Hello ... I have programmed many PLCs, but I never needed to know the answers of following questions untill yet. I got always the PLC and then I wrote the PLC code. 1. How is the way to select the right PLC? 2. I only found data about user memory and I/O memory. Is the CPU usage also important? 3. How can I determine the memory, if I want to implement a PID controller? 4. Which CPU usage is critical to implement an additional PID controller. Maybe there is a list or tool with the information about the needed memory and the process time, for example for a PID controller. Thank you so much for your answers.