The tools to Zoom In and Zoom Out on the Y-axis can be used to adjust the scale ranges for pens plotting analog values. These tools do not work for digital tags, as digital values are typically either "0" or "1".
By default, the scale ranges for an analog pen are set to the values configured for the tag's "Scaled Process Data Min" and "Scaled Process Data Max" properties. In the case of the "AI20_1 Booster Tank Level" analog input tag, the minimum scale range has been configured as "0", and the maximum scale range has been configured as "120". These scale values are displayed along the graph's y-axis.
In this exercise you will see how to view a different scale range for one or more analogs.
1. Click the Zoom In Y-axis (Analogs Only) button in the tool bar. (Remember that each tool has its own descriptive tooltip that appears when you rest your mouse pointer over it.)
2. Position your mouse pointer over the graph.
3. Click to zoom in. The minimum and maximum scale values along the graph's y-axis adjust to display a lesser scale range.
4. Click the Zoom Out Y-axis (Analogs Only) button in the tool bar.
5. Position your mouse pointer over the graph.
6. Click to zoom out. The minimum and maximum scale values along the graph's y-axis adjust to display a greater scale range.
7. Experiment with the Zoom In Y-axis and Zoom Out Y-axis buttons to adjust the scale range.
8. Click the Reset Y-axis (Analogs Only) button to reset the scale range to its default (0 –120).