I'm trending pressure PV and SP at a pump.I'm experiencing the following issue: the trend in the Easy Chart randomly shows gaps in one of the two measures (not always the same measure), while the other keeps being printed correctly - sometimes those gaps are as wide as 5/6 days.
If I select the raw data from the database table e.g. for the SP value I get the following list:
If I compare the gaps with the values in the list, I really cannot catch any relationship.
A colleague of mine suggested to check the Disable Tag History Data Cache in the project properties, but it does not seam to take me further
Your gaps are being caused by tag quality being some value other than good. You can tweak chart settings to interpolate these gaps. Check the documentation.
Hi Frank, if your suggestion is pointing to the 600 values in the dataintegrity field, I'm not sure that is the cause: I cannot see any relationship at all between those 600s and the missing portions of trend.
Anyway I will try what @cmallonee is suggesting and I will back to you.
Hi @cmallonee, I'm back on this topic after a while. I've just started a new project, this time a Perspective project. I must say I'm really upset this time, because the same gap problems appear in the Perspective PowerChart component too. Just for test I'm trending Memory tags - tag quality is constant and Good. Nontheless the trend is showing gaps, whereas all samples appear with dataintegrity=192 in the sqlt_data_xxxxx trend table. Same behavior in a Vision page with an EasyChart.
Sorry, but I'm really starting to loose confidence in the Ignition chart components.
Any suggestion is appreciated, regards
When it comes to gaps in History, you should probably reach out to support instead of the forums, because there's almost always multiple things which could be happening - each of which requires a different approach.
This isn't surprising, because your data hasn't changed. Neither chart can make a guess as to what value is supposed to be displayed at a given point.
While using the Perspective Power Chart, you might need to manipulate the pen of the tag being charted; the default behavior of pens is to break the line where there is missing data:
Edit: This screenshot was taken by clicking the edit icon (pencil) of a displayed pen, then scrolling down in the resulting panel.
My suggestion is to spend some time researching how the charts are supposed to work when data is missing, and to also examine why data is missing so that you can prevent the data loss and minimize the impact such loss can have on projects.
Hi @cmallonee, thanks for your support. There's no data loss at all: next the data that Ignition collected from my tests:
In the PowerChart and in the EasyChart as well values 4, 3, 6 do not appear in a 15 minutes time representation and if I tick the Show a break in the line when data is missing prop, I just get a straight line from 5 to 2.
I really cannot manage to see where the problem is, other than in the way the component is collecting and plotting the values.
That screenshot doesn't tell me enough -- there's every possibility those returned values belong to a different tag or have a "non-good" quality (which would not be charted). Like I said previously, it seems like it is time to contact support because this could be a larger issue and the forums will not be able to help you do a deep-dive into what could be causing your issue.
That screenshot gives me much more important data, and does raise the question of why those valid points are not being charted. Unfortunately, all I can tell you is that I would expect the chart to use those points, and that you should reach out to support. Please have a screenshot of the gaps you're referencing handy, along with a way to correlate the gaps to this data.
