The Zoom facility is available for all graph types. The current zoom can be operated by using the Zoom option on the sub-menu bar or by the right-clicking on the main graph graticule.

The Zoom sub-menu enables you to zoom-in, zoom-out, reset zoom, and zoom into a section of the graph.

Auto-scale

To ensure that the entire signal is visible click the Zoom menu at the top of the panel and select the Auto-Scale option. This will automatically scale the Y axis of the trace to a factor of 2, 5, or 10 in a way that will ensure that all trace data is retained.

Change Scale

To change the X and Y axis scales for a given graph, click the Zoom menu at the top of the panel and select the Change Scale option. This prompts the scaling screen as shown in the following image:

The way you specify the scale of the X and Y axes depends on the type of data that the active graph is displaying. The different methods are as follows:

Frequency: Center, Span

Use this to specify a scale in terms of a center point and a span.

Power: Reference, Scale/Division

Use this to specify a scale in terms of a reference, which is the maximum value of the display, and value for each division of the graph.

Minimum/Maximum

Use this to specify a scale in terms of a start and stop limit.

Axis Limits

There are normally limits on the scales you can enter on this screen, and these depend on the measurement that is being made.

Zooming In

To zoom in on the information displayed on the Graph display panel, click Zoom, then click Zoom In (x2). This zooms in by a factor of 2.

To select a region to zoom, click Zoom from the menu at the top of the panel and click the Selection option. Notice that the graph now displays the co-ordinates of the mouse cursor. To zoom in on a region of the display graph, click and hold the left mouse button and drag it to select the region of the graph you want to zoom into.

After the zoom has been completed, the graph display reverts to its default selection mode.

Zooming Out

To zoom out, click the Zoom menu at the top of the panel and select the Zoom Out (x2) option. This causes the graph display to zoom out on the x-axis by a factor of 2, maintaining the current central point. If the graph display cannot achieve this zoom factor, as doing so exceeds the graph's maximum scale limits, the maximum possible scale is set instead.

Zoom Selection

This control lets you zoom into a section of the graph. This control provides the ability to select a region in both the X and Y domain. Immediately after this region is selected, the graph will be readjusted to the selected area.

Select the Zoom Selection control. Left click and drag the cursor to produce a square or rectangle. Once the required area is selected let go of cursor to see the changes. This can be seen in the following figure.

Selection

For non-polar plots, the Zoom selection feature allows you to select a region of the graph in the X domain. When this option is selected, you can click and drag the mouse in the graph to select a region of the graph as shown in the following figure.

The region will stay selected until this option is de-selected.

When a particular region is selected, you can then right-click the selection to where you will be presented with a Zoom to this selection feature as shown figure.

When this option is selected, the trace will be zoomed to the specific selected area.

Reset Zoom

Resets the zoom factor of the current graph’s X and Y axes to their default values.