Abstract: An aperture piece to be used in conjunction with backscatter instruments for measuring the thickness of a coating on a substrate of a concave workpiece. The aperture piece being selectively shaped so that a sample support surface, including an aperture through which radiation from a radioisotope is transmitted, may be inserted into the interior space defined by the concave workpiece to engage the concave surface. A method of calibrating backscatter instruments using the aperture piece to make correction for the failure to have a planar mating relation between the sample support surface and the concave workpiece.

Abstract: A backscatter measurement device for measuring the thickness of a coating on a strip of substrate material moving from a feed supply to a take up location at a predetermined speed. A measurement wheel is provided on the rim of which are mouted backscatter probes for irradiating and detecting the backscattered radiation from the coated substrate. The coated strip of substrate material is threaded around the outer surface of the rim. The measurement wheel is rotated at a speed such that the tangential speed of a point on the rim equals the speed of the moving strip whereby the probe and an adjacent point on the strip are stationary relative to one another while the point on the strip is adjacent the rim. Thus thickness measurements may be taken without stopping the movement of the coated strip.

Abstract: A backscatter measurement device for measuring the thickness of a coating on elements forming a web of substrate material moving from a feed supply to a take-up location at a predetermined speed. A measurement wheel is provided, adjacent to the rim of which is mounted a backscatter probe for irradiating and detecting the backscattered radiation from a coated substrate. The web of substrate material is threaded around the outer surface of the rim. The measurement wheel is rotated at a speed such that the tangential speed of a point on the rim equals the speed of the moving web whereby the probe and an adjacent point on the web are stationary relative to one another while the point on the web is adjacent the rim. Thus thickness measurements may be taken without stopping the movement of the coated web. This backscatter measurement device is further provided with indexing apparatus to position automatically the probe directly adjacent an element to be measured on the web.

Abstract: A backscatter measurement device for measuring the thickness of a coating on a strip of substrate material moving from a feed supply to a take up location at a predetermined speed. A measurement wheel is provided on the rim of which are mounted backscatter probes for irradiating and detecting the backscattered radiation from the coated substrate. The coated strip of substrate material is threaded around the outer surface of the rim. The measurement wheel is rotated at a speed such that the tangential speed of a point on the rim equals the speed of the moving strip whereby the probe and an adjacent point on the strip are stationary relative to one another while the point on the strip is adjacent the rim. Thus thickness measurements may be taken without stopping the movement of the coated strip.