With invention of programmable controllers, much has changed in how an process control system is designed. Many advantages appeared. Typical example of control panel with a PLC controller is given in the following picture.Advantages of control panel that is based on a PLC controller can be presented in few basic points:1. Compared to a conventional process control system, number of wires needed for connections is reduced by 80%2. Consumption is greatly reduced because a PLC consumes less than a bunch of relays3. Diagnostic functions of a PLC controller allow for fast and easy error detection.4. Change in operating sequence or application of a PLC controller to a different operating process can easily be accomplished by replacing a program through a console or using a PC software (not requiring changes in wiring, unless addition of some input or output device is required).5. Needs fewer spare parts6. It is much cheaper compared to a conventional system, especially in cases where a large number of I/O instruments are needed and when operational functions are complex.7. Reliability of a PLC is greater than that of an electro-mechanical relay or a timer.