PCT No. PCT/US93/02621 Sec. 371 Date Dec. 10, 1993 Sec. 102(e) Date Dec. 10, 1993 PCT Filed Mar. 22, 1993 PCT Pub. No. WO93/19473 PCT Pub. Date Sep. 30, 1993.A nuclear gauge (7) for making measurements of traveling webs (11) in continuous sheet-making processes includes an enclosure (20), an encapsulated nuclear source (28), and a wheel-like member (10) mounted in the enclosure means for carrying the encapsulated nuclear source between two angularly-displaced positions. The first of the angularly-displaced positions is the position whereat the encapsulated nuclear source makes measurements of a web that travels past the gauge, and the second position is the location whereat the encapsulated nuclear source faces a sidewall of the enclosure means at a location remote from the first position. The nuclear gauge also has an aperture (16) which is formed through the enclosure for providing a window through which the encapsuled nuclear source, when located in the first position, can emit radiation onto a web that travels past the window.
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