Abstract: A width gauge for measuring the width of self-radiating (i.e. hot) rolled material comprises a camera containing two linear arrays of photodiodes, the camera being arranged to produce on each array an image of a respective one of the edges of the material. To avoid problems in detecting the edges caused by dark spots which may be produced on the material by slag or uneven cooling, both arrays are scanned from the less illuminated end of the array to the more illuminated end.Other embodiments employ multi-camera arrangements to improve accuracy and/or correct errors due to changes in the position of the material, and a further embodiment employs a monochromatic light source to back-light the material and a filter in the camera matched to the light source.

Abstract: A calibration device for calibrating gauges for measuring the width, diameter or length of luminous material, such as hot strip-, rod- or tube-like material, comprises an elongated tube of sintered quartz having an elongated light source disposed along its axis. The quartz has good dimensional stability, and diffuses the light produced by the source. It therefore simulates the hot luminous material normally measured by the gauge, without itself being very hot.