User Function - Power Spectral Density Function

Access the Power Spectral Density Function Definition form as follows:

Click the Define menu > Functions > Define Power Spectral Density command to display the Define Power Spectral Density Function form.
Select User Function in the Choose Function Type to Add drop-down list. Then do one of the following:

Click the Add New Function button.
Select a previously defined user function definition in the Functions display area and click the Modify/Show Function button.

When defining a user defined power spectral density function, the Power Spectral Density Function Definition form has the following areas:

Function name edit box. Specify the name of the function.
Frequency Units options. Choose to specify the frequency as Hz (cycles per second) or RPM (cycles per minute). Internally, the program always uses Hz, and results are reported in Hz. Note that the frequency units also affect the function values, since they are specified per unit of frequency.
Define Function area. Input pairs of frequency and function values in this area. Type the Frequency (in the chosen units) and function Value corresponding to a single point of the function into the edit boxes at the top of this area. Then click the Add button. Repeat this process until points have been entered. Enter the points in any order; they will be sorted by ascending frequency. A frequency value may not be duplicated. Function values may not be negative.

To modify an existing pair of values, first highlight the appropriate values in the list box. Note that when you highlight them, they appear in the edit boxes at the top of the area. Modify the values in the edit boxes and then click the Modify button.

To delete an existing pair of values, first highlight the appropriate values in the list box. Then click the Delete button.
Function graph area. This area displays a graph of the function. It updates automatically as additional points are defined for the function. If your computer has any problem with the automatic update, click the Display Graph button located just below the graph.

Run the mouse pointer over the function graph and a dot appears along the line representing the function. The coordinates of the dot are reported in the box just below the graph.

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