Two tanks with three continuos, redundant level sensors each need to be supervised so that when a certain total volume is reached, a specific actor is triggered. This could be done via the installed PLC system, however it is likely that a regulatory body will demand a hardware solution. However SIL compliance is not demanded. The important thing is that it's hard to alter the function or change parameters.
So I need a device that can do the following:
- Take average from three analog signals for tank 1, add offset
- same for tank 2
- add both values and give a digital signal to trigger if total exceeds a certain value
- don't add value for tank 1 or 2 to the total, if a maintenance switch assigned to this tank is on
Can this be done in a logic module? If so what specifications (not the specific model) do I need? If not, what's the device called and how to specify?