EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: drDuesentrieb on January 22, 2022, 04:50:14 pm
-
Hello, first post in this forum after some time of reading and learning.
I am looking for a way to teach my SDG2042x performing a single sweep or ramp-up and keeping the final frequency.
It should be some kind of a single cycle sweep burst with clamped stop-frequency.
The application is similar to a common stepper motor control which uses the STEP-Input for a single step. The goal is to have a
defined speed-up of the motor. Translated to the the signal which I have in mind, it can be separated into three steps:
1. Square-wave (e.q. 50 %) starting at 0 Hz
2. Sweep/Ramp-up to e.g. 1 kHz
3. Maintain e.g. 1 kHz
Ideally this is triggered manually or by the external trigger.
If I use the square-wave + sweep of the SDG (and set the trigger to manual), it will fall back to the "Start Freq" after reaching the "Stop-Freq".
Single repetition of an Arb-Waveform behaves similarly.
Other combinations of wave + modulation also didn't work for me.
Now I am thinking of combining the two channels (e.g. CH1 doing the sweep, CH2 set to the final frequency with the delay defined by the sweep time), but this seems a bit complicated for this simple task.
Any hints in the right direction?
-
As the bandwidth and frequency lie within the audio range, my goto for these sorts of signals is to generate them programmatically, or in an audio editor (e.g. Audacity, or my editor of choice, RX), then replay them through an audio DAC. Now my bench has computers as part of my test equipment, so this is easy enough for me, and I have a dedicated cheap 4 channel audio interface for generating such signals. This relies on you being ok with the square wave to be bandlimited to, say, 22Khz or whatever your nyquist is.
-
This is a piece of cake on a waveform generator which supports sequences where the final waveform is build from smaller chunks of waveforms. One chunk would be the sweep and the other the fixed frequency (which is repeated infinitely).
Alternatively you need a generator with more sweep controls. On my Tektronix AFG31000 I can set the sweep time, hold time (time it stays at the stop frequency) and return time (reverse sweep). Maybe other Tektronix units which are more budget friendly on the used market can be found which support the same settings.
All in all I don't see how you can achieve your goal with the SDG2024; changing the frequency through remote control likely introduces a large disturbance in the output.
-
Some old school signal generators work the way you describe, e.g. the hp 3325A will sweep from start to stop, and remain at the stop frequency.
There are probably newer / more compact models around that still work the same way?