I can't find anything that will plot 2 pens (tags) something like every 1 minute.
Everything I see is that they all have to get they data from a "Tag History"?
Tags hold a single value. By themselves, they retain no knowledge of prior values. That's why you keep bumping into references to history. If you want to plot anything, it has be placed in history as it happens. Or it won't exist to be put on a trend.
Set up a history provider. Turn on history for the tags you want to be able to plot.
Just so I'm clear on this? I have setup trending charts in other software 100's of times and I have always had the ability to actually see the Graph being populated from the tag data in realtime.
Example: My tags are being updated in realtime "as they change", so if I setup a xy graph to read the tag values every 1 minute and plot as time move forward. "This would be realtime".
But in Ignition I can only generate a trend graph from a "History of Data"?
Is this correct?
Sorry for the confusion.
Yes.
There's always a trade-off. "Automatic" short-term history (a few minutes, perhaps an hour) on every possible tag, in a system with unlimited tags, is a recipe for extreme memory (RAM) overload.
Or you can allow UI elements to buffer in memory on demand, but there are two negatives you must accept for that:
- The trend will start when the UI opens, and will be forgotten when the UI closes.
- If multiple copies of the UI run the same trends, they'll all use RAM separately. (Pretty likely in multi-user SCADA, as opposed to single-user HMIs.)
Since there are occasional uses for memory buffers for such short term trends, I created a tool for this ages ago: the recorder() expression function in my Integration Toolkit.
You can even use it in an expression tag to selected source tags could avoid the two problems mentioned above.
Anyways, not available out of the box. My Integration Toolkit should work fine in Maker though. (I don't test Maker, in general.)
Another option would be to set up a RAM-based database and configure history storage within it to prune by the hour. Point selected tags to store history there.
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Thank you so much, as always you have been of great help and I appreciate your patience with me being slow to understand.
You can display any data that you'd like to see in a chart - static data, historical data from a query, or data populated dynamically at runtime based on an event.
For starters, take a look at some of the example XY Charts:
XY Chart Example - Line Chart Target Area
Assuming you're looking for a chart to be blank each time the chart is opened, & populated as data changes, you could:
- Create a custom property (on the chart) which is (in?)directly bound to your tag.
- Add a script transform on that tag binding which adds a new entry to your existing chart data. Handle maximum number of data points, etc.
Optionally, allocate some disk space and create a SQLite DB file as your playground historian, then use tag history bindings on your chart. While SQLite is not recommended for use as a production historian, I believe it can be a perfect candidate for a Maker Edition project.
Disclaimer: I am unaware of any limitations of Maker Edition that would render the above useless to you.