Isolation of the RIGOL DS1054Z from the mains with three transformers - Page 1
Forum section: electronics / projects

author: eneuro
author_rank: Super Contributor
timestamp: December 29, 2023, 07:57:16 pm
content: Continuation of this topic because I have three transformers instead of two:Isolation of the RIGOL DS1054Z from the mains with two transformershttps://www.eevblog.com/forum/projects/isolation-of-the-oscilloscope-from-the-mains-with-two-transformers/msg5244183/#msg5244183A successful investment in copper transformers 3x 230VAC T250mA 50Hz 24VAC 1.65A 40VA

author: eneuro
author_rank: Super Contributor
timestamp: December 29, 2023, 08:24:43 pm
content: Quote from: Andy CheeBecause of physics worksQuote

author: Warhawk
author_rank: Frequent Contributor
timestamp: December 29, 2023, 08:41:38 pm
content: There is a special department in the hell for people that use an isolation transformers for the oscilloscope. This section is right next to people that take out the trash but don't replace the garbage bag.

author: eneuro
author_rank: Super Contributor
timestamp: December 29, 2023, 08:55:46 pm
content: Quote from: Warhawk on December 29, 2023, 08:41:38 pmI intend to use these three transformers to isolate not only the oscilloscope but also the ~230VAC electronic system under test from the mains power supply from the wall grid socketI am currently preparing a computer simulation of such an electrical circuit and creating a PCB design so as not to make any mistakes, and I need to put a fuse between the plug in the power socket and the 230VAC input of the main first transformer.By the way, do not suggest connecting the black wires in this illustrative photo of these transformers, because according to the description plate on the transformer, the black cables are ~230VAC input and not 24VAC output.Nicely made transformer with a 5mm hole in the center and a round elastic deck underneath for attachment

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 29, 2023, 09:21:23 pm
content: scope isolation is clearly a thinghere is more about what i worked outhttps://webx.dk/oz2cpu/230V-trafo-isolation-low-capacity/230V-trafo.htm

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 29, 2023, 09:24:11 pm
content: my next design is here:https://youtu.be/4rNubfeICOEcheck also the follow up 1https://youtu.be/eSZdO_Uca40and follow up 2https://youtu.be/H4WUNACZ-rA

author: tszaboo
author_rank: Super Contributor
timestamp: December 29, 2023, 09:27:02 pm
content: Quote from: Warhawk on December 29, 2023, 08:41:38 pmNow let's talk about the people, who make a special power lead for it by removing the ground pin.If anyone reading it and wondering: NO, DON'T.

author: tggzzz
author_rank: Super Contributor
timestamp: December 29, 2023, 09:39:21 pm
content: Quote from: eneuro on December 29, 2023, 08:55:46 pmThree transformers isn't enough. You need four. Or five. Or maybe six.What type of fuse is the right type for this circuit?What are you expecting the fuse to protect, and how? (Murphy's law states that transistors protect fuses, not the other way round).A computer simulation, even if it is accurate, will only tell you what you are looking for. So, what will you be looking for? How will it help you discover the dangerous characteristics you haven't thought about? (I can guarantee there will be some) AN-47, p131, IV-21https://www.analog.com/media/en/technical-documentation/application-notes/an47fa.pdf

author: bdunham7
author_rank: Super Contributor
timestamp: December 29, 2023, 09:53:01 pm
content: Quote from: eneuro on December 29, 2023, 07:57:16 pmIf you are buying the transformers new as opposed to using what is at hand, why bother with the double-conversion at all? You could have ordered 1x 100VA 1:1 transformer (or a 234:240 version), isolated the circuit you are testing and left the scope connected normally.

author: tggzzz
author_rank: Super Contributor
timestamp: December 29, 2023, 09:55:44 pm
content: Quote from: tszaboo on December 29, 2023, 09:27:02 pmI discovered the scope I was using had a lead like that, even after putting warning information around the place.I cut the mains lead to make the point that the scope could not be used until it had been checked.Nobody confessed, so we don't know the voltages involved.

author: eneuro
author_rank: Super Contributor
timestamp: December 29, 2023, 09:57:04 pm
content: Quote from: oz2cpu on December 29, 2023, 09:21:23 pmUnfortunately, I don't have a 230VAC<->230VAC transformer and it wasn't easy to find one to buy quickly at the end of the year, so I ordered three 230VAC<->24VAC transformers because the idea is to additionally power the tested electrical circuit with 230VAC voltage from the second one if necessary. connected in the same way as the oscilloscope to the first 230VAC>24VAC transformer, of course remembering that the tested system cannot draw too much power, because both the oscilloscope and the tester use the same first transformer, but in my case it is not a problem, because I just need to replace the 100W IR bulb much weaker, because this system can be programmed so that only about 12.5%-25% of the maximum power of the IR lamp is controlled in a specific way in order to generate infrared waves of specific wavelengths by manipulating the temperature of the IR bulb

author: tggzzz
author_rank: Super Contributor
timestamp: December 29, 2023, 09:58:17 pm
content: Quote from: bdunham7 on December 29, 2023, 09:53:01 pmWhy not? Those with Dunning-Krueger syndrome don't realise they have it.That's confirmed by his statement "...the IR lamp is controlled in a specific way in order to generate infrared waves of specific wavelengths by manipulating the temperature of the IR bulb"Or maybe theindicates he is a troll?

author: eneuro
author_rank: Super Contributor
timestamp: December 29, 2023, 10:01:04 pm
content: Quote from: tggzzz on December 29, 2023, 09:39:21 pmThe transformer manufacturer stated 230Vac@T250mA 50Hz -> 24VAC@1.65A 40VAC, just look at the plate on the transformer

author: tggzzz
author_rank: Super Contributor
timestamp: December 29, 2023, 10:04:53 pm
content: Quote from: eneuro on December 29, 2023, 10:01:04 pmSo your plan is to protect the transformer. From what error condition? What could cause that?

author: eneuro
author_rank: Super Contributor
timestamp: December 29, 2023, 10:26:53 pm
content: Quote from: tggzzz on December 29, 2023, 09:39:21 pmThat's not true, all I need is maybe this one 100W 230VAC->230VAC 50Hz T500mA as in the photo below for the oscilloscope, and the weaker transformers I have can be used to isolate the tested electrical circuits from the mains power supply from the wall socket

author: tggzzz
author_rank: Super Contributor
timestamp: December 29, 2023, 11:05:38 pm
content: Quote from: eneuro on December 29, 2023, 10:26:53 pmNobody cares about a picture of a "weaker" transformer.Are you going to ignore the other questions in my post, the ones you snipped? Here they are again....What type of fuse is the right type for this circuit? [Hint:a transformer specification is not a fuse type!]What are you expecting the fuse to protect, and how? (Murphy's law states that transistors protect fuses, not the other way round).A computer simulation, even if it is accurate, will only tell you what you are looking for. So, what will you be looking for? How will it help you discover the dangerous characteristics you haven't thought about? (I can guarantee there will be some) AN-47, p131, IV-21https://www.analog.com/media/en/technical-documentation/application-notes/an47fa.pdf

author: eneuro
author_rank: Super Contributor
timestamp: December 29, 2023, 11:58:05 pm
content: Quote from: oz2cpu on December 29, 2023, 09:24:11 pmI additionally ordered a 1:1 50Hz 230VAC T500mA/230VAC safety transformer Breve STM 100 230/230V shown in the photo above in case there are any power transfer issues with these two smaller cascaded transformersWeighs about 2 kg

author: coromonadalix
author_rank: Super Contributor
timestamp: December 30, 2023, 12:54:25 am
content: ok you're back from your previously blocked thread, AND you still gives a go at itand your next one would be 4 transformers ??

author: coppercone2
author_rank: Super Contributor
timestamp: December 30, 2023, 12:55:20 am
content: I wonder if there is a amount of transformers you can add to make this stop being stupid

author: tggzzz
author_rank: Super Contributor
timestamp: December 30, 2023, 12:58:36 am
content: Quote from: coppercone2 on December 30, 2023, 12:55:20 amI've tried six, but he hasn't bitten.

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 02:22:58 am
content: Proof of concept by using three transformers to isolate both the oscilloscope (T2) and the electronic system under test (T3) from the mains supply (T1) powered by isolated 230VACDon't think too much, just perform

author: Andy Chee
author_rank: Super Contributor
timestamp: December 30, 2023, 03:04:39 am
content: Do it like this:

author: coppercone2
author_rank: Super Contributor
timestamp: December 30, 2023, 03:20:19 am
content: Quote from: Andy Chee on December 30, 2023, 03:04:39 amI like bypassing problems

author: johansen
author_rank: Super Contributor
timestamp: December 30, 2023, 03:23:53 am
content: No need for isolation, stand on a plastic bucket.

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 03:27:13 am
content: Quote from: Andy Chee on December 30, 2023, 03:04:39 amShow that you are able to do something yourself, and not just use the eraser in Paint to clear part of what someone else did, but that's typical of spammersI will do as I planned in that blocked thread, in a similar way as shown here by oz2cpu - I've attached below screen shoot from his experiment I'd like to see to know that it is doable, while I was waiting for the delivery of transformersQuote from: oz2cpu on December 29, 2023, 09:21:23 pm

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 03:36:29 am
content: Quote from: coppercone2 on December 30, 2023, 03:20:19 amYou've made post in the wrong place because your spam has nothing to do with this topic

author: coppercone2
author_rank: Super Contributor
timestamp: December 30, 2023, 03:37:38 am
content: I support getting rid of dangerous circuit elements by running a bypass

author: Someone
author_rank: Super Contributor
timestamp: December 30, 2023, 03:38:57 am
content: Quote from: johansen on December 30, 2023, 03:23:53 amDo you believe that isolated ground is possible in a plastic bucket?

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 03:42:30 am
content: Since on of my screenshots were used by a spammer, I replaced the last one with a much lower resolution.

author: Andy Chee
author_rank: Super Contributor
timestamp: December 30, 2023, 03:43:14 am
content: Quote from: eneuro on December 30, 2023, 03:27:13 amIt's not just me. Everyone has been telling you;1) isolate the device under test, AND2) do NOT isolate the scope.That's why your original thread was locked, you kept ignoring safety advice.

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 03:46:44 am
content: Quote from: Someone on December 30, 2023, 03:38:57 amI hope that DAVE will also block this thread, because everything is clear and the topic is exhausted, so spammer entries that contribute nothing should be deleted.

author: Ian.M
author_rank: Super Contributor
timestamp: December 30, 2023, 03:48:07 am
content: Has anyone got a copy of the *other* ridiculous grounding photo?IIRC it had a ground wire running to a pot-plant in a bathroom wall-mounted cupholder on a tiled wall!

author: coppercone2
author_rank: Super Contributor
timestamp: December 30, 2023, 03:48:20 am
content: just buy this and stop posting about isolationhttps://www.amazon.com/Micsig-DP750-100-Voltage-Differential-Attenuation/dp/B0B74CD6WZyou can use a probe, and see what its actually doing when its running how its gonna run when its used, or you can fuck around with transformers and not know wtf is going on under unrealistic conditions

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 03:49:43 am
content: Quote from: Andy Chee on December 30, 2023, 03:43:14 amThis has nothing to do with the topic of this thread, so your entries should be deleted, similarly to my previous thread.I don't need your spam

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 03:56:22 am
content: Quote from: coppercone2 on December 30, 2023, 03:48:20 amKupuję to co mi pasuje i już to mam.

author: Andy Chee
author_rank: Super Contributor
timestamp: December 30, 2023, 03:57:07 am
content: Quote from: eneuro on December 30, 2023, 03:49:43 amThe topic of your thread is "Isolation of the RIGOL DS1054Z from the mains with (x amount of) transformers"It doesn't matter how many transformers you use, isolation of the scope is;a) not required for your test setup, andb) has safety risks.The thread should be locked because you have not shown any understanding of the safety risks. The danger is that someone could copy your technique and get killed.

author: johansen
author_rank: Super Contributor
timestamp: December 30, 2023, 04:10:59 am
content: Quote from: Andy Chee on December 30, 2023, 03:57:07 amBetter cancel the internet.If every post about isolating scopes ends with people arguing about it, you really think people will be more likely to do it?

author: Andy Chee
author_rank: Super Contributor
timestamp: December 30, 2023, 04:24:59 am
content: Quote from: johansen on December 30, 2023, 04:10:59 amI should clarify.Argument and debate about the merits of isolating scopes is ok.But abusing people for having contradictory opinions, is clearly a thread locking situation (and indeed, abuse is in the forum rules.... if anyone bothers to read them).Otherwise, what other explanation for the previous locked thread?

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 04:32:15 am
content: Quote from: johansen on December 30, 2023, 04:10:59 amDefinitely don't try this with a prototype board, but it's not a problem for someone who knows what they're doing, and it looks like there are people who have already managed to do it and survived because todayoz2cpusent a link about their experiences and don't cry, just show something usefulQuote from: oz2cpu on December 29, 2023, 09:21:23 pm

author: Andy Chee
author_rank: Super Contributor
timestamp: December 30, 2023, 04:42:45 am
content: https://www.tek.com/en/documents/technical-brief/floating-oscilloscope-measurements-and-operator-protectionQuote

author: bdunham7
author_rank: Super Contributor
timestamp: December 30, 2023, 04:51:53 am
content: Quote from: eneuro on December 30, 2023, 04:32:15 amWith what appears to be pictured (a large audio amplifier with a large toroid for a linear power supply?) unless there is something like an NTC or soft-start circuit, 1R would not be a very smart choice at all as it would have a significant effect on the inrush. Actually, even with the NTC or soft-start 1R would be a terrible choice. 0R01, kelvin-sensed, might work.But you're right, it isn't a problem for someone who knows what they are doing as that person would just use an inexpensive current clamp that probably would cost a lot less than the isolation transformer.

author: Someone
author_rank: Super Contributor
timestamp: December 30, 2023, 05:07:34 am
content: Quote from: Ian.M on December 30, 2023, 03:48:07 amFine choice of imagery

author: Ian.M
author_rank: Super Contributor
timestamp: December 30, 2023, 05:24:34 am
content: That's certainly similar, but the plant and cupholder stuck in my memory as notably funny. I guess this sort of 'earthing' isn't uncommon in 3rd world hotel "suicide" shower installations.

author: Andy Chee
author_rank: Super Contributor
timestamp: December 30, 2023, 05:24:51 am
content: Ah yes, the electric heated water shower head!

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 05:25:47 am
content: Quote from: Andy Chee on December 30, 2023, 04:42:45 amThis article promotes TEK's products, so obviously they won't show you how to isolate an oscilloscope with a transformer for <$40, only their "wonderful" inventions useless for me

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 05:30:06 am
content: Quote from: Andy Chee on December 30, 2023, 05:24:51 amI'm just reporting crappy spam of this type to the moderator and blocking your profile in my custom web browser

author: Andy Chee
author_rank: Super Contributor
timestamp: December 30, 2023, 05:31:33 am
content: Quote from: eneuro on December 30, 2023, 05:25:47 amThere is no RIGOL document showing isolation of oscilloscope with a transformer for <$40.

author: bdunham7
author_rank: Super Contributor
timestamp: December 30, 2023, 05:32:52 am
content: Quote from: eneuro on December 30, 2023, 05:25:47 amDid you know that you actually don't even need a transformer to isolate your scope? Are you a transformer salesperson?

author: djacobow
author_rank: Super Contributor
timestamp: December 30, 2023, 05:35:55 am
content: Floating My Scope: A Socratic DialogueStudent: I would like to float my scope using a transformer.Socrates: Do not do that. Float your DUT, or better yet, get a differential probe.Student: Yes, but I want to. It should work.Socrates: Yes, of course it will work, for certain definitions of "work", but it is a bad idea.Student: What makes it a bad idea?Socrates:<< explains at length >>Student: I don't think any of those apply to me. I'm smart and understand what I'm doing and will definitely not make any dumb or careless mistakes, ever.Socrates: Then why did you come to me with this question?Student: Just to be sure. I'm all set, thanks for nothing.<< the next day >>Student: ha ha, you're a loser. I floated my scope, and it was fine.Socrates: <sigh><< three weeks later >>Student, in new thread on Socrates message board: my scope was working just fine and now one of the channels is completely dead. How can I fix this?ORStudent receives shock of a lifetime from carelessly touching exposed metal on his now high-potential scope; keeps it to himselfORStudent is dead. Survivors do not know Socrates, do not invite him to the funeral.

author: magic
author_rank: Super Contributor
timestamp: December 30, 2023, 05:37:07 am
content: What's the point of putting a scope on an isolation transformer?What's the point of doing it instead of isolating the DUT?What's the point of doing it if the DUT is isolated?

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 05:39:24 am
content: Quote from: bdunham7 on December 30, 2023, 05:32:52 amI invest in rare metals such as copper in transformer windings, I don't buy aluminum windings because copper is worth more than crappy plastic probes

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 05:48:30 am
content: Quote from: djacobow on December 30, 2023, 05:35:55 amYou don't leave such people at home with electricity in the socket, you just lock the fuse box with a padlock and put nails into the sockets after cutting off the power

author: coppercone2
author_rank: Super Contributor
timestamp: December 30, 2023, 05:51:54 am
content: the source impedance is all fucked up with a transformer its not a real measurement, the differential probe gives you a realistic measurement. even if it works.tektronix does not recommend it because1) its not safe2) you are measuring some seriously contrived parameters

author: JeremyC
author_rank: Regular Contributor
timestamp: December 30, 2023, 06:16:37 am
content: Quote from: eneuro on December 30, 2023, 05:25:47 amYou could use 2 x 100X scope probes and A - B math channel in your scope. Most of the 100X probes are rated up to 2000V, you may get them for <$20, below is an example:https://www.amazon.com/Oscilloscope-Accessory-Voltage-100MHz-Bandwidth/dp/B07F65SZMV/ref=sr_1_4?crid=26HVQFB28J5JY&keywords=100x+oscilloscope+probe&qid=1703915253&sprefix=100x+ocilloscope+probe%2Caps%2C168&sr=8-4

author: coppercone2
author_rank: Super Contributor
timestamp: December 30, 2023, 07:15:48 am
content: also how do you standardize measurements with a isolation transformer? Like tektronix needs to sell a measurement system. That is some chaos. Transformers probobly not even characterized well enough to be used with the kind of measurements and standard tektronix sells/develops. YOu would simply not know if the results are the same without the transformer.They might make shitty chassis and get a little cheap/greedy but they know what they are doing when it comes to understanding how the electronics works and what makes the measurement accurate. Adding a random impedance between the DUT is not one of those things. Compared to the probe its probobly mostly not usable.it has a unknown effect on the scope, and an unknown effect on the DUT. You can make guesses but the fact is, its super different then being at line impedance and also not having the RF filtering from the ground caps.do you really think tektronix is that stupid? they wrote the book on accurate AC/pulse measurements as engineers understand them today. They deal with the top echelons of industry/science. They have spare no expenses government/commercial contracts too (but not for the gear you get). What do you get behind the cutting edge electrical pulse/signal science? most likely a tektronix or tektronix derivative.And you think tektronix would not sell a cheap isolation transformer if it was any good? the prices lock out tons of market. But its beneath their standards so they cannot realistically sell it. That many unknowns is just considered SHADY measurements in the industry. You are making a fool out of yourself.if the conditions presented by the isolation transformer were like a parameters the oscilloscope designers had to consider they would be like WTF> !! There would likely be huge design changes to actually make it compatible with some specific transformer and there would still be deviated specifications (all the safety shit aside, assuming it as OK to make it unsafe)and even then, you put some random bullshit frankenformer made from multiple random ass transformers it would probobly still not be in any kind of spec.

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 07:41:09 am
content: Quote from: JeremyC on December 30, 2023, 06:16:37 amThis might make sense, but these 100X <$20 are suspiciously cheap, compared to the four PVP3150 passive probes ~40$ which I got when I bought the oscilloscopeRIGOL PVP3150 Passive Probe:QuoteI do not need to measure the maximum values of the 230VAC power supply network, though Max Input Voltage: 300 V of this PVP3150 Passive Probe probably at 10M it's not crazy but still ~325Vmax/10M it is only ~33uA @ 230VAC mainsUPDATE:QuoteIt seems that Rigol PVP3150 Passive Probe Max. Rated Input Voltage @10X is300VRMSso there it is~424Vpeakwhich would be consistent with what is in this guideQuote

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 07:45:14 am
content: Quote from: coppercone2 on December 30, 2023, 07:15:48 amI don't need any standardization, I just sometimes estimate how much the simulation results of the system differ from the one run after soldering in reality

author: eneuro
author_rank: Super Contributor
timestamp: December 30, 2023, 11:42:55 pm
content: Quote from: tggzzz on December 30, 2023, 12:58:36 amIf you do not have one 230/230V transformer to isolate the oscilloscope, you need two 230/24V transformers, as in this simulation below, where I am testing a device connected directly to the mains power supply with an oscilloscope isolated from the 230V 50Hz mains supply using T1 230/24V and T2 24/230V

author: johansen
author_rank: Super Contributor
timestamp: December 31, 2023, 01:20:14 am
content: For like 50$ you can buy 96 AA batteries and run your scope off a battery pack.anyone tried to measure the capacitance to ground, and compare the waveform of what a high side 370vdc mosfet at 100Khz looks like with a floating scope, compared to a good quality differential probe? (yes, your scope would be floating at 370vdc to ground at 100khz)...I don't have a differential probe otherwise i would try this myself.

author: eneuro
author_rank: Super Contributor
timestamp: December 31, 2023, 02:04:51 am
content: Quote from: johansen on December 31, 2023, 01:20:14 amMeasuring differential signal with single ended probe(s)Quote

author: johansen
author_rank: Super Contributor
timestamp: December 31, 2023, 05:51:14 am
content: Quote from: eneuro on December 31, 2023, 02:04:51 amI am not trolling. Why are you?

author: eneuro
author_rank: Super Contributor
timestamp: January 02, 2024, 11:32:14 am
content: Quote from: oz2cpu on December 29, 2023, 09:24:11 pmInteresting experiments with toroidal transformersElectronic system with opto-isolation for detecting the polarization of the 230VAC primary and 24VAC secondary windings of the transformer, ready for soldering on an80mmx20mm prototype boardThere should now be no problem with cascading several transformers in such a way as to obtain the desired polarization on the secondary winding

author: Spar59
author_rank: Contributor
timestamp: January 02, 2024, 04:21:19 pm
content: Just a point here - I will take criticism if someone poiunts out it has alredy been mentioned in this thread or they have technical knowledge to the contrary.True safety isolation transformers intended for that purpose either use seperate bobbins on an E-I core or else have an inter-winding screen to reduce capacitive coupling and to provide a safety barrier if the inter-winding insulation fails.While it appears you are determined to do a floating scope arrangement it is something I personally would avoid at all costs if measuring mains voltages on the unit under test, to avoid ground loops when testing a low voltage system, maybe. A differential probe would be bettter or possibly use 2 channels and the maths function to subtract one input from the other to create a differential measurement with suitably rated single-ended probes which would be cheaper than a dedicated differential probe.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 02, 2024, 04:32:28 pm
content: @Spar59you're absolutely right, but this thread as derailed a lot from the previouly locked one, its no longer relevant, lots of stupid ideas and stubbornessyou have optically linked probes, differential probes ... all safenow when you have gimmicks for phase detection / polarity etc .... pffffffff it's because you know zits ........you want to try poor solutions while playing with safety, yeah go burn yourself ...wating for the 4 5 6 transformers ideas pffffffffffff

author: eneuro
author_rank: Super Contributor
timestamp: January 02, 2024, 04:50:22 pm
content: Quote from: coromonadalix on January 02, 2024, 04:32:28 pmI've four RIGOL PVP3150 Passive Probes so it's easy to make one differential probe out of two by connecting the crocodile clips togetherI have PC817 optocouplers and they are sufficient for such simple things @50HzMeanwhile, the electronic circuit for transformer polarization tests was sent to the PCB factory

author: eneuro
author_rank: Super Contributor
timestamp: January 02, 2024, 05:18:15 pm
content: Quote from: johansen on December 31, 2023, 05:51:14 amI am not joking.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 02, 2024, 05:47:10 pm
content: Read OP's original thread. Looks like the lamp was initially intended to run directly from mains but now wants to isolate the entire system with a separate transformer for the low voltage supply. Maybe I miss-read.Personally, I tend to leave the equipment as is. Can't think of a time I have ever needed to isolate a scope or other equipment. Looking at their ZCD and driver for the lamp, I still don't see the need. I would use a proper probe or isolate the device. In cases where the device is intended to be directly connected to the mains, I normally have to pass various EMC tests anyway so we are making our own mains. I am not going to run it on the actual mains and assume that is good enough to test the products performance. Again, maybe I am missing something.

author: eneuro
author_rank: Super Contributor
timestamp: January 03, 2024, 03:40:09 pm
content: Quote from: joeqsmith on January 02, 2024, 05:47:10 pmYes, It's not rocket scienceThe PCB for testing the polarity of transformers is already in production, and slow fuses (T500mA,T250mA,T2A) have been ordered in the meantime and one circuit will be soldered on a prototype PCB and flooded with an insulatorPCBWay Factory Tour:

author: johansen
author_rank: Super Contributor
timestamp: January 04, 2024, 06:11:13 am
content: Why does the polarity of the transformer matter?You already have isolation in the power supply of the oscope.

author: tggzzz
author_rank: Super Contributor
timestamp: January 04, 2024, 09:19:21 am
content: Quote from: johansen on January 04, 2024, 06:11:13 amThe smell of "cargo cult engineering" is overpowering.

author: tom66
author_rank: Super Contributor
timestamp: January 04, 2024, 09:25:24 am
content: Whilst everyone argues about whether it is safe or not to float your scope (it's not, but I'm guilty of doing it, so sue me) - you can power a Rigol DS1xxxZ scope off approximately 50V DC placed across the live and neutral terminals. That is enough for the internal flyback stage on the PSU to function. It'll pull around 12W in this configuration. I have a little magic box somewhere that has a boost converter in it that powers my scope from a 12-24V battery or car cigarette lighter. It cost probably £10 in parts from eBay. No need to overcomplicate things.

author: magic
author_rank: Super Contributor
timestamp: January 04, 2024, 09:52:33 am
content: I can't even understand what this guy is trying to do at this point.Last time I thought I knew, I was under impression he is isolating his scope only to connect it to an already isolated device (i.e. the device could be grounded by the scope without smoking anything).... and it doesn't help that the @#$$$% started to upload ant-scale images because somebody "pirated" one and defaced it with alternative suggestions

author: eneuro
author_rank: Super Contributor
timestamp: January 04, 2024, 03:34:44 pm
content: Quote from: tom66 on January 04, 2024, 09:25:24 amYou're right, that's why I use transformers for this purposeI need to know the polarity of the transformers not only in the case of cascade connection but also a 1:1 transformer, because I can also use it to isolate the tested systems, so I want the output to be the same as the input, not an inverted sine wave of mains 230VACProfessionalism means attention to detail.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 04, 2024, 04:04:13 pm
content: Quote from: eneuro on January 04, 2024, 03:34:44 pmwe talk about "phase" here not polarity if you where that professional, you should use the right termsyou're in phase or out of phase ...and normally since you don't get the scope grounded all your gimmick serve nothingi never had any problems with 1 isolation transformer loll if you know how to use them

author: eneuro
author_rank: Super Contributor
timestamp: January 04, 2024, 05:55:19 pm
content: Quote from: tom66 on January 04, 2024, 09:25:24 amGood to knowOn the label on the back, the minimum frequency range is 44Hz to 400Hz max, so I didn't expected that this oscilloscope could be powered by DC voltage.

author: Edison
author_rank: Frequent Contributor
timestamp: January 16, 2024, 01:10:46 am
content: Quote from: eneuro on December 29, 2023, 08:24:43 pmWell, physics may work, but the head doesn't - a floating oscilloscope is nonsense - there is a filter on the power three-wire socket that is connected to the ground, and in that case the supply voltage will reach the frame of the oscilloscope. The oscilloscope may be more susceptible to interference from the environment. The device under test is connected via an isolating transformer. If you have a necessary need, buy a battery oscilloscope or an oscilloscope that has galvanically isolated inputs by the manufacturer (for example Tektronix 🤔 but for that price you have about twenty of your own)Well, if the head works as it should, then when a galvanically isolated measurement is needed with a classic oscilloscope, a normal galvanically isolated differential probe is used.

author: bdunham7
author_rank: Super Contributor
timestamp: January 16, 2024, 01:13:11 am
content: Quote from: Edison on January 16, 2024, 01:10:46 amCan you provide an example of one? They typically either have significant performance limitations or are very expensive.

author: Edison
author_rank: Frequent Contributor
timestamp: January 16, 2024, 01:20:46 am
content: Differential optical probes measure from DC to GHz, but you're right, they are expensive, the cheap Chinese ones work wonders, so I solved it with a 2x 100Mhz battery oscilloscope, which is enough for my purposes

author: Edison
author_rank: Frequent Contributor
timestamp: January 16, 2024, 01:36:08 am
content: Quote from: eneuro on January 02, 2024, 04:50:22 pmIn this type of measurement, the ground clamps are not used at all, thanks to the activated mathematical function, the signal from both channels is calculated, one probe with the tip, for example, on GND and the other on the test pinThe differential probe is galvanically separated - two probes against each other are not - it uses mutual isolation of the active part of the oscilloscope input

author: Edison
author_rank: Frequent Contributor
timestamp: January 16, 2024, 01:40:44 am
content: Quote from: coromonadalix on January 02, 2024, 04:32:28 pmDon't be surprised, the more transformers, the more Adidas 🤣

author: Edison
author_rank: Frequent Contributor
timestamp: January 16, 2024, 01:48:20 am
content: Quote from: eneuro on January 04, 2024, 03:34:44 pmIf you do not understand from what has been written here by everyone that the isolation transformer should not be connected to the power supply of a classic oscilloscope, take your oscilloscope, open the window and throw it out of the window and the transformers behind it - that will be the most professional thing you can do

author: coromonadalix
author_rank: Super Contributor
timestamp: January 16, 2024, 02:03:34 am
content: loll i'm waitning for the op answer to that loll this is a joke

author: bdunham7
author_rank: Super Contributor
timestamp: January 16, 2024, 02:30:35 am
content: Quote from: Edison on January 16, 2024, 01:36:08 amDifferential probes are not truly galvanically isolated, they have an input impedance spec to ground of xM + ypF and a probe-to-probe spec of 2xM + ypF/2. The circuit doesn't look much different then two probes on a scope. That was sort of my point--true galvanic isolation comes at steep price.

author: Edison
author_rank: Frequent Contributor
timestamp: January 16, 2024, 02:38:28 am
content: sorry I left out the word opticaledit: my heart almost stopped when I first saw the price of a galvanically separated probe up to 1GHz 😂

author: Andy Chee
author_rank: Super Contributor
timestamp: January 16, 2024, 04:33:12 am
content: 30 years ago there was a Silicon Chip project for galvanically isolated differential probes based on the IL300 linear optocoupler. It only had a measly bandwidth of 100kHz, so it's almost useless in today's high speed switching environment.Perhaps the design could be re-worked to use a modern device like Broadcom HCPL-4562? (still limited to 17MHz bandwidth)Turns out that device has worse THD due to lack of feedback photodiode. Neverthless, Broadcom has an improved IL300 drop-in replacement, HCNR200 with 1.5MHz bandwidth, which is still slow but might be a tad more useful.

author: bdunham7
author_rank: Super Contributor
timestamp: January 16, 2024, 04:56:13 am
content: Quote from: Edison on January 16, 2024, 02:38:28 amTrue, but the specs on those Iso-Vu units are jaw-dropping as well. 160dB CMRR and 60kV common mode voltage! I wonder if that 60kV is good all the way to 1GHz?

author: bdunham7
author_rank: Super Contributor
timestamp: January 16, 2024, 05:04:49 am
content: Quote from: Andy Chee on January 16, 2024, 04:33:12 amSiglent had an isolation module, the two-channel ISFE, that used regular probes and had a 1MHz BW. Perhaps they used this part or something like it. Unfortunately they discontinued it for unknown reasons.

author: magic
author_rank: Super Contributor
timestamp: January 16, 2024, 09:33:58 am
content: Quote from: Edison on January 16, 2024, 01:20:46 amThis sounds like an ordinary oscilloscope with GND connected to all probes?It still has most of the problems:- common mode of both channels must be the same- loads the "negative" input with capacitance to ambient (even more so when you are touching the device)- can be dangerous if common mode is high voltage with respect to earthIt eliminates one disadvantage of "ungrounding" a mains scope:- no mains noise injection through capacitance of the PSU

author: Edison
author_rank: Frequent Contributor
timestamp: January 16, 2024, 10:52:23 am
content: Quote from: magic on January 16, 2024, 09:33:58 amYes, the inputs have a common GND, because I only use one probe, so it doesn't matter, but as I wrote - it's enough for my needs.Connecting the oscilloscope through the isolation transformer just solves the removal of the connection to the ground, but badly - strangely floating oscilloscope, capacitive coupling of the transformer, etc.

author: magic
author_rank: Super Contributor
timestamp: January 16, 2024, 02:38:47 pm
content: I have only ever lifted ground to test power supply primaries, where capacitive current from the scope's PSU is irrelevant since it's absorbed by the low impedance (and high voltage) negative rail.Safety nuts hate me

author: Zero999
author_rank: Super Contributor
timestamp: January 16, 2024, 11:33:52 pm
content: Quote from: eneuro on January 04, 2024, 05:55:19 pmOf course it'll work off DC. The input to the power supply is just a bridge rectifier. The minimum frequency will be specified because of the size of the smoothing capacitor.It will work at lower DC voltages, because the smoothing capacitor doesn't have to do any work. I found mine works down to 36V. I considered making a battery pack for it, but lost interest when I bought an oscilloscope with a battery. Others decided to make their own battery pack with tool batteries. Refer to the following thread.https://www.eevblog.com/forum/testgear/battery-pack-for-rigol-ds1054z/msg717702/#msg717702

author: eneuro
author_rank: Super Contributor
timestamp: January 25, 2024, 05:51:50 pm
content: Quote from: Edison on January 16, 2024, 01:48:20 amPCBs designed to determine transformer polarization have just arrived, so after soldering optoisolators, a few resistors and diodes, it will be possible to connect all transformers to isolate the oscilloscope and the tested 230VAC system as shown in earlier simulations.Throw your computer out the window because your typing on the keyboard makes no sense Pepiczku

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 26, 2024, 12:12:55 pm
content: I think it is better to isolate the circuit, rather than the oscilloscope.