"Squeak noise : I mean a funny noise similar to what you get when you touch the volume antenna on analog theremins, but much lower volume." - André
This is new to me. Does it happen when you touch one of the antennas, or instead at a specific volume or pitch, or perhaps location in one of the fields? Could you provide a video of it happening?
"At the output of the 5V supply : 5.04V and 0,44 A."
This is normal.
"At the main board : 4,92V. This means a voltage drop of 0.12V and a cable resistance of 0.27 ohm."
This is excellent.
"Ripple voltage of 40mV at 200Hz approx. Complex wave form. Other frequencies are present but I couldn't identify them."
I would guess this is from the USB source? 200Hz seems like a rather low switching frequency though?
"1.4Vpp, limits 0.6V and 2V, clean sine wave for both."
Seems a bit small and offset towards ground, but your 1x scope probe is most likely contributing to both.
"800kHz for pitch and 1280kHz for volume."
This is normal when the coils are swapped.
"With this kind of probe, directly connected to the 1 Mohm - 25 pf input + 50 pF cable, the c-divider signal must be inaccurate."
Yes, even a 10x probe loads down the "C divider" point somewhat. You can work it backwards knowing the probe impedance to some degree, but in general the strong electric field in the region confounds precise measurement.
"I'm thinking of buying a OWON SDS1102 or similar. Any advice ?"
After reading some of the Amazon reviews I'd go with "or similar". ;-) The input sensitivity doesn't look the best, and the internal digital noise looks pretty bad. Not sure who is designing test equipment lately, but internal switching supplies can spray the guts with crazy amounts of noise. I had to return a UNI-T function generator (of all things) due to this.
I own a Rigol DS1054Z and it covers the basics well. I really do like it, but the FFT isn't as useful as I'd hoped, the inexplicably non-detented multi-function encoder is a constant source of minor frustration, and many times the UI stymies me to the point where I can't figure out how to enter certain modes or display certain measurements. A touch screen could go a really long way to cleaning up the UI. The vast majority of the time 2 channels are sufficient, and 4 are overkill, particularly on this low end. I'd say look at Rigol and Siglent (never played with Siglent myself but from a distance the knobs and buttons look cleaner) offerings and see what folks over at EEVblog are recommending these days.
"Of course you can post a couple of pictures on the D-Lev site! Thanks for that!"
Will do, thank you!
