Using Trend objects
A trend is a visual representation, chart of real-time, or historical data. A trend provides operators with a way of tracking plant activity as it is happening.
Pens on the runtime chart represent data from the tags and expressions that you add to the trend object. The trend object provides extensive, flexible runtime control. You can add pens, toggle between isolated and non-isolated graphing, specify unique line settings, plot one variable against another in XY plots, and print chart data.
Runtime flexibility
The trend object provides exceptional flexibility at runtime. You can click any point on the chart to show a value bar that indicates the date, time, and numerical values of the pens for that horizontal position. In addition, you can allow operators to make changes to charts at runtime, including adding and removing pens, creating snapshots of current data, and overlaying snapshots on current data. To relocate an overlay's position on a chart, simply click and drag. During set up, you determine which properties operators can access at runtime.
Zooming and panning
At runtime, operators can use zoom for a closer look at trend chart data. Runtime charts also allow quick panning through data. VCR-style scroll buttons allow easy navigation through data.
Templates
Save the settings for a trend object in a template, and then apply those settings to other trend charts for a consistent appearance. Templates are also a good way to create a set of different views of the same data, or a quick way to return to a standard display after experimenting with display options.
Object model
The trend object model provides programmatic access through Microsoft Visual Basic for Applications (VBA), an embedded programming language.
TIP:
If you plan to create trends using data log information that has been logged to a remote computer, you will have to change the DCOM security settings on that computer.
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