Hi
I’m not sure I’m in the right forum, but I couldn’t find any specifically for AC line problems.
So I couldn’t get rid of some bad noise, then I connected my scope to my AC, and the sinewave is horrible. I wonder what can be done to fix it?
Thx
Mark
I’m not sure I’m in the right forum, but I couldn’t find any specifically for AC line problems.
So I couldn’t get rid of some bad noise, then I connected my scope to my AC, and the sinewave is horrible. I wonder what can be done to fix it?
Thx
Mark
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The prevalence of Switch Mode Power Supplies (SMPS) soared around the 1990s, with the resulting increase in electrical interference being picked up by AC line supplies.
jean-paul's advice is good - switch off all unnecessary electrical devices in your home, including LED lighting, and see if that improves your waveform.
jean-paul's advice is good - switch off all unnecessary electrical devices in your home, including LED lighting, and see if that improves your waveform.
Before 1990 there was already some interference, mainly from phase cutting light dimmers (still in use today). Being on stage for many years, the rattling of the par-cans when on 50% was clearly audiable. The triacs switched them on on the very peak, and the corresponding sine wave was horrible.
Other nasty stuff are phase inverters, another means to regulate large power. Harmonics up to the MHz's.
Other nasty stuff are phase inverters, another means to regulate large power. Harmonics up to the MHz's.
Hah! Hah! (Or is this no time for humour?)
I didn't mean for that to be funny, it was "dead" serious.
I thought you knew but the GND of your scope may be connected to PE. This may cause a hefty short circuit. Using the wrong probe may also be the end of the scope. In general it is advised to keep from measuring mains voltage with a scope unless you really know what to do and if you know the tricks. Although experienced in mains measurements I always do this with battery operated devices, never with a mains connected oscilloscope even though I have a differential one meant for mains measurements 
Some simple appearing things can also be done dangerously wrong with a simple mistake.
As, like you, I experience pollution even though SMPS are mostly avoided like the Black Plague (one can not replace ALL of those) I do have LED lighting and a cell phone /wireless internet. I ended up building a switchable power distributor in a metal casing with a filter per group of course with use of PE. It is nearly finished and will be powder coated etc. I also like that I can switch all devices on/off at once when I leave the home. Filters often solve issues and you may find them an improvement. Use quality ones from A brands and don't choose too high ratings. Of course use appropriate fuses and build stuff the good way and always with PE.
In my experience a medical isolation transformer improves the situation even better than just filtering (this was already a very long time ago but it is always in my system for the sources). You can't improve the waveform in case it is severely distorted except for a regenerator but those are expensive. Toroids may buzz and that can be solved with a DC blocker.
Some simple appearing things can also be done dangerously wrong with a simple mistake. As, like you, I experience pollution even though SMPS are mostly avoided like the Black Plague (one can not replace ALL of those) I do have LED lighting and a cell phone /wireless internet. I ended up building a switchable power distributor in a metal casing with a filter per group of course with use of PE. It is nearly finished and will be powder coated etc. I also like that I can switch all devices on/off at once when I leave the home. Filters often solve issues and you may find them an improvement. Use quality ones from A brands and don't choose too high ratings. Of course use appropriate fuses and build stuff the good way and always with PE.
In my experience a medical isolation transformer improves the situation even better than just filtering (this was already a very long time ago but it is always in my system for the sources). You can't improve the waveform in case it is severely distorted except for a regenerator but those are expensive. Toroids may buzz and that can be solved with a DC blocker.
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Do that and see what happens. Toroids are most susceptible for any DC component on the mains voltage (because of the distortion). Other types of transformers don't have that issue as much.
In most cases the voltage comes in your home already distorted and the mains impedance is generally very low so unless you don't now heavy machinery with inverters, frequency controllers etc it just is a fact and you will have to take action to enjoy your audio stuff if you don't like it.
In most cases the voltage comes in your home already distorted and the mains impedance is generally very low so unless you don't now heavy machinery with inverters, frequency controllers etc it just is a fact and you will have to take action to enjoy your audio stuff if you don't like it.
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I had similar at my last place as it shared the substation with some industrial units with AC motor inverters and spot welders. Biggest problem it caused was the peak voltage was too low and this made DC rails too low on anything with a transformer, rectifier, smoothing capacitor power supply
There are regulations for mains supply quality, so might be worth calling your supplier
I called ours and they wanted a lot of money to investigate. Didn’t pay, but they must have had other calls and moved our supply eventually as the problem went away
Brian
There are regulations for mains supply quality, so might be worth calling your supplier
I called ours and they wanted a lot of money to investigate. Didn’t pay, but they must have had other calls and moved our supply eventually as the problem went away
Brian
The supplier can't do much about the mains voltage sine wave fidelity and probably not abusing but rather caused by consumers and isn't by far as easily solvable by the supplier, they are probably already supplying fine enough sine shaped AC at their supply sites but it gets distorted on the way to the consumer.
There are also regulations on PSU manufacturers to follow PFC standards, generally, any PSU over 75 Watts capacity should comply with it, but too many manufacturer (usually lesser know brands, and usually from far East) and consumer aren't enough aware of it or don't care.
To OP, as already mentioned avoid connect scope directly to the mains, you can check the mains quality with a transformer on its galvanically isolated secondary side, the mains voltage quality should reflect there.
There are also regulations on PSU manufacturers to follow PFC standards, generally, any PSU over 75 Watts capacity should comply with it, but too many manufacturer (usually lesser know brands, and usually from far East) and consumer aren't enough aware of it or don't care.
To OP, as already mentioned avoid connect scope directly to the mains, you can check the mains quality with a transformer on its galvanically isolated secondary side, the mains voltage quality should reflect there.
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