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Document Type: Example Program
NI Supported: Yes
Publish Date: Sep 6, 2006

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Aliasing and sampling rate

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Filename: aliasing.zip
Requirements: View

Theory: The Sampling Rate should be set at least twice the highest Frequency (This is known as the Nyquist criteria). If you are using a sine wave, this is easy, because a sine wave only contains one frequency. However, a square wave contains many higher frequency components in addition to its fundamental repetition frequency. You can see this on the Frequency Spectrum.
Aliasing is the appearance of phantom frequencies when a signal is not sampled at a high enough rate. In films (which are normally sampled at 24 frames per second) you can often see the wheels of cars or stagecoaches slow down, stand still, or even appear to rotate backwards. This is aliasing. If the sampling of the camera is precisely synchronized with the rotation of the wheel, it will appear to stand still. This is similar to the effect causes by a stroboscope.
Experiments: See the ExampleDescriptions.txt file for 5 experiments which demonstrate these principles.

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Filename: aliasing.zip

Software Requirements


Application Software: LabVIEW Full Development System 6.0
Language(s): LabVIEW

 
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This example program (this "program") was developed by a National Instruments ("NI") Applications Engineer. Although technical support of this program may be made available by National Instruments, this program may not be completely tested and verified, and NI does not guarantee its quality in any way or that NI will continue to support this program with each new revision of related products and drivers. THIS EXAMPLE PROGRAM IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND AND SUBJECT TO CERTAIN RESTRICTIONS AS MORE SPECIFICALLY SET FORTH IN NI.COM'S TERMS OF USE (http://ni.com/legal/termsofuse/unitedstates/us/).