W.E.T. sensor


The W.E.T. sensor has been developed together with, amongst others, the Institute of Agricultural and Environmental Engineering (IMAG-BV), Wageningen, the Netherlands. The WET sensor measures three vital soil properties directly within the soil: Water content, Electrical conductivity and Temperature. The sensor is unique in its ability to measure pore water conductivity, which is the EC of the water that is available to the plant. Traditionally this measurement has been made by the time-consuming and error-prone method of extracting pore water from the soil by suction, before measuring it with a standard conductivity meter. In contrast, the WET sensor is simply pushed into the soil (or other growing medium) and then read directly using the hand held meter.

The measurement is made possible by use of an integrated circuit specially developed at IMAG in order to measure accurately the permittivity and conductivity of the bulk soil. From this the conductivity of the pore water is calculated using a unique mathematical model. The model eliminates the need for soil specific calibration and makes the readings insensitive to the degree of contact between probe and soil. The three-pin probe is specially designed both for ease of insertion into the soil and to enable local measurements of permittivity and conductivity. It is the combination of these features which enables the pore water conductivity to be calculated reliably from the dielectric readings. The software provided with the WET sensor processes the dielectric data from the probe, calculates and displays the pore water conductivity, and saves the readings to a data file.

Applications
- Salinity monitoring;
- Pollution and land reclamation;
- Soil moisture mapping;