Frequency measurements (high-speed/high accuracy)
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Filename: fast_frequency.llb
Requirements: View
Experiment #1: Click the cursor to the right of the last digit in the Frequency display of the Input Signal. Hit the Up key on your keyboard to change the Frequency to 10.000001 Hz. Note that Detected Frequency also changes precisely the same.
Experiment #2: Set the Noise level to its maximum value of 20 dB. Note that you no longer can see the sinewave in the waveform graph. Nor can you see it in the Frequency Spectrum. And the Detected Frequency is also "pure noise". Now change the Duration of Measurement to 10 s. Now note that the Detected Frequency can still measure it with 2 to 3 digits resolution, even though the signal to noise ratio is negative, that is, there is 10 times as much signal as noise!
Experiment #3: With the same settings as in Experiment #2, change the Duration of the measurement to 100 s. Notice how this gives much more accarate Frequency and Amplitude values, but at the expense of longer measurement and computation times. To make this measurement, your computer is now performing 100k FFTs as part of this technique.
Experiment #4: Explore on your own.
Requirements
Filename: fast_frequency.llb
Software Requirements
Application Software: LabVIEW Full Development System 6.0
Language(s): LabVIEW
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