AutoPowerSpectrum
Advanced Analysis Library Only
AnalysisLibErrType AutoPowerSpectrum (double inputArray[], ssize_t numberOfElements, double dt, double autoSpectrum[], double *df);
Purpose
Calculates the single-sided, scaled auto power spectrum of a time-domain signal. The auto power spectrum is defined as shown in the following figure:
| where | numberOfElements is the number of points in the signal array X |
| * denotes a complex conjugate |
AutoPowerSpectrum converts the auto power spectrum to a single-sided form.
Parameters
| Input | ||
| Name | Type | Description |
| inputArray | double [] | The time-domain signal. |
| numberOfElements | ssize_t | Number of elements in the input array. Default Value: 1024. |
| dt | double | Sample period of the time-domain signal, usually in seconds. dt = 1/fs, where fs is the sampling frequency of the time-domain signal. Default Value: 1.0. |
| Output | ||
| Name | Type | Description |
| autoSpectrum | double [] | Single-sided power spectrum in volts rms squared, if the input signal is in volts. If the input signal is not in volts, the results are in input signal units rms squared. This array must be at least numberOfElements/2 elements long. |
| df | double | Points to the frequency interval, in Hertz, if dt is in seconds. df = 1/(numberOfElements × dt) |
Return Value
| Name | Type | Description |
| status | AnalysisLibErrType | A value that specifies the type of error that occurred. Refer to analysis.h for definitions of these constants. |
Additional Information
Library: Advanced Analysis Library
Include file: analysis.h
LabWindows/CVI compatibility: LabWindows/CVI 3.1 and later
Examples
Refer to the following examples that use the AutoPowerSpectrum function:
- analysis\cxwindowing.cws
Open example - analysis\peakest.cws
Open example - analysis\thd.cws
Open example - analysis\windowng.cws
Open example