PLC Programming

[Timmy01]

I'm currently working on a project in which I'm using a PLC as a supervisory system to monitor an Arduino uno that's controlling a process with a PID algorithm. I'm looking for advice on how to construct the ladder logic. I completed the conversion from integer to floating-point, as well as the supervisory part of determining whether the feedback is within the tolerance range of the feedback. Can you tell me what to tell the PLC if the condition is met or not? Also, how can I make the PLC programming more robust by requiring meaningful actions to be performed?

[panic mode]

if you are working on a system where product B is monitored by product A, you should have some idea about the purpose of monitoring, what is acceptable deviation and what a suitable response is when that deviation is encountered. that would dictate what values need to be exchanged between A and B. so far it is unclear why there is need for two products (seem to be an unnecessary complication).in some cases this added complexity may be intentional for the sake of redundancy. but as stated not enough is known...

[Crossbow]

Why not use the PLC to run the process?  They can do PID control too.  Seems like two controllers where only one is needed.