Tensiometer (soil science)

A tensiometer in soil science is a measuring instrument used to determine the matric water potential (

This device typically consists of a glass or plastic tube with a porous ceramic cup and is filled with water.

The top of the tube has either a built-in vacuum gauge or a rubber cap used with a portable puncture tensiometer instrument, which uses a hypodermic needle to measure the pressure inside the tensiometer.

The tensiometer is buried in the soil, and a hand pump is used to pull a partial vacuum.

As water is pulled out of the soil by plants and evaporation, the vacuum inside the tube increases.