Abstract: A radiation gauge for measuring the profile of a moving strip, e.g. strip issuing from a strip rolling mill, comprises two X-ray tubes arranged on one side of the strip. The X-ray tubes are connected in push-pull configuration, for pulsing in alternation, and they each produce a respective curtain of radiation which intersects the strip in a respective straight line extending across the width of the strip, perpendicular to its direction of travel: these two straight lines are aligned with each other and overlap slightly in the center of the strip. A linear array of radiation detectors is disposed on the other side of the strip, so as to receive the radiation which passes through the strip. Signal processing circuitry processes the detector output signals to display the deviation of the thickness profile of the strip from a predetermined thickness profile.