Onset RXW-SMD-900 Operating Manual

HOBO® RX Wireless Sensor Network

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RXW EC-5 or 10H Soil Moisture Sensor (RXW-SMx-xxx) Manual

This sensor measures soil moisture and is designed to work with the HOBOnet Wireless Sensor
Network in which data is transmitted wirelessly from the sensor mote across the network to
the RX3000 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

RXW 10HS model shown

RXW EC-5 or 10H Soil
Moisture Sensor

Models:

• RXW-SMC-900 and
RXW-SMD-900 (US)

• RXW-SMC-868 and
RXW-SMD-868 (Europe)

• RXW-SMC-922 and
RXW-SMD-922
(Australia/NZ)

Included Items:

• Protective cap

• Cable ties

• Screws

RXW-SMC-xxx RXW-SMD-xxx

Measurement Range In soil: 0 to 0.550 m³/m³ (volumetric

Extended Range -0.401 to 2.574 m³/m³; see Note 1 -0.659 to 0.6026 m³/m³; see Note 1

Accuracy ±0.031 m³/m³ (±3.1%) typical 0 to

Resolution 0.0007 m³/m³ (0.07%) 0.0008 m³/m³ (0.08%)

Volume of Influence 0.3 liters (10.14 oz) 1 liter (33.81 oz)

Sensor Frequency 70 MHz 70 MHz

METER ECH2O Probe Part
No.

Sensor Operating
Temperature Range

ireless Mote

perating Temperature

Range

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

Wireless Data Standard IEEE 802.15.4

Radio Operating
Frequencies

Modulation Employed OQPSK (Offset Quadrature Phase Shift Keying)

Data Rate Up to 250 kbps, non-adjustable

Duty Cycle <1%

Maximum Number of
Motes

Battery Type/
Power Source

Battery Life With NiMH batteries: Typical 3–5 years when operated in the temperature

water content)

50°C (32° to 122°F) for mineral
soils up to 8 dS/m and ±0.020
m³/m³ (±2%) with soil specific
calibration; see Notes 2 and 3

EC-5 10HS

0° to 50°C (32° to 122°F). Although
the sensor probe and cable can
safely operate at below-freezing
temperatures (to -40°C/F), the soil
moisture data collected at these
extreme temperatures is outside
of the sensor’s accurate
measurement range.

-25° to 60°C (-13° to 140°F) with rechargeable batteries

-40 to 70°C (-40 to 158°F) with lithium batteries

Reliable connection to 609.6 m (2,000 ft) line of sight at 3 m (10 ft) high

RXW-SMC-900 and RXW-SMD-900: 904–924 MHz
RXW-SMC-868 and RXW-SMD-868: 866.5 MHz
RXW-SMC-922 and RXW-SMD-922: 916–924 MHz

50 motes per one RX Wireless Sensor Network

Two AA 1.2V rechargeable NiMH batteries, powered by built-in solar
panel or two AA 1.5 V lithium batteries for operating conditions of -40 to
70°C (-40 to 158°F)

range -20° to 40°C (-4°F to 104°F) and positioned toward the sun (see
Deployment and Mounting), operation outside this range will reduce the
battery service life

With lithium batteries: 1 year, typical use

In soil: 0 to 0.570 m³/m³ (volumetric
water content)

±0.033 m³/m³ (±3.3%) typical 0 to
50°C (32° to 122°F) for mineral soils
up to 10 dS/m and ±0.020 m³/m³
(±2%) with soil specific calibration;
see Notes 4 and 5

0° to 50°C (32° to 122°F). Although
the sensor probe and cable can
safely operate at below-freezing
temperatures (to -40°C/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 mote battery life.

22241-A

Specifications (continued)

C

RXW EC-5 and 10H Soil Moisture Sensor (RXW-SMx-xxx) Manual

Memory 16 MB

Dimensions RXW-SMC-xxx soil probe: 89 x 15 x 1.5 mm (3.5 x 0.62 x 0.06 in.)

Weight RXW-SMC-xxx sensor and cable: 180 grams (6.3 oz)

Materials Sensor: Weatherproof

Environmental Rating Mote: IP67, NEMA 6

ompliance Marks RXW-SMC-900 and RXW-SMD-900: See last page

Note 1: (RXW-SMC-xxx and RXW-SMD-xxx) 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 Sensor Operation
section for more details.

Note 2: (RXW-SMC-xxx) 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 mote 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 mote is negligible.)

Note 3: (RXW-SMC-xxx) 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.

Note 4: (RXW-SMD-xxx) 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 mote 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 mote is negligible.)

Note 5: (RXW-SMD-xxx): 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.

RXW-SMD-xxx soil probe: 160 x 32 x 2 mm (6.5 x 1.25 x 0.08 in.)
Cable length: 5 m (16.4 ft)
Mote: 16.2 x 8.59 x 4.14 cm (6.38 x 3.38 x 1.63 inches)

RXW-SMD-xxx sensor and cable: 190 grams (6.7 oz)
Mote: 223 g (7.87 oz)

Mote: PCPBT, silicone rubber seal

RXW-SMC-868 and RXW-SMD-868: The CE Marking identifies
this product as complying with all relevant directives in the
European Union (EU).

RXW-SMC-922 and RXW-SMD-922: See last page

Mote Components and Operation

Mounting
Tab

Solar Panel

Sensor Cable

Sensor Mote Closed, Front Sensor Mote Closed, Back

Latch

Eyelet

Ground Wire
Port

Solar Panel Cable

Mounting Tab: Use the tabs at the top and bottom of the mote
to mount it (see Deploying and Mounting).

Solar Panel: Position the solar panel towards the sun to charge

LEDs

Antenna

LCD Screen

Button

USB Port

Battery Holder

Sensor Mote Opened

the mote batteries (see Deploying and Mounting).

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RXW EC-5 and 10H Soil Moisture Sensor (RXW-SMx-xxx) Manual

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.

Latch: Use the two latches to open and close the mote door.

Ground Wire Port: Use this port to connect a ground wire (see

Deploying and Mounting).

Antenna: This is the built-in antenna for the radio
communications across the RX Wireless Sensor Network.

Solar Panel Cable: This cable connects the built-in solar panel
to the mote circuitry.

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.

Battery Holder: The location where the batteries are installed
as shown (see Battery Information).

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 an RX Wireless Sensor
Network to join (see Adding the Mote to the RX Wireless Sensor
Network).

LCD Screen: The mote is equipped with an LCD screen that
displays details about the current status. This example shows all
symbols illuminated on the LCD screen followed by definitions
of each symbol in the table.

LCD Symbol Description

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 Operation

The soil moisture 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

3/m3

are
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.

The soil moisture 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. Readings outside the sensor frequency range may
result in errors in HOBOlink.

Adding the Mote to the RX Wireless Sensor
Network

The mote must join an RX Wireless Sensor Network before it
can begin measuring soil moisture and transmitting data. This
requires accessing the RX3000 station and the mote at the
same time so it is recommended that you complete these steps
before deploying the mote.

Important: If you have not configured the RX3000 station with
the RXW Manager, follow the instructions in the RX3000 Quick
Start before continuing.

To add a mote to the RX Wireless Sensor Network:

1. If the LCD is blank on the RX3000 station, press any button

to wake it up.

2. Press the Select button once (which shows the number of

smart sensors installed) and then press it again once if the
HOBO RXW Manager is installed in the left slot (module 1)
or twice if it is installed on the right slot (module 2).

Press this button to view the module
where the RXW Manager is installed

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 an RX 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 RX 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 RX
Wireless Sensor Network for details).

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