Abstract: An ultrasonic probe for measuring liquids at high temperature and under high pressure. The ultrasonic probe comprises a leak-tight protective sleeve which has an end face closed by a thin metallic wall. The protective sleeve contained internal elements which are in particular a transducing piezoelectric plate and a damping cylinder. The piezoelectric element has one face which is in mechanical and electrical contact with the internal face of the thin sleeve wall and the other face which is supported on a damping cylinder. The thin sleeve wall of the sleeve end face is constituted by a metallic layer obtained by cathodic sputtering.