Configuring the Moving FFT block

Select the Input field for which you require FFT frequency values. (NOTE: Input fields must be of type double).
Configure the sampling period in seconds. The sampling period determines the minimum period (displayed next to the sampling period and calculated dynamically by the block) for the calculated FFT.

NOTE: The minimum period is inversely proportional to the maximum frequency.
Configure the number of output samples required in the window period for which the FFT is calculated.

NOTE: The maximum frequency is inversely proportional to the maximum period.
Example:

If the user wants to identify or expects a specific event at a frequency of 0.1 Hz (a period of 10 seconds) then the sampling period must be set to 5 seconds or less.

Add the required output fields by clicking the Add button. The Add FFT Outputs dialog is displayed as shown below:

Specify a default name for the output fields (NOTE: The index will automatically be appended to the default name specified), and provide a range of indexes. A field for each index in the specified range will be created in the Output Port. Index ranges may be specified using a dash, with specified required indexes listed using a comma (see examples below).

Examples:
- 2,4,7
- -3,5,8
- 4,8,9-
- -8
- 8-
- -4,8-
- 2,5-9,12
- -3,7-10,12-

NOTES: Using a dash at the start or end of the range (Example: -100 or 0-) will automatically add ally indexes from the start or end of the specified index to the minimum or maximum index in the range. The range is from 0 to the number of samples - 1.

Output field names may be edited and changed in place after using the Add FFT Outputs dialog.

Specify a Calculation trigger. Valid options are:
- On every execute: FFT frequency values will be calculated on every execute
- On value change: If the "On value change" option is selected, the user must select a trigger field from the list of available fields on the parameter port. Frequency values will only be calculated if the selected field value changes across good samples. Bad quality samples are ignored.
Specify the number of Top frequency values. The configured number of Top frequency values determines the number of fields calculated and output in the Top Frequencies and Top values ports.

NOTE: The limit for the Top frequency values field is between 1 and the number of output fields added.