Apparatus and method for sensing multiple parameters of sheet material

Abstract From the Canadian patent

A method and apparatus for simultaneously generating spatial profiles of moisture, thickness, and basis weight across a moving web of paper in a paper making machine. The apparatus includes a plurality of means for generating first and second beams of coherent microwave radiation and for generating signals proportional to the intensity of radiation applied to reflected from, and transmitted through the web. The incident reflectance, and, transmittance signals for the two frequencies are used to solve simultaneous equations to generate moisture thickness, and basis, weight values at various positions across the web.