5TE
Water Content, EC
and Temperature Sensors
Operator’s Manual
Ve rsio 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
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
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5TE Operator’s Manual
Table of Contents
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
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5TE Operator’s Manual
1. Introduction
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
: 0.1
ε
a
(unitless) from 1-20, <0.75
a
ε
(unitless) from 20-80
a
VWC: 0.0008 m3/m3 (0.08% VWC) from 0 to 50% VWC
Accuracy:
(
ε
): ±1
a
ε
(unitless) from 1-40 (soil range), ±15% from 40-80
a
(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 m
3/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
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5TE Operator’s Manual
1. Introduction
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 (509) 332-2756
• Fax us at (509) 332-5158
• E-mail us at support@decagon.com.
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5TE Operator’s Manual
1. Introduction
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 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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5TE Operator’s Manual
2. About the 5TE
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 dielectric permittivity of soil to determine the water content. A thermistor 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 conductivity.
Background Info
In 2006, Decagon incorporated research from its EC-5 volumetric 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 accurate than the previous ECH
O-TE.
2
4
5TE Operator’s Manual
2. About the 5TE
Figure 1: 5TE Components
5
5TE Operator’s Manual
3. Theory
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 temperature 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 overmold in the sun.
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5TE Operator’s Manual
3. Theory
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 applying an alternating electrical current to two electrodes, and
measuring the resistance between them. Conductivity is then
derived by multiplying the inverse of the resistance (conductance) 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 calibrated 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 manual if you plan to measure the EC of salty soils.
7
5TE Operator’s Manual
3. Theory
Converting Bulk EC to Pore EC
For many applications, it is advantageous to know the electrical conductivity of the solution contained in the soil pores
(σp), which is a good indicator of the solute concentration in
the soil. Traditionally, σp has been obtained by extracting pore
water from the soil and measuring σp directly. 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 σb and σp. Recent work by Hilhorst (2000), has taken
advantage of the linear relationship between the soil bulk
dielectric permittivity (εb) and σp to allow accurate conversion
from σb to σp if the εb is known. The 5TE measures εb and
σb nearly simultaneously in the same soil volume. It is there-
fore well suited to this method.
The pore water conductivity can be determined from (see Hilhorst, 2000 for derivation):
'
σε
b
p
σ
=
p
'
'
εε
−
=
b
0σ
b
(1)
where σp is the pore water electrical conductivity (dS/m); εP is
the real portion of the dielectric permittivity of the soil pore
water (unitless); σ
is the bulk electrical conductivity, (dS/m),
b
which is measured directly by the 5TE; εb is the real portion
of the dielectric permittivity of the bulk soil (unitless); is the
real portion of the dielectric permittivity of dry soil (unitless).
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5TE Operator’s Manual
ε
ε
can be calculated from soil temperature using:
p
ε
= 80.3 - 0.37 * (T
p
- 20) (2)
soil
3. Theory
where T
ε
is also measured by the 5TE. Raw VWC counts can be con-
b
is the soil temperature (C) measured by the 5TE.
soil
verted to bulk dielectric by the ECH2O-TE dielectric calibration:
ε
b
=
Raw
(3)
50
Finally,
ε
= 0 is an offset term loosely representing the
σb
dielectric permittivity of the dry soil. Hilhorst (2000) recommended that
ε
= 4.1 be used as a generic offset. However,
σb
our research in several agricultural soils, organic, and inorganic
growth media indicates that
ε
= 6 results in more accurate
σb
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 σp in most cases.
Our testing indicates that the above method for calculating σ
results in good accuracy (± 20%) in moist soils and other
growth media. In dry soils where VWC is less than about 0.10
3/m3
m
, the denominator of equation 1 becomes very small,
leading to large potential errors. We recommend that σ
be calculated in soils with VWC < 0.10 m3/m3 using this
method.
Pore Water vs. Solution EC
As noted in the previous section, pore water electrical conductivity can be calculated from bulk EC using the probe-mea-
p
not
p
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5TE Operator’s Manual
ρ
3. Theory
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 conductivity 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/m3 VWC, 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.
b
ρ
11
s
φ
=
In this example, ø is the porosity,
5.1
43.0
=−=−=
65.2
()
θφσθσ
φ
−+
dp
=
()
+
01.07.0
ECSolution
0.43
ρ
is bulk density,
b
=
dS/m 162.0
ρ
is den-
s
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 practice, 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.
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5TE Operator’s Manual
4. Calibration
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 various 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
3
ε
- 5.5X10-4 ε
a
2
+2.92X10-2 εa - 5.3X10
a
-2
-6
Our tests have shown that a properly installed 5TE sensor
installed in a normal mineral soil with saturation extract electrical 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
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5TE Operator’s Manual
4. Calibration
soil with very high electrical conductivity, or non-normal mineralogy, then it may be necessary to conduct a soil specific calibration for your 5TE sensor which will improve the accuracy
to 1-2% for any soil. For more information on how to perform 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 permittivity of non -soil media to VWC. As with the former
ECH2O TE sensor, we plan to publish calibrations for common 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.
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5TE Operator’s Manual
5. Connecting Sensors
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 terminal-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.decagon.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 ECH
O Utility, ECH2O Utility Mobile, DataTrac
2
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5TE Operator’s Manual
5. Connecting Sensors
Mobile, or DataTrac software (see respective manuals) to configure 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 connection 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.
Digital
out
Ground
Excitation
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
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5TE Operator’s Manual
5. Connecting Sensors
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 customer’s request. Below is a diagram showing the wiring configuration for this connector.
Digital out (Red)
Sensor cable
Ground (Bare)
Excitation (White)
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 supply 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
Supply
out
Ground
Switched
3-15V DC
G
Digital
In
Datalogger
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5TE Operator’s Manual
5. Connecting Sensors
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 datalogger. 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 termination as seen above; the white wire is excitation, red is output, and the bare wire is ground.
Logger Communications
When excitation voltage is applied, the 5TE makes a measurment. 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
16
5TE Operator’s Manual
σ
−
+
σ
5. Connecting Sensors
is raw electrical conductivity and the third number is raw temperature. The following explains how to convert the raw values into their standard units.
Dielectric Permittivity
The raw dielectric value (ε
), is valid in the range 0 to 4094.
Raw
This corresponds to dielectric permittivity values 0.00 to
81.88. The 5TE uses the ε
value of 4095 to indicate the
Raw
dielectric permittivity portion of the sensor is not working as
expected.
The ε
value is converted to dielectric permittivity with the
Raw
following equation:
ε
Raw
Dielectric Permittivity =
ε
-----------
=
a
50
Electrical Conductivity
The raw electrical conductivity value (σ
range 0 to 1022. The 5TE uses a compression algorithm to
extend the range of electrical conductivity that can be repre-
), is valid in the
Raw
sented by a 10-bit value. σ
cal conductivities using the following algorithms.
σ
If
If σ
< 700 then EC (dS/m)=
Raw
> 700 then EC (dS/m)=
Raw
can be converted to bulk electri-
Raw
Raw
100
Raw
100
17
)700(5700
5TE Operator’s Manual
5. Connecting Sensors
Electrical conductivities above 23.1 are truncated to this maximum value. The 5TE uses the σ
value of 1023 to indicate
Raw
the electrical conductivity portion of the sensor is not working
as expected.
Temperature
The raw temperature value, (T
1022. The 5TE uses a compression algorithm to extend the
range of temperatures that can be represented by a 10-bit
value. The sensor sends temperature with 1/10 of a degree
Celsius resolution for the range -40 to 50.0°C. For the range
50.5 to 111.0 the sensor sends temperature with a 1/2 of a
degree resolution. Temperatures outside this range are truncated to the maximum or minimum values as appropriate.
The 5TE uses the T
value of 1023 to indicate the tempera-
Raw
ture portion of the sensor is not working as expected.
), is valid in the range 0 to
Raw
If T
If T
< 900 then T
Raw
> 900 then T
Raw
Temperature(°C)=
= T
Raw2
= 900 +5 (T
Raw2
T
Raw2
-------------------------------
Raw
400∠
10
- 900)
Raw
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5TE Operator’s Manual
6. Installing the Probes
6. Installing the Probes
NOTE 1: Make sure the screw electrodes on the 5TE are clean before
installing the sensors. See the sensor cleaning section at the end of the
manual.
NOTE 2: Decagon advises that you test the sensors with your data logging device and software before going to the field.
Before you select a site for installation, remember that the soil
next to the probe surface has the strongest influence on its
readings. It is important to avoid air gaps or extremely compact soil around the probe, which can skew readings. Do not
install the 5TE next to large metal objects, which can attenuate
the probes’ electromagnetic field and distort output readings.
Because the probes have gaps between their prongs, it is also
important to consider the size of the media you are inserting
the probe into. It is possible to get sticks, bark, roots or other
material stuck between the probe prongs, which will adversely
affect readings. Finally, be careful when inserting the probes
into dense soil, as the prongs can break if excessive force is
used when pushing them in.
Procedure
The 5TE can be inserted directly into growing media or soil.
The tip of each prong has been sharpened to make it easier to
push the probe in. Be careful around the sharpened tips! The probe
needs to be completely covered by soil, as shown in Figure 2.
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5TE Operator’s Manual
6. Installing the Probes
Figure 2: 5TE installed correctly
The probes may be difficult to insert into extremely compact
or dry soil. If you have difficulty inserting the probe, try loosening the soil somewhat or wetting the soil. Never pound the
probe in.
Method 1. : Horizontal Installation
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 5TE is inserted.
The tip of each prong has been sharpened to make it easier to
20
5TE Operator’s Manual
6. Installing the Probes
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 5TE.
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 or the sensor cable
in the process.
Orientation
The 5TE can be oriented in any direction. Because the probes
have prongs instead of a blade (like the EC-10 and EC-20), the
probe can be placed in any orientation that meets your
requirements.
Removing the Probes
When removing the 5TE probe, do not pull it by the cable!
This could break the internal wires and cause the probe to
malfunction or not function at all.
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5TE Operator’s Manual
6. Installing the Probes
Multiple Probe Installation
‘The 5TE sensor makes eletrical conductivity (EC) measurements by exciting one screw on the sensor and measuring the
current that moves from that screw to the adjacent screw that
is grounded. The distance between the screws is an important
part of the EC calculation. If 5TE sensors are placed close
together (within 20cm), it is possible for some of the current
that leaves the excited screw to pass through the nearby sensor’s ground screw, thus producing an erroneous sensor reading.
This problem occurs regardless of what logging system you
are using if the ground wires are connected at all times. If you
must have your sensors close together, (i.e. column experiments, etc) consider a multiplexing option that would isolate
the ground wires.
If you are installing sensors vertically at short depth intervals,
do not bury them directly over the top of each other.
Although at times the vertical distance may be less than 20cm,
the sensors can be staggered horizontally so they are not
directly above each other, thus meeting the distance requirement.
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5TE Operator’s Manual
7. Campbell Scientific Programs
7. Campbell Scientific Programs
Because the probes use digital rather than analog communication, they require special considerations when connecting to a
Campbell Scientific datalogger. The following application
notes containing Campbell Scientific sample programs are
available for the 5TE:
• Using the 5TE with Campbell Scientific CR10X Data
logger
• Using the 5TE with Campbell Scientific CR1000
• Multiplexing the 5TE using the AM16/32
To access these Campbell Scientific Programs, please visit
http://www.decagon.com/home/downloads.php
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5TE Operator’s Manual
8. Troubleshooting&Sensor Care
8. Troubleshooting&Sensor Care
If you encounter problems with the 5TE sensor, they most
likely will manifest themselves in the form of incorrect or
erroneous readings. Before contacting Decagon about the
sensor, do the following:
Datalogger
1. Check to make sure the connections to the data logger are
both correct and secure.
2. Ensure that your data logger's batteries are not dead or
weakened.
3. Check the configuration of your data logger in ECH2O
Utility or ECH2O DataTrac to make sure you have
selected 5TE.
Probes
1. Ensure that your probes are installed according to the
“Installation” section of this manual.
2. Check probe cables for nicks or cuts that could cause a
malfunction.
3. Check your electrical conductivity sensor screws to ensure
that they are not damaged or contaminated.
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5TE Operator’s Manual
8. Troubleshooting&Sensor Care
Sensor Cleaning
The EC measurement is very sensitive to the presence of nonconducting contamination on the screws, especially at high
EC. The most common source of contamination is skin oil
from handling the screws traces with bare hands. Figure 3a
and 3b show the simplified electrical circuit resulting from a
finger print on the screw in a low EC soil and high EC soil,
respectively. It is apparent that in a low EC soil, the effects of
contamination are relatively small, because the resistance in
the soil dominates the total resistance. However, in a high EC
soil, the effects of contamination become very large. This
demonstrates the need to keep the screws clean, especially
when the probe is to be used in high EC soil. Contamination
of the screws during handling and shipping prevent the factory calibration from being valid past 8 dS/m, although the
probes will measure accurately at much higher EC with proper
cleaning and calibration by the user.
Figure 3a: Simplified circuit of con-
Figure 3b: Simplified circuit of
taminated probe in low EC (high
resistance) soil. R
fingerprint causes 1% error.
=101Ω,
total
contaminated probe in high EC
(low resistance) soil. R
fingerprint causes 25% error
25
total
=5Ω,
5TE Operator’s Manual
8. Troubleshooting&Sensor Care
Cleaning Method
1. Wash the screws thoroughly with a drop of Dawn or other
grease cutting dish soap and warm water. Be sure that the
soap doesn’t contain skin conditioners or moisturizers.
2. Rinse the probe and screws thoroughly with tap water to
remove all remnants of soap.
3. Dry the screws with a clean paper towel. Use a scrubbing
motion to dry the screws to be sure any particles have
been detached. Be sure that the paper towel does not have
any skin conditioners or moisturizers in it, as this will
undo all of the cleaning that you have just accomplished.
Be sure not to touch the screws with an un-gloved hand or to
contact them with any source of oil or other non-conducting
residue.
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5TE Operator’s Manual
Declaration of Conformity
Declaration of Conformity
Application of Council Directive:89/336/EE6
Standards to Which Conformity EN61326 : 1998
is Declared: EN51022 : 1998
Manufacturer’s Name: Decagon Devices, Inc.
2365 NE Hopkins Court
Pullman, WA 99163 USA
Type of Equipment: Dielectric soil
moisture probe
Model Number: ECH2O-TE/ECH2O EC-TM 5TE
Year of F ir st Man uf act ur e: 2005
This is to certify that the ECH2O-TE, ECH2O EC-TM and
5TE dielectric soil moisture probes, 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.
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5TE Operator’s Manual
Index
B
Bulk EC 8
C
Campbell Scientific Data Logger 15
Campbell Scientific Programs 23
Cleaning
probe
26
Index
screws
Contact Information 2
Converting bulk EC to pore EC 8
CSI loggers
using 5TE probes with
26
23
D
Declaration of Conformity 27
Dielectric Permittivity 11, 17
E
ECH2O Utility 1.10 13
Electrical Conductivity 7
Extension Cables 14
H
Horizontal Installation 20
How the TE works
electrical conductivity
7
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5TE Operator’s Manual
Index
temperature
volumetric water content
6
6
I
Installation
orientation
removing the probe
21
21
L
Logger Communication 16
M
Mineral Soil Calibration 11
P
Pore Water EC 8
Power Requirements 2
R
Raw Values 17
S
Screws 7
Seller’s Liability 3
Sensor Accuracy 1
Sensor Cleaning 25
Sensor Components 5
Sensor Installation 19
Sensor Range 1
Sensor Resolution 1
Solution EC 9
29
Specifications 1
T
Temperature 6, 18
Troubleshooting 24
V
Vertical Installation 21
Volumetric Water content 6
W
Warranty Information 3
5TE Operator’s Manual
Index
30
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