|Definition:|| function to work on process variable quantities, which is composed of basic functions of process control, specific to particular functional units of the plant|
Note 1 to entry: In addition to process control functions associated with specific control levels, there can also be process control functions that link input and output variables across several control levels. For instance, a process control function in the feedback path with the controlled variable as input variable and the manipulated variable as output variable, describes the action path from the sensing element via the controller to the final controlling element. Another process control function connects the operator with the indicators for the process variables. In view of the diversity of definitions of process control functions, standardization is not appropriate at this time.
Note 2 to entry: This entry was numbered 351-31-17 in IEC 60050-351:2006.