Discover how to produce a multiple output arbitrary signal generator cheaply and quickly with low-cost, hobbyist-level microcontroller development boards.

EEVblog #396 – Bode Plotting on Your Osciloscope
https://www.youtube.com/watch?v=uMH2hGvqhlE

Dave shows you a neat trick on how to get a real time frequency response bode plot on your oscilloscope using your function generator. Useful for filter or system response characterisation.

FY6800 Series Fully Numerical Control
Dual Channel Function/Arbitrary Waveform Generator
User’s Manual
https://gotronik.pl/images/FY6800Manual.pdf

Curb your expectations, there’s a reason for the quotation marks in the title. You won’t see a real Bode plot in this video, at least not on the scope. We’ll go for a poor man’s frequency response measurement, magnitude only.

Intro …
00:00 Intro – curbing expectations, looking at viewer questions
04:46 Bode plots – frequency response of a circuit visualized
09:37 Frequency sweeps – Bode plots automated
Frequency sweeps using VCO …
13:19 VCO linearity – reports of its non-linearity are greatly exaggerated, but it sucks anyway
22:09 Voltage ramp – controlling the VCO with a signal the oscilloscope can trigger on
27:48 Summary – nice for a qualitative analysis, but not for quantitative measurements
Frequency sweeps using FM …
32:39 FM linearity – reported as better than the VCO’s, but it’s actually worse
38:39 Summary – same setup as for the VCO, worse performance than the VCO
Audio amplifier as DUT …
40:51 Audio amplifier as DUT – you always wanted to know how a frequency sweep sounds
Wrap-up …
45:07 Wrap-up – it’s fun and it certainly has its uses, but not for quantitative measurements

Viewer comments:

I have found another way to achieve this that I believe is more accurate. Simply pass the trigger output through a low-pass filter and a peak detector. This will produce a signal that has a rising edge only at the start of the sweep. This you can use to trigger the scope. To produce a log log diagram you can set the sweep to be logarithmic and you can use the math channel of the scope to log the y-axis.

A very simple and elegant solution! But it’s kind of cheating using extra hardware

But then, it’s not cheating … if it yields better results Any yes, I guess everybody can cobble together a RC low pass, a diode peak detector and two BNC sockets if the need arises – no PCB necessary. Put the whole thing into a copper or steel tube with the BNC sockets sealing the openings and you’re done.

Teardown of the new Keysight EDU33212A 20MHz Function Generator

https://www.eevblog.com/forum/blog/eevblog-1431-keysight-edu33212a-function-generator-teardown/