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Tag ExcDev and CompDev changing automatically in SMT

Question asked by MikeMander on Dec 5, 2016
Latest reply on Dec 5, 2016 by tmcmanus



I am working on a system where the Tag ranges have not been set correctly for a lot of tags. As users are finding and reporting that the ranges are wrong and don't reflect where the data sits, we are updating the tag's Zero and Span in PI-SMT PointBuilder. What we have been seeing is that when the tag is saved with the new span, the ExcDev value and CompDev value are also being automatically updated to reflect the same ExcDevPercent and CompDevPercent as the previous range. it only shows the updated ExcDev/CompDev values once the tag has been saved and we were missing this and so didnt realise we were losing data. The problem is that we don't want this to happen as the original exception and compression settings were correct. I know that the CompDevPercent is preferred over CompDev, but in SMT the values are shown in CompDev and the dropdown is always selected to Eng. Units. Does anyone know why or whether there a way to stop this from happening? I would prefer not to have to download the tag attributes into Excel using the PI-SMT add-in as this is more work for individual tags.