Abstract: A capacitive sensor device for use at least up to 1300.degree. C. and 40 bar, including a coaxial cable comprising a conductive sleeve (10) and at least one inner conductor (21) which are separated by an insulator (19), said cable having an end portion (1) of enlarged diameter forming a probe in which the insulator is an anticorrosive refractory element (9, 29) locked by a first and a second anticorrosive refractory metal protection element (5, 4), welded to the sleeve and to said inner conductor, respectively, which second protection element forms an electrode (4) having a flat surface (4a) of an area larger than the cross-sectional area of the end portion of the inner conductor.