Decagon Devices 5TE User manual

5TE
Water Content, EC
and Temperature Sensors
Operator’s Manual
Ve r s i o n 2

©2008 Decagon Devices, Inc.
All rights reserved.
Decagon Devices, Inc.
2365 NE Hopkins Court
Pullman WA 99163
www.decagon.com

5TE Operator’s Manual
Table of Contents
i
Contents
1. Introduction . . . . . . . . . . . . . . . . . .1
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . 2
Warranty Information . . . . . . . . . . . . . . . . . . . . . . . 3
Seller’s Liability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. About the 5TE . . . . . . . . . . . . . . . . 4
Background Info . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Theory . . . . . . . . . . . . . . . . . . . . . 6
Volumetric Water Content . . . . . . . . . . . . . . . . . . . 6
Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electrical Conductivity . . . . . . . . . . . . . . . . . . . . . . . 7
Converting Bulk EC to Pore EC . . . . . . . . . . . . . . 8
Pore Water vs. Solution EC . . . . . . . . . . . . . . . . . . . 9
4. Calibration . . . . . . . . . . . . . . . . . . 11
Dielectric Permittivity . . . . . . . . . . . . . . . . . . . . . . . . 11
Mineral Soil Calibration . . . . . . . . . . . . . . . . . . . . . 11
Calibration in Non-Soil Media . . . . . . . . . . . . . . . 12
5. Connecting Sensors . . . . . . . . . . .13
Using the 5TE with Em50/50R data loggers. . . . 13
3.5mm Stereo Plug Wiring . . . . . . . . . . . . . . . . . . . 14
Extending sensor cables . . . . . . . . . . . . . . . . . . . . . 14
Connecting to a non-Decagon Data logger . . . . . 15
Logger Communications . . . . . . . . . . . . . . . . . . . . . 16

5TE Operator’s Manual
Table of Contents
ii
Dielectric Permittivity . . . . . . . . . . . . . . . . . . . . . . . 17
Electrical Conductivity . . . . . . . . . . . . . . . . . . . . . . 17
Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6. Installing the Probes . . . . . . . . . .19
Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Removing the Probes . . . . . . . . . . . . . . . . . . . . . . . 21
Multiple Probe Installation . . . . . . . . . . . . . . . . . .22
7. Campbell Scientific Programs . . 23
8. Troubleshooting&Sensor Care . 24
Datalogger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Probes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Sensor Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Cleaning Method . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Declaration of Conformity . . . . . . 27

5TE Operator’s Manual
1. Introduction
1
1. Introduction
Thank you for choosing Decagon’s 5TE for measuring water
content, temperature, and EC. This manual is designed to help
you understand the probe’s features and how to use this
device successfully.
Specifications
Volumetric water content:
Range:
Apparent dielectric permittivity (εa): 1 (air) to 80 (water)
Resolution:
ε
a:0.1
ε
a(unitless) from 1-20, <0.75
ε
a(unitless) from 20-80
VWC: 0.0008 m3/m3(0.08% VWC) from 0 to 50% VWC
Accuracy:
( ε
a): ±1
ε
a(unitless) from 1-40 (soil range), ±15% from 40-80
(VWC):
• Using Topp equation: ±0.03 m3/m3(±3% VWC) typical
in mineral soils that have solution electrical conductivity <
10 dS/m
• Using medium specific calibration, ±0.01 - 0.02 m3/m3
(± 1-2% VWC) in any porous medium
Electrical Conductivity (bulk):
Range: 0-23 dS/m (bulk)
Resolution: 0.01 dS/m from 0 to 7 dS/m, 0.05 dS/m from 7
to 23 dS/m
Accuracy: ±10% from 0 to 7 dS/m, user calibration required
above 7 dS/m

5TE Operator’s Manual
1. Introduction
2
Temperature
Range: -40-50 °C
Resolution: 0.1 °C
Accuracy: ±1 °C
General
Dimensions: 10 cm (1) x 3.2 cm (w) x 0.7 cm (d)
Prong Length: 5.2 cm
Dielectric Measurement Frequency: 70 MHz
Measurement Time: 150 ms (milliseconds)
Power requirements: 3.6 - 15 VDC, 0.3 mA quiescent, 10
mA during 150 ms measurement
Output: RS232 or SDI 12 (contact Decagon for information
on SDI-12 mode)
Operating Temperature: -40-50 °C
Connector types: 3.5 mm “stereo” plug or stripped and
tinned lead wires
Cable Length: 5m standard; custom cable length available
upon request
Datalogger Compatibility (not exclusive):
Decagon: Em50, Em50R
Campbell Scientific: Any logger with serial I/O (CR10X,
CR850, 1000, 3000, etc.)
Contact Information
If you need to contact Decagon:
•Call us at 800-755-2751 or [phone]
•Fax us at [phone]
•E-mail us at [e-mail].

5TE Operator’s Manual
1. Introduction
3
Warranty Information
All Decagon products 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 deterio-
ration due to corrosion from any cause are not to be consid-
ered 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 equip-
ment 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 per-
sons (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 of said mate-
rial 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, represen-
tations, or warranties of any kind, express, implied, statutory
or otherwise (including, but without limitation, the implied
warranties of merchantability and fitness for a particular pur-
pose), not expressly set forth herein.

5TE Operator’s Manual
2. About the 5TE
4
2. About the 5TE
The 5TE is designed to measure the water content, electrical
conductivity, and temperature of soil and growing media.
Using an oscillator running at 70 MHz, it measures the dielec-
tric permittivity of soil to determine the water content. A ther-
mistor in thermal contact with the probe prongs provides the
soil temperature, while the screws on the surface of the sensor
form a two-probe electrical array to measure electrical con-
ductivity.
Background Info
In 2006, Decagon incorporated research from its EC-5 volu-
metric water content sensor into the ECH2O-TE, a sensor
which measured volumetric water content, temperature, and
electrical conductivity. The new 5TE uses the same theory as
the ECH2O-TE, but the location of the EC measurement is in
the stainless steel screws instead of gold traces. The use of
stainless steel screws has made the 5TE a more robust sensor.
Additionally, the 5TE utilizes a 5 point dielectric calibration to
provide dielectric permittivity measurements far more accu-
rate than the previous ECH2O-TE.

5TE Operator’s Manual
2. About the 5TE
5
Figure 1: 5TE Components

5TE Operator’s Manual
3. Theory
6
3. Theory
Volumetric Water Content
The 5TE probe uses an electromagnetic field to measure the
dielectric permittivity of the surrounding medium. The probe
supplies a 70 MHz oscillating wave to the probe prongs that
charges according to the dielectric of the material. The stored
charge is proportional to soil dielectric and soil volumetric
water content. The 5TE microprocessor measures the charge
and outputs a value of dielectric permittivity from the probe.
Temperature
The 5TE uses a surface-mounted thermistor to take tempera-
ture readings. It is located underneath the probe overmold,
next to one of the prongs, and will read the temperature of the
prong surface. The 5TE will output temperature in °C unless
otherwise stated in your preferences file in either the ECH2O
DataTrac or ECH2O Utility programs.
It is important to note that if the black plastic overmold of the
probe is in direct sunshine, the temperature measurement may
read high. Exposure of the overmold to solar radiation will
also drastically decrease the life expectancy of the sensor. We
do not recommend that the sensor be installed with the over-
mold in the sun.

5TE Operator’s Manual
3. Theory
7
Electrical Conductivity
Electrical conductivity (EC) is the ability of a substance to
conduct electricity and can be used to infer the amount of
polar molecules that are in solution. EC is measured by apply-
ing an alternating electrical current to two electrodes, and
measuring the resistance between them. Conductivity is then
derived by multiplying the inverse of the resistance (conduc-
tance) by the cell constant (the ratio of the distance between
the electrodes to their area).
The 5TE uses a 2-probe array to measure the EC. The array is
located on the screws of two of the 5TE prongs. Small
amounts of oil from skin contact with the screws will
cause significant inaccuracy in the EC measurement. See
the sensor cleaning section at the end of this manual for
instructions on cleaning the probes if contamination occurs.
The 5TE uses a two electrode array to measure the bulk EC of
the surrounding medium. The bulk EC measurement is cali-
brated at the factory to be accurate within ±10% from 0 to 7
dS/m. This range is adequate for most field, greenhouse and
nursery applications. However, some special applications in
salt affected soils may requires measurements with bulk EC
greater than the specified range. The 5TE will measure up to
23.1 dS/m bulk EC, but user calibration is required above 7
dS/m. Additionally, EC measurements above 7 dS/m are very
sensitive to contamination of the electrodes by skin oils, etc.
Be sure to read sensor cleaning section at the end of the man-
ual if you plan to measure the EC of salty soils.

5TE Operator’s Manual
3. Theory
8
Converting Bulk EC to Pore EC
For many applications, it is advantageous to know the electri-
cal conductivity of the solution contained in the soil pores
(σp), which is a good indicator of the solute concentration in
the soil. Traditionally, σphas been obtained by extracting pore
water from the soil and measuring σpdirectly. As one would
expect, this is a time consuming and labor intensive process.
The 5TE measures the electrical conductivity of the bulk soil
surrounding the probes (σb). A considerable amount of
research has been conducted to determine the relationship
between σband σp. Recent work by Hilhorst (2000), has taken
advantage of the linear relationship between the soil bulk
dielectric permittivity (εb) and σpto allow accurate conversion
from σbto σpif the εbis known. The 5TE measures εband
σbnearly simultaneously in the same soil volume. It is there-
fore well suited to this method.
The pore water conductivity can be determined from (see Hil-
horst, 2000 for derivation):
where σpis the pore water electrical conductivity (dS/m); εPis
the real portion of the dielectric permittivity of the soil pore
water (unitless); σbis the bulk electrical conductivity, (dS/m),
which is measured directly by the 5TE; εbis the real portion
of the dielectric permittivity of the bulk soil (unitless); is the
real portion of the dielectric permittivity of dry soil (unitless).
'
0σ
'
b
b
'
p
p
b
εε
σε
σ
=
−
=
(1)

5TE Operator’s Manual
3. Theory
9
ε
p can be calculated from soil temperature using:
ε
p= 80.3 - 0.37 * (Tsoil - 20) (2)
where Tsoil is the soil temperature (C) measured by the 5TE.
ε
b is also measured by the 5TE. Raw VWC counts can be con-
verted to bulk dielectric by the ECH2O-TE dielectric calibra-
tion:
Finally, ε
σb = 0 is an offset term loosely representing the
dielectric permittivity of the dry soil. Hilhorst (2000) recom-
mended that ε
σb= 4.1 be used as a generic offset. However,
our research in several agricultural soils, organic, and inorganic
growth media indicates that ε
σb = 6 results in more accurate
determinations of σp. Hilhorst (2000) offers a simple and easy
method for determining for individual soil types, which will
improve the accuracy of the calculation of σpin most cases.
Our testing indicates that the above method for calculating σp
results in good accuracy (± 20%) in moist soils and other
growth media. In dry soils where VWC is less than about 0.10
m3/m3, the denominator of equation 1 becomes very small,
leading to large potential errors. We recommend that σpnot
be calculated in soils with VWC < 0.10 m3/m3using this
method.
Pore Water vs. Solution EC
As noted in the previous section, pore water electrical conduc-
tivity can be calculated from bulk EC using the probe-mea-
50
Raw
b
ε
ε =(3)

5TE Operator’s Manual
3. Theory
10
sured dielectric permittivity of the medium. However, pore
water EC is not the same as solution EC. Pore water EC is the
electrical conductivity of the water in the pore space of the
soil. One could measure this directly if the soil was squeezed
under high pressure to force water out of the soil matrix and
that water was collected and tested for EC. Solution EC is the
electrical conductivity of pore water removed from a saturated
paste. In this case, the soil is wetted with distilled water until
the soil saturates, then the soil is placed on filter paper in a
vacuum funnel and suction is applied. An electrical conductiv-
ity measurement on the water removed from the sample will
give the solution electrical conductivity. Theoretically, the two
are related by the bulk density. An example calculation will
illustrate this relationship: A soil is at 0.1 m3/m3VWC, has a
pore water EC of 0.7 dS/m, and a bulk density of 1.5 Mg/m3.
We can calculate the solution EC as follows.
In this example, ø is the porosity, ρ
bis bulk density,
ρ
sis den-
sity of the minerals (assumed to be 2.65 Mg/m3), subscript d
is distilled water, and θ is volumetric water content. We
assume that the EC of the distilled water is 0 dS/m. In prac-
tice, solution EC calculated from this method and solution EC
taken from a laboratory soil test may not agree well because
wetting soil to a saturated paste is very imprecise.
() ()
dS/m162.0
0.43
01.07.0
ECSolution
43.0
65.2
5.1
11
=
+
=
−+
=
=−=−=
φ
θφσθσ
ρ
ρ
φ
dp
s
b

5TE Operator’s Manual
4. Calibration
11
4. Calibration
Dielectric Permittivity
Each 5TE sensor has been calibrated to measure dielectric
permittivity (εa) accurately in the range of 1 (air) to 80 (water).
The unprocessed raw values reported by the 5TE have units
of εa*50.
Mineral Soil Calibration
Numerous researchers have studied the relationship between
dielectric permittivity and volumetric water content (VWC) in
soil. As a result, the soil science literature is littered with vari-
ous transfer equations used to predict VWC from measured
dielectric permittivity. You are free to use any of these various
transfer equations to convert raw dielectric permittivity data
from the 5TE into VWC. In Decagon’s ProCheck reader and
DataTrac and ECH2O Utility software packages, if the mineral
soil calibration option is chosen, raw dielectric permittivity
values from are converted to VWC using the well known
Topp equation (Topp et al, 1980):
VWC=4.3X10-6 εa3- 5.5X10-4 εa2+2.92X10-2 εa- 5.3X10-2
Our tests have shown that a properly installed 5TE sensor
installed in a normal mineral soil with saturation extract elec-
trical conductivity <10 dS/m, the Topp equation will result in
measurements within ±3% VWC of the actual soil VWC. If
you require more accurate VWC than ±3% or are working in a

5TE Operator’s Manual
4. Calibration
12
soil with very high electrical conductivity, or non-normal min-
eralogy, then it may be necessary to conduct a soil specific cal-
ibration for your 5TE sensor which will improve the accuracy
to 1-2% for any soil. For more information on how to per-
form your own soil-specific calibration, or to have Decagon’s
calibration service perform one for you, visit us online at
http://www.decagon.com.
Calibration in Non-Soil Media
At the time of publication of this manual version, Decagon
has not conducted any studies to correlate the dielectric per-
mittivity of non -soil media to VWC. As with the former
ECH2O TE sensor, we plan to publish calibrations for com-
mon non-soil media such as potting soil, rockwool, perlite,
etc., but those investigations have not been performed yet.
Please check the Decagon website http://www.decagon.com
or contact Decagon for the status of this ongoing research.
The 5TE can accurately read VWC in virtually any porous
medium if a custom calibration is performed. For information
on how to perform your own medium-specific calibration, or
to have Decagon’s calibration service perform one for you,
visit http://www.decagon.com.
Reference
Topp, G.C., J.L. David, and A.P. Annan 1980. Electromag-
netic, Determination of Soil Water Content: Measurement
in Coaxial Transmission Lines. Water Resources Research
16:3. p. 574-582.

5TE Operator’s Manual
5. Connecting Sensors
13
5. Connecting Sensors
The 5TE sensor was designed to work most efficiently with
Decagon’s Em50, Em50R or our ProCheck handheld reader.
They can be adapted for use with other data loggers, such as
those from Campbell Scientific, Inc. for example. The 5TE
requires an excitation voltage in the range of 3-16V.
Using the 5TE with Em50/50R data
loggers.
The 5TE has been designed to work specifically with the
Em50 datalogger. To download data to your computer, you
will need to install ECH2O Utility, ECH2O DataTrac or a ter-
minal-port program on your computer.
The following software support the 5TE sensor:
ECH2O Utility 1.10 or greater
ECH2O Utility Mobile 1.17 or greater
ECH2O DataTrac 2.77 or greater
Please check your software version to ensure it will support
the 5TE. To update your software to the latest versions, please
visit Decagon’s software download site: http://www.deca-
gon.com/home/downloads.php
To use the 5TE with your Em50 data logger, simply plug the
stereo plug into one of the five ports on the data logger and
use either ECH2O Utility, ECH2O Utility Mobile, DataTrac

5TE Operator’s Manual
5. Connecting Sensors
14
Mobile, or DataTrac software (see respective manuals) to con-
figure that port for the 5TE and set the measurement interval.
3.5mm Stereo Plug Wiring
5TE sensors used with Decagon loggers come with a 3.5mm
“stereo plug” connector. The stereo plug allows for rapid con-
nection directly to Decagon’s Em50 and Em50R dataloggers
and to the hand-held ProCheck readers. Below is a diagram
showing the wiring configuration for this connector.
Extending Sensor Cables
Decagon supplies 10-foot (3m) and 50-foot (15.25m)
extension cables for use with the stereo plug type 5TE
sensors. You can safely connect up to four of the 50-foot
cables without signal attenuation. For field applications, it is
critical to seal the connections 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. On the Decagon website you can access a step by step
photo tutorial of how to seal the connection. To access this
file go to www.decagon.com/literature/app_notes and click
Digital
out
Ground
Excitation

5TE Operator’s Manual
5. Connecting Sensors
15
on the Wire Splicing and Sealing Technique for Soil Moisture
Sensors.
Connecting to a non-Decagon Data logger
5TE sensors for use with non-Decagon data loggers come
pre-configured with stripped and tinned lead wires at the cus-
tomer’s request. Below is a diagram showing the wiring con-
figuration for this connector.
5TE sensors with stripped and tinned cable option can be
made with custom cable lengths (up to 250ft) on a per-foot
fee basis. This option gets around the need for splicing wire (a
possible failure point).
Connect the wires to the data logger as shown, with the sup-
ply wire (white) connected to the excitation, the digital out
wire (red) to a digital input, the bare ground wire to ground as
seen below.
Digital out (Red)
Ground (Bare)
Excitation (White)
Sensor cable
Switched
3-15V DC
G
Supply Digital
out Ground
Datalogger
Digital
In

5TE Operator’s Manual
5. Connecting Sensors
16
NOTE: The acceptable range of excitation voltages is from 3-15 VDC.
If you wish to read the 5TE with the Campbell Scientific Data Loggers,
you will need to power the sensors off of the switched 12V port.
If your 5TE is equipped with the standard 3.5mm plug, and
you wish to connect it to a non-Decagon datalogger, 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 un-plugged; however,
it then cannot be easily used in the future with a Decagon
readout unit or datalogger. 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 datalogger (this
type of wire is often referred to as a “pigtail adapter”). Both
the stripped and tinned adapter cable wires have the same ter-
mination as seen above; the white wire is excitation, red is out-
put, and the bare wire is ground.
Logger Communications
When excitation voltage is applied, the 5TE makes a measur-
ment. Within about 50 ms of excitation three measurement
values are transmitted to the data logger as a serial stream of
ASCII characters. The serial out is 1200 baud asynchronous
with 8 data bits, no parity, and one stop bit. The voltage levels
are 0-3.6V and the logic levels are TTL (active low). The
power must be removed and reapplied for a new set of values
to be transmitted.
The ASCII stream contains 3 numbers separated by spaces.
The stream is terminated with the carriage return character.
The first number is raw dielectric output. The second number