麻烦高人翻译一下，正弦扫频的步骤如下：
Steps:1.Initialize a swept sine measurement by specifying the hardware device and channel settings.
2.Specify the scaling that will be applied to the acquired stimulus and response data.
3.Configure the source by specifying the test frequencies, amplitude, and whether or not you want the sweep to continue repeating.
4.Set the settling and integration parameters to allow sufficient time for the DUT to settle before the measurement is performed at the new test frequency and sufficient integration time to achieve the desired level of precision.
5.Set the block duration for the measurement to be small enough to give a reasonable test time and large enough so as to not overload the processor of the test computer. The smaller the block size, the faster the swept sine can transition from one test frequency to the next.
6.Explicitly set the sample rate for the measurement. The rate is automatically selected if this VI is not used. The same rate is used for input and output channels.
7.Specify the device propagation time specific to the data acquisition device being used for the measurement. The device propagation time can be measured using the SVS Measure Propagation Delay VI.
8.Configure the harmonic distortion measurement by specifying the maximum harmonic to use in the computation of the THD. Individual harmonic components will only be returned for those harmonics specified in the harmonics to visualize array.
9.Start the swept sine to perform the hardware configuration and start the output and input tasks. Synchronization of the channels is performed internally in this VI.
10. Generate the excitation and acquire the stimulus and response data at each test frequency.
11. Convert the raw data for displaying and reporting measurement results.
12. Stop the swept sine measurement and clear the output and input tasks to release the device.
13. Use a popup window to show any errors and warnings. 本帖最后由 xiaogengniu 于 2011-4-5 22:37 编辑
回复 1 # xiaogengniu 的帖子
不明白， 上面的第4、5、7步是什么意思？？先谢过了 自己顶一下！！？？？上面的第4、5、7步具体是什么意思？？先谢过了 试验带宽：即试验的频率范围，最低频率至最高频率
频率分辨率：相邻频率的差值，即试验的最高频率/试验谱线
5、试验谱线：参与快速傅立叶变换的数据块的大小（block size） This VI measures the frequency response of the device under test (DUT) with a swept sine technique. The example generates a tone for the excitation signal and measures the root-mean-square (RMS) levels of the stimulus and response channels, the frequency response (magnitude and phase), and the total harmonic distortion (THD) (including contributions from individual harmonics) of the DUT. The measurements are performed at each test frequency, one frequency at a time.
Refer to the wiring diagram to physically connect the DSA or DAQ device to the DUT.This example uses two analog input channels and one analog output channel.Note that the analog output is connected to both the DUT input and to the first analog input channel on the measurement device.
The wiring diagram assumes that you use the default channel settings.If you change the channel settings in the VI front panel you should adjust the physical connections appropriately.
NI strongly recommends that you take precautions to limit the effects of out-of-band aliasing in your frequency domain measurements.DSA devices use transparent digital and analog hardware filtering to eliminate aliased input and output frequencies.Multifunction DAQ devices are more susceptible to the effects of aliased frequencies.If you are using a non-DSA measurement device, we recommend addressing potential aliasing through high sampling rates, built-in analog filters on S Series devices, and/or external analog filters.
KEY PARAMETERS
DAQ Configuration:propagation time
This parameter quantifies the time, measured in sample intervals, between when a sample of data is generated on analog output and when it is read on the analog input.Common sources of delay are analog or digital filters and propagation time for acoustical or mechanical signals.The combined delay of the digital anti-aliasing and anti-imaging filters on the NI PCI-4451 and PCI-4551 devices is approximately 77 samples.When using a multifunction E Series or S Series device, we recommend entering a delay of 1 sample.An easy way to determine this delay for any given measurement system is to run SVT Measure Propagation Delay.vi.This VI is available from the LabVIEW Functions palette under Sound and Vibration >> Calibration.
DAQ Configuration:sampling frequency
This control overwrites the automatically generated sample rate for input and output. To use the automatic rate (2.5 * max(start frequency,stop frequency)), set the value of this control to -1.
DAQ Configuration:block duration
By default the block duration is initialized to 100 ms. You can overwrite the value of the block duration control with a shorter duration to improve the swept-sine measurement time. You can overwrite the value with a longer duration to decrease the load on the processor and possibly avoid performance related errors.
Source Settings:amplitude
This control allows you to specify the peak amplitude of the tone used to perform the swept-sine measurement.
Source Settings:sweep frequencies
The start frequency and stop frequency determine the frequency range of the swept-sine measurement. You could set the start frequency to be 20 Hz and the stop frequency to be 20 kHz to sweep up in frequency, or you could set the start frequency to be 20 kHz and the stop frequency to be 20 Hz to sweep down in frequency. The number of steps determines the total number of test frequencies.
Processing Settings: settling
The "settle time" and "settle cycles" parameters allow you to specify a delay between the start of the stimulus and the beginning of the measurement.Some DUTs have a significant transient response to sudden changes in frequency, select the appropriate settling settings to allow this transient response to pass.At each frequency, the VI will wait for a number of seconds equal to either "settle time" or "settle cycles" divided by the stimulus frequency, whichever is greater.
Processing Settings:integration
The "integration time" and "integration cycles" parameters allow you specify how much data is averaged at each frequency step.Each average will process data for a number of seconds equal to either "integration time" or "integration cycles" divided by the stimulus frequency, whichever is greater.
THD Settings:maximum harmonic
This setting determines how many harmonics should contribute to the THD calculation.For instance, assume the "maximum harmonic" is set at 5 and the excitation frequency is set at 2 kHz.In this case, the THD will be the ratio of the RMS sum of powers at 4 kHz, 6 kHz, 8 kHz, and 10 kHz to the power at 2 kHz (the fundamental).If you select "-1" for this parameter, the VI will compute the power for all harmonics whose frequencies lie below the Nyquist frequency
THD Settings:harmonics to visualize
This array determines which harmonics will be displayed in the "Harmonics" graph on the "Harmonics Distortion" tab.Harmonics 4 and 6, for example, are 4 and 6 times the frequency of the fundamental.
Engineering Units:stimulus channel
The stimulus channel control allows you to input the sensor sensitivity and engineering units for the stimulus channel so the measured results will be returned in engineering units.
Engineering Units:response channel
The response channel control allows you to input the sensor sensitivity and engineering units for the response channel so the measured results will be returned in engineering units.
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