Abstract: Process and apparatus for measuring variations in a stream of material, such as thickness in a strip from a mill. A radiation source and detector are positioned at a gauging station. The stream of material moves past the station providing an electrical signal varying as a function of material at the station which signal includes a lower frequency component, a higher frequency cyclical component, and a higher frequency noise component. A circuit for providing a thickness output varying as a function of the lower frequency component of the signal, and a circuit providing an output indicating chatter varying as a function of the higher frequency cyclical component. Digital and analog versions are disclosed.

Abstract: Apparatus and method for measuring thickness of sheet material, particularly in a rolling mill, and controlling a roll stand. An X-ray florescence analyzer for determining the components of the sheet material, a radiation thickness gauge with a calibration system for gauging material of varying composition, and a computer for calculating a calibration signal for the thickness gauge based on the output of the analyzer, with the thickness gauge output providing a measure of the thickness of the sheet material at the gauge and a control signal for controlling the roll stand.