The PLC offers many advantages over conventional relay control.
The flexibility is much easier for a PLC because it is easy to change the program, rather than rewire a circuit with conventional relay control.
Reliability– the PLC takes the place of many wires and relays in a conventional relay system. Once a program is written it can be saved and easily reused or downloaded to other PLC’s.
Lower Cost– it is less expensive to install a PLC instead of many relays and wires to complete circuits.
Communication Capability– The PLC is capable of communicating with other devices or computer equipment for data gathering, supervisory control, process parameters, monitoring devices, and download/upload programs.
Troubleshooting – Troubleshooting is easier because a technician can watch the PLC scan in real time on a display. This allows for much faster finding and repairing of problems than the standard relay system.
Faster Response Time – The PLC operates in a fast reliable response time. It takes only fractions of a second for a PLC to execute an operation.