the invention relates to apparatus for detecting the stuck point of a conduit , such as drill pipes , in a borehole while eliminating any stress on the detection means during the measurement . a two - part body member is suspended from a cable with the two parts mounted movably with respect to each other . each part is anchored independently in the drill pipes and movements between these parts are detected when stresses are applied to the drill pipes from the surface . after anchoring , a spring , designed to bias the two parts of the body member toward each other , is disconnected from the top part of the body member . an angular detection means is mounted between a mobile sleeve and the top part of the body member . before the measurement , the sleeve is uncoupled from the bottom part and reset in relation to the top part . during the measurement , the sleeve is blocked in the bottom part .