Abstract: The tubing system comprises a number of measuring stops or surfaces arranged in a predetermined mutual spaced relationship. The spacing is utilized for determining the displacements in the material enclosing the tubing. This displacement is ascertained by a measuring probe introduced into the tubing from the outside. The measuring stops are provided on measuring tube unions or coupling sleeves in order to ensure that displacements in the material can also be transmitted to the measuring stops even in relatively soft material without a stiffening effect of the tubing. The connection between the measuring tube unions or coupling sleeves takes place exclusively through a telescope-type protecting tube insert. A rigid anchoring of the measuring tube unions or coupling sleeves to the inner wall of an accommodating hole or bore hole provided in the material to be investigated takes place through filling collars fastened to the outside of the measuring tube unions or coupling sleeves.

Abstract: In the medium to be examined there is embedded a measuring tube which possesses at its inner surface essentially equidistantly spaced measuring markers. These measuring markers are in the form of mechanical stops or impact members having an impact surface forming part of a right circular cone. To determine the spacing between neighboring measuring markers there is provided a measuring probe or sensor having two measuring heads connected with one another, by means of a connection tube, such that they are relatively shiftable in the lengthwise axis of the measuring probe. Each measuring head is constructed as a mechanical counter stop having an impact or stop surface forming part of a spherical surface. Internally of the connection tube there is arranged an inductive length transmitter producing an output signal characteristic of the spacing between the measuring heads.