Really i don’t inderstood how the intermpolation think that like easy chart do is nice:
if I have a value in the historian at (for ex.) 1000 for 1000000 years and one day the value change to 1 the easy chart interpolate from last recording value and the new one;
practically show me the value decrease very slowly in the last 1000000 years in my mind this is not an interpolation is an error!!! I try to read every place in the forum but no one has the same idea of the interpolation; means that the function is too smart for me
If you give the component two data points, no matter how much time they’re separated by it’s going to draw a straight line between those two points. The length of time between will only change the slope of that line.
The chart has no idea what actually happened it can only try an interpret what “might” have happened based on the data it is given.
this is what happens; not what my mind aspect:
if we save the data only at value change the value is 1000 (like my example) until the new value comes. The system decides to interpolate… why?
for me, this is a very big mistake of the system:
I understood: if I save the value every 1 second the system works fine, but in that case, I lose completely the possibility to save space in my database (and the space in a DB has a huge cost).
I typically find that visualizing how interpolation applies to different tag types is very helpful. Here is a screenshot where each column represents a tag type using the different Deadband Styles:
I would draw our attention to the Float Tag (left most column). Similar to how you described the Auto/Analog Deadband Style for our Float Tag shows the value rapidly decreasing until around 12:30 PM. If we compare this to the Discrete Style for the same tag we can see the chart instead looks like a series of smaller steps.
It seems like you do not want interpolation to be on for your tags. You can likely switch the Deadband Style on your tags to resolve this. If your tags are Double or Float tags, they will need “Discrete” Deadband Style set on the Tag History settings.
There is an Allow Tag History Interpolation property on the Easy Chart. Set that to false and the Chart will not interpolate the data, however, you may (probably will) end up with gaps in the data.
If that doesn’t suit your needs, then your best bet is to move away from the Easy Chart and build the dataset yourself. I often find that the Easy Chart isn’t so easy and the Classic Chart allows me to do what I need to get what I’m looking for.
