Delta-T Devices Ltd.

- Model WET-2 - Irrigation Research WET Sensor


In just 5 seconds the WET Sensor checks 3 crucial variables that influence plant growth: water content, temperature and pore water conductivity (ECp), the EC of the water that is available to the plant.

  • Measures Water content, EC and Temperature
  • Measures directly within the root zone
  • Rapid checks of growing conditions
  • Ideal for precision irrigation

Vital tool for precision horticulture
The WET Sensor is used throughout horticulture, especially by soft fruit growers and for crops grown in protected environments, where correct growing conditions are critical to both yield and flavour. The compact sensor can be inserted directly into the growing medium with minimal disturbance to either roots or shoots, and provides information for process optimisation, checking growing condition uniformity and precision irrigation.


WET Sensors are normally ordered as a complete kit that includes a WET Sensor, an HH2 Moisture Meter and a handy carry case. There are three types of Kit – each with a different set of substrate calibrations, including coir, peat and mineral wool. Please see below for further information on substrate calibrations and kits.

Fertigation and hydroponics
Where plants are grown in artificial substrates using hydroponic or fertigation systems, nutrients are routinely supplied in irrigation water. Nutrient levels are controlled by monitoring the water content and conductivity (EC) and adjusting the injection of liquid fertiliser into the irrigation water. The Delta-T WET Sensor excels in monitoring this vital information for precision irrigation.

Article featuring the WET Sensor – exploring Cultilene’s approach to measuring growing conditions in substrate slabs (HortiBiz 2015).

Container-grown shrubs and trees

  • Nutrients are sometimes provided by fertigation but are often provided by Controlled Release Fertilisers (CRF).
  • The rate at which these are taken up depends on several factors, including the weather conditions and precision irrigation regime.
  • The Delta-T Devices WET Sensor can be used to measure the EC within the growing media and so take much of the guesswork out of this process.

Soil salinity

If the irrigation water is recycled or abstracted from rivers and aquifers with high levels of dissolved salts, over time there can be a build up of soil salinity. Soil salinisation will eventually reduce crop yields. The WET Sensor is fast and efficient for sampling soil salinity, ensuring that farmers have the essential information they need to take remedial action as quickly as possible.

Readout and data logging

For portable applications, readout and data storage are handled by the HH2 Moisture Meter. Alternatively, the WET Sensor can be connected to a GP2 or GP1 Data Logger, making it possible to monitor growing conditions over a period of hours, days or longer. The GP2 and GP1’s smart relay capabilities allow them to control water content in response to EC or temperature.

WET Sensors used aboard China’s Tiangong-2 Space Station

The WET Sensor has been used by Chinese astronauts to conduct horticultural experiments in space. find out more.

Wet Kit Systems

Wet Kits are available with alternative sets of substrate calibrations pre-installed:

Standalone Wet Sensor

WET Sensor (bare wires)
Combined water content, electrical conductivity and temperature probe. Includes sensor calibration on CD-ROM. 5m cable.

The WET-2/w is only suitable for use with the GP1 or GP2 Data Loggers and other specially enabled devices. 

If additional horticultural substrate calibrations are required, they should be ordered at the time of purchase of the GP1 or GP2 Substrate calibration upgrades are factory installed into the GP1 or GP2 at Delta-T’s premises.

Measured parameters

  • Permittivity, ε′: 1 to 80 ± 2.5 [1]
  • Bulk conductivity: 0 to 300 mS.m-1 ± 10 (ECb)
  • Temperature: -5 to 50°C ± 1.5°C

Calculated parameters

  • Volumetric Soil Moisture, θ: 0 to 100% ± 3% [2]
  • Pore water conductivity: see graph below (ECp)

Other specifications

  • Calibration: Individual sensor calibrations stored within sensor EEPROM
  • Output: Serial data (TTL)
  • Environmental: IP68, 0 to 50°C
  • Power: 6 to 10V, ~38mA for 2.5s
  • Dimensions: ~120 x 45 x 13mm
  • Rods: ~68mm long
  • Sample volume: ~500ml

[1] Permittivity is a measure of the dielectric properties of materials, e.g. soils and substrates.
[2] Soil moisture accuracy refers to errors after applying a soil-specific calibration, within 10°C of calibration temperature.