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FRF mode specifies how to compute the frequency response function (FRF). FRF mode determines whether H1, H2, or H3 is computed when performing frequency response measurements.
 | Note FRF mode only applies to RMS or vector averaging. FRF mode changes the result in RMS averaging but not in vector averaging. In vector averaging, H1 = H2 = H3. |
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stimulus signal X contains the scaled signal acquired from the stimulus channel expressed in the selected engineering units.
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response signal Y contains the scaled response signal expressed in the selected engineering units.
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zoom settings determines the properties of the zoom analysis.
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frequency range defines the frequency band of analysis. The valid range for the start frequency and for the stop frequency is between 0 and the Nyquist frequency.
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start frequency specifies the lowest frequency of interest for the analysis band in hertz. The valid range is between 0 and the Nyquist frequency.
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stop frequency specifies the highest frequency of interest for the analysis band in hertz. The valid range is between 0 and the Nyquist frequency. Specify a value of –1 to select the highest frequency as the maximum frequency of interest.
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window specifies the time-domain window used.
| Note The Zoom FFT VIs do not apply the window to each incoming block of data. Instead, the Zoom FFT VIs apply the window to the decimated set of data used by the Discrete Zak Transform (DZT). |
| 0 | None | | 1 | Hanning (default) | | 2 | Hamming | | 3 | Blackman-Harris | | 4 | Exact Blackman | | 5 | Blackman | | 6 | Flat Top | | 7 | 4 Term B-Harris | | 8 | 7 Term B-Harris | | 9 | Low Sidelobe |
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number of lines specifies the number of spectral lines to compute between start frequency and stop frequency.
number of lines determines the size of the FFT that is computed.
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% overlap specifies the percentage of data reused by consecutive FFT computations. The valid range is between 0 and 100.
You can use % overlap to make the zoom more responsive when the values of frequency range and number of lines require a longer measurement time.
The Zoom FFT VIs typically do not return a spectrum each time the VI is called. You can use % overlap to increase the rate at which a new spectrum is computed by reusing acquired data. For example, setting % overlap to 50 causes the VI to compute a new zoom spectrum twice as often as a setting of 0 because half the data is reused with each computation.
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view defines how the different results from this VI are returned.
view allows you to choose whether magnitude results are displayed in dB, phase results are unwrapped, and phase results are converted from radians to degrees.
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dB On specifies if results are expressed in decibels. The default is TRUE.
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unwrap phase specifies whether to unwrap the phase. Unwrapping eliminates discontinuities that have an absolute value greater than pi. The default is FALSE, meaning the phase is not unwrapped.
When unwrap phase is TRUE, the phase is unwrapped.
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convert to degree specifies whether the phase results are converted from radians to degrees. The default is FALSE, which means that results are expressed in radians.
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error in describes error conditions that occur before this VI or function runs.
The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use exception control to treat what is normally an error as no error or to treat a warning as an error. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.
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status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE.
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code is the error or warning code. The default is 0.
If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.
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source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
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averaging parameters defines how the selected averaging type is computed.
| Note When averaging mode is set to No averaging, the VI ignores the weighting mode, number of averages, and linear mode settings. |
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averaging mode specifies the averaging mode.
| 0 | No averaging (default) | | 2 | RMS averaging |
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weighting mode specifies the weighting mode.
| Note RMS and linear averaging support linear weighting and exponential weighting. |
| 0 | Linear | | 1 | Exponential (default) |
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number of averages specifies the number of averages used by the selected weighting mode.
If weighting mode is set to Linear, the measurement stops or automatically restarts after the value of number of averages has been reached. Whether the measurement stops or automatically restarts depends on the linear mode setting.
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linear mode specifies the behavior of the averaging if you set the value of the weighting mode parameter to Linear. If you set weighting mode to Exponential, linear mode is ignored.
| 0 | One shot (default)—Specifies that the averaging process stops once the value of number of averages is reached. | | 1 | Auto restart—Specifies that the averaging process automatically restarts after the value of number of averages is reached. |
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restart averaging specifies if the selected averaging process has to be restarted. The default is FALSE. When you call this VI for the first time, the averaging process restarts automatically.
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new spectrum available, when TRUE, indicates that the output data is valid, or not empty.
Use the output value as the switch to a Case structure. You can perform subsequent measurements or display the results in the TRUE case of the Case structure.
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coherence contains information about the coherence.
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f0 is the start frequency of the coherence expressed in hertz.
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df is the frequency resolution of the coherence expressed in hertz.
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coherence returns the coherence.
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magnitude returns the magnitude of the frequency response.
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f0 returns the start frequency, in hertz, of the spectrum.
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df returns the frequency resolution, in hertz, of the spectrum.
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magnitude returns the magnitude of the frequency response.
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magnitude unit label returns the unit label for the selected magnitude units.
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phase returns the phase of the frequency response.
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f0 returns the start frequency, in hertz, of the spectrum.
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df returns the frequency resolution, in hertz, of the spectrum.
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phase returns the phase of the frequency response.
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phase unit label returns the unit label for the selected phase units.
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spectrum info returns information about the spectrum needed by the Spectrum Extended Measurements VIs, the Waterfall Display VIs, the Distortion VIs, and the Single Tone Measurements VIs. Do not modify the spectrum info values.
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error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces.
Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error.
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status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.
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code is the error or warning code.
If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.
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source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.
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averages completed returns the number of averages completed by the VI at that time.
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averaging done returns TRUE when the number of averages completed equals or exceeds the number of averages specified in averaging parameters and new spectrum available is TRUE. Otherwise, averaging done returns FALSE.
averaging done is always TRUE if averaging mode is No averaging.
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Data is accumulated each time the SVFA Zoom Frequency Response (Mag-Phase) VI is called. However, it returns a new spectrum only when sufficient data has been accumulated. Indicators and subsequent processing should only be called when new spectrum available is TRUE.
Zoom frequency response is typically an averaged measurement.
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