Onset Hobonet rxw teros-21 User manual

HOBOnet® Wireless Sensor Network

RXW TEROS-21 Soil Water Potential Sensor (RXW-T21-xxx) Manual

24850-B

This sensor measures water potential and temperature in numerous soil types. 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

Water Potential

Measurement Range

-2,000 to -9 kPa in soils up to 10 dS/m

Accuracy

* ±10% of reading + 2 kPa from -100 to -9 kPa

Resolution

0.1 kPa

Dielectric Measur

ement

Frequency

70 MHz

Temperature

Measurement Range

-40° to 60°C (-40° to 140°F)

Accuracy

±1°C (1.8°F)

Resolution

0.1°C (0.18°F)

Wireless Mote

Operating Temperature

Range

Sensor: -40° to 60°C (-40° to 140°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-T21-900: 904–924 MHz

RXW-T21-868: 866.5 MHz

RXW-T21-921: 921 MHz

RXW-T21-922: 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

1 minute to 18 hours

Number of Data Channels

Battery Type/

Power Source

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)

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 lithium batteries: 1 year, typical use

Memory

16 MB

Dimensions

Sensor: 9.6 x 3.5 x 1.5 cm (3.8 x 1.4 x 0.6 inches)

Sensor diameter: 3.2 cm (1.3 inches)

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)

Weight

RXW-T21-xxx sensor and cable: 103 g (3.65 oz)

Mote: 223 g (7.87 oz)

RXW Soil Water Potential

Sensor

Models:

•RXW-T21-900 (US)

•RXW-T21-868 (Europe)

•RXW-T21-921 (Taiwan)

•RXW-T21-922

(Australia/NZ)

Included Items:

•Cable ties

•Screws

Test Equipment Depot - 800.517.8431 - 5 Commonwealth Ave, MA 01801 - TestEquipmentDepot.com

RXW TEROS-21 Soil Water Potential Sensor (RXW-T21-xxx) Manual

•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.

Sensor Accuracy and Calibration

The sensor is calibrated at a saturated state (0 kPa), at a dry

state equivalent to -2,000 kPa, and at four calibration points

between 0 kPa and -100 kPa, resulting in accuracy of ±10% of

reading + 2 kPa over the range of -9 to -100 kPa.

At water potentials drier than -100 kPa, the sensor relies on the

linear relationship between the logarithm of water content and

the logarithm of water potential. Laboratory evaluations have

shown good accuracy to at least -1,500 kPa (plant permanent

wilting point). Independent field evaluations have also shown

low sensor-to-sensor variability down to permanent wilting

point.

Sensor calibration is not affected by soil type because the

sensor only measures the water potential of the ceramic discs

in equilibrium with the soil. The sensor works in any soil type or

other porous media as long as it is installed correctly with

adequate hydraulic contact (to ensure timely water potential

equilibrium between the sensor and the medium of interest). In

most situations, soil undergoes brief periods of wet up followed

by longer dry down periods. The sensor calibrates during the

the drying period after the soil wets up. Therefore, the readings

are most accurate as the soil dries, as that is most important for

irrigation.

The sensor can be used in frozen soils, but it does not

accurately measure water potential in frozen soil conditions.

However, the water potential of the soil under frozen soil

conditions can be estimated by measuring the soil temperature

accurately. For each 1°C (0.8°F) decrease in temperature below

0°C (32°F), the water potential in the soil decreases by ~1,200

kPa. This relationship has been shown to be valid in field soils

for water potentials below about -50 kPa.

Maintenance

The ceramic discs in the sensor are brittle and can chip or crack

under duress. The metal screens afford the discs some amount

of protection, but sharp trauma on the disc edges or massive

impact (such as dropping the sensor onto a hard surface) can

cause the ceramic to break. One or two small chips on the edge

of the disc do not affect the sensor accuracy significantly.

However, a cracked ceramic disc results in a loss of accuracy.

The ceramic discs must readily take up water to accurately

measure water potential. Exposure to oils or other hydrophobic

substances compromises the ability of the discs to take up

water from the soil, which can lead to slow equilibration times

and loss of accuracy. Minimize exposure of the ceramic

material to skin oils, grease, synthetic oils, or other

hydrophobic compounds.

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.

•Make sure the interior seal is intact and the latches are

fully locked when the mote door is closed.

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

RXW TEROS-21 Soil Water Potential Sensor (RXW-T21-xxx) Manual

registered trademarks of Onset Computer Corporation. Some material reprinted with permission of METER

Group, Inc. Mac is a registered trademark of Apple Inc. All other trademarks are the property of their

respective companies.

24850-B

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-