Daqarta
Data AcQuisition And Real-Time Analysis
Scope - Spectrum - Spectrogram - Signal Generator
Software for Windows
The following is from the Daqarta Help system:

# Frequency Sweep Delta

Macro: SweepDelta

This is a special-purpose control that can normally be left at zero. To understand how to use it, consider a case where you want sweeps on two different Streams. Suppose you set them to use identical Start and End frequencies, and identical Lengths. Assuming both streams had the same wave type and no other modulation, they would be identical.

But now suppose you want to keep these exact same sweep parameters, but start one sweep earlier in time than the other. Let's say the sweeps are linear, from 440 to 880 hertz, and you want one to start 220 Hz ahead of the other, so that it will be at 660 Hz when the other is just starting at 440 Hz. You do that by entering a Delta of 220 Hz. Once everything is running, they will continue to maintain this same offset of 220 Hz; when the offset sweep reaches 880 and resets, the other will just be reaching 660.

Note that when using Sweep Stairs to create a stepped sweep, the Delta control only allows values that correspond to actual frequency steps in the series.

The Delta control produces identical sweeps, stepped or continuous, that are offset in time. If you instead want sweeps that are offset in frequency, you can just set the appropriate Start and End frequencies. For example, if you want one to run from 440 to 880 Hz and the other to be always 10 Hz higher, set its Start to 450 and End to 890.

Macro Notes:

L.1.SweepDelta=220 sets the Left Stream 1 Sweep Delta Frequency to 220 hertz.

L.1.SweepDelta=>1 increments the frequency to the next higher Frequency Entry Step, while L.1.SweepDelta=>-1 decrements to the next lower step. Only +/-1 step is accepted, but the step size and type can be controlled via the Frequency Step dialog. Note: The Frequency Step setting affects the behavior of almost all Generator frequency controls.

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