Decagon Devices 10HS Manuale utente

Decagon Devices, Inc.

Version: July 7, 2016 — 14:04:38

10HS

Decagon Devices, Inc.

2365 NE Hopkins Court

Pullman WA 99163

Phone: 509-332-5600

Fax: 509-332-5158

Website: www.decagon.com

Email: supp[email protected] or [email protected]

Trademarks

2007-2013 Decagon Devices, Inc.

10HS CONTENTS

Contents

1 Introduction 1

1.1 Warranty ......................... 1

1.2 Seller’s Liability . . . . . . . . . . . . . . . . . . . . . . 2

2 About the 10HS 3

2.1 BackgroundInfo ..................... 3

2.2 Speciﬁcations ....................... 4

3 Theory 5

4 Installing the Sensor 6

4.1 Procedure......................... 6

5 Connecting Sensors 9

5.1 Wiring........................... 9

6 Calibration 12

6.1 Dielectric calibration . . . . . . . . . . . . . . . . . . . 12

6.2 Mineral Soil Calibration . . . . . . . . . . . . . . . . . 12

7 Sample Programs 14

8 Declaration of Conformity 17

iii

10HS 1 INTRODUCTION

1 Introduction

Thank you for choosing the 10HS soil water content sensor. This

innovative sensor enables you to monitor volumetric water content

of soil accurately and aﬀordably. This manual helps you understand

the sensors features and how to use this device successfully.

There are several ways to contact Decagon if you ever need assis-

tance with your product, have any questions, or feedback. Decagon

has Customer Service Representatives available to speak with you

Monday through Friday, between 8am and 5pm Paciﬁc time.

Note: If you purchased your sensor through a distributor, please con-

tact them for assistance.

Email:

supp[email protected] or [email protected]

Phone:

509-332-5600

Fax:

509-332-5158

If contacting us by email or fax, please include as part of your mes-

sage your instrument serial number, your name, address, phone, fax

number, and a description of your problem or question.

Please read these instructions before operating your sensor to en-

sure that it performs to its full potential.

1.1 Warranty

The sensor has a 30-day satisfaction guarantee and a one-year war-

ranty on parts and labor. Your warranty automatically validates

upon receipt of the instrument.

1 INTRODUCTION 10HS

1.2 Seller’s Liability

Seller warrants new equipment of its own manufacture against de-

fective workmanship and materials for a period of one year from the

date of receipt of equipment.

Note: We do not consider the results of ordinary wear and tear,

neglect, misuse, accident as defects.

The Seller’s liability for defective parts shall in no event exceed the

furnishing of replacement parts “freight on board” 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 instal-

lation, 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 con-

stitutes 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 with-

out limitation, the implied warranties of merchantability and ﬁtness

for a particular purpose), not expressly set forth herein.

10HS 2 ABOUT THE 10HS

2 About the 10HS

The 10HS measures the dielectric constant of the soil in order to ﬁnd

its volumetric water content (VWC). 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 volumetric water content.

The 10HS has a low power requirement and very high resolution.

This gives you the ability to make as many measurements as you

want (i.e hourly) over a long period of time with minimal battery

usage.

2.1 Background Info

In 2005, the Decagon research team optimized a sensor oscillator fre-

quency for very high accuracy soil moisture measurements. The ﬁrst

sensor to incorporate the new frequency was our EC-5 sensor. The

EC-5 quickly became Decagon’s most popular soil moisture sensor.

The new 10HS sensor uses the same 70 MHz oscillator frequency

as the EC-5, but has a larger soil volume and requires no special

calibration when you use it with other systems. The 10HS has two

features that distinguish it from the EC-5.

•The on board voltage regulator allows you to power the sensor

with a wide range of excitation voltages (3 to 15 VDC) without

changing the calibration.

•Large sensing area (1,100 cubic centimeters) that provides a

more representative measurement of soil VWC.

The 10HS sensor runs at the same oscillator frequency that has given

the EC-5 exceptional performance in soils (Kizito et.al, 2008, Bogena

et. al, 2007). We recommend the 10HS sensor for mineral soil appli-

cations where soil heterogeneity is a concern. However, we continue

to recommend the smaller EC-5 sensor for soilless substrate appli-

cations or applications where VWC measurements on smaller scales

(e.g. near surface measurements, laboratory column studies, green-

house applications) are desired.

2 ABOUT THE 10HS 10HS

2.2 Speciﬁcations

Range:

Apparent Dielectric Permittivity (εa): 1 (air) to 50

Soil Volumetric Water Content (V W C): 0 to 0.57 m3/m3

(0 to 57%VWC)

Accuracy:

εa:±0.5 from εaof 10 to 50 (VWC)

VWC: With standard calibration equation, ±0.03 m3/m3(±

3% VWC) typical in mineral soils that have solution electrical

conductivity <10 dS/m

Note: With soil speciﬁc calibration, ±0.02 m3/m3(±2%

VWC) is typical in any soil.

Resolution:

εa: 0.1 from εaof 1 to 30, 0.2 from εaof 30 to 50

VWC: 0.0008 m3/m30.08% VWC) in mineral soils from 0 to

0.50 m3/m3(0 to 50% VWC)

Measurement Time: 10 ms (milliseconds)

Power Requirements: 3 VDC @ 12 mA to 15 VDC @ 15 mA

Output: 300 to 1,250 mV, independent of excitation voltage

Operating Temperature: 0 to 50 ◦C

Survival Temperature: -40 to 50 ◦C

Connector types: 3.5 mm stereo plug or stripped and tinned leads.

Cable length: 5 m standard; custom cable lengths up to 40 m avail-

able upon request

Data Logger Compatibility (non-exclusive):

•Decagon: Em50, Em50R, Em5b, ProCheck handheld reader.

•Campbell Scientiﬁc: CR10X, 21X, 23X, CR850, 1000,

3000, etc

•Other: Data acquisition systems capable of switched 3 to

15 V excitation and single ended voltage measurement at

≥12 bit resolution

10HS 3 THEORY

3 Theory

The 10HS sensor measures the volumetric water content of the soil

using a capacitance technique. Rapidly charging and discharging

a positive and ground electrode (capacitor) in the soil generates an

electromagnetic ﬁeld whose charge time tis related to the capacitance

t=RC ln V−Vf

Vi−Vf(1)

where Ris the series resistance, Vis voltage at time t, Viis the

starting voltage and Vfis the applied or supply voltage. Further,

for a capacitor with a geometrical factor of F, the capacitance is

related to the dielectric permittivity (ε) of the medium between the

capacitor electrodes by

C=ε0εF (2)

where ε0is the permittivity of free space. Thus, the εof the soil can

be determined by measuring the change time tof a sensor buried in

the soil. Consequently, as water has a dielectric permittivity that is

much greater than soil minerals or air, the charge time tin the soil

of Equation 1 can be correlated with soil volumetric water content.

4 INSTALLING THE SENSOR 10HS

4 Installing the Sensor

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 of the soil. Therefore any air gaps or excessive soil

compaction around the sensor and in between the sensor prongs can

profoundly inﬂuence the readings.

•If you are installing sensors in a lightning prone area with

a grounded data logger, please see our Application Note at

www.decagon.com/lightning.

•Decagon advises that you test the sensors with your data log-

ging device and software before going to the ﬁeld.

Also, do not install the sensor adjacent to large metal objects such

as metal poles or stakes. This can attenuate the senors electromag-

netic ﬁeld and adversely aﬀect readings. In addition, the 10HS sensor

should not be installed within 5 cm of the soil surface, or the sensing

volume of the electromagnetic ﬁeld can extend out of the soil and

reduce accuracy.

Because the 10HS has gaps between its prongs, it is also impor-

tant to consider the particle size of the medium 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 can break if excessive sideways force is used when pushing

them in.

4.1 Procedure

When installing the 10HS it is imperative to maximize contact be-

tween the sensor and soil. For most accurate results, the sensor

should be inserted into undisturbed soil. There are two basic meth-

ods to accomplish a high quality installation.

Method 1. Horizontal Installation

10HS 4 INSTALLING THE SENSOR

Excavate a hole or trench a few centimeters deeper than the depth

at which the sensor is to be installed. At the installation depth,

shave oﬀ some soil from the vertical soil face exposing undisturbed

soil. Insert the sensor into the undisturbed soil face until the entire

sensing portion of the 10HS is inserted. The tip of each prong has

been sharpened to make it easier to push the sensor in - be careful

with the sharp tips! Backﬁll the trench taking care to pack the soil

back to natural bulk density around the black plastic portion of the

10HS.

Method 2. Vertical Installation

Auger a 4 inch hole to the depth at which the sensor is to be in-

stalled. Insert the sensor into the undisturbed soil at the bottom

of the auger hole using your hand or any other implement that will

guide the sensor into the soil at the bottom of the hole. Many peo-

ple have used a simple piece of PVC pipe with a notch cut in the

end for the sensor to sit in, with the sensor cable routed inside the

pipe. After inserting the sensor, remove the installation device and

backﬁll the hole taking care to pack the soil back to natural bulk

density while not damaging the black plastic portion of the sensor of

the sensor cable in the process.

With either of these methods, the sensor may still be diﬃcult to

insert into extremely compact or dry soil.

Note: Never pound the sensor into the soil! If you have diﬃculty

inserting the sensor, you may need to wet the soil.

This will obviously result in inaccurate VWC measurements until

the water added during installing redistributes into the surrounding

soil.

Orientation

The sensor can be oriented in any direction. However, orienting

the ﬂat side perpendicular to the surface of the soil will minimize

Indice

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