ABSTRACT
Analog systems and computer-based systems carry out the same functions though the methods employed differ. Indeed, the analog instrument-based systems involve the use of analog computers to solve the valve positioning problem. The typical process computer handles from eight to several dozen control loops: thus, the failure of a process computer has a more dramatic effect. Any modern system will accomplish the first two functions automatically whether it is built using analog devices or process control computers. With computer technology the process computers can deliver process information to a spreadsheet program or statistical analyzer for on-the-spot analysis. Process computers provide enhancements to measurement and control functions. The mathematical precision of the computer allows for more accurate modeling of the process being controlled. Complex continuous simulations can be carried out that result in optimized plant operations. Systems using computers to run wastewater and water treatment plants have been in use the late 1960's.
