When defining a power spectral density function from file, the Power Spectral Density Function Definition form has the following areas:
Function name edit box. Specify the name of the function or use the default.
Function File area. Click the Browse button to display the Pick Function Data File form and select the name of the text file that includes the power spectral density function data. The name of the selected file will appear in the File Name display box. Click the View File button to display the selected file in text format in WordPad.
Typically, the program does not import the file into its database. It simply maintains a link to the file location. Thus, if the power spectral density function file or the .SDB file is moved to another location, the program may be unable to locate the function file. If the Convert to User Defined button is clicked, the program imports the function into its database file and the data will always be available to the model. Do not click the Convert to User Defined button until all information in the Function File, Values are and Format Type areas has been specified.
Header Lines to Skip edit box, Prefix Characters per Line to Skip edit box, and Number of Points per Line edit box. Note that when reading the function file, the program skips the number of lines at the top of the file indicated in the Header Lines to Skip edit box. It also skips the number of characters at the beginning of each line specified in the Prefix Characters per Line to Skip edit box. The Number of Points per Line edit box tells the program how many function values or pairs of frequency and function values are specified on each line. Additional data on each line will be ignored. Thus, the program reads the file as follows:
First, the program skips the specified number of header lines.
Next, the program checks to see if a line has a $ symbol as the first character. If it does, the program skips to the next line.
If a $ symbol is not the first character on the line, the program reads the information on the line, skipping the specified number of characters at the beginning of the line.
If the line is blank or if the end of the file is reached, the program stops reading and closes the file.
Values are area. Specifies whether the text file contains pairs of Frequency and Function Values or Values at Equal Intervals of (i.e., function values that are spaced at equal frequency intervals). If the file contains only function values, specify the equal frequency interval.
Format type options. The format type can be specified as Free Format or Fixed Format. In free format, items on the lines can be separated by spaces or tabs. If the fixed format type is chosen, also specify the number of Characters per item. Each item on a line is assigned the same number of character spaces. The program begins counting the spaces after it skips the number of prefix characters specified in the Function file area.
Frequency Units options. Choose whether the frequency data in the file is given in 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.
Function graph display area. This area displays a graph of the function. First specify all of the data in the Function File, Values are and Format type areas. Then click the Display Graph button in the Function Graph area of the form to display the graph of the function.
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.
|
Access the Power Spectral Density Function Definition form for a Function Form File as follows:
|