A detector with a telescopic carrier/guide rod at which a measuring probe is disposed at one end, wherein the carrier/guide rod features at least two tubes longitudinally movable inside one another, in which respectively two tubes disposed adjacently in radial direction form an outer tube and an inner tube, whereby the respective outer tube at its overlapping tube end facing the measuring probe features a clamping means for engaging the inner tube. In accordance with this invention, the clamping means is formed as a clamping device that features a profile clamp with a quick-locking device. The profile clamp comprises a holding ring with two half shell-shaped clamping ring segments that are interconnected flexibly on one side and on the opposite side they can be clamped together with a clamping lever. The holding ring features ring breakthroughs and the outer tube the corresponding tube breakthroughs for the accommodation of clamping pieces that are pressed against the inner tube when clamping the clamping ring segments together under pressure. Preferably a clamping ring segment is formed on the holding ring.