Description

A tensiometer is a device for measuring, when the soil is not too dry, the soil matric potential. In old terminology, the matric potential was called the soil moisture tension. Because the instrument measures tension, it was called a tensiometer. Tensiometers are the only instruments capable of providing a direct measurement of soil matric potential due to the hydraulic connection between soil water and the water inside the tensiometer shaft. Soil water potential is thus translated into a negative pressure inside the tensiometer. At equilibrium, the partial vacuum inside the tensiometer equals the sum of soil matric potential.