WET150 Multi-Parameter Soil Sensor

The new digital multi-parameter WET150 soil sensor represents the culmination of forty years research and development at Delta-T Devices. Through a number of key design innovations it delivers researc

  • Product Name:WET150 Multi-Parameter Soil Sensor
  • Model:WET150
  • Maunufactor:Delta-T
  • Country:United Kingdom

The new digital multi-parameter WET150 soil sensor represents the culmination of forty years research and development at Delta-T Devices. Through a number of key design innovations it delivers research-grade accuracy and build quality at a price point not previously thought possible. It is the ideal sensor for research of soil conditions – and for integration into SDI-12 environmental and horticultural measurement/control systems.

- NEW lower cost research-grade multi-parameter sensor

- Measures moisture, temperature and EC

- Digital SDI-12 for easy system integration

- Rugged, buriable and low power

- Accurate monitoring of growing conditions

- Detachable and extendable cable system

- 5 year warranty

A digital SDI-12 sensor that measures three crucial variables

When buried in soil or substrate the WET150 Sensor simultaneously measures three crucial variables that influence plant growth: moisture content, temperature, and electrical conductivity (EC) – a strong indicator of the general nutrient level.

A key strength of the WET150 is its ability to reliably calculate pore water conductivity (ECp), which is the ion content of the water available to the plant.

The WET150s patented sensor electronics produce research grade measurement accuracy with exceptional salinity and temperature stability ‐ essential for critical control and irrigation decisions. When the sensor is buried, temperature measurement (essential for compensating the EC measurement – to obtain optimum accuracy) is taken directly from the root zone.

Accurate monitoring of soil and substrate conditions

When installed in growing media, the WET150 can provide the accurate data required to power effective SDI-12 enabled automatic precision irrigation and environmental control systems – enabling reduced use of water/fertilizer whilst improving yields and quality of produce.

The rugged watertight build of the WET150 also makes it ideal for use in field research and outdoor farming – sensors can be left buried over very long periods of time without loss of performance. WET150 sensors can also be buried at different depths to enable monitoring of soil moisture, temperature and EC profiles.

Digital SDI-12 Interface

The WET150 is a digital SDI-12 sensor (fully compliant with SDI-12 version 1.3 standards). SDI-12 is a standardised interface for connecting digital sensors to a master device – typically an SDI-12 compatible data logger, wireless node, controller, or computer. SDI-12 defines both the digital communications and sensor power standards.

A key strength of SDI-12 is that it supports the connection of multiple networked sensors to a single input on a SDI-12 enabled master device – cutting costs and complexity.

The WET150 (like all SDI-12 Sensors) is low power and features an integrated microprocessor that enables it to perform two way communication with an SDI-12 master device.

The WET150 outputs readings in a standard SDI-12 format which can be sent to, and recognised by, the master device. The inclusion of a microprocessor also gives the WET150 the ability to perform complex internal correction, compensation and averaging algorithms that enhance the quality of the data.

SDI-12 protocol is based on a master-slave configuration. When installed in an SDI-12 network, individually addressed WET150s (slaves) are sent data requests by the master device. These requests briefly wake all WET150s in the network – and result in a measurement and data sending response from the targeted WET150. When not responding to a master request, all WET150s remain in a dormant energy saving state.

Cables and connectors

The WET150 has a high quality, stainless steel IP68 rated connector (M12 x 5-way) – connecting to the standard Delta-T range of M12 x 5-way cables and accessories.

GP2 SDI-12 Data Logger – an ideal partner for the WET150

The WET150 is fully compatible with the SDI-12 enabled GP2 Data Logger and Controller – which features simple point & click configuration.

Up to 62 WET150s can be connected to a single GP2 SDI-12 Data Logger (subject to cable length and power requirements).

In addition to SDI-12 input, the GP2 can log 12 analogue channels. The SDI-12 enabled GP2 Data Logger and DeltaLINK enable quick and easy creation of sensor networks – without need to resort to the often complex programming methods typically employed by other manufacturers.

Due to the flexibility of the SD1-12 interface and the GP2 Logger, multiple power and cabling configurations may be possible when building a sensor network. Please refer to the WET150 User Manual for further information. Alternatively please contact sales@delta-t.co.uk to discuss your application in detail.

Easy installation

The WET150’s sharp and strong pins minimise soil and substrate disturbance, preserving the original structure around the measurement rods, and making the probe easy to insert and install. For burial at depth the cylindrical shape facilitates installation in augured holes. Optional extension tubes assist with placement and removal (50 cm and 100 cm lengths, connectable).


Soil science – The WET150 is easily integrated into SDI-12 systems and delivers research-grade accuracy and reliability for researchers monitoring soil or substrate conditions. Typical areas of use include irrigation research, crop trials, phenotyping, hydrology, soil water profiling, and forestry.

Horticulture and Agriculture – The WET150 Sensor is available with a comprehensive set of calibrations and provides a simple, effective, rugged solution to checking the uniformity of growing conditions for many types of growing media. The WET150 excels in measuring the variables required to monitor and control fertigation. It is also a powerful tool for sampling soil salinity levels (which can affect crop yields).

Precision Irrigation – The WET150 sensor is ideal for precision irrigation applications. The WET150’s compact design allows it to be easily installed in grow bags. The WET150’s accurate sensor data can be used to optimise irrigation scheduling, or drive an SDI-12 enabled automatic irrigation system.

System integration – The WET150’s accurate and stable three parameter measurement, simple SDI-12 output and low power make it the ideal sensor for system integrators. Industrial rated, UV resistant cable fitted with a waterproof IP68 connector allows the sensor to be buried indefinitely, whilst still permitting easy cable exchange or extension if necessary.

Data Logging and portable readout

The WET150 is a dual purpose soil moisture sensor. It can be installed in soil or substrate and connected to a SDI-12 master device (e.g. data logger) to provide long-term moisture, temperature and EC data. Alternatively it can be used in kit form as a portable sensor connected to the WET150 readout meter to take instant spot measurements of moisture content and EC (when used in portable mode the WET150 Sensor does not provide temperature indication).


The WET150 Sensor comes complete with calibrations for mineral and organic soils plus coir, peat, and mineral wool substrates soils.

WET150 Sensor development collaboration with National Physical Laboratory (NPL)

Measurement technologies developed by the UK’s prestigious National Physical Laboratory (NPL) have played an important part in the development of the WET150 sensor.

The National Physical Laboratory’s involvement in the project centred around the challenges of calibrating a sensor that simultaneously measures both the conductivity of soil (EC) and the permittivity of soil – from which readings of soil moisture are generated.

The collaborative work between Delta-T Devices and NPL enabled the creation of new dielectric fluids with permittivity and conductivity properties that are representative of those typically found in soils and soil-free growing media.

± 0.03 m3.m-3 (3%)
See graph below this table

± (3% of reading + 0.8 ε’) 

1 → 40

± 5% of reading

40 → 80

± (10mS.m-1 + 6%) 

± 0.5°C

(0°C to +40°C range)

± 0.7°C

(-20°C to +60°C range)


Full range:

0 to 1.0 m3.m-3

Accurate range:

0.05 to 1.0 m3.m-3

ECb 0 to 500 mS.m-1

See graph below this table

for ECp ≤ 800 mS.m-1

1 → 40

for ECp ≤ 500 mS.m-1

40 → 80

from 0 to 1200 mS.m-1

Full range:

-20°C to +60°C

Accurate range:

0°C to +40°C


SDI-12 protocol 1.3 (www.sdi-12.org)

Providing water content, pore water conductivity, and temperature - together with base readings of permittivity and bulk conductivity.

Outputs are exceptionally configurable.

Operating voltage: 6 to 20 Volts


Current consumption (typical values powered from 12 Volts):

Active sensing: 22 mA average over 12 ms (average includes short peaks at 45 mA)

Active results computation: 2 mA over 188 ms


IP68, - 20 to + 60°C

~55 x 70 mm diameter

Sample volume is weighted towards soil immediately surrounding the rods


Overall: 143 x 40 mm dia

Rods: 51 mm x 2.5 mm dia

Weight: 77g (excl. cable)

Individual sensors are interchangeable

Recalibration advised every 5 years (depending on use)

The WET150 Sensor comes complete with calibrations for mineral and organic soils plus coir, peat, and mineral wool substrates



Notes: [1] The WET150 has been carefully optimised to provide accurate readings in soils and substrates - readings taken in water or air may not meet the full specification. [2] The ECp contour map is based on measurements from 30 sensors at 20°C in NPL* traceable media. Calculated ECp readings are derived from the Hillhorst equation, using the generalised “mineral” soil calibration and the default soil parameter = 4.1 * NPL is the UK's National Metrology Institute, developing and maintaining the national primary measurement standards.