Abstract: The invention relates to a device for the measurement of the thickness profile of a metal product in the form of a moving strip or a moving plate, of the type composed of an X-ray source emitting in the direction of the said product, an X-ray detection unit (21) located on the other side of the product with respect to the said source, means (22) for processing the signals emitted by the detection unit enabling the thickness profile of the said product to be measured, and means (23, 24) for cooling the detection unit and means for processing its signals, wherein the detection unit and the means for processing its signals are arranged on a support plate (18) fitted with a closure plate (19), the closure plate including electrical (27) and fluid (25, 26) connections necessary for the operation of the detection unit and of the means for processing its signals, in that the support plate is inserted into a box of which one of the side faces has an opening, means (20) for the attachment of the closure plate and mean