Full Spectrum FFT

Full Spectrum FFT

Use this dialog box to diagnose damage on rotating shafts. Synchronous and equidistant sampling was executed on the signals of two vibration sensors which are positioned perpendicular to each other. First, single spectra are calculated from the two vibration signals and then connected to a full spectrum FFT.

Settings

	Time channel	Specifies the data channel with the common time values of the input signals.
	Input channels 1	Displays the data channels with the signals of the first sensor. The input channels must not contain NoValues.
	Select Channels	Opens the channel selection list. The number of first input channels must be the same as the number of second input channels.
	Input channels 2	Displays the data channels with the signals of the second sensor. The input channels must not contain NoValues.
	Select Channels	Opens the channel selection list. The number of first input channels must be the same as the number of second input channels.
Window Functions
	Window type	Specifies the window function for the FFT. You can select: Rectangle, Hanning, Hamming, Blackman, FlatTop.
	Amplitude attenuation correction	Specifies whether DIAdem corrects the damping effect of the window function on the amplitude. You can select either periodic or random correction.
Time Intervals If you select exactly one input channel, you can split the calculation into intervals.
	Include all values	Specifies that DIAdem uses all measured values in the calculation.
	Number of intervals	Specifies that DIAdem divides the input channels into a specified number of equidistant intervals and calculates an individual result for each interval. The calculation ignores surplus values.
	Number	Specifies the number of intervals.
	Length of the intervals	Specifies that DIAdem divides the input channels into intervals of a specified number length and calculates an individual result for each interval. The calculation ignores surplus values.
	Length	Specifies the number of values in an interval.

If you want to use waveform channels in this dialog box, follow Rule 2.2 for Calculating with Waveform Channels. If you specify a time channel although the input channels are waveform channels, the sampling rate is specified from the time channel.

Result

DIAdem generates for every time interval and for every input channel pair one result channel with the calculated amplitudes.

First, the bias is removed from both input channels with AC/DC coupling in a full spectrum FFT calculation. The amplitudes of the power spectrum are calculated from the AC component with the FFT with a time channel. Additionally the phase of the cross spectrum is calculated from both input channels. The full spectrum FFT is established by further connections of both amplitudes and the phase.

To calculate quantity-based in DIAdem, click the Calculate Quantity-Based button on the DIAdem ANALYSIS toolbar. When executing quantity-based calculations, DIAdem checks whether the program can also execute calculations on physical quantities in the same calculation. If DIAdem cannot execute the calculation because the physical quantities are unsuitable, the program displays an error message. Refer to the Help page Calculating Quantity-Based and Non-Quantity-Based in DIAdem for the conditions and rules for quantity-based calculations.

Script Call

Call SUDDlgShow("Main", ResourceDrv & "AnaChnFullSpectrumFFT")

ChnFullSpectrum

Procedures

Examining Measurement Signals in the Frequency Domain

Examples

AC/DC Coupling | Adapted DIAdem Functions | Calculate Characteristics of an Oscillation | Communicating with MATLAB | Frequency Weighting (A-, B-, C-Filtering) | Hysteresis Analysis | Optimized Heating Control