Process for determining the value of a physical quantity

A process for determining the value of a physical quantity for a desired product comprising the steps of:

• successively feeding at least one measuring device with a plurality of model products for which corresponding values of said physical quantity are known;
• successively measuring a plurality of model measured values of said physical quantity on said at least one measuring device for said plurality of model products to produce numerical initial data;
• recording said numerical initial data to create an initial file of data;
• distributing said numerical initial data into a plurality of sub-groups which are homogeneous and have the property that each sub-group is representative in relation to each other sub-group and with respect to said initial file of data;
• constructing a model which establishes a mathematical relationship between said numerical initial data and said corresponding value of said physical quantity which is known for each of said plurality of model products;
• validating said model;
• feeding said at least one measuring device with said desired product;
• measuring a plurality of sample measured values of said physical quantity on said at least one measuring device for said desired product to produce sample data;
• recording said sample data;
• and
• applying said model for said sample data to determine said value of said physical quantity for said desired product.