A measuring arrangement for radiometric density-or fill level measurement of a medium in a measuring tube in the field of automation technology. The measuring arrangement is composed of a radioactive radiation source, a detector unit and a clamping apparatus for the radiation source as well as the detector unit. The invention is distinguished by features including that the clamping apparatus has blocking elements, which make the radiation cone of the radioactive radiation source between the measuring tube and the clamping apparatus laterally inaccessible. In such case, the blocking elements are arranged in such a manner that the measuring arrangement is suitable for different diameters of the measuring tube, without the blocking elements losing their protective action.
