05 Domains and Axes

impulse can display waveforms using multiple domains (e.g., time and frequency) in one view. If your signals are using the same domain, it allows you to display them on multiple axes. 

This article is based on impulse 1.8.

Domain Axes

When you open a file in impulse, it is possible that it contains signals with multiple domains (e.g., time and frequency). impulse allows you to show them all in a single view.

Multiple Domains

The actual axis uses the domain of the selected signals; for example, if you select a signal that has a time domain, then the axis will show nanoseconds or another measurement of time. Those signals whose axes are displayed look normal, and those based on a different domain (e.g., frequency) are coloured in a light grey. Furthermore, you can see which domain is displayed when you look at the cursor. It is only shown in colour for those signals that come from the domain that is used in the axis. With all other signals, it is displayed only with grey lines.

Dedicated Axes

If you have signals from the same domain but, nevertheless, want to show them on a different axis (e.g., to see the total and a snippet, side by side), then you have to create a new folder for the chosen signals. To create a folder, you right click the view, choose "Add" and then "Folder". In the dialogue that now opens, you click "Dedicated Axis" and then add signals by dragging and dropping them to the folder. Now you can vary the way that those signals are displayed from the others; for example, you can zoom in and out to gain a general overview of the signal or a close-up view of a section. A 'star' is added to the folder icon when you set the dedicated axis.

Axes Types

There are two types of axis. One is the linear, which is the normal case and the other is log10. When you choose log10, the value appears in the same intervals but increases tenfold.

Moving the axis

There are four ways to move your axis. When you click the axis and hold it, you can move it to view its different parts. You can also use the scrollbar to move the axis. Furthermore, you can move the axis by clicking on the graph, and by using SHIFT and the wheel.

In or Out

Looking at the track of the axis, you can see in which domain areas are the locations of your signals. The colour of this area is usually light/dark grey depending on if its in or outside of signals.

View dialogue

With the view dialogue, you can choose settings for the domain axis and the domain base. There are two different modes that you can use for the domain base. The default setting is "Use signal domain base". impulse determines a domain base from the signal. If you do not want the determined domain, or there are none that you want, then you click "Override domain base with". With this option, you have to set a domain base yourself.

Folder dialogue

The folder dialogue is similar to the view dialogue. You have three domain axis options that you can select. "No dedicated axis" is the default, and the global axis is displayed, "Dedicated axis" is the setting that you choose when you want an axis especially for this folder that is independent of the other axes and "Dedicated axis with overriding domain base" is the setting you choose if your axis should be independent of the others and you also want to set a specific domain base.

How are domain values represented in impulse ?

  • Time, Frequency,... define the multiple domain classes used in impulse.
  • The actual domain base also gets a unit, depending on the class and with the option of milliseconds, seconds, nanoseconds, etc., for the time domain class. 
  • impulse uses 64-bit signed integer values as domain values (the multiple of its domain base).

Find more in chapter: 02 Signal Basics.

Value Axes

Some diagram types can show a value axis (line and area diagram). You need to activate the axis in the plot configuration.  Furthermore you can define the axis range and type. 
When no range set, the signal would be drawn to its extent. You might use the context menu to set the range automatically.