Collection: Tensiometer sensors

Tensiometers are used to continuously measure soil moisture based on soil moisture tension. The drier the soil, the greater the potential for adsorption and capillary forces that bind water in the soil. Depending on their design, tensiometers can measure soil moisture tensions from 0 to approximately −850 hPa.

Soil moisture is measured via soil moisture tension, i.e., the drying out of the soil. The measurement is performed using a water-filled, hermetically sealed, porous ceramic cell ("ceramic candle") (1) with maximum pore diameters of approximately 1 µm, which is placed in the soil. A transparent plastic tube (2) is used to monitor the fill level. Degassed water is used for filling, which can also be colored if desired.

As the soil around the ceramic cell dries out, enough water is "drawn" from the ceramic cell until equilibrium with the surrounding soil water is reached. The resulting negative pressure is displayed on a manometer or can be further processed electronically using a pressure sensor (4).