Rate of Change Alarm

I am looking to generate a Rate of Change alarm on some floating values. I am in the process of converting a Wonderware site to Ignition. In WW, there is a simple checkbox with the % per Sec/Min/Hour that generates the alarm. Any suggestions for an easy way to generate/re-create this alarm?

There are a few ways that I can think to do this, but none of them are all that simple.
You could:
create a UDT
-with a trigger expression tag, evaluating on the Sec/Min/Hour,
-and a memory tag, that stores the value of the source tag.
On a tag value change script in the expression tag, you could write to the memory tag, which would have another tag value change script where you could then compare the previousValue vs the currentValue and determine if the threshold had been surpassed and alarm if it did.

EDIT: Another UDT structure you could use that might be a little easier.

RateOfChangeUDT.json (1.2 KB)


Hi @KMuldoon im also trying to implement a rate of change alarm for a temp, idea is to analyze the ROC as well as high and highhigh alarms, because in some instances the ROC implications far exceed the high temp average, your comment is the closest ive seen to what appears to be a working structure but i was hoping you could assist me more by breaking down your script so i can better understand it?
particularly the tags that need to be replaced and how to implement it to alarm at a particular ROC.

thanks ! much appreciated

Honestly, I never implemented it. It wasn’t of concern to the customer. Sorry.

Sure! I’d be happy to go over any part of the script. Feel free to PM me and we can talk about it.

This works really well, thank you!