The first thing you must do in order to scroll a chart is determine the direction of the scroll. The scroll direction determines whether the data on the chart plots left-to-right or right-to-left. You can specify a scroll direction for the chart by selecting the appropriate option button in the Scroll Direction area of the General tabbed page.
The following figure illustrates a chart configured with both a real-time and historical pen, with a right-to-left scroll.
For a left-to-right scroll, you can also assign a reset value by entering a value in the Reset field. When the data plot reaches the right edge of the chart, a reset occurs and the pen fetches new data. The data and its time shifts according to the reset percentage. For example, if you enter a reset value of 50, the data plot will shift back one-half of the chart's time axis when it hits the right edge.
To scroll the chart, use the Historical Dynamo, available in the Dynamo Sets folder in the iFIX WorkSpace system tree. To use the Historical Dynamo, add the Dynamo to your picture and double-click it. The Chart Configuration dialog box appears, which lets you make changes to the chart's properties. Click the Left and Right arrows on the bottom-left and bottom-right of the chart to scroll the chart in a particular direction.
NOTE: The Quick Dynamo Updater and Dynamo Updater Wizard are not available for the Chart Dynamo, and other pre-canned Dynamos that were available before iFIX 4.5. This is because they are not true Dynamo objects.
You can also configure AutoUpdate to scroll the chart forward automatically.
You can change the chart's scroll percentage using VBA scripts. For more information on using scripts to scroll charts, refer to the Writing Scripts manual.
Plotting Ideal Curves
A chart's left-to-right scrolling functionality helps you easily determine how close your data is to a desired value. It does so by letting you easily recognize ideal and actual curves in the same chart. An ideal curve is an existing historical plot that represents an ideal condition in your process. The actual curve is a real-time plot that represents current conditions. Depending on your process, it may be crucial that the actual curve come as close as possible, if not exactly match, the ideal curve.
For example, let's say you want to plot real-time data so that it shows the proper variation in temperature of a process, determined by a plot collected previously. Using multiple pens and scrolling in iFIX charts, you can view the real-time and historical data simultaneously to determine whether data that is currently being fetched matches the ideal scenario.
First, configure both a real-time and a historical pen. Then, for example, assign a green color property for the real-time pen, and a red color property for the historical pen. Then specify a left-to-right scroll with a reset value of 50. When you switch to the run-time environment, you can watch the real-time pen follow the ideal curve. When the data reaches the right edge of the chart, the data is reset and the plot resumes in the middle of the graph. You do not have to manually position, change the shape of the chart, or leave the run-time environment.
Thanks to the real-time monitoring of all types of data in a scrollable format, iFIX charts give you the ability to monitor crucial fluctuations in data which, in many cases, can greatly impact your process. The following figure illustrates a chart plotting both a real-time and historical pen with a left-to-right scroll. Notice how easy it is to evaluate the ideal curve.
Scroll direction also appears in the Standard Chart Preferences tabbed page of the User Preferences dialog box. If you change the scroll direction in Standard Chart Preferences, you change the default value for all new standard charts. To access this dialog box, select User Preferences from the WorkSpace menu (Classic view) or on the Home tab, in the WorkSpace group, in the Settings list, click User Preferences (Ribbon view), and click the Standard Chart Preferences tab. For more information on the User Preferences dialog box, refer to the Setting User Preferences section of the Understanding iFIX manual.
