Hobo RXW series User manual

HOBOnet® Wireless Sensor Network
RXW Multi-Depth Soil Moisture Sensor (RXW-GPx-xxx) Manual
25115-A
This sensor measures soil moisture and temperature over multiple zones with a single probe
using GroPoint™ TDT technology. It is designed to work with the HOBOnet (HOBO® RX) Wireless
Sensor Network in which data is transmitted wirelessly from the sensor mote across the
network to the station and then uploaded to HOBOlink® web-based software. With HOBOlink,
you can monitor sensor readings, view graphs, set up alarms, download data, and more.
Specifications
Soil Moisture: Volumetric Water Content (VWC)
Measurement Range
0.000 to 1.000 m³/m³ in most soils
Accuracy
±0.02 m³/m³ (±2%) in most soils typical from 0° to 50°C (32° to 122°F)*
Resolution
0.001 m³/m³
Temperature
Measurement Range
-20° to 70°C (-4° to 158°F)
Accuracy
±0.5°C (0.9°F)
Resolution
0.1°C (0.18°F)
Depths Measured (s
ee diagram on page 3)
RXW
-GP3-xxx 45 cm (18 inches) total; three soil moisture zones, six temperature depths
RXW
-GP4-xxx 60 cm (24 inches) total; four soil moisture zones, seven
temperature depths
RXW
-GP6-xxx 90 cm (35 inches) total; six soil moisture zones, eleven temperature depths
Wireless Mote
Operating Temperature
Range
Sensor: -20° to 70°C (-4° to 158°F)
Mote: -25° to 60°C (-13° to 140°F) with rechargeable batteries
-40° to 70°C (-40° to 158°F) with lithium batteries
Radio Power
12.6 mW (+11 dBm) non-adjustable
Transmission Range
Reliable connection to 457.2 m (1,500 ft) line of sight at 1.8 m (6 ft) high
Reliable connection to 609.6 m (2,000 ft) line of sight at 3 m (10 ft) high
Wireless Data Standard
IEEE 802.15.4
Radio Operating
Frequencies
RXW-GPx-900: 904–924 MHz
RXW-GPx-868: 866.5 MHz
RXW-GPx-921: 921 MHz
RXW-GPx-922: 916–924 MHz
Modulation Employed
OQPSK (Offset Quadrature Phase Shift Keying)
Data Rate
Up to 250 kbps, non-adjustable
Duty Cycle
<1%
Maximum Number of
Motes
Up to 50 wireless sensors or 336 data channels per one HOBO RX station
Logging Rate
Maximum logging interval: 18 hours
Recommended minimum logging interval:
Using Solar Power with
Rechargeable Batteries
Using Non-Rechargeable
Lithium Batteries
RXW
-GP3-xxx: 5 minutes year round 10 minutes
RXW
-GP4-xxx: 5 minutes summer,
10 minutes winter
15 minutes
RXW
-GP6-xxx: 5 minutes summer,
10 minutes winter
15 minutes
See Battery Life specification for more details.
Number of Data Channels
RXW-GP3-xxx: 10
RXW-GP4-xxx: 12
RXW-GP6-xxx: 18
RXW Multi-Depth Soil
Moisture Sensor
Models:
•RXW-GP3-900 (US)
RXW-GP3-868 (Europe)
RXW-GP3-921 (Taiwan)
RXW-GP3-922 (Australia/NZ)
•RXW-GP4-900 (US)
RXW-GP4-868 (Europe)
RXW-GP4-921 (Taiwan)
RXW-GP4-922(Australia/NZ)
•RXW-GP6-900 (US)
RXW-GP6-868 (Europe)
RXW-GP6-921 (Taiwan)
RXW-GP6-922 (Australia/NZ)
Included Items:
•Cable ties
•Screws

RXW Multi-Depth Soil Moisture Sensor (RXW-GPx-xxx) Manual
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Specifications (continued)
Battery Type/
Power Source
Two AA 1.2V rechargeable NiMH batteries, powered by built-in solar
panel or two AA 1.5 V non-rechargeable lithium batteries for operating
conditions of -40 to 70°C (-40 to 158°F)
Battery Life
With NiMH batteries: Typical 3–5 years when operated in the temperature
range -20° to 40°C (-4°F to 104°F) and positioned toward the sun (see
Mounting and Positioning the Mote), operation outside this range will
reduce the battery service life
With non-rechargeable lithium batteries:
RXW-GP3-xxx: 1 year with a 10-minute logging interval
RXW-GP4-xxx: 1 year with a 15-minute logging interval
RXW-GP6-xxx: 7 months with a 15-minute logging interval
Memory
16 MB
Dimensions
RXW-GP3-xxx sensor length: 53.2 cm (20.9 inches)
RXW-GP4-xxx sensor length: 68.2 cm (26.9 inches)
RXW-GP6-xxx sensor length: 98.2 cm (38.7 inches)
Sensor diameter: 3 cm (1.2 inches)
Cable length: 3 m (9.8 ft)
Mote: 16.2 x 8.59 x 4.14 cm (6.38 x 3.38 x 1.63 inches)
Weight
RXW-GP3-xxx sensor: 351 g (12.4 oz)
RXW-GP4-xxx sensor: 408 g (14.4 oz)
RXW-GP6-xxx sensor: 526 g (18.6 oz)
Cable: 190 g (6.7 oz)
Mote: 223 g (7.87 oz)
Materials
Sensor: Polycarbonate housing encasing epoxy sealed circuit board
Cable: Polyurethane
Mote: PCPBT, silicone rubber seal
Environmental Rating
Mote: IP67, NEMA 6
Compliance Marks
RXW-GPx-900: See last page
RXW-GPx-868: The CE Marking identifies this product as
complying with all relevant directives in the European Union
(EU).
RXW-GPx-921: See last page
RXW-GPx-922: See last page
•Soil-specific calibration requires user post-processing in a spreadsheet program such as Microsoft® Excel® or a utility
and connector as recommend by RioT Technology Corp., manufacturer of GroPoint sensors. Refer to Performing a Soil-
Specific Calibration for details.
Mote Components and Operation
Sensor Mote Closed, Front Sensor Mote Closed, Back
Sensor Mote Opened
Mounting Tab: Use the tabs at the top and bottom of the mote
to mount it (see Mounting and Positioning the Mote).
Solar Panel: Position the solar panel towards the sun to charge
the mote batteries (see Mounting and Positioning the Mote).
Sensor Cable: This is the cable that connects the mote to the
sensor.
Eyelet: Use this eyelet to attach a 3/16 inch padlock to the
mote for security.
Mounting
Tab
Solar Panel
Latch
Eyelet
Ground Wire
Port
Sensor Cable
Solar Panel Cable
Button
USB Port
Battery Holder
LCD Screen
Antenna
LEDs
Calibration Connection Pins

RXW Multi-Depth Soil Moisture Sensor (RXW-GPx-xxx) Manual
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Latch: Use the two latches to open and close the mote door.
Ground Wire Port: Use this port to connect a ground wire (see
Mounting and Positioning the Mote).
Antenna: This is the built-in antenna for the radio
communications across the RX Wireless Sensor Network.
LEDs: There are two LEDs to the left of the LCD screen. The
green LED blinks during the process of joining a network,
blinking quickly while the mote searches for a network and
then slowly as the mote registers with the network. Once the
network registration process is complete, the blue LED blinks at
4 seconds to indicate normal operation. If the mote is not
currently part of a network, the blue LED will be off. If the blue
LED is on and not blinking, there is a problem with the mote.
Contact Onset Technical Support.
Solar Panel Cable: This cable connects the built-in solar panel
to the mote circuitry.
Battery Holder: The location where the batteries are installed
as shown (see Battery Information).
Calibration Connection Pins: Use these pins to connect a
programming tool. See Performing a Soil-Specific Calibration for
details.
USB Port: Use this port to connect to the mote to a computer
via USB cable if you need to update the firmware (see Updating
Mote Firmware).
Button: Push this button for 1 second to illuminate the LCD or 3
seconds for the mote to search for a HOBOnet Wireless Sensor
Network to join (see Adding the Mote to the HOBOnet Wireless
Sensor Network).
LCD Screen: The mote is equipped with an LCD screen that
displays details about the current status. The following example
shows all symbols illuminated on the LCD screen followed by
definitions of each symbol in the table.
LCD Symbol
Description
The battery indicator shows the approximate battery
charge remaining.
This is a signal strength indicator. The more bars, the
stronger the signal between motes. If there is no x
icon next to the signal strength indicator, then the
mote is part of a HOBOnet Wireless Sensor Network.
An empty signal strength icon plus the x icon
indicates that the mote is not currently part of a
network. See Adding the Mote to the HOBOnet
Wireless Sensor Network for details on how to add a
mote to the network.
When the mote is in the process of joining a
network, the signal strength icon will blink and then
the bars in the icon will cycle from left to right. The x
icon will blink during the last step in the network
registration process (see Adding the Mote to the
HOBOnet Wireless Sensor Network for details).
This indicates a problem with the sensor itself (the
mote is operational). Check the sensor and make any
adjustments to it as needed. Contact Onset
Technical Support if the problem persists.
Sensor Components and Operation
The sensor measures soil moisture and temperature over
several zones using a single probe. Designed for vertical
installation, the sensor takes measurements over multiple soil
layers, with each measurement zone providing the average
volumetric soil moisture content over a 15 cm (5.9 inch) zone.
Water can be detected as much as 5 cm (2 inches) from the
surface of the probe. However, moisture closest to the surface
of the probe has more influence on the readings than moisture
further away. Each 15 cm (5.9 inch) zone has a 2.78 L (169.6 in3)
volume of influence.
Probes are divided into sensor segments as shown in the
following diagram. Each segment measures soil moisture over
the corresponding soil depth zone. Temperature sensors within
the probe measure the soil temperature at different depths
(refer to the tables later in this section for the specific depth of
each temperature sensor).
The following table shows how many channels are logged
for each of the three sensor models.
Part number
Channels logged
RXW-GP3-xxx
10 total channels:
•3 soil moisture (water content)
•6 soil temperature
•
1 mote battery
RXW-GP4-xxx
12 total channels:
•4 soil moisture (water content)
•7 soil temperature
• 1 mote battery
RXW-GP6-xxx
18 total channels:
•6 soil moisture (water content)
•11 soil temperature
•1 mote battery

RXW Multi-Depth Soil Moisture Sensor (RXW-GPx-xxx) Manual
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In HOBOlink, measurement channels are listed as <sensor
serial number>-<number>, where <number> represents
the soil moisture zones followed by the temperature
sensor depths in order from the top down to the tip of
the probe. The following tables show the soil moisture
zones and temperature sensor depths associated with
each channel number for the three RXW-GPx models. It is
recommended that you label each channel in HOBOlink
for each soil moisture zone or temperature depth. To
change the label for a channel, go to your RX station page
in HOBOlink. Click next to a channel and then enter a
label and click Save.
RXW-GP3 HOBOlink Channels
RXW GP3 Sensor Channel
Corresponding Channel
Number in HOBOlink
Soil moisture (water content)
measurement zone 1: 0 to 15 cm (0 to
5.91 inches)
<serial number>-1
Soil moisture (water content)
measurement zone 2: 15 to 30 cm
(5.91 to 11.81 inches)
<serial number>-2
Soil moisture (water content)
measurement zone 3: 30 to 45 cm
(11.81 to 17.72 inches)
<serial number>-3
Temperature at 3.5 cm (1.38 inches) <serial number>-4
Temperature at 10 cm (3.94 inches) <serial number>-5
Temperature at 20 cm (7.87 inches)
<serial number>-6
Temperature at 30 cm (11.81 inches)
<serial number>-7
Temperature at 40 cm (15.7 inches) <serial number>-8
Temperature at 45 cm (17.72 inches) <serial number>-9
RXW-GP4 HOBOlink Channels
RXW GP4 Sensor Channel
Corresponding Channel
Number in HOBOlink
Soil moisture (water content)
measurement zone 1: 0 to 15 cm (0 to
5.91 inches)
<serial number>-1
Soil moisture (water content)
measurement zone 2: 15 to 30 cm
(5.91 to 11.81 inches)
<serial number>-2
Soil moisture (water content)
measurement zone 3: 30 to 45 cm
(11.81 to 17.72 inches)
<serial number>-3
Soil moisture (water content)
measurement zone 4: 45 to 60 cm
(17.72 to 23.62 inches)
<serial number>-4
Temperature at 3.5 cm (1.38 inches)
<serial number>-5
Temperature at 10 cm (3.94 inches)
<serial number>-6
Temperature at 20 cm (7.87 inches)
<serial number>-7
Temperature at 30 cm (11.81 inches) <serial number>-8
Temperature at 40 cm (15.7 inches)
<serial number>-9
Temperature at 50 cm (19.69 inches)
<serial number>-10
Temperature at 60 cm (23.62 inches)
<serial number>-11
RXW-GP6 HOBOlink Channels
RXW GP6 Sensor Channel
Corresponding Channel
Number in HOBOlink
Soil moisture (water content)
measurement zone 1: 0 to 15 cm (0 to
5.91 inches)
<serial number>-1
Soil moisture (water content)
measurement zone 2: 15 to 30 cm
(5.91 to 11.81 inches)
<serial number>-2
Soil moisture (water content)
measurement zone 3: 30 to 45 cm
(11.81 to 17.72 inches)
<serial number>-3
Soil moisture (water content)
measurement zone 4: 45 to 60 cm
(17.72 to 23.62 inches)
<serial number>-4
Soil moisture (water content)
measurement zone 5: 60 to 75 cm
(23.62 to 29.53 inches)
<serial number>-5
Soil moisture (water content)
measurement zone 6: 75 to 90 cm
(29.53 to 35.43 inches)
<serial number>-6
Temperature at 3.5 cm (1.38 inches) <serial number>-7
Temperature at 10 cm (3.94 inches) <serial number>-8
Temperature at 20 cm (7.87 inches)
<serial number>-9
Temperature at 30 cm (11.81 inches)
<serial number>-10
Temperature at 40 cm (15.7 inches) <serial number>-11
Temperature at 50 cm (19.69 inches)
<serial number>-12
Temperature at 55 cm (21.65 inches)
<serial number>-13
Temperature at 65 cm (25.59 inches)
<serial number>-14
Temperature at 75 cm (29.53 inches) <serial number>-15
Temperature at 85 cm (33.47 inches)
<serial number>-16
Temperature at 90 cm (35.43 inches)
<serial number>-17
Adding the Mote to the HOBOnet Wireless
Sensor Network
The mote must join a HOBOnet Wireless Sensor Network
before it can begin measuring water potential and transmitting
data. This requires accessing the station and the mote at the
same time so it is recommended that you complete these steps
before deploying the mote.
Important: If you are setting up a new station, follow the
instructions in the station quick start before setting up this
mote (go to www.onsetcomp.com/support/manuals/24380-
man-rx2105-rx2106-qsg for RX2105 and RX2106 stations or go
to www.onsetcomp.com/support/manuals/18254-MAN-QSG-
RX3000 for RX3000 stations).
To add a mote to the network:
1. If the LCD is blank on the station, press any button to wake
it up.

RXW Multi-Depth Soil Moisture Sensor (RXW-GPx-xxx) Manual
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2. Press the Select button once (which shows the number of
smart sensors installed) and then press it again to switch to
the module with the manager.
3. Press the Search button (the magnifying glass). The
magnifying glass icon will blink while the station is in search
mode.
4. Open the mote door and install the batteries if you have not
already done so.
5. Press the button on the mote for 3 seconds. The signal
strength icon will flash and then cycle.
6. Watch the LCD on the mote.
The green LED blinks quickly while the mote searches for a
network to join and then blinks slowly while it completes
the network registration. Once the mote has finished
joining the network, the green LED turns off and the blue
LED then blinks indefinitely while the mote is part of the
network.
Note: If the mote cannot find the network or has trouble
remaining connected during this process, make sure the
mote is in a vertical, upright position and within range of
the station.
7. Press the Search button (the magnifying glass) on the
station to stop searching for motes.
If you added more than one more mote to the network, then
the total channel count on the station LCD for the manager
module will represent all measurement channels plus a battery
channel for each mote in the network.
Sensor measurements will be recorded at the logging interval
specified in HOBOlink, transmitted to the station, and uploaded
to HOBOlink at the next connection interval (readout).
Important: Because this sensor provides multiple soil
moisture and temperature measurements, the battery
usage can be too high at fast logging rates. It is
recommended that you set the logging interval in
HOBOlink for wireless sensors to be no faster than the
following rates.
Part
Number
Minimum Logging
Interval Using Solar
Power with
Rechargeable Batteries*
Minimum Logging
Interval Using
Non-Rechargeable
Lithium Batteries
RXW-GP3-
xxx
5 minutes year round 10 minutes with a 1-year
battery life
RXW-GP4-
xxx
5 minutes summer,
10 minutes winter
15 minutes with a 1-year
battery life
RXW-GP6-
xxx
5 minutes summer,
15 minutes winter
15 minutes with a
7-month battery life
*Requires the solar panel is positioned directly toward the sun and
without shade (see Mounting and Positioning the Mote)
Note that this logging interval will be applied to all wireless
sensors in the HOBOnet® wireless network. For solar powered
RXW-GPx motes, logging intervals faster than the
recommended minimum can result in missing data because
there will be insufficient charge for the batteries. For RXW-GPx
motes with non-rechargeable lithium batteries, faster intervals
will require more frequent battery replacement.
Use HOBOlink to monitor mote status and health. If a mote is
temporarily offline, any logged data is saved until it is back
online. In addition, if a mote is offline for 30 minutes, the
Press this button for 3
seconds for the mote to
join the network
This signal strength icon
blinks while searching for
a network.
Press this button to view the module
Press this button so the station is ready
to have motes join the network
Once a network is found,
the icon will stop flashing
and the bars will cycle from
left to right.
Press this button again to
stop searching for motes
c.
d.
This network connection
“x” icon blinks while the
mote completes the
registration process,
which may take up to
five minutes.
Once the mote has finished
joining the network, the “x”
icon is removed and the
channel count on the station
LCD increases by the total
channel count for that sensor
model.
a.
b.

RXW Multi-Depth Soil Moisture Sensor (RXW-GPx-xxx) Manual
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station will automatically connect to HOBOlink and report the
mote as missing. Once the mote is back online, any logged data
will be uploaded the next time the station connects to
HOBOlink.
See the HOBOlink Help for details on how to change the logging
and connection intervals, view data, check mote status, add the
mote to a map, and more.
Installing the Sensor
To install the sensor, it is recommended that you use a slide
hammer (Onset part number SLIDE-HAMMER) and pilot rod to
form a hole to insert the sensor probe (use Onset part number
PILOT-ROD4 with RXW-GP3 and RXW-GP4 models or use PILOT-
ROD6 with the RXW-GP6 model). These tools will create a pilot
hole that is the exact size and shape of the sensor without air
gaps to ensure good soil contact with the sensor and accurate
measurements. You may also need tape, two adjustable
wrenches, a dead blow hammer, and water. There are also two
alternate installation methods described later in this section if a
slide hammer and pilot rod are not available.
WARNING: Follow these important safety guidelines when
working with a slide hammer and pilot rod:
●Be careful when carrying and using the slide hammer as the
bottom part of the slide may drop down, potentially causing
injury. Steel-toed work shoes are recommended to prevent
possible injury to toes and feet.
●Eye and ear protection are recommended at all times when
using the slide hammer. When in use, the slide hammer
generates harmful levels of acoustic energy. Hearing
protection with a Noise Reduction Rating of 20 decibels
should always be worn.
●Wear work gloves and keep both hands on the slide hammer
when driving the pilot rod. Be careful to avoid getting fingers
caught in the slide mechanism.
Sensor Installation Guidelines
Before installing the sensor, follow these guidelines.
•Install the probe when the soil is dry to minimize the air
gaps that can form around the probe as wet soil dries out.
Also avoid excessively rocky soil whenever possible as
cavities may form when rocks are pushed out of the way
when creating the pilot hole.
•The sensor probe must be installed vertically. Hold the
slide hammer and pilot rod perfectly vertical to avoid
making the hole larger than the size of the sensor.
•Always maintain control of the slide hammer with a firm
grip to avoid wobbling or moving the hammer side-to-side.
This is especially important while the first half of the pilot
rod is being hammered in place.
•Check that the pilot rod is tightly screwed to the slide
hammer during the insertion process as the threads may
loosen during repeated impacts. Failure to check the
connection may place excessive force on the threads and
damage them.
•Drive the pilot rod only as far as needed for the length of
probe being used. A hole that is too short may cause
damage to the probe during insertion. A hole that is too
long may allow water to collect in the void below the
probe and cause inaccurate readings.
•When extracting the pilot rod, make sure it remains
vertical so the hole does not become enlarged, which may
result in air gaps forming between the probe and soil and
potentially incorrect soil moisture readings.
•Once the pilot rod is removed, insert the probe as soon as
possible. Any delay may allow moisture to swell the sides
of the hole or water to enter the hole.
•If the pilot hole is larger at the top than the bottom due to
side-to-side movement of the slide hammer during
installation, it may take a few days to a week for the soil to
settle back and seal against the probe. You can also create
a soil slurry at the surface to fill the hole. See Maintenance
for more details on using a slurry.
•To reduce air gaps from forming over time as soil expands
and contracts, limit the variation of moisture content of
the soil if possible, such as by periodic irrigation.
•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.
Slide Hammer and Pilot Rod Installation Method
1. For assembled pilot rods, skip to step 2. For disassembled
pilot rods, select the appropriate number of middle rod
segments based on the length of your probe: two segments
for RXW-GP3 and RXW-GP4 models, or three for the RXW-
GP6 model. Assemble the pilot rod by screwing one
segment into the other, connecting each rod segment
together to form the body of the pilot rod, making sure all
edges are aligned. Screw in the pilot rod tip to one end of
the pilot rod body and the top cap to the other end.
2. Lay the pilot rod down next to the sensor probe, with both
tips aligned. Wrap a piece of tape around the pilot rod at
the depth the rod should be driven into the soil (which
should line up with the top of the sensor).
3. Screw the pilot rod into the slide hammer as shown. Use
two adjustable wrenches to make sure the threads are
tight. A loose connection can damage the threads as you
are hammering.

RXW Multi-Depth Soil Moisture Sensor (RXW-GPx-xxx) Manual
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4. At the location where you want to install the probe, use a
repetitive up-then-down motion on the slide hammer to
vertically drive the pilot rod into the soil. Be sure to hold
the slide hammer vertically without side-to-side movement.
Drive the pilot rod in until it reaches the tape marking made
in step 2.
5. Once the pilot rod reaches the desired depth, extract the
pilot rod by using the slide hammer in reverse, lifting it
rapidly to hammer upwards. Be sure to hold the slide
hammer vertically without side-to-side movement to
extract the pilot rod straight up.
6. Once the pilot rod is extracted, clear away any loose soil at
the top edges of the hole so that it doesn’t fall into the
hole.
7. Insert the sensor probe into the hole, pressing it in as far as
possible by hand. Pour a bit of water around the probe at
the top of the hole if the soil is very tightly packed to help it
slide more smoothly into the hole. You can use a dead blow
hammer to gently tap the top of the sensor if you are
having trouble pushing in the sensor by hand.
Important: Never use a regular hammer or other tool to
push in the sensor because other tools can damage the
internal electronics.
8. Once the probe is fully inserted in the hole, pack the soil
around the top of the sensor to prevent water from
entering the hole. The sensor should be completely covered
with soil and only the sensor cable visible.
See Checking Sensor Readings with HOBOlink for details on
verifying that you have consistent sensor readings.
Auger Installation Method
1. Drill a vertical hole with a 3 inch auger.
2. Insert the sensor into the hole, making sure the entire
sensor body is in the hole.
3. Make a slurry of the soil from the hole and pour it down
slowly so that it settles evenly around the sensor. Stop
pouring every few inches and give it time for the water to
drain from the soil and the soil to settle. Allow more time
for soils that retain water, such as clay soils.
4. Make sure the sensor is completely covered with soil and
only the sensor cable visible.
See Checking Sensor Readings with HOBOlink for details on
verifying that you have consistent sensor readings.
Excavation Installation Method
1. Dig a hole deep enough for the sensor probe and save the
soil on a plastic tarp or sheet. Lay out the soil on the tarp in
a row for the different depths so that you will be able to
easily return all the soil to the excavated hole in the correct
order.
2. Place the sensor probe vertically in the hole.
3. While supporting the sensor at the top and bottom so that
it does not move, backfill the hole with the soil that was
removed from the hole, restoring the original soil at each
depth as laid out on the tarp. To ensure the same soil
density as before the probe was installed, return the soil to
the hole in 8 to 10 cm (3 to 4 inch) layers. Tamp down each
layer with a 2.54 cm (1 inch) diameter metal rod, making
sure the soil is packed around and into the sensor so that
there is good soil contact on all sensor surfaces. The
accuracy depends on not having any air gaps around the
sensor. Be sure to keep the sensor vertical while backfilling
the hole.
4. Once all soil has been returned to the hole, make sure the
excavation surface is level with the surrounding soil. The
sensor should be completely covered with soil and only the
sensor cable visible.
5. Water the soil thoroughly after installation to help ensure
that the soil has filled in around the sensor.
See the next section for details on verifying that you have
consistent sensor readings.

RXW Multi-Depth Soil Moisture Sensor (RXW-GPx-xxx) Manual
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Checking Sensor Readings with HOBOlink
Use HOBOlink to check for consistent sensor readings, which
can indicate that the installation was successful with minimal
air pockets.
1. Temporarily set the logger interval in HOBOlink to 1 minute
and Save.
2. Press the Connect button on the station.
3. Press the Start button if the station is not logging. Let the
station log data for a few minutes.
4. Connect to HOBOlink again so that the station can upload
the soil moisture data.
5. Export the data for the sensor and check that the readings
are similar between adjacent segments (it is normal to have
significant differences in readings from one end of the
probe to the other). If any segments have significantly low
readings compared to their adjacent segments, that could
be a sign of an air gap. Try pouring water on the soil around
the sensor and repeating steps 4 and 5. If that does not
work, you may need to remove the sensor from the hole
and redo the installation.
6. Once the readings are consistent, change the logging
interval in HOBOlink back to your desired interval for the
deployment.
Mounting and Positioning the Mote
•Mount the mote to a mast or pipe using cable ties or affix
the mote to a wooden post or flat surface with screws.
Insert the cable ties or screws through the holes on the
mounting tabs.
•Consider using plastic poles such as PVC to mount the
mote as certain types of metal could decrease signal
strength.
•Make sure the mote remains in a vertical position once it
is placed in its deployment location for optimal network
communications.
•Make sure the mote door is closed, with both latches fully
locked to ensure a watertight seal.
•Consider using a 3/16 inch padlock to restrict access to the
mote. With the mote door closed, hook a padlock through
the eyelet on the right side of the door and lock it.
•Position the mote towards the sun, making sure the solar
panel is oriented so that it receives optimal sunlight
throughout each season. It may be necessary to
periodically adjust the mote position as the path of the
sunlight changes throughout the year or if tree and leaf
growth alters the amount of sunlight reaching the solar
panel.
•Make sure the mote is mounted a minimum of 1.8 m (6 ft)
from the ground or vegetation to help maximize distance
and signal strength.
•Place the mote so there is full line of sight with the next
mote. If there is an obstruction between two sensor
motes or between the sensor mote and the manager, then
use a repeater mounted on the obstruction. For example,
if there is a hill between the sensor mote and the
manager, place a repeater at the top of the hill between
the sensor mote and the manager.
•There should not be more than five motes in any direction
at their maximum transmission range from the manager.
Data logged by a wireless sensor must travel or “hop”
across the wireless network from one mote to the next
until it ultimately reaches the manager connected to the
station. To make sure the data can successfully travel
across the network, the mote should not be more than
five hops away from the manager.
•The HOBOnet Wireless Sensor Network can support up to
50 wireless sensors or 336 data channels per one HOBO
RX station.
•Use a #4-40 screw to attach a ground wire to the port on
the back of the mote if you are deploying the mote in a
location where lightning is a concern.
Performing a Soil-Specific Calibration
The sensor is factory-calibrated for use in most soils. The
GroPoint user manual provides instructions on how to perform
soil-specific calibrations using a GP-USB Connect SDI-12
programming tool (GroPoint part number 6300 available from
www.gropoint.com). Refer to Appendix A of the GroPoint
manual available at https://www.gropoint.com/products/soil-
sensors/gropoint-profile/ from the Downloads tab. Use wires
with clips to connect to the pins on the mote pointed out in the
following instructions. Connect the other ends of the wires to
the screw terminals on the SDI-12 programming tool.
To connect an SDI-12 programming tool to the mote:
1. Remove the mote batteries (see Battery Information).
2. Connect the programming tool to the mote, using the three
J2 connection pins labeled PWR, DATA, and GND on the
mote circuit board.
Be sure to disconnect the programming tool before reinstalling
the batteries in the mote.
Maintenance
The soil may pull away from the side of the probe over time,
creating a crack in the soil. Use a slurry to fill it. Mix some of the
soil in the immediate vicinity of the probe with water to make
the slurry. Pour the slurry down the crack and allow it dry out
and shrink. Repeat this process until the crack remains filled.
The mote is designed for outdoor use, but should be inspected
periodically. When inspecting the mote, do the following:
•Verify the mote is free of visible damage or cracks.
•Make sure the mote is clean. Wipe off any dust or grime
with a damp cloth.
•Wipe off any water before opening the mote.
Connect the programming tool to
these connection pins

RXW Multi-Depth Soil Moisture Sensor (RXW-GPx-xxx) Manual
1-800-LOGGERS 9 www.onsetcomp.com
•Make sure the interior seal is intact and free of any debris,
and the latches are fully locked when the mote door is
closed.
Removing the Sensor from the Soil
To remove a sensor probe from the soil:
1. Carefully dig out the soil around the top of the probe with a
hand shovel, being sure not to damage the probe or cable.
Dig out the hole until at least 30 cm (11.8 inches) of the
probe is exposed.
2. Grasp the probe firmly with two hands as you pull it
upwards. Do not grab onto the black probe head as it is not
secured with enough strength for probe extraction. Do not
pull the probe up by the sensor cable.
Updating Mote Firmware
If a new firmware version is available for the mote, use
HOBOlink to download the file to your computer.
1. In HOBOlink, go to Devices, then RX Devices, and click your
station name.
2. On the station page, click Overview and scroll down to
Device Information.
3. Click the Wireless tab. This icon appears next to the
mote if there is a new version of firmware available.
4. Click the firmware upgrade link. Click Download and
save the firmware .bin file to your computer.
5. Connect the mote to the computer with a USB cable (open
the mote door and use the USB port to the right of the
LCD). The blue LED is illuminated while connected.
6. The mote appears as a new storage device in the
computer’s file storage manager. Copy the downloaded
firmware file to the new storage device (the mote). The
blue LED will blink slowly while the file is copying.
7. After the file is copied to the mote, the LED will stop
blinking and remain a steady blue. Eject the storage device
from the computer and disconnect the cable from the
mote. The firmware installation process will begin
automatically on the mote. The blue LED will blink rapidly
while the firmware is installed. Once the firmware
installation is complete, the LCD symbols return and the
mote will automatically rejoin the network.
Notes:
•Mac® users: A message may appear indicating the disk
has not ejected properly when disconnecting the mote
from the computer. The mote is operational and you can
ignore the message.
•If the blue LED turns off abruptly while copying the file or
installing the firmware, a problem has occurred. Contact
Onset Technical Support for help.
Battery Information
The mote uses two 1.2 V rechargeable NiMH batteries, charged
by the built-in solar panel. The quality and quantity of solar
light can affect whether the battery is sufficiently charged to
last through the night and cloudy periods. Make sure the mote
is placed in a location that will receive several hours of sunlight
each day. If the mote does not receive enough sunlight to
recharge the batteries, the battery life is estimated at 3–4
months. When batteries are regularly recharged, expected
battery life is estimated at 3–5 years. Battery life varies based
on the ambient temperature where the mote is deployed, the
logging interval, the number of tripped alarms, and other
factors. Minimum recommended logging intervals as described
in the specifications should be followed to keep the batteries
charged. Deployments in extremely cold or hot temperatures
can impact battery life. Estimates are not guaranteed due to
uncertainties in initial battery conditions and operating
environment.
Mote operation will stop when battery voltage drops to 1.8 V.
Mote operation will return if the battery recharges to 2.3 V. If
the batteries are unable to be recharged, replace them with
fresh rechargeable batteries. Note: if you install used
rechargeable batteries that together are less than 2.3 V, the
mote will not resume operation.
To replace rechargeable batteries:
1. Open the mote door.
2. Remove the old batteries and install fresh ones observing
polarity.
3. Make sure the solar panel cable is plugged in.
The mote contacts the network once the new batteries are
installed. The green LED blinks quickly while the mote searches
for a network to join and then blinks slowly while it completes
the network registration. Once the mote has finished joining
the network, the green LED turns off and the blue LED then
blinks indefinitely while the mote is part of the network.
Lithium Batteries
You can use two 1.5 V non-rechargeable lithium batteries
(HWSB-LI) for operation at the extreme ends of the mote
operating range. The estimated battery life is one year with a
minimum logging interval of 10 minutes for the RXW-GP3-xxx
model or 15 minutes for the RXW-GP4-xxx model. The
estimated battery life for the RXW-GP6-xxx model is seven
months with a logging interval of 15 minutes. In addition,
battery life is based on the ambient temperature where the
mote is deployed, the number of tripped alarms, and other
factors. Estimates are not guaranteed due to uncertainties in
initial battery conditions and operating environment. When
using lithium batteries, you must disconnect the solar panel
cable because the batteries will not be recharged.
To install lithium batteries:
1. Open the mote door.
2. Remove any old batteries and install the new ones
observing polarity.
3. Push in the side tab of the solar panel cable connector and
pull the connector out of the cable port.
Make sure
solar panel
cable is
installed
when using
rechargeable
batteries

RXW Multi-Depth Soil Moisture Sensor (RXW-GPx-xxx) Manual
1
-800-LOGGERS (564-4377) • 508-759-9500
www.onsetcomp.com/support/contact
© 2020 Onset Computer Corporation. All rights reserved. Onset, HOBO, HOBOnet, and HOBOlink are registered trademarks
of Onset Computer Corporation. GroPoint is a trademark of RioT Technology Corp. Some material reprinted with permission
of RioT Technology Corp Microsoft and Excel are registered trademarks of Microsoft, Corp. All other trademarks are the
property of their respective companies.
25115-A
4. Place the connector in the slot on the inside of the mote
door. Make sure the solar panel cables are tucked inside the
door so that they do not interfere with the interior seal
when the mote is closed.
The mote contacts the network once the new batteries are
installed. The green LED blinks quickly while the mote searches
for a network to join and then blinks slowly while it completes
the network registration. Once the mote has finished joining
the network, the green LED turns off and the blue LED then
blinks indefinitely while the mote is part of the network.
WARNING: Do not cut open, incinerate, heat above 85°C
(185°F), or recharge the lithium batteries. The batteries may
explode if the mote is exposed to extreme heat or conditions
that could damage or destroy the battery cases. Do not mix
battery types, either by chemistry or age; batteries may rupture
or explode. Do not dispose of the logger or batteries in fire. Do
not expose the contents of the batteries to water. Dispose of
the batteries according to local regulations for lithium
batteries.
Federal Communication Commission Interference Statement
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide
reasonable protection against harmful interference in a residential installation. This equipment generates uses and can radiate radio frequency energy and, if not installed and
used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a
particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user
is encouraged to try to correct the interference by one of the following measures:
•Reorient or relocate the receiving antenna
•Increase the separation between the equipment and receiver
•Connect the equipment into an outlet on a circuit different from that to which the receiver is connected
•Consult the dealer or an experienced radio/TV technician for help
This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device
must accept any interference received, including interference that may cause undesired operation.
FCC Caution: Any changes or modifications not expressly approved by the party responsible for compliance could void the user's authority to operate this equipment.
Industry Canada Statements
This device complies with Industry Canada license-exempt RSS standard(s). Operation is subject to the following two conditions: (1) this device may not cause interference, and
(2) this device must accept any interference, including interference that may cause undesired operation of the device.
Avis de conformité pour l’Industrie Canada
Le présent appareil est conforme aux CNR d'Industrie Canada applicables aux appareils radio exempts de licence. L'exploitation est autorisée aux deux conditions suivantes : (1)
l'appareil ne doit pas produire de brouillage, et (2) l'appareil doit accepter tout brouillage radioélectrique subi, même si le brouillage est susceptible d'en compromettre le
fonctionnement.
To comply with FCC and Industry Canada RF radiation exposure limits for general population, the logger must be installed to provide a separation distance of at least 20cm from
all persons and must not be co-located or operating in conjunction with any other antenna or transmitter.
NCC Statement
經型式認證合格之低功率射頻電機，非經許可，公司、商號或使用者均不得擅自變更頻率、加大功率或變更原設計之特性及功能。
低功率射頻電機之使用不得影響飛航安全及干擾合法通信；經發現有干擾現象時，應立即停用，並改善至無干擾時方得繼續使用。前項合法通信，指依電信法規定作
業之無線電通信。低功率射頻電機須忍受合法通信或工業、科學及醫療用電波輻射性電機設備之干擾。
Translation:
Article 12
Without permission granted by the NCC, any company, enterprise, or user is not allowed to change frequency, enhance transmitting power or alter original characteristic as well
as performance to an approved low power radio-frequency device.
Article 14
The low power radio-frequency devices shall not influence aircraft security and interfere with legal communications. If found, the user shall cease operating immediately until no
interference is achieved. The said legal communications means radio communications is operated in compliance with the Telecommunications Act. The low power radio-
frequency devices must be susceptible with the interference from legal communications or ISM radio wave radiated devices.
Store the solar
panel connector
here when using
lithium batteries