1991.064.422
Print, Photographic
Black and white photographic print depicting a man operating a Jones & Lamson optical comparator at the Champion Spark Plug Co.
Caption reads: Comparator. An optical comparator is used to measure insulator contour dimensions. A powerful beam of light projects a sharp silhouette of the insulator onto a screen. The shadow, magnified to twenty times actual size, must fall within tolerance lines representing a few thousandths of an inch. This precise test is typical of the exacting controls demanded by Champion.
