Soil Moisture Smart Sensor (S-SMx-M005) Manual
C
Soil moisture smart sensors are used for measuring soil water content and are designed to
work with smart sensor-compatible HOBO® stations. They combine the innovative ECH2O®
Dielectric Aquameter probe from Decagon Devices, Inc. with Onset’s smart sensor technology.
All sensor conversion parameters are stored inside the smart sensor adapter so data is provided
directly in soil moisture units without any programming or extensive user setup.
Specifications
S-SMC-M005
Measurement Range In soil: 0 to 0.550 m³/m³ (volumetric water content)
Extended Range -0.401 to 2.574 m³/m³; see Note 1
Accuracy ±0.031 m³/m³ (±3.1%) typical 0 to 50°C (32° to 122°F) for mineral soils
Resolution 0.0007 m³/m³ (0.07%)
Volume of Influence 0.3 liters (10.14 oz)
Soil Moisture
Smart Sensor
Models: S-SMC-M005
S-SMD-M005
Sensor Frequency 70 MHz
Soil Probe Dimensions 89 x 15 x 1.5 mm (3.5 x 0.62 x 0.06 in.)
Weight 180 grams (6.3 oz)
Decagon ECH2O Probe Part No. EC-5
Sensor Operating Temperature 0° to 50°C (32° to 122°F). Although the sensor probe and cable can
Item included:
• Protective cap
Bits per Sample 12
Number of Data Channels* 1
Measurement Averaging Option No
able Length Available 5 m (16 ft)
Length of Smart Sensor
Network Cable*
* A single HOBO station can accommodate 15 data channels and up to 100 m (328 ft) of smart sensor cable (the digital
communications portion of the sensor cables).
Note 1: The sensor is capable of providing readings outside the standard volumetric water content range. This is
helpful in diagnosing sensor operation and installation. See the Operation section for more details.
Note 2: This is a system level accuracy specification and is comprised of the probe’s accuracy of ±0.03 m³/m³ typical
(±0.02 m³/m³ soil specific) plus the smart sensor adapter accuracy of ±0.001 m³/m³ at 25°C (77°F). There are
additional temperature accuracy deviations of ±0.003 m³/m³ / °C maximum for the probe across operating
temperature environment, typical <0.001 m³/m³ / °C. (The temperature dependence of the smart sensor
adapter is negligible.)
Note 3: Given the nature of the sensor design and sensor operating frequency, the system has inherent
susceptibilities to Radio Frequency signals. The accuracy specification when subjected to certain RFI
environments, such as those outlined in IEC 61000-4-3 and IEC 61000-4-6, is reduced to 0.061 m³/m³.
The system level accuracy will be particularly affected when placed in an electric field of 3 V/m or greater in
the 70 MHz range. RFI mitigation practices and physical deployment changes may reduce the systems
susceptibility.
up to 8 dS/m and ±0.020 m³/m³ (±2%) with soil specific calibration;
see Notes 2 and 3
safely operate at below-freezing temperatures (to -40°C/F) and the
smart sensor tube (the white portion of the sensor cable that houses
the electronics) can be exposed to temperatures up to 70°C (158°F),
the soil moisture data collected at these extreme temperatures is
outside of the sensor’s accurate measurement range.
0.5 m (1.6 ft)
The CE Marking identifies this product as complying with all relevant
directives in the European Union (EU).
15081-E MAN-S-SM
Soil Moisture Smart Sensor (S-SMx-M005) Manual
C
Specifications (continued)
S-SMD-M005*
Measurement Range In soil: 0 to 0.570 m³/m³ (volumetric water content)
Extended Range -0.659 to 0.6026 m³/m³; see Note 1
Accuracy ±0.033 m³/m³ (±3.3%) typical 0 to 50°C (32° to 122°F) for mineral soils
Resolution 0.0008 m³/m³ (0.08%)
Volume of Influence 1 liter (33.81 oz)
Sensor Frequency 70 MHz
Soil Probe Dimensions 160 x 32 x 2 mm (6.5 x 1.25 x 0.08 in.)
Weight 190 grams (6.7 oz)
Decagon ECH2O Probe Part No. 10HS
Sensor Operating Temperature 0° to 50°C (32° to 122°F). Although the sensor probe and cable can
Bits per Sample 12
Number of Data Channels** 1
Measurement Averaging Option No
able Length Available 5 m (16 ft)
Length of Smart Sensor
Network Cable**
* HOBOware® 3.2.1 or greater is required for the S-SMD-M005 model only (if using HOBOware).
** A single smart sensor-compatible HOBO station can accommodate 15 data channels and up to 100 m (328 ft) of smart
sensor cable (the digital communications portion of the sensor cables). Note that the S-SMD-M005 smart sensor uses
more battery power than other models. Therefore, when connecting this smart sensor to H21-00x loggers that use 4 AA
batteries, attach no more than 6 of these sensors to maintain battery life of one year.
Note 1: The sensor is capable of providing readings outside the standard volumetric water content range. This is
helpful in diagnosing sensor operation and installation. See the Operation section for more details.
Note 2: This is a system level accuracy specification and is comprised of the probe’s accuracy of ±0.03 m³/m³ typical
(±0.02 m³/m³ soil specific) plus the smart sensor adapter accuracy of ±0.003 m³/m³ at 25°C (77°F). There are
additional temperature accuracy deviations of ±0.003 m³/m³ / °C maximum for the probe across operating
temperature environment, typical <0.001 m³/m³ / °C. (The temperature dependence of the smart sensor
adapter is negligible.)
Note 3: Given the nature of the sensor design and sensor operating frequency, the system has inherent
susceptibilities to Radio Frequency signals. The accuracy specification when subjected to certain RFI
environments, such as those outlined in IEC 61000-4-3 and IEC 61000-4-6, may be significantly reduced.
The system level accuracy will be particularly affected when placed in an electric field of 3 V/m or greater in
the 150 KHz to 1000 MHz range. RFI mitigation practices and physical deployment changes may reduce the
systems susceptibility, however will yield reduced system accuracy. If deployments are planned in high RFI
energy environments, Onset recommends on-site testing to determine system level accuracy.
up to 10 dS/m and ±0.020 m³/m³ (±2%) with soil specific calibration;
see Notes 2 and 3
safely operate at below-freezing temperatures (to -40°C/F) and the
smart sensor tube (the white portion of the sensor cable that houses
the electronics) can be exposed to temperatures up to 70°C (158°F),
the soil moisture data collected at these extreme temperatures is
outside of the sensor’s accurate measurement range. Extended
temperatures above 50°C (122°F) will decrease logger battery life.
0.5 m (1.6 ft)
The CE Marking identifies this product as complying with all relevant
directives in the European Union (EU).
1-800-LOGGERS 2 www.onsetcomp.com
Soil Moisture Smart Sensor (S-SMx-M005) Manual
Installation
This sensor measures the water content in the space
immediately adjacent to the probe surface. Air gaps or
excessive soil compaction around the probe can profoundly
influence soil water content readings. Do not mount the probes
adjacent to large metal objects, such as metal poles or stakes.
Maintain at least 8 cm (3 inches) of separation between the
probe and other objects. Any objects, other than soil, within 8
cm (3 inches) of the probe can influence the probe’s
electromagnetic field and adversely affect output readings. The
S-SMC-005 sensor must be installed at least 3 cm (1.18 inches)
from the surface and the S-SMD-005 sensor must be installed at
least 10 cm (3.94 inches) from the surface to obtain accurate
readings.
It is important to consider the particle size of the medium in
which you are inserting the sensor because it is possible for
sticks, tree bark, roots, or other materials to get stuck between
the sensor prongs, which will adversely affect readings. Be
careful when inserting these sensors into dense soil as the
prongs can break if excessive sideways force is used to push
them into the soil.
To install the soil moisture sensors, follow these guidelines:
• Good soil contact with the sensor probes is required.
• Install the sensor probes into undisturbed soil where there
aren’t any pebbles in the way of the probes.
• Use a soil auger to make a hole to the desired depth (an
angled hole is best) and push the probes into undisturbed
soil at the bottom of the hole. Alternatively, dig a hole and
push the probes into the side of the hole.
• If the probe has a protective cap on the end, remove it
before placing the probe into the hole.
• To push the probe into the soil, use a PVC pipe with slots
for the sensor and a longer slot for the cable.
• Thoroughly water the soil around the sensor after it is
installed with the hole partially backfilled to cause the soil
to settle around the sensor.
• As the hole is back-filled, try to pack the soil to the same
density as the undisturbed soil.
• To provide long-term protection from moisture entry, the
smart sensor adapter must be mounted horizontally and
with the cable wires routed with drip loops so that water
drains away from the cable entry point as shown in the
example below. When mounted properly, the housing is
weatherproof (but not waterproof).
Smart
sensor
adapter
mounted
horizontally
Drip
loop
Drip loop
• Secure the sensor cable to the mounting pole or tripod
with cable ties.
• Use conduit to protect the cable against damage from
animals, lawn mowers, exposure to chemicals, etc.
If you need to calibrate your probe for the soil, you may want
to gather soil samples from each sample depth at this time.
When removing the probe from the soil, do not pull it out of
the soil by the cable! Doing so may break internal connections
and make the probe unusable.
Connecting the Sensor to a Station
To connect the sensor to a station, stop the station from
logging and insert the smart sensor’s modular jack into an
available smart sensor port on the station. See the station
manual for details on operating stations with smart sensors.
Operating Environment
The soil moisture smart sensor provides accurate readings for
soil between 0 and 50°C (32° and 122°F). The sensor will not be
damaged by temperatures as low as -40°C (-40°F); it is safe to
leave the sensor in the ground year-round for permanent
installation. The smart sensor adapter electronics (housed in
the white tube on the sensor cable) are rated to 70°C (158°F)
and are mounted outside the logger enclosure and secured to
the mounting pole. The cable and smart sensor adapter are
weatherproof.
Operation
The soil moisture smart sensor measures the dielectric constant
of soil in order to determine its volumetric water content. The
dielectric constant of water is much higher than that of air or
soil minerals, which makes it a sensitive measure of the water
content. During operation, values of 0 to 0.5 m
possible. A value of 0 to 0.1 m3/m3 indicates oven-dry to dry
soil respectively. A value of 0.3 or higher normally indicates a
wet to saturated soil. Values outside the operating range may
be a sign that the sensor is not properly installed (poor soil
contact or foreign objects are adjacent to the sensor) or that a
soil-specific calibration is required. Note that sudden changes in
value typically indicate that the soil has settled or shifted,
which are signs that the sensor may not be installed properly or
that it has been altered or adjusted during deployment. This
sensor does not support measurement averaging.
3/m3
are
Maintenance
The soil moisture smart sensor does not require any regular
maintenance. If cleaning, rinse the sensor with mild soap and
fresh water.
Calibration
The soil moisture smart sensor comes pre-calibrated for most
soil types. If, however, your soil type has high sand or salt
content, the standard calibration will not be accurate. In such
cases, you will need to convert the data provided by the probe
with a specific calibration for your individual soil type. To
determine the soil specific calibration formula, refer to the
Calibrating ECH
available at: http://www.onsetcomp.com/files/support/pdfs/
Soil_calibration.pdf.
O Soil Moisture Probes application note,
2
1-800-LOGGERS 3 www.onsetcomp.com
Soil Moisture Smart Sensor (S-SMx-M005) Manual
Verifying Sensor Functionality
To quickly check sensor functionality before deployment,
perform the following two tests:
1. Wash the probe with water and let it dry.
2. Plug the sensor into the logger.
3. Open the logging software and go to the status screen.
4. Conduct an air test: Hold the sensor by the cable letting the
sensor hang freely in the air, and compare the value in the
status screen with the table below.
Sensor Air Water
S-SMC-M005 -0.193 to -0.139 +0.521 to +0.557
S-SMD-M005 -0.473 to -0.134 +0.474 to +0.692
5. Distilled water test: Insert the probe in a room temperature
container of fresh water, completely covering the entire
O probe. Compare the value in the status screen with
ECH
2
the table above.
If these tests pass, your sensor is working normally. If not,
please contact Onset for assistance. If you believe your sensor
is defective or broken, you can send the smart sensor back to
Onset for testing if needed. Contact Onset or your place of
purchase for a Return Merchandise Authorization (RMA)
number and associated costs before sending it.
© 2010–2015 Onset Computer Corporation. All rights reserved. Onset and HOBO are trademarks or
1-800-LOGGERS (564-4377) • 508-759-9500
www.onsetcomp.com • loggerhelp@onsetcomp.com
registered trademarks of Onset Computer Corporation. ECH2O is a registered trademark of Decagon
Devices. All other trademarks are the property of their respective companies.
15081-E MAN-S-SM
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