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| Spikes and noise on Rigol DHO814 |
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| shapirus:
--- Quote from: csuhi17 on March 15, 2024, 08:38:07 am ---The early sales gave a noisy power supply, then if I remember correctly they switched to LiteOn and Lenovo. --- End quote --- Mine is LiteOn. --- Quote from: csuhi17 on March 15, 2024, 08:38:07 am ---I didn't see in the above posts which one was added for those of you who find it noisy. --- End quote --- Mine isn't particularly noisy and isn't a problem in practice, as the emitted interference quickly drops down to undetectable levels as you get farther away from it, but its noise is easy to detect when you look for it. Some other switching supplies around me are noisier. All kinds of noise can be seen when probing with an alligator clip ground strap. Using a spring attachment, or, if possible, a coaxial adapter, helps. --- Quote from: csuhi17 on March 15, 2024, 08:38:07 am ---I use it with a sound technician's 12V power supply, but the LiteOn that comes with it doesn't make more noise for me either. --- End quote --- How did you capture the attached waveforms (how was the probe connected)? They don't look like typical switch mode PSU EMI spikes. |
| csuhi17:
--- Quote from: shapirus on March 15, 2024, 09:38:28 am --- --- Quote from: csuhi17 on March 15, 2024, 08:38:07 am ---I use it with a sound technician's 12V power supply, but the LiteOn that comes with it doesn't make more noise for me either. --- End quote --- How did you capture the attached waveforms (how was the probe connected)? They don't look like typical switch mode PSU EMI spikes. --- End quote --- I charged an Allpowers 288Wh solar power bank/generator with the LiteOn power supply. Between the two is a USB-C male female test connector. I measured between Vcc and Gnd, with 10x. If I have time, I'll try with an adjustable linear load, I couldn't find anything else at the moment. |
| shapirus:
--- Quote from: csuhi17 on March 15, 2024, 10:05:19 am ---I charged an Allpowers 288Wh solar power bank/generator with the LiteOn power supply. Between the two is a USB-C male female test connector. I measured between Vcc and Gnd, with 10x. --- End quote --- That makes sense then. What we've been discussing is this: To capture the radiated interference. |
| csuhi17:
--- Quote from: shapirus on March 15, 2024, 10:21:31 am ---To capture the radiated interference. --- End quote --- Everything is clear now. I misunderstood, I thought he could see the noise from the power supply on the channels. I checked my nearby switching power supplies using that method. For me, they were all much noisier than the Rigol power supply. I measured 2 power supplies of Micsig, an LED light source, a computer, the power supply for a 12V refrigerator, and even my Chinese metal housing power supply. In all the videos I've watched so far, the power supply had a metal housing in the scopes. Maybe they could have added a properly insulated laptop charger with a metal housing, if such exists at all. Wouldn't a thicker metal box have been better than the aluminum foil? |
| shapirus:
--- Quote from: csuhi17 on March 15, 2024, 11:07:27 am ---Everything is clear now. I misunderstood, I thought he could see the noise from the power supply on the channels. --- End quote --- It's possible to see this noise during normal measurements too. The signal being measured must not be too noisy itself, the ground strap instead of the ground spring must be used. Sometimes it's possible to catch it even with the ground spring. --- Quote from: csuhi17 on March 15, 2024, 11:07:27 am ---I checked my nearby switching power supplies using that method. For me, they were all much noisier than the Rigol power supply. I measured 2 power supplies of Micsig, an LED light source, a computer, the power supply for a 12V refrigerator, and even my Chinese metal housing power supply. --- End quote --- Yeah, even if we power the scope with the cleanest PSU possible, then there still will be a lot of crap around emitting all sorts of switching noise, so really the solution is to use probing techniques that help minimize their influence, and to get rid of the worst offenders: for example, in one case, when measuring how well an RC filter on a DC power rail worked, I saw some switching noise and thought that it was coming from a switching PSU powering the circuit, until I saw that the noise remained even after switching the PSU off. It turned out that the interference was coming from a generic chinese DC/DC step-down module used in a homemade device sitting ~3 meters (!) away from the probe. That one must be really poorly designed, I'll have to replace it some day, or make one myself, or maybe just wrap it in foil. |
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