It is important that you know and understand the following terms:
| A process - in control engineering this is something which converts a input information flow into an output information flow |
| A manipulation - this is a process input which can be altered by the local control system to bring about a desired change in the process |
| A disturbance - this is a process input which changes outside of the influence of the local control system and disturbs the controlled variables. Typical disturbances are raw material variations, rain on the outside of a distillation column, changes in plant steam pressure and changes in upstream and downstream process units. |
| A controlled variable - this is a process output which we wish to control at a particular value. |