At what pressure tensiometer is used?

A tensiometer is a device used for measuring soil water tension. It is used at a pressure of 0 - 0.8 bar. It is effective up to a tension of 0.8 bar. At this pressure, air enters the closed system through the pores of the cup and makes the unit operative. It is useful to check the moisture in the soil and help in deciding when to irrigate the field.