Abstract: A method and apparatus are disclosed wherein a plurality of basis weight sensors are interleaved with one or more processing stations used to conjoin or apply one or more layers to a base substrate to form a multilayer product such that a sensor is located on the input and output sides of each processing station. Each of the sensors can be calibrated with a plurality of product calibrations such that multiple output signals corresponding to multiple products can be generated simultaneously by the sensors. Each of the sensors is calibrated with product calibrations corresponding to the product or intermediate stage of the product which it monitors, the layer applied by the processing station preceding it, if any, and the layer applied by the processing station succeeding it, if any.

Abstract: Method and apparatus for measurement and control of an industrial process by detecting the average transmittance of a radiation beam which passes through the process material. A radiation source (28) having an intensity I.sub.o is positioned on one side of the material to be measured and a suitable radiation detector (32) is positioned on the other side. The transmitted radiation intensity, I, is measured by the sensor. An index Z commensurate with the degree of nonuniformity of the variable in the material is determined, and a process signal is generated from a quantitative relationship among I, I.sub.o, and the index Z. In a first embodiment implementedd in a system for measurement and control of the basis weight of paper in a paper production process, the index Z is indicative of the nonuniformity of the material mass distribution in the sheet and is determined by measurements with a separate formation gauge operating on-line with, but independently of, the basis weight sensor.