenching shovel, gar-dening spade, or flat bar to make a pilot hole in thesoil. Then insert the probe into the hole, makingsure the entire length of the probe is covered.Finally, insert the shovel again into the soil a fewinches away from the probe, and gently force soiltoward the probe to provide good contact


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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 toremember that the soil adjacent to the probe surfacehas the strongest influence on the probe reading andthat the probe measures the volumetric water content.Therefore any air gaps or excessive soil compactionaround the probe can profoundly influence the read-ings. Also, do not install the probes adjacent to largemetal objects such as metal poles or stakes. This canattenuate the probe’s electromagnetic field andadversely affect output readings.

Turf InstallationWhen installing the EA-10, the installation procedureis almost the same, except that the probe must beplaced at a 45° angle to the ground, instead of straightdown.

OrientationThe 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 ProbeWhen removing the probe from the soil, do notpull it out of the soil by the cable! Doing so maybreak internal connections and make the probe unu-able.


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EA-10 turf placement

Electrical ConnectionThe EA-10 is a 2 wire, 4 - 20 mA transmitter. Whenconnected to a 7 - 32 volt source (line power), the cur-rent is linearly proportional to the water content of thesoil. Below is an EA-10 wiring diagram:

The red wire connects to the positive supply and thewhite wire to the negative supply. The shield (bare

45°

1.0" (2.54 cm)

Analog out (Red)

Ground (Bare)

Excitation (White)

Sensor cable

ground level


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wire) can be connected to a shield terminal, if avail-able, or left open. The probe is electrically floating,and the shield is not electrically connected to theprobe circuitry. Extension wire can be used to connectthe EA-10 to the 4-20 mA receiver. The extensionwire should be a 2 conductor shielded, direct burialcable.

NOTE: It is essential that sensor wire connec-tions be watertight! Use wire nuts with grease orsilicon gel caps for all splices.

Extension CablesDecagon supplies bulk cable for use as extensioncables with the EA-10. For most applications, we rec-ommend sealing the connections from the elements tomaintain a good connection and to prevent corrosion.Decagon supples 2 conductor shielded cable, and thisis the best type to use if you supply your own cable.

Hardware Requirements The EA-10 is designed to work with industrial controland acquisition devices. The EA-10 is loop powered,drawing its operational power from the current usedto measure volumetric water content. Any devicecapable of producing a 7 - 32 mA loop voltage shouldbe compatible with the EA-10. The EA-10 is alsoreverse-polarity protected. If it is installed in thewrong direction, it will not operate, but will be pro-tected from electrical overload.

NOTE: The EA-10 is intended for use with indus-trial control and acquisition devices which can


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provide a short pulse, leaving the probes turnedoff most of the time. Continuous power maycause the probe to exceed government FCC limitson electromagnetic emissions.

Troubleshooting If you encounter problems with the EA-10, they willusually be in the form of negative or erroneous VWCreadings. The most common solution to this problemis to make sure that you have adequate probe-to-soilcontact. When inserted, the EA-10 should be com-pletely covered up to the black overmolding. Doingthis should remedy any reading errors. If it does not,please contact Decagon for assistance.

EA-10 Soil Moisture Sensor Integrator’s Guide3. How the EA-10 Works

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3. How the EA-10 Works

In essence, the EA-10 monitors the water budget ofthe soil in which it is placed. It senses water additionand water loss. If the soil is too wet, irrigation can bestopped. If the soil becomes too dry, additional irriga-tion time can be programmed.

Proper monitoring of the water budget requires thatthe moisture sensor be located in the active root zoneof relatively homogeneous vegetation, and in well-drained soil of above-average moisture holding capac-ity. Avoid locations where water can run-on or pool,and locations with poor vegetative cover, or wherevegetation tends to water stress because of poor mois-ture holding capacity of the soil or shallow root zone.

Vegetation in non-monitored zones will use water at arate proportional to water use in the monitored zone.Water application rates in these zones must thereforebe proportional for the entire system to remain prop-erly irrigated. If trees use 30% more water than turf,and turf is being monitored, then the tree zone needsto be irrigated for 30% more time than the monitoredturf to maintain adequate soil moisture.

Since dielectric probes (such as the EA-10) measurethe moisture in the immediate vicinity of the probe, itis essential that the probe be installed so that the entirelength of the probe is in intimate contact with the soil

EA-10 Soil Moisture Sensor Integrator’s Guide3. How the EA-10 Works

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(no air gaps). The soil must therefore be packed tightlyaround the entire probe length during installation. Theprobe is installed with the blade perpendicular to thesurface to interfere as little as possible with watermovement through the soil.

CalibrationThe probe reading is converted to volumetric watercontent using the following equation:

Volumetric Water Content = 0.0425 x Current - 0.342

Water content is in m3 m-3, and current is in milli-amps. For water content in terms of percent of totalvolume, use the following equation:

Volume percent = 4.25 x Current - 34.2.

These calibrations are for typical soils with mid rangetexture, and are accurate enough for most irrigationscheduling purposes. For greater accuracy, a soil spe-cific calibration should be undertaken, as outlined onthe Decagon website.

Functional TestingECH2O EA-10 sensors are tested to perform cor-rectly in the following conditions:Sensor output in air : 4.3 - 4.9 mASensor output in distilled water: 17.6 - 18.2 mA

EA-10 Soil Moisture Sensor Integrator’s GuideFurther Reading

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Further Reading

ECH2O Probes Soil-Specific Calibrationhttp://www.decagon.com/appnotes/echocal.pdf

ECH2O Dielectric Probes vs. Time DomainReflectometers (TDR)http://www.decagon.com/appnotes/echovstdr.pdf

ECH2O Probe insertion guidehttp://www.decagon.com/appnotesprobeinsert2.pdf

EA-10 Soil Moisture Sensor Integrator’s GuideIndex

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Index

Ccalibration 9contact information 2

Ee-mail address 2

F functional testing 9

I installation

electrical connection 5hardware requirements 6procedure 4

Sseller’s liability 2specifications 1

Ttroubleshooting 7

Wwarranty 2

Documents

10458-01 EA-10 manual · EA-10 Soil Moisture Sensor Integrator’s Guide 1. Introduction 1 1. Introduction Thank you for using the ECH 2O EA-10 Dielectric Soil Moisture sensor. The