A setup for metrological measurements of X rays in the energy range of 50–1000 eV is described. A Z pinch with a discharge time of a few microseconds is used as the X-ray source. Radiation of a given energy is selected with the help of multilayer X-ray mirrors in combination with special X-ray filters. Along with the tested detector, an absolutely calibrated reference AXUV-5 detector is used to determine the density of incident X-ray flux in each energy range. The measured characteristics of some detectors are presented.