The term tensiometer applies to at least two different devices, one designed to measure the surface tension (scriptstylegamma) of liquids and the other to determine matric water potential (Psi_m) (soil moisture tension) in the vadose zone. Construction A tensiometer for measuring matric water potential 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 tensi… (More on Tensiometer)