Try to solve this problem (Siemens)

Ok folks I posted this problem last spring and I would like to thank each and every one who replied. The problem that I have is yet to be resolved. I have not had to deal with this issue until now so I really need your help.

The Problem: I have a Vitrification furnace that burns oxygen enriched fuel at 2900 F. I have 2ea. Inlet oxygen analyzers that monitor how much O2 is being added to the furnace (Melter). The range of the O2 is from 20% to 35%, now I need to develop an alarm that will activate when one analyzer drifts + or - 5% from the other analyzer.

The alarm is intended to alert the operator that one or the other analyzer may need servicing. Both analyzers will be online at the same time and will be reading the same oxygen stream. I am programming with Siemens Simatic S7 and programming a Siemens CPU 414-3.

Here's an old S5 function block written to do pretty much what you require...you should be able to convert this to S7 easily enough

Thank you kirk, But I don't understand STL programming is there anybody who can help me using Ladder or Logic Block diagrams.

strebej said:

But I don't understand STL programming is there anybody who can help me using Ladder or Logic Block diagrams.

Click to expand...

Oh, without trying to sound harsh..

Perhaps this would be a good time to learn.

What Kevin has posted is fairly easy to follow as it has been annotated pretty well.

Perhaps you could write down psuedo code of the FB that Kevin posted, then use this to develop your ladder logic.

All Kevin is doing in the block is comapring the two analogue inputs, then depending on the result he either sets an alarm or resets the alarm bit and timer, as explained in his annotation.

Paul

Just read your previous post on this....

http://www.plctalk.com/qanda/showthread.php?t=14566

....Willy Maas posted a ladder solution there!!