Portable measuring system for leafs water potential. The instrument provides accurate and secure measurements of the water stress of leafs. The design of the sealing system of the chamber minimizes the damaging of the leaf. The provided pressure is measured continuously by a semiconductor type pressure converter. The user at any time can “freeze” the pressure indication with just one click. It has needle valve, in order the user to be able to adjust with precision the anode speed of the pressure to the chamber.