The apparatus contains a measuring comb for the material to be tested. The plate like projections of the comb define measuring gaps of different widths through which the material passes to be tested for determining characteristic magnitudes associated with that material. The measuring comb is adjustable transversely to the direction of movement of the test sample and each measuring gap is adjustable to a nominal position. Consequently, the test sample passes through each measuring gap under the same geometrical conditions and is not subjected to deflections which vary from one measuring gap to another. Thus, the method improves the testing result and provides the value of the material. |