Hi,
Is there a way to run a sparkline chart in real time without having to select historical data? I looking for a way to use this component to display the trend of a tag value
But isn't a trend just a history of what the value was?
Where would such a component get its data?
If for some reason you cannot use the historian, or some other database, you might find my Integration Toolkit module's recorder() expression function helpful. Use it with a Vision Client Tag if you want it to retain its content as a user switches windows.
The component will get the data from either a OPC server tag or an memory tag, I don't need historical data to display and as I have noticed you can not scroll back in time in this chart, so I don't see the need of using historical data as data source.
If I understand correctly, the sparkline chart buffers the data that is in the chart so it scrolls what is in the chart when a new value is added to the collection.
You do not.
It does not.
You supply a dataset that it plots. Typically a polling tag history binding.
If I understand correctly the component should not go back to the historical data stored in a database. I should assume that it is buffered inside the component as a collection of value, date/time and is scrolled when a new value is added.
It does not. There is no buffer within the sparkline component.
That is why a function like my recorder() exists.
Thanks Phil,
Is too bad that it has to do that because there is no point in using historical data if you can not go back like in other trending charts.
How does this chart determine the range of time to display, I didn't find any property that allows me to select the span of time to display?
This component's purpose is to provide an operator with a quick view of what is happening in a small bit of screen real estate. It is not a substitute for ordinary charts, and is commonly configured (by script) to open a proper chart when clicked.
It is expected to be used in multiple places on process overview windows.
It's time span is precisely the timespan of the dataset it is given.
Thank you Phil for the explanation.