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: support@decagon.com or sales@decagon.com
Trademarks
c
2007-2013 Decagon Devices, Inc.
All Rights Reserved
ii
10HS CONTENTS
Contents
1 Introduction 1
1.1 Warranty . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Seller’s Liability . . . . . . . . . . . . . . . . . . . . . . 2
2 About the 10HS 3
2.1 Background Info . . . . . . . . . . . . . . . . . . . . . 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 assistance 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 contact them for assistance.
Email:
support@decagon.com or sales@decagon.com
Phone:
509-332-5600
Fax:
509-332-5158
If contacting us by email or fax, please include as part of your message 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 ensure that it performs to its full potential.
1.1 Warranty
The sensor has a 30-day satisfaction guarantee and a one-year warranty on parts and labor. Your warranty automatically validates
upon receipt of the instrument.
1
1 INTRODUCTION 10HS
1.2 Seller’s Liability
Seller warrants new equipment of its own manufacture against defective 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 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.
2
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 frequency 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 applications where soil heterogeneity is a concern. However, we continue
to recommend the smaller EC-5 sensor for soilless substrate applications or applications where VWC measurements on smaller scales
(e.g. near surface measurements, laboratory column studies, greenhouse applications) are desired.
3
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/m
3
(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
4
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 t is related to the capacitance
(C) of the soil by Equation 1.
t = RC ln
V − V
f
Vi− V
f
(1)
where R is the series resistance, V is 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 ε of the soil can
be determined by measuring the change time t of 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 t in the soil
of Equation 1 can be correlated with soil volumetric water content.
5
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 logging 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 electromagnetic 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 important 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 between the sensor and soil. For most accurate results, the sensor
should be inserted into undisturbed soil. There are two basic methods to accomplish a high quality installation.
Method 1. Horizontal Installation
6
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 installed. 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 people 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
7
4 INSTALLING THE SENSOR 10HS
effects on downward water movement. Keep in mind that the sensor
measures the average VWC along its length, so a vertical installation
will integrate VWC over a 10 cm depth wile a horizontal orientation
will measure VWC at a more discrete depth.
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 internal connections and make the
sensor unusable.
8
10HS 5 CONNECTING SENSORS
5 Connecting Sensors
Decagon designed the 10HS sensor for use with our Em50 series data
loggers, the Em5b, or the ProCheck handheld reader. The standard
sensor (with a 3.5 mm “stereo plug” connector) quickly connects to
and is easily configured within a Decagon logger or ProCheck.
The 10HS sensor incorporates several features that also make it an
excellent sensor for use with third party loggers. Customers may
purchase the sensor with stripped and tinned wires (pigtail) for terminal connections.
The 10HS sensor comes standard with a five meter cable. Customers
may purchase sensors with custom cable lengths for an additional
fee (on a per-meter fee basis). Obtaining custom length cables eliminates the need for splicing the cable (a possible failure point). The
10HS is accurate with cable lengthes up to 40 m.
Connecting to an Em50/Em50R Logger
The 10HS to works well with the Em50 data logger. Simply plug
the 3.5 mm stereo plug connector directly into one of the five sensor
ports. Next, configure the logger port for the 10HS and set the measurement interval.
Connecting to ECH2O Utility
Please check your software version to ensure it will support the 10HS.
To update your software to the latest version, please visit Decagon’s
software download site at www.decagon.com/support/downloads.
Note: You must use the ECH2O Utility, DataTrac 3 or a terminal program on your computer to download data from the logger to
your computer.
5.1 Wiring
3.5 mm Stereo Plug Wiring
9
5 CONNECTING SENSORS 10HS
Figure 1: Stereo Connector
The following software support the 10HS sensor:
• ECH2O Utility 1.12 or greater
• ECH2O DataTrac 2.77 or greater
Connecting to a non-Decagon Logger
Customers may purchase 10HS sensors for use with non-Decagon
data loggers. These sensors typically come configured with stripped
and tinned (pigtail) lead wires for use with screw terminals. Refer
to your distinct logger manual for details on wiring.
Pigtail End Wiring
Figure 2: Pigtail End Wiring
Connect the wires to the data logger as Figure 2 shows, with the
supply wire (white) connected to the excitation, the analog out wire
(red) to a analog input, the bare ground wire to ground as illustrated
below.
10
10HS 5 CONNECTING SENSORS
Figure 3: Pigtail End Wiring to Data Logger
Note: The acceptable range of excitation voltages is from 3 to 15
VDC. If you wish to read your Decagon sensor with the Campbell
Scientific Data Loggers, you will need to power the sensors off of the
switched 12 V port.
If your 10HS is equipped with the standard 3.5 mm plug and you
want to connect it to a non-Decagon data logger, you have two options. First, you can clip off the plug on the sensor cable, strip and
tin the wires, and wire it directly into the data logger. This has
the advantage of creating a direct connection with no chance of the
sensor becoming unplugged; however, it cannot be easily used in the
future with a Decagon readout unit or data logger.
The other option is to obtain an adapter cable from Decagon. The
3-wire sensor adapter cable has a connector for the sensor jack on
one end, and three wires on the other end for connection to a data
logger (this type of wire is often referred to as a “pigtail adapter”).
Both the stripped and tinned adapter cable wires have the same termination as seen above; the white wire is excitation, red is output,
and the bare wire is ground.
11
6 CALIBRATION 10HS
6 Calibration
6.1 Dielectric calibration
The 10HS comes pre-calibrated to measure the dielectric permittivity
of the soil with the accuracy stated in the specification section above.
With Decagon’s Em50, Em50R, Em5B, and Pro Check readers, the
following standard calibration function can be applied
εa= 7.449 x 10
−11
∗ raw counts4− 1.969 x 10−7∗ raw counts3+
1.890 x 10−4∗ raw counts2− 6.691 x 10−2∗ raw counts + 7.457
(3)
With non-Decagon data acquisition equipment, the following calibration can be applied. Note the this calibration function is valid for
any sensor excitation between 3 and 15 V DC.
εa= 2.589 x 10
−10
∗ mV4x − 5.010 x 10−7∗ mV3+
3.523 x 10−4∗ mV2− 9.135 x 10−2∗ mV + 7.457 (4)
6.2 Mineral Soil Calibration
For convenience, Decagon has also developed a standard calibration
equation for mineral soils to be used with the 10HS. With this standard calibration equation and careful sensor installation, accuracy of
better than ±3% VWC (0.03 m3/m3) is possible with most mineral
soils. In these soils , it is generally not necessary to calibrate the
10HS for your particular soil type, and the standard mineral calibration below can be used. Em50, Em50R, Em5B and ProCheck:
V W C(m3/m3) = 1.17 x 10−9∗ raw counts3−
3.95 x 10−6∗ raw counts2+ 4.90 x 10−3∗ raw counts − 1.9 (5)
With non-Decagon data acqusition equipment, the following calibration can be applied. Note that this calibration function is valid for
12
10HS 6 CALIBRATION
any sensor excitation between 3 and 15 V DC.
V W C(m3/m3) = 2.97x10−9∗ mV3− 7.37 x 10
−6
∗ mV2+ 6.69 x 10−3∗ mV − 1.92 (6)
Due to the complexity of soils, the accuracy of the VWC measurement can be poor despite an accurate measurement for dielectric
permittivity. Some examples of this are highly compacted soils, very
low bulk density soils, soils with abnormally high organic matter content, and soils with high-dielectric mineral composition (e.g. TiO2
sands). Additionally, the accuracy of the 10HS may suffer in soils
with very high electrical conductivity (> 10 dS/m solution EC). In
these soils, it may be necessary to calibrate the 10HS to your specific
soil type. With a soil-specific calibration, the accuracy of the VWC
measurements will be improved to 1 to 2% in any soil or other porous
medium.
If you are interested in a soil-specific calibration for your 10HS,
there are two options available. You can create your own sensor
calibration by following the directions in our application note titled
Calibrating ECH2O soil moisture probes from the Decagon website
(http://www.decagon.com) and following the step-by-step instructions for calibrating your soil moisture sensors. Since some users do
not have the time or equipment to conduct their own calibration,
Decagon now offers a service providing soil specific calibrations to
our customers.
This calibration service also applies to non-soil materials, such as
compost, potting materials, etc. Contact Decagon for more information on this service (sales@decagon.com).
13
7 SAMPLE PROGRAMS 10HS
7 Sample Programs
You can use the following examples with data loggers from Campbell
Scientific. The first program is for a CR1000 data logger, but can
be easily adapted for other “CRBasic” type loggers. The second
program is for a CR10X data logger, but can be easily adapted to
other Edlog type loggers. The 10HS needs 3 to 15 V DC excitation,
and therefore cannot be excited with the 2.5 V excitation port of
many Campbell Scientific data loggers. We recommend that the
switched 12 V or CAO port be used to excite the 10HS.
Cr Basic type data logger
"CR1000 Series Datalogger
’program to read one Decagon 10HS sensor
’
’wiring
’white - SW - 12
’red - SE CH1
’bare - gnd
Public tenHSmV, VWC
DataTable (Table1,1,-1)
DataInterval (0,60,Min,10)
Average (1,VWC,FP2,False)
BeginProg
Scan(10,Sec,0,0)
SW12(1)
Delay (0,10,mSec)
VoltSe (tenHSmV,1,mV2500,1,1,0,_60Hz,1.0,0)
SW12 (0)
VWC = $2.97e-9 * tenHSmV^3 - 7.37e-6 *
tenHSmV^2 + 6.69e-3 * tenHSmV - 1.92 ’mineral soil calibration updated 8/09
CallTable Table1
NextScan
EndProg
14
10HS 7 SAMPLE PROGRAMS
Edlog type data logger
;{CR10X}
;
;program to read 10HS sensor with CR10X
;
;wiring:
;Jumper from C1 to SW 12V CTRL - C1 is used to turn on the
switched 12V port
;10HS white - excitation - SW 12V
;10HS red - Vout - SE CH1
;10HS bare - gnd - G or AG
*Table 1 Program
01:10 Execution Interval (seconds)
;set C1 high to pull SW 12 port high
;
1: Do (P86)
1: 41 Set Port 1 High
;delay program 10 ms and measure SE channel 1 in units of
volts
;
\: 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: 0000 mV Excitation
7:1 Loc [ ten_HS_V ]
8:.001 Multiplier
9:0.0 Offset
;turn off excitation
;
3: Do (P86)
15
7 SAMPLE PROGRAMS 10HS
1: 51 Set Port 1 Low
;apply calibration (updated 8/09)
;
4: Polynomial (P55)
1: 1 Reps
2: 1 X Loc [ ten_HS_V ]
3: 2 F(X) Loc [ VWC ]
4: -1.92 C0
5: 6.69 C1
6: -7.37 C2
7: 2.97 C3
8: 0.0 C4
9: 0.0 C5
5: If time is (P92)
1: 0000 Minutes (Seconds --) into a
2: 60 Interval (same units as above)
3: 10 Set Output Flag High (Flag 0)
6: Real Time (P77)^18390
1: 1110 Year,Day,Hour/Minute (midnight = 0000)
7: Average (P71)^12836
1:1 Reps
2:2 Loc [ VWC ]
*Table 2 Program
02: 0.0000 Execution Interval (seconds)
*Table 3 Subroutines
End Program
16
10HS 8 DECLARATION OF CONFORMITY
8 Declaration of Conformity
Application of Council Directive: 2004/108/EC and 2011/65/EU
Standards to which conformity is
declared:
EN 61326-1:2013 and
EN 50581:2012
Manufacturer’s Name: Decagon Devices, Inc 2365 NE
Hopkins Ct. Pullman, WA 99163
USA
Type of Equipment: Dielectric Soil Moisture Sensor
Model Number: 10HS
Year of First Manufacture: 2008
This is to certify that the 10HS dielectric soil moisture sensor, manufactured by Decagon Devices, Inc., a corporation based in Pullman,
Washington, USA meet or exceed the standards for CE compliance
as per the Council Directives noted above. All instruments are built
at the factory at Decagon and pertinent testing documentation is
freely available for verification.
17
Index
Accuracy, 4
Background, 3
Cable length, 4
Calibration, 12
Dielectric, 12
Service, 12
Campbell Scientific, 14
Capacitance Technique, 5
Connecting
ECH2O Utility, 9
Em50 Series Data Logger, 9
Connection
Alternative Methods, 10
Connector Types, 4
Contact Information, 1
Customer Support, 1
Data Logger
Cambell Scientific, 4
Communications, 11
Compatibility, 4
Decagon, 4
Non-Decagon, 10
Other, 4
Dielectric Permittivity, 12
ECH2O Utility, 10, 14
Email, 1
Installation
Horizontal, 6
Vertical, 7
Measurement Time, 4
Mineral soil calibration, 12
Operating Temperature, 4
Orientation, 7
Output, 4
Particle Size, 6
Power Requirements, 4
Programs, 14
Range, 4
Removing the sensor, 8
Resolution, 4
Sample Programs, 14
Seller’s Liability, 2
Specifications, 4
Survival Temperature, 4
Theory, 5
Warranty, 1
Wiring
Pigtail, 10
Stereo Plug, 9
18
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