Data AcQuisition And Real-Time AnalysisScope - Spectrum - Spectrogram - Signal Generator
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The following is from the Daqarta Help system:
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Main Tone Frequency
Controls: Gen Dlg >> Stream >> Tone Freq >> Main Freq
Controls the frequency of the waveform for the stream.
Frequency may be set to any value up to the Nyquist frequency, which is half the actual sample rate.
This control is present in the main Tone Frequency dialog, and also in the AM, FM, and PM modulator dialogs for convenience. It is not available when the main Wave is one of the Noise types.
The maximum frequency resolution is limited by the effective sample rate:
Resolution (Hz) = Sample Rate / (65536 * 8192)
For a sample rate of 48000 Hz, the resolution is thus 0.000089 Hz.
The actual frequency entry process is controlled by the Step Mode shown on the button below the frequency control. This defaults to Step Direct. If you click on this button to open the Step Mode dialog, and enter 0 in the value under Step Direct (or under Step Hertz if selected), the step value will show as 0.00001 Hz. Daqarta interprets this to allow scrolling of the Tone Frequency at the finest (89 ppm) resolution.
You may want 6 or more decimal places for this. By default, all Generator frequency controls show 5 digits after the decimal. You can adjust this between 0 and 9 using the Frequency Places control in the Step Mode dialog.
Step Modes allow you to step to only certain frequencies that are Step Hertz apart, or to exact spectral Lines, or by Octave or musical steps (or fractions or multiples).
When Play Wave type is active, the Freq control changes to Rate. The Play Rate control allows Rate to be set relative to the absolute rate (Abs), as recorded originally, or relative to the current sample rate (Rel).
Note that when Freq is set to 0, the output is a constant level controlled by the Phase setting; at a Phase of 90 degrees the output of a Sine wave is a constant 100%, for example. This can be useful when used with Burst or Phase Modulation to modulate another stream.
L.1.ToneFreq=1k sets Left Stream 1 Tone Frequency to 1000 hertz.
L.1.ToneFreq=>1 increments the frequency to the next higher Frequency Entry Step, while L.1.ToneFreq=>-1 decrements to the next lower step. Only +/-1 step is accepted.
Note that the ToneFreq command will change the internal frequency value even if that stream is using a Noise-type Wave that doesn't display it or allow normal user access to the Frequency dialog. In that case, there will be no change to the output signal until a non-noise Wave type is selected.
The same ToneFreq command is also used to control Play Rate when a Play Wave is active, and the value set depends on the Play Rate Absolute / Relative mode.
See also Main Phase, Tone Frequency Dialog, Waveform Stream Controls.
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