Automatic Process Control with Radiation Gauges

The optimum automatic process control system requires a continuous flow of information relating to the process variations. Radiation gauges utilizing absorption or scattering of radiation produced by a radioisotope source as a means of measuring thickness, weight per unit area, or density of a product offer a means for obtaining this information. Process control utilizing these gauges differs from the usual control system in that large delays exist between the measuring point and the control point. The existence of such delays requires the use of specialized control systems, usually utilizing interrupted control. A typical control system of this type is described and the safety precautions required to prevent malfunction or damage are discussed.