HOBOnet T21 Soil Water Potential/Temp Sensor


HOBOnet T21 Soil Water Potential/Temp Sensor

  • Vendor:Onset

Availability: Available Item
Qty Price
Buy 1 $986.00 ea
Buy 10 $936.70 ea

A complete system requires at least one HOBO RX3000 Remote Monitoring Station, a HOBOnet Wireless Manager (RXMOD-RXW-xxx), and a HOBOnet Wireless Sensor, OR one HOBO MicroRX station (which has an integrated HOBOnet Wireless Manager) and a HOBOnet Wireless SensorHOBOnet Wireless Repeaters (RXW-RPTR-900) can be added to extend the range.


The HOBOnet T21 is a wireless sensor that works with the HOBOnet system to measure both soil temperature and soil water potential, a more accurate way to measure how much water is available to plants. The HOBOnet T21 Sensor is designed to withstand harsh environmental conditions, and it does not require calibration for different soil types or salinity.  Featuring the METER TEROS 21 sensor which is calibrated in a chamber system that allows the TEROS 21 set calibration points from -10KPa to -80KPa. With its durable epoxy coating, you can be confident these sensors can be deployed in the ground for long periods while providing data you can trust.

The HOBOnet system is a cost-effective and scalable option for web-enabled monitoring of field conditions for applications such as crop management, research, and greenhouse operations. And because it’s wireless, you can deploy a network of sensors to easily monitor multiple points with a single system, while avoiding the risk of long cables that can interfere with field operations and are potentially vulnerable to nearby lightning strikes.

Sensors are easily linked to the network, and data can be accessed through HOBOlink®, Onset's innovative cloud-based software platform.

Highlighted Features

  • Soil water potential and soil temperature measurements with one device
  • A more accurate picture of the amount of water available to plants than volumetric water content sensors
  • No calibration required for soil type or salinity
  • Long-lasting and maintenance-free with durable epoxy construction
  • Wide measurement range: -9 to -2000 kPa

In what environment does this sensor operate?

This sensor operates in an outdoor environment.

What measurements does this sensor support?

The RXW-T21-xxx sensor supports the following measurements: Soil Moisture, Soil Temperature and Soil Water Potential

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 Measurement Frequency 70 MHz
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 50 motes per one HOBOnet Wireless Sensor Network
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)
Materials Sensor: Vinyl body with polyurethane resin, stainless steel and ceramic sensor head
Cable: PVC, UV resistant and rodent repellent
Mote: PCPBT, silicone rubber seal
Environmental Rating Mote: IP67, NEMA 6
Compliance Marks Federal Communication Commission     RXW-T11-900
European Union Compliance     RXW-T11-868
Taiwan Compliance     RXW-T11-921
Australia and New Zealand Complicance     RXW-T11-922

* The sensor is not well calibrated beyond -100 kPa. For more information on using the sensor beyond this range, see Sensor Accuracy and Calibration.

** Temperature measurement, for applicable sensors, may not be accurate if sensor is not fully immersed in medium of interest, due to longer equilibration time.

Data Loggers
RX3000               RX3000 Remote Monitoring Station Data Logger
RX2100               MicroRX Station

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