Tensiometers are used to continuously measure soil moisture based on the suction tension. The tensiometer measures the suction tension from 0 to approx. -600 mbar. In a dry environment, the clay cell of the tensiometer transports water from the inside to the outside due to its capillarity, creating a negative pressure in the closed tube. This negative pressure is a measure of the humidity. The suction tension is the force with which the water is held in the soil or is available. The plant roots must provide this force in order to absorb water. Intensive substrate contact is a prerequisite for a rapid tensiometer reaction and for measuring typical values for certain soil and substrate types.