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How Can I Calculate the Output Frequency of My Analog Output?

Hardware: Multifunction DAQ (MIO), Signal Sources (AWG/FG/AO)

Problem: What equations should I use to programmatically set my output frequency in LabVIEW? Is the update rate the output frequency?

Solution: In general, the rule of thumb to calculate the output frequency is as follows:

Output Frequency = Update Rate / Samples per Period

Therefore, if you have a desired output frequency and know the number of samples in one period of the waveform you are outputting, you can calculate the target update rate to specify. When you use one of the custom waveform generation VIs in LabVIEW, the calculation gets more involved. The waveform generation VIs have inputs for Frequency and Sampling Information. The Sampling Information contains a setting for the Sampling Frequency and the Number of Samples. To calculate the number of samples per period that the waveform generation VIs generate, use the following equation:

Samples per Period = Sampling Frequency / Frequency

Therefore, if you are using the waveform generation VIs to generate the waveform you are outputting, calculate the output frequency with the following equation:

Output Frequency = [Update Rate × Frequency] / Sampling Frequency



Related Links: KnowledgeBase 26E7LUIJ: Frequency Resolution of the Analog Output of a DAQ Device


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Report Date: 12/11/2003
Last Updated: 06/29/2004
Document ID: 34AFFR59

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