How to measure mains voltage with a bench oscilloscope safely.

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@Lenny-kt2th 10 ай бұрын

The only safe way to measure mains voltage on a mains powered scope is through a high voltage differential probe. Safe for your scope, that is. Personal safety is a whole different matter and depends on the knowledge and behaviour of the operator. Mains in Europe is actually a threephase system at 400 V, not a split phase system. Single phase power is derived from one of the three phases with a neutral as the return path to become 230 V.

@thetechgenie7374 10 ай бұрын

Yes highly recommend using an active differential probe which is what I use and you need a proper rated HV probe of higher voltages. I going to do a video soon on how people can make a active differential probe if on a budget. Did this video as have seen and people ask about probing mains and had people do dead shorts to ground as some don’t know better and forget a bench oscilloscope is reference to earth. At least it keep people safer and from blowing up front end and ground plane on scope as seen to many time. It safer then how I seen a lot of technicians do as most remove the ground pin off cord and etc. Yes for us that engineers or advanced know better and have active differential probes and etc. Yes in the UK and European have 3 phrase 380v to 460v phase to phase and phase to neutral is 220v to 240v in a lot of areas beside mostly US use split phase but a lot of oversea area use split phase as well. We also have 3 phase mostly available to commercial areas but residential homes here are usually served by a single-phase in some case you have 3 phase and can get installed if you have three phase on pole as some do as they run shops out of house. I just finish about a month back installing a 3 phase 1200 amp service as that customer was running welders motors and furnaces and shop business out of garage. Plus method in video only works with mains 50/60 hz and not switching supplies at higher frequencies which then you need a isolated signal generator or differential probes and even then you can run into common-mode noise can get mixed with differential probe voltage inputs. A whole another topic in its own plus would have to go over ground loops duty cycle and etc. Working with mains or HV is dangerous and can be lethal. If people don’t have knowledge to, don’t at least not without supervision from someone that has experience.

@thatsme1268 10 ай бұрын

Please review your statements regarding the UK and US "mains supplies". You are incorrect regarding the UK supplies which are ONLY EVER 1 x Neutral and 1 x Live (at 240V only for domestic supplies). The US has split supplies with 1 x Neutral and 2 x Live (at 120V each out of phase with each other). I suggest you pull this video (until you have corrected your errors) to prevent some-one being harmed or potentially killed.

@thetechgenie7374 10 ай бұрын

I see your correct as UK use a single phase L1 N to ground in some areas where US is L1 L2 to ground or older 4 wire isolated to ground. But also large variance in how L-N-G are installed onto receptacles in Europe / overseas (even within the same country). EG with L-N tied to L1-L2. Since half the time you can't trust the L-N polarization anyway in the plugs/receptacles. No one would get hurt, or kill themselves, as you wouldn’t be grounding out as measuring this way so they be safe. The two probe method would still work as you essentially use two channels as a " pseudo differential input you put Ch1 probe on one leg, & Ch2 probe on the other. Plus didn’t go into that method showing it yet as doing a separate video on it once I run 240v to the bench for my pre heaters and reball station. Plus want to go deeper and explain AC and DC coupling as not what most think it is and harmonics and using a current probe and power measurements. It safe as you are relying upon the return circuit already existing via the 'scope Earth lead & the power point Earth circuit, back to where the Earth & Neutral are bonded at the building power entry, so your not risking grounding out the circuit your attempting to measure, or creating a ground loop, or making the chassis live. There is one other method that I didn’t mention as this of course, as this method will introduce errors if you are trying to look at higher frequency artefacts upon the basic 50 or 60Hz Mains waveform, like a switch-mode power supply but I do a completely separate video on that as a whole another topic in itself. It involves the use of using a battery operated signal generator. I was also going to do a video down the road showing how to make an active differential probe as they are not to hard to make and the best way to measure. This video was done as had people leave ground clip attached and cause injuries to themselves and equipment, or remove ground pin on cord which is even more dangerous, as if equipment develop a fault goodbye lab and potentially house.

@thetechgenie7374 10 ай бұрын

Plus measuring mains in general is not recommended period if you never worked on mains or have enough experience working with mains or higher voltages. Mains voltages are lethal and yes will kill you if you don’t follow safety precautions. Reason why I did the video is essentially to stop people from ground out Live side as seen way to many do so and even in some viewer comments on other videos asking about how to measure mains voltages. I seen other engineers over the years even make the mistake at times.

@andydelle4509 10 ай бұрын

Yes that is a common misconception that the UK is two hots out of phase and a ground just like American residential 240v. Like you said, the UK wall outlet ground/neutral configuration is exactly the same as the USA. It's just at 250v versus 120v. And because it's 250v, they don't need a split phase system to run large residential appliances. The bonded neutral is a safety feature in any grounded electrical system, even in three phase wye services.