RADIATION PYROMETER

摘要

A radiation pyrometer has an inner tube with a lens mounted in a rear portion which is stepped to a forward portion of reduced diameter that is open at its forward end. An outer tube extends coaxially around the inner tube and is separated from it by an annular gas passage. The outer tube has an aperture at its forward end that is smaller that the external diameter of the forward end of the inner tube and larger than the internal diameter. The outer tube has gas inlets into the passage while are located rearwardly of the forward end of the inner tube, the area of the gas inlets being greater than the gap between the forward end of the inner tube and the outer tube. Gas flows through the inlets, along the passage, across the forward end of the inner tube and out the aperture, thereby setting up a substantially constant pressure in the rear portion of the inner tube and reducing the entry of contaminants.