direction parallel to the axis of tubular member 10 support member 34 may be mounted on a rack and pinion mechanism for example that is actuated by a reversable dc motor in the preferred embodiment of the invention that will be described it will be assumed that non destructive inspection of tubular member 10 and coupling 12 will be performed by the well known eddy current method although this invention is not so limited top arm 16 has four individual eddy current probe assemblies 20 evenly distributed along its length with the active end of each probe not illustrated extending downwardly so that it may ride on the outer surfaces of tubular member 10 and coupling 12 in like manner bottom arm 18 has four equally spaced probe assemblies 22 with respective probe elements 22a 22d extending transversely of the arm and riding on the inner walls of tubular member 10 and coupling 12 each of the probe assemblies has two or more electrical wires that extend through the center of its respective inspection arm 16 or 18 to form a bundle or cable 40 42 that exits from the interior of the arm by means of an appropriate connector 44 preamplifiers 46 and 48 are mounted on brackets 26 and receive the respective cables 40 and 42 to amplify the inspection signals the outputs of preamplifiers 46 and 48 pass through the hollow interior of rotor member 28 and motor 30 and couple to slip ring brush assembly 32 terminals on the stator of assembly 32 are.