Measuring mains with an oscilloscope - Page 1
Forum section: electronics / beginners

author: robsims
author_rank: Frequent Contributor
timestamp: June 08, 2025, 02:25:28 am
content: Hi, i have a Hantek 5072P 70 Mhz DSO. It came with two 10X probes. I want to troubleshoot powersupplies. Mains voltage in my country is 127 volts AC. To troubleshoot the powersupplies i'm going to use an isolation transformer. Are the 10X probes enough or do i need 100X probes?

author: ataradov
author_rank: Super Contributor
timestamp: June 08, 2025, 04:02:22 am
content: If you are going to use a transformer anyway, why not make it 10:1 transformer and not deal with dangerous voltages on the secondary side?

author: AlexRG
author_rank: Regular Contributor
timestamp: June 08, 2025, 04:34:13 am
content: Quote from: robsims on June 08, 2025, 02:25:28 amYour oscilloscope can measure up to 30V with a 1:1 probe and up to 300V with a 1:10 probe. If your power net has 127V, then the power supply may have a voltage of up to 190V. Therefore, a 1:10 probe should be enough for a safe study. The power supply unit under study must also be isolated from the general power net. I recommend double insulation, for example two 127/24 or 127/48V transformers.

author: robsims
author_rank: Frequent Contributor
timestamp: June 08, 2025, 09:33:23 am
content: Many many thanks AlexRG

author: robsims
author_rank: Frequent Contributor
timestamp: June 08, 2025, 03:16:03 pm
content: If i measure the voltage on a switch mode powersupply after rectification i find around 180 volts. I think the peak voltage will be around 255 volts, am i correct? Can i still go along with the 10X probes?

author: Ian.M
author_rank: Super Contributor
timestamp: June 08, 2025, 03:34:09 pm
content: It used to be extremely common for power supplies that could switch (or be switched) between 115V and 230V AC input, to use a voltage doubling rectifier circuit when switched to 115V. That would give approx 360V on the primary side DC bus, in excess of your scope's input rating with a x10 probe. Also, older universal input supplies with power factor correction may also boost to over 360V as it simplifies the design of the next stage, which can now operate at constant voltage. Therefore always check with a DMM before scoping the high side of the DC.Also, it is almost invariably unsafe to scope the collector or drain waveform of the main switching transistor(s) on the primary side as the peak voltage can exceed double the DC bus voltage, with fast edges. Even a x100 probe is likely to have trouble with the high amplitude edges, as they contain high frequency components that typically exceed what is permitted by the probe's derating curve with respect to frequency.

author: radiolistener
author_rank: Super Contributor
timestamp: June 08, 2025, 03:34:30 pm
content: Quote from: robsims on June 08, 2025, 03:16:03 pmNo, your assumption is not correct. While the nominal peak voltage of a 230 V AC mains supply is around 325 V (RMS x √2), real-world mains systems often experience transient overvoltages - short high-voltage spikes, which can reach 1000 to 2000 V or even higher. These surges can be caused by switching inductive loads, lightning strikes, or faults in the distribution network.The critical issue is that if you use oscilloscope probes with a voltage rating that is too low, these transients can exceed their insulation limits, causing internal breakdown. Worse, this can result in an arc to mains, which may self-sustain until a circuit breaker or fuse trips. Such events are extremely hazardous and can damage your equipment or worse, pose a serious safety risk.Always ensure your probes are rated not just for the expected peak voltage, but also for transient overvoltage (CAT rating). Using 10x probes might be fine for typical operation if they're rated for ≥600 V CAT II or better, but you must check the maximum input voltage specification and CAT rating of your particular probes and oscilloscope.In RF systems, it is standard practice to maintain at least a 2x Upeak voltage safety margin to prevent dielectric breakdown due to the superposition of forward and reflected waves. The resulting voltage at certain points in the transmission line can momentarily exceed the nominal level, especially in the presence of high VSWR (Voltage Standing Wave Ratio), making this margin essential for reliable and safe operation.For mains measurements - especially when working with switch-mode power supplies - it is strongly recommended to use 100x probes and exercise extreme caution. Ideally, use a battery-powered oscilloscope or one that is galvanically isolated from the mains via an isolation transformer. Otherwise, connecting the oscilloscope's ground lead can create a short circuit to earth, potentially causing equipment damage or posing a serious safety hazard.

author: robsims
author_rank: Frequent Contributor
timestamp: June 08, 2025, 04:29:19 pm
content: Please guys read this first before commenting, because i'm getting confused a little bit. I know the dangers of measuring with an oscilloscope. I already watched dave's video about blowing up scopes. the only thing I want to know is if i need 100X probes or not.I want to troubleshoot SMPS powersupplies like e-bike battery chargers and television smps powersupplies. I want to check if the PWM chip is switching (if it pulses). i'm going to use an isolation transformer for the devices under test and one also for my oscilloscope. Mains voltage in my country (suriname) is 127 volts.When i'm measuring the voltage on the powersupplies after full wave rectification with my DMM i measure around 179 volts. My question is do i need to buy 100X probes or are the 10X probes the scope came with, enough?

author: calzap
author_rank: Frequent Contributor
timestamp: June 08, 2025, 04:38:32 pm
content: I won't address the probe issue.But if you haven’t done it before, use your DMM to check that the isolation transformer is really isolating secondary from primary. Some transformers sold as “isolation” did not provide galvanic isolation; they were line conditioners. In addition, even a true isolation transformer can develop insulation faults over timer.Mike

author: radiolistener
author_rank: Super Contributor
timestamp: June 08, 2025, 05:26:27 pm
content: Quote from: robsims on June 08, 2025, 04:29:19 pmIn typical conditions for 127 VAC, 10x probes may be sufficient, provided they are rated for at least 300-400 V and have a suitable CAT (category) rating for mains use.However, when working with mains circuits or switch-mode power supplies, it's not just the steady-state voltage that matters - transient spikes can occur, sometimes well over 1000 V, especially during switching events. These can easily exceed the safe limits of 10x probes.Therefore, for safety and headroom, especially in SMPS or high-energy environments, 100x probes are strongly recommended, as they are typically rated for higher voltages and provide better isolation.Also be aware that there are many counterfeit oscilloscope probes on the market - particularly from unverified sources, often labeled as CAT II 600 V, yet using components such as coaxial cables that are clearly marked for only 300 V or less. I've personally encountered such cases. Using these probes for mains measurements is dangerous, as they may not withstand real-world transients and can fail catastrophically. Always verify the quality and authenticity of your probes before using them on high-voltage circuits.

author: tggzzz
author_rank: Super Contributor
timestamp: June 08, 2025, 05:47:08 pm
content: Quote from: robsims on June 08, 2025, 04:29:19 pmI doubt you knowallthe dangers of using scopes and probes on high energy circuits; I certainly don't.If you want to measure high voltages where it can be difficult to find a point to attach a probe's shieldsafely, then you should understand the characteristics of HV differential probes. Alternatively you could investigate the (rare) scopes where the inputs are fully isolated.For the class of probe to use in different circumstances, see the references inhttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/especially the Tektronix documents and the safety section.

author: Terry Bites
author_rank: Super Contributor
timestamp: June 08, 2025, 05:56:05 pm
content: AC, linear power supplies or switchers?Isolation transformers can put you at risk.Because the output side is not connected to ground your RCD/ GFCI wont trip when you accidentally touch something you oughtn't.Best solution: Use isolated probes. eg Hantek HT8050/8100.

author: robsims
author_rank: Frequent Contributor
timestamp: June 08, 2025, 06:33:02 pm
content: Ok i will buy 100X probes. My scope is 70 mhz. Are these probes good?https://www.amazon.com/Voltage-Oscilloscope-Probe-Accessory-100MHz/dp/B083LM4P9T/ref=sr_1_3?crid=2YT9PDXFRVM27&dib=eyJ2IjoiMSJ9.msGl_-N9__FpKzg_FLoBi9dIW3Wh9_cHStbewVPB18uicw2Vbz717LKauxyYhPe6YiaO2bIyjKUi6WugbF_GlNWg-htxqDNatOohjKvYwFT_vO3ZvQsUSZaKPVAscAiRT9ywpHSRUMKKqcePohHIqFJyDvcaa5BrK-eaUJa0e5Og8cPTGKeVL5u8sxT47EA1XgorZkUjH3pHV798YzoeNZb3OrFdrYCqG_24N_U6SeaL-YmMxxBrX_yTUNDQEJP8_Tv0fQZMbkrxzTAIEDUwjDoKT-PrAqg9qKaj8J0Z_QQ.mKiiP1i5v1PJnxowHwmU9AofHhxUw6-T0TAwPqmKVZg&dib_tag=se&keywords=1%3A100%2Boscilloscope%2Bprobe&qid=1749395444&s=industrial&sprefix=1%2B100%2Boscilloscope%2Bprobe%2Cindustrial%2C157&sr=1-3&th=1https://www.amazon.com/100MHz-Oscilloscope-P4100-Voltage-Bandwidth/dp/B0DK1B96HN/ref=sr_1_20?crid=3PD2PFRW8N1YZ&dib=eyJ2IjoiMSJ9.owsknh8JlW03qnt5POLYQcOzHV9pXu23x9cpvjfdYrCiHHUStE5rTTv2PK9zkQPLWk33SB5cO-M6oY8-oRD5YaMF0c9YSSCzepxorSAwumLT2t8fpHwiVOTUS8JJKTiBqDjIX5S-8NGS5hjp64v25OhlvpM5-tEA_CqI8kAIpZE-gxrrRGdULw4ET5mSi9AWip7tW_RcS_M-K9TAEYXtxU0gQdr0VH5NeX0nXl3AJMdGRRCvf3KXttgN1jRzsu9bJA7qawgOsXkXIScD_KU8cAJ9r1_9gA3hciRhvy9yDwE.Fp9KNaRy7FGCgN9iRXPSp-HVpWoYETLJ_iri8saOJnE&dib_tag=se&keywords=X100+Oscilloscope+Clip+Probe&qid=1749407380&s=industrial&sprefix=x100+oscilloscope+clip+probe%2Cindustrial%2C143&sr=1-20

author: bdunham7
author_rank: Super Contributor
timestamp: June 08, 2025, 06:55:07 pm
content: Quote from: robsims on June 08, 2025, 06:33:02 pmP4100 are OK, but look at the P2301C. 100M, 100x, 300MHz, low capacitive circuit loading and a safer HV design IMO. IDK what they cost in your area, they've gotten expensive in the US due to the trade war.

author: robsims
author_rank: Frequent Contributor
timestamp: June 08, 2025, 07:31:58 pm
content: Many thanks bdunham7. The P2301C. 100M, 100x, 300MHz is out of my budget range. I think for now i will settle with the $20 p4100Thanks again

author: joeqsmith
author_rank: Super Contributor
timestamp: June 08, 2025, 08:04:45 pm
content: Just be aware of the derate curves. Personally, I value my scopes too much to risk them like this.

author: robsims
author_rank: Frequent Contributor
timestamp: June 08, 2025, 09:33:39 pm
content: joeqsmith, if you won't risk them like you say, how would you measure the signals of a pwm chip of a switch mode powersupply?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 09, 2025, 01:20:13 am
content: The standard probes from both my rigol and siglent scope has the text "x10 300V CAT II" written on them. So that is already quite marginal where I live (230Vac mains). Little mistakes such as accidentally moving that x1 / x10 switch can also become expensive (Although it probably won't kill you (not right away at least).

author: joeqsmith
author_rank: Super Contributor
timestamp: June 09, 2025, 02:38:03 am
content: Quote from: robsims on June 08, 2025, 09:33:39 pmI've never designed a line powered SMPS and over the years, the ones I have repaired, I have just used a meter. That said, if I needed to measure anything on the AC mains, that required any sort of bandwidth, most likely I would purchase a diff probe.

author: radiolistener
author_rank: Super Contributor
timestamp: June 09, 2025, 03:11:24 am
content: Quote from: Doctorandus_P on June 09, 2025, 01:20:13 amNote that the nominal mains voltage of EU mains is actually 240 V with a ±10% tolerance. This means the voltage can reach up to about 264 V AC RMS, which corresponds to approximately 373 V peak. Sometimes it going even higher. And with broken neutral it can get up to 509 V peak and even higher.The second question - are you sure that the "300 V CAT II" marking refers to 300 V AC RMS and not 300 V peak? Since these probes are just generic unnamed Chinese models without a clear manufacturer, their true specifications can be quite questionable.Even if the "300 V" rating on the probe refers to RMS voltage rather than peak voltage, I would still advise against using such probes for mains measurements. The mains voltage is very close to the probe’s maximum rating, which is very risky - any transient spike or surge (which happens very-very often on mains) could easily exceed the limit and cause the probe to fail and ignite powerful arc.

author: radiolistener
author_rank: Super Contributor
timestamp: June 09, 2025, 03:22:57 am
content: By the way, in all my years of experience, I have never directly measured mains voltage with an oscilloscope - even with using 100x probes. While I understand it is technically possible, I am fully aware of the potential risks and consequences involved. Therefore, whenever I needed to observe the mains waveform, I always used an isolation transformer to ensure galvanic isolation and have never connected the oscilloscope directly to the mains.This is likely because, over the years, I have experienced electric shocks from mains voltage firsthand and witnessed the serious consequences that can result from accidental incorrect connections. Had I not had such experiences, I might have been less cautious about these risks.

author: chilternview
author_rank: Frequent Contributor
timestamp: June 09, 2025, 10:16:25 am
content: Quote from: radiolistener on June 09, 2025, 03:11:24 amIn the UK it's 230v, -6 +10%.

author: bdunham7
author_rank: Super Contributor
timestamp: June 09, 2025, 11:04:02 am
content: Quote from: joeqsmith on June 08, 2025, 08:04:45 pmActually, beware of the implausible fiction that is printed as derate curve in the "manual" for some of those clone probes.Also not mentioned in this thread is that the front panel of the OP's scope is labelled 'CAT II 400V' or "300V CAT II" depending on what picture you're looking at. And the website says this:CAT I and CAT II: 300VRMS (10×), Installation Category;CAT III: 150VRMS (1×);Installation Category II: derate at 20dB/decade above 100kHz to 13V peak AC at 3MHz* and above. For non-sinusoidal waveforms, peak value must be less than 450V. Excursion above 300V should be of less than 100ms duration. RMS signal level including all DC components removed through AC coupling must be limited to 300V. If these values are exceeded, damage to the oscilloscope may occur.I won't pretend to know exactly what that means.

author: robsims
author_rank: Frequent Contributor
timestamp: June 09, 2025, 11:41:17 pm
content: I saw some youtube videos of the inside of an oscilloscope. The powersupply of the oscilloscope is a switch mode powersupply (SMPS). Switch mode powersupplies have a hot and cold side wich are separated. The only things connecting the hot and cold side is the transformer and optocouplers. So there is galvanic separation from mains in the oscilloscope itself. The only potential component that can cause a hazard is the probe clip which is connected to ground. If the clip is disconnected by using a two prong cable the oscilloscope probes are fully disconnected from mains, meaning they are safer to work with. Am i correct?

author: themadhippy
author_rank: Super Contributor
timestamp: June 10, 2025, 12:05:50 am
content: Quoteapart from all the shiny bits that should be safely connected to ground are now are possible connected to live waiting to bite

author: watchmaker
author_rank: Unknown
timestamp: June 10, 2025, 12:33:17 am
content: Quote from: robsims on June 09, 2025, 11:41:17 pmYou asked for the advice of professionals and they gave it. If you have the time, research some of the terms they introduced; do not think one or two YT videos are going to help you accomplish your goal.You could even consider that your goal is not reasonable given your budget and knowledge.I used to do a fair amount of chainsaw and rigging work. Professionals want to go home with all their fingers, amateurs seem to want to prove they are manly men who do not need physics.If this seems judgmental, I suppose it is. But I mean it in kindness.

author: tggzzz
author_rank: Super Contributor
timestamp: June 10, 2025, 01:17:48 am
content: Quote from: robsims on June 09, 2025, 11:41:17 pmSigh.Please read the reference I gave you earlier:https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/Concentrate on the paragraph beginning '“floating” the scope', since that is what you are proposing. Then read the paragraphs 'high voltages' and 'practical safety'.There is an English proverb which is relevant here: "you can lead a horse to water, but you can't make it drink".

author: tggzzz
author_rank: Super Contributor
timestamp: June 10, 2025, 01:20:19 am
content: Quote from: watchmaker on June 10, 2025, 12:33:17 amIt is judgemental. Good. Better that than treating all ideas and opinions as being equally valid

author: radiolistener
author_rank: Super Contributor
timestamp: June 10, 2025, 02:57:32 am
content: Quote from: robsims on June 09, 2025, 11:41:17 pmNot exactly. While it's true that switch-mode power supplies in oscilloscopes provide galvanic isolation between the primary (hot) and secondary (cold) sides via a transformer and optocouplers, the situation is more complex when it comes to safety.Oscilloscopes typically have Y-class safety capacitors between each mains input line (L and N) and the instrument’s chassis or signal ground. These form a capacitive voltage divider, which result in the oscilloscope's ground terminal having a floating AC voltage, often around 100-150 V AC with respect to earth ground. The current is limited to a relatively safe level for humans, but it can still damage electronics or cause erratic behavior if improperly connected.But the most critical safety risk arises when the oscilloscope's ground lead is connected to a circuit that is not at earth potential. This is very dangerous even if your oscilloscope is battery powered and don't have connection to mains. If, for example, you connect the ground clip to a live part of the circuit (intentionally or not), you may create a short circuit to earth through the probe, which can cause sparks, equipment damage, or serious electric shock - especially if any exposed metal parts of the circuit become live as a result and you can touch it.Using a two-prong power cable to "float" the oscilloscope does not eliminate the hazard - it may a little bit reduce the immediate fault current, but the instrument is still not truly isolated in the way an isolation transformer would provide. In fact, floating the oscilloscope can lead to unpredictable and unsafe conditions, including shock hazards and damage to the scope itself.The core issue is that you're attempting to probe a circuit that operates at mains high-voltage potential, which is inherently dangerous. Even a minor mistake can lead to serious consequences, including electric shock or equipment damage.To ensure safety, the device under test should be powered through an isolation transformer, so that no part of the circuit maintains a galvanic connection to the mains supply. This isolation significantly reduces the risk during measurements and allows for safer oscilloscope probing.

author: tggzzz
author_rank: Super Contributor
timestamp: June 10, 2025, 09:05:47 am
content: Quote from: radiolistener on June 10, 2025, 02:57:32 amAs I'm sure you are aware, to avoid that there are specialised scopes with isolated input channels. Even the part of the input BNC connector that you can touch is made of plastic. It is highly unlikely that is relevant to the OP.QuoteAnd to your equipment. A floated scope will have a poorly defined capacitance between the case (and probe shield) and protective mains earth. Attach the probe shield to the "wrong" node and the capacitance may change the operation too much. Consider trying to measure Vgson the high FET in an SMPS.QuoteJust so. As you know, but the OP might not, using an isolation transformer in that way canincreasethe danger of electrocution, since the transformer defeats an RCD.

author: bdunham7
author_rank: Super Contributor
timestamp: June 10, 2025, 09:43:44 am
content: Quote from: robsims on June 09, 2025, 11:41:17 pmNo, that's exactly the scenario where you end up killing yourself or blowing something up.There are floating (isolated) scopes and there are safe ways to float a regular scope (along with manyunsafeways) but either of those options will cost a lot more or take a lot more effort to use than just getting a pair of Micsig HV differential probes and an isolation transformer.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2025, 02:17:09 pm
content: Quote from: bdunham7 on June 09, 2025, 11:04:02 amTrue. I looked at a low cost 100x probe. At DC they rated that probe at 2kV. 200V at 1MHz. 100V at 100MHz. Cutting it open, it appeared to use two 0.25W axial resistors and a cap. There's no way I would use a probe like this at 2kDC with my scope. Max working voltage is 250V * 2. Even if it was 1kV, if they break down at double, there goes your front end. Why would anyone risk it?I fully understand why they make products like this. High voltage resistors cost too much money and would cut into their profits. Hobbyist are not normally working at 2kVDC. They could have just as easily provided realist data in their manual but I assume it is similar to China's stating all their low end bargain basement meters are CAT III 600V rated.Buyer beware.

author: robsims
author_rank: Frequent Contributor
timestamp: June 10, 2025, 08:03:12 pm
content: Here is a video how to use a scope for measuring mainsIn this video the same man uses an oscilloscope to measure pwm chip switching frequencyMains voltage in my country is 127 volts RMS. Peak voltage is around 180 volts. If i want to measure if a pwm chip is switching i will connect the alligator clip of my oscilloscope on the negative side of the filter cap and the probe on the gate of the mosfet. So i wont be measuring voltages around 1 kV. I think an isolation transformer connected to my scope, a two prong powercable for my scope, 100X probes and not touching metal parts of the scope are enough and safe to do the job

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2025, 08:32:11 pm
content: Your the expert...I read that post today about the person who damage their arb. Oops...Last SMPS I looked at had a PFC stage running around 400V. Pretty close to the 2 X 250V the 1/4W axial parts are rated to. Of course, they do have the high freq. comp capacitor in their to improve the response time of the probe. Again, your equipment and your the expert.

author: tggzzz
author_rank: Super Contributor
timestamp: June 10, 2025, 09:01:02 pm
content: Quote from: robsims on June 10, 2025, 08:03:12 pmI have a video where I am telling my audience that it is OK to run into the road without looking. I demonstrate it is safe by doing that - and not being killed (or worse, seriously injured). Should I put that video on yooootooob so that people like you can see it and do the same?In short the first video you reference is dangerous bollocks, pure and simple.You have been pointed to this anecdote (twice); which bit do you find it difficult to comprehend? It is about aprofessional engineerthat took considerable precautions:https://groups.io/g/TekScopes/message/10754Key sentence: "This guy was WELL AWARE of the danger and took a lot of precautions to prevent shock . . . Bottom Line: He died anyway." You understand much less than that professional engineer.If you really want to play silly buggers, do this:To trap out some traditional comments. I'm not risk averse and do take risks. Overall, some risks are worth taking, because the benefits cannot be obtained otherwise. I've even encouraged my 15yo daughter to do them, e.g. being a solo pilot before she could learn to drive a car, in an aircraft where every landing is aforcedlanding.Floating a scope is not such a risk: there are other easy ways to gain the benefits without any risk. relax: I don't, and even if I did I wouldn't post a video about it!

author: themadhippy
author_rank: Super Contributor
timestamp: June 10, 2025, 09:20:25 pm
content: Quoteto quote me ole mate del " a little knowledge is a dangerous thing, so some clever bar steward said"

author: robsims
author_rank: Frequent Contributor
timestamp: June 10, 2025, 10:30:31 pm
content: You all took you're precious time to give me good information and advice. What to do and what not to do. I appreciate all comments and i'm going to take all of them into account when using my scope for powersupply repairs. Many thanks to all of you

author: tggzzz
author_rank: Super Contributor
timestamp: June 10, 2025, 11:10:12 pm
content: Quote from: robsims on June 10, 2025, 10:30:31 pmYou are welcome.Good luck, and keep one hand behind your back.

author: robsims
author_rank: Frequent Contributor
timestamp: June 11, 2025, 12:13:38 am
content: of course tggzzz

author: tooki
author_rank: Super Contributor
timestamp: June 11, 2025, 07:22:44 am
content: Quote from: radiolistener on June 09, 2025, 03:11:24 amNo it isn’t, and never was.Mainland Europe was 220V ±10% in the past, then raised to 230V.UK was 240V ±10% in the past, then lowered to 230V.For 220V countries:Starting in 1987, the voltage was gradually raised to 230V +6/-10%, which kept the upper voltage limit very close to the upper bound of 220V +10V.The energy providers have adjusted the actual voltages — as IEC 60038 compliance required them to do by 2003.Effective 2009, the voltage range changed to 230V ±10%, whose upper bound is significantly higher than that of old 220V ±10% appliances.

author: radiolistener
author_rank: Super Contributor
timestamp: June 11, 2025, 07:45:39 pm
content: Quote from: tooki on June 11, 2025, 07:22:44 amPreviously possible, in USSR and Ukraine we had 220 V.But recently it was changed (in this year) to 230 V in order to comply with EU requirements.Now I have about 235 V at day and about 245-248 V at night.Sometimes (rarely), for example during shelling/bombing it may raise to 260-270 V RMS or go below 160 V, especially when some bombs hit some high power consumption facilities.

author: armandine2
author_rank: Frequent Contributor
timestamp: June 11, 2025, 09:29:02 pm
content: ... JW's advice, if you haven't seen.

author: TimFox
author_rank: Super Contributor
timestamp: June 11, 2025, 09:59:04 pm
content: Two perennial questions that occur here regularly:1. How to measure mains with an oscilloscope.2. Why don't we all change the definition of electrical current to correspond to the (negative) charge on the electron?

author: tooki
author_rank: Super Contributor
timestamp: June 12, 2025, 08:15:52 am
content: Quote from: radiolistener on June 11, 2025, 07:45:39 pmFrankly, I don’t believe you, for three reasons:1. There is no way that Russia and Ukraine would chooseexactly that momentto change the line voltage. I’m pretty sure both countries had, and continue to have, much more pressing issues.2. If we browse the edit histories of the Wikipedia article “Mains electricity by country” in both English and Russian, they all state 230V for both Ukraine and Russia and have done so since at least 2016 (I didn’t bother looking farther back). For both countries, links to the relevant national standards or regulations (I can’t tell what exactly since I can’t read either language).3. Your history of posting incorrect statements.Quote from: radiolistener on June 11, 2025, 07:45:39 pmOof, that sucks.

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 12, 2025, 11:21:01 am
content: Quote from: radiolistener on June 11, 2025, 07:45:39 pmActually, everywhere I have seen (in Ukraine) it was changed to 230 VAC almost 10-15 years ago (I can't say exact year, it could be very different in different regions). So, at least 10 years ago I see 225-235 VAC in central and east of Ukraine, and in west too.Recently it was just de-jure accepted a new standard with 230VAC is now an only one rated voltage, instead of previous 2014 'transition 220/230 standard'.

author: Ian.M
author_rank: Super Contributor
timestamp: June 12, 2025, 11:35:34 am
content: There's also the issue of utility companies choosing to set distribution transformer taps in some areas for a higher line voltage (predominantly in dense urban areas with relatively little solar) to get more out of their heavily stressed grid as in many cases they cant or don't want to afford the infrastructure improvements needed to properly support new build developments and mass EV charging.Then there is solar, which if there is a lot of it about in excess of customer usage typically raises the mains voltage towards its upper limit on sunny days.The days of stable 240V in the UK and 220V in Europe are long gone. Harmonisation was *supposed* to move everyone towards 230V as equipment was replaced or reconfigured, but in practice seems to have resulted in greater voltage variation, exploiting the increased permissible range.

author: radiolistener
author_rank: Super Contributor
timestamp: June 12, 2025, 02:29:51 pm
content: Quote from: tooki on June 12, 2025, 08:15:52 amI don't surprised, since according to your history of posting, you never believe to truth and always name correct things as incorrect, so it would be strange if you did the opposite this time.Here is link on news site:https://lider.112.ua/en/ukraina-perehodit-na-230-volt-ak-zminatsa-cifri-u-platizkah-za-svitlo-64099Quote from: 24-MAY-2025And here is the link on government regulatory site:https://www.nerc.gov.ua/news/yevropejska-napruga-i-novi-standarti-shcho-zminitsya-u-kodeksi-sistem-rozpodiluQuotein English:QuoteAs for the fact that during the USSR era the voltage standard was 220 V, this is written in the official standard ГОСТ-21128-83.Here (see attachment) is a standard series of voltages for DC (upper part) and for AC (lower part - first line for single phase and second line for 3-phase) which was defined by the standard in the USSR for electricity grids and electricity receivers, as you can see there is no 230 V in that series, just 220 V. However, the same standard in some cases allowed the use of the value 230 V, but not as the main value, but as an alternative option in exceptional cases.As for electricity grid voltage standard in Russia, I don't know it, so I cannot comment it.PS: By the way, your trolling tactic of derailing technical discussions by shifting the focus to discuss personalities and then resorting to insults closely resembles the behavior of a known professional troll here -Nominal Animal, who employs exactly the same approach. Just curious - are you a clone of his account?

author: radiolistener
author_rank: Super Contributor
timestamp: June 12, 2025, 03:28:06 pm
content: Quote from: Vovk_Z on June 12, 2025, 11:21:01 amthe actual voltage in the mains grid has been around 215V during the day and about 230V at night for a long time, as I recall, for more than 17 years. I remember it because I bought and installed voltage protection relay at about 2008 to protect my computer PSU which was burned out too often and I suspected mains overvoltage above 240V because PSU was rated for 220V, and my protection relay was configured for 232V threshold for a long time, later I slightly increased threshold because it started to trigger sometimes. But since the war began, I’ve noticed a gradual increase in the upper voltage margin - from 230V to around 240V and even higher.Interestingly, after installing an overvoltage protection relay, a new power supply unit purchased in 2008 operated reliably until 2023. Prior to that, even branded (Zalman, Corsair, etc), high-quality PSUs failed within a year for some unknown reason. This supports the my theory that overvoltage issues were the likely root of cause of those earlier failures.And what is even more interestingly, that after many years of reliable service, the power supply failed almost immediately after I raised the protective relay's voltage threshold to 242V. This adjustment was made in 2023, during a period of frequent power outages caused by bombings. When power was restored, voltage levels often exceeded normal limits for a long periods. And to avoid long delays waiting for the voltage to stabilize, I increased the upper limit threshold and ironically, the power supply failed that very same day...Now I see 245V at night, whereas before the war, my voltage protection relay was set to trigger at 236V, and it very rarely triggered (maybe once per several months or something like that). Now it is impossible to use this threshold, because at night time the voltage is almost always above 240V.I'm living in a one of the largest city, so situation in a small cities may be different. At the moment when I wrote this message the voltage in the mains is 225 V.Since the new standard hasn’t taken effect yet (it will be in a month), I’m not sure if it will change the actual voltage range and it going to even higher values or simply legalize the new values. We’ll see soon.

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 13, 2025, 03:04:30 am
content: For 230 VAC rated voltage higher limit has to be set as 253 VAC typically (230+10%).And I use this exact setting about 10 or more years.Your power supply must have been too tired and so couldn't survive switching off and on while you worked with your voltage protection relay.

author: tooki
author_rank: Super Contributor
timestamp: June 13, 2025, 02:38:32 pm
content: Quote from: radiolistener on June 12, 2025, 02:29:51 pmI only call things out thatareincorrect. You just have the dumb luck to be a frequent source of incorrect statements.Quote from: radiolistener on June 12, 2025, 02:29:51 pmI didn’t insult you, I just stated facts.I listed averifiablereason why you’re wrong on this matter. The verification I did, you can do, too.Quote from: radiolistener on June 12, 2025, 02:29:51 pmYou clearly haven’t noticed the many times (s)he and I have disagreed on things! :pQuote from: radiolistener on June 12, 2025, 02:29:51 pmAnd what you’re missing is that the change fundamentally happened long ago. The reports you cite aren’t the complete picture.If you look at the wikipedia article history,an edit on May 24, 2023added this note to Ukraine’s line in the table: “Temporarily the nominal voltage in the low-voltage network is 220V”. It — and the link to the standards document showing Ukraine’s long-standing 230V nominal — were removed inan edit on April 18, 2025, replacing them with a link to the latest update.Unfortunately I can’t read the2014 documentdirectly, but through machine translation it seems to support the temporary drop to 220V (see page 7).So basically, as I interpret it:At some point Ukraine adopted 230V like everyone else, and then at some point temporarily dropped it to 220V without actually formally changing the nominal voltage as such; it remained defined as 230V. Then they recently discontinued the “temporary” situation.It would require a more thorough study of the materials (and likely of older ones, too) to know precisely what was changed when.

author: tggzzz
author_rank: Super Contributor
timestamp: June 13, 2025, 03:06:46 pm
content: Quote from: tooki on June 13, 2025, 02:38:32 pmAs someone who often disagrees with you, all I can say to your three responses is yes, yes, and yes.

author: radiolistener
author_rank: Super Contributor
timestamp: June 13, 2025, 09:42:42 pm
content: Quote from: tooki on June 13, 2025, 02:38:32 pmAll you ever do here is derail technical discussions into personal attacks, insults and stupid dismissing official regulatory documents with childish "I don't believe you, because you always incorrect". Sorry for the directness, but you reek of a cheap troll or a washed-up propagandist with nothing of value to say.Quote from: tooki on June 13, 2025, 02:38:32 pmWhen you're trying to dispute official documents or established standards, you need to rely on credible, peer-reviewed, or institutionally approved sources - not crowd-edited articles filled with footnotes you barely understand. Your vague interpretations and childish confidence don't qualify as verification.Quote from: radiolistener on June 12, 2025, 02:29:51 pmYou're making confident claims about on-the-ground conditions in Ukraine without actually being here or having firsthand experience. I’ve provided both official regulatory sources and direct observational data from real equipment in real conditions from 2008 year - data that reflects the actual state of the grid over time, including variations before and after the war began.Your assertion that "the change fundamentally happened long ago" directly contradicts with the real observable state of the voltage range, which was keep within 205-235V range, in average 220V for very long period and started to change when war began.Speculating from afar and dismissing documented local experience while lacking any credible data of your own isn’t a valid argument - it’s just arrogance. If you want to contribute meaningfully, base your claims on verified facts, not assumptions.Quote from: tooki on June 13, 2025, 02:38:32 pmDismissing official regulatory announcements because you “didn’t find it on Wikipedia”, "don’t believe" - is not only intellectually dishonest - it’s absurd and stupidity.The information I provided comes directly from the official website of the National Energy and Utilities Regulatory Commission of Ukraine (NERC):https://www.nerc.gov.ua/news/yevropejska-napruga-i-novi-standarti-shcho-zminitsya-u-kodeksi-sistem-rozpodiluIt clearly states:"з 01.07.2025 в Україні почнуть діяти європейські підходи до визначення параметрів якості електроживлення, зокрема — перехід на номінальну напругу 230/400 В."in English: "from July 1, 2025, European approaches to determining power supply quality parameters will come into effect in Ukraine, in particular, the transition to a nominal voltage of 230/400 V."This isn’t speculation, opinion, or interpretation -it’s a formal regulatory claim backed by official documents on the official website.If your idea of “verification” is limited to whether something shows up on Wikipedia, while ignoring primary sources from the regulator itself, then you're not participating in a technical discussion -you're just trolling.Given your repeated personal attacks, dismissiveness, and naive arguments, I see no point in wasting further time responding to you. I’d rather focus on something that actually yields value - like debugging the code.

author: radiolistener
author_rank: Super Contributor
timestamp: June 13, 2025, 10:34:10 pm
content: Quote from: tggzzz on June 13, 2025, 03:06:46 pmDisagreeing with someone occasionally doesn't automatically make you objective or credible - nor does it disprove coordination or connection between trolls. Especially when your input amounts to endorsing baseless claims and personal attacks. This kind of behavior doesn't contribute to a meaningful discussion, it just amplifies noise and undermines constructive dialogue. In fact, this is what trolling is.I feel like I’m interacting with a group of trolls operating as a crowd, rather than independent participants genuinely interested in the topic.If the intention behind coordinating as a crowd of trolls is to create the illusion of broad consensus and pressure me into silence or respect - you're seriously mistaken. I don’t respect trolling, no matter how many voices it tries to hide behind.Since the discussion has clearly drifted away from the original topic, I’ll step away and leave the trolls to entertain each other.

author: tooki
author_rank: Super Contributor
timestamp: June 15, 2025, 11:03:03 am
content: Quote from: radiolistener on June 13, 2025, 09:42:42 pmI provided you with verifiableofficial(primary) sources documenting the earlier situation. (And I did look at them, as my prior reply makes obvious. How could I refer you to a specific page if I hadn’t looked at it myself?) You’re the one ignoring things, not me.So it’s not trolling, it’s just pointing out that you are wrong, or at absolute minimum, not acknowledging the much more complex history than the simplistic one you present.

author: tooki
author_rank: Super Contributor
timestamp: June 15, 2025, 11:13:51 am
content: Quote from: radiolistener on June 13, 2025, 10:34:10 pmThat’s a “you” problem: you elicit this kind of thing because of your persistent incompetence and/or overconfidence, forcing others to correct the nonsense you post so as to not leave behind, as the last word, uncorrected erroneous information.Let me also make it completely clear that correcting misinformation or other errors is NOT trolling. Full stop. Trolling is deliberately disruptive behavior done only for the point of being disruptive. Correcting errors isn’t that.You could end this cycle (of you feeling bullied by groups of people here) by simply a) not posting incorrect stuff to begin with, and b)listening to othersand engaging with them meaningfully when they tell you you’re wrong. But you never, ever listen, you just pretend you’re right and everyone else is stupid. So we get frustrated with you, and rightfully so.There are other members I also get into disagreements with, but we also have respect for each other, because when presented with evidence of a mistake, we listen.You could start by looking at the primary sources I provided, and then engaging with the subject matter: yes, the authorities stated a change to 230V just recently. But they also did long ago… So rather than tell me I’m a troll, and pretend that I didn’t do my homework (when I very clearly did), you could help explain the real situation, as evidenced by the older primary sources.

author: jonpaul
author_rank: Super Contributor
timestamp: June 15, 2025, 11:28:35 am
content: Hello all, Bonjour a tous.Just saw this now,We use isolation with a mains transformer.240/120 main>>>240:12V transformer>>scopezero cost, totally safe.Your utility uses a :potential transformer to measure high voltage T&D lines,240 kV>>PT>>120VThe waveforms are identical on P and S. Just scaled by the transformer ratio.Jon

author: radiolistener
author_rank: Super Contributor
timestamp: June 15, 2025, 05:52:30 pm
content: Quote from: tooki on June 15, 2025, 11:13:51 amI didn’t ask for your opinion on my competence - and frankly, I couldn’t care less about it.If you have something to say about the technical subject, say it. Otherwise, keep your personal judgments to yourself.Quote from: tooki on June 15, 2025, 11:13:51 amThere is no actual error correction in your posts. What you consistently do is derail technical discussions into personal attacks, dismiss valid sources - like official regulatory documents published on authoritative websites - simply with lines like "I don’t believe you, because you’re always incorrect".That’s not error correction. That’s trolling - low-effort, low-quality trolling.Claiming that personal insults are "just correcting mistakes" is as absurd as saying: "I’m not insulting someone - I’m just telling the truth when I label them and attack them personally, because I’m always right and they’re always wrong". This is exactly the kind of childish reasoning your trolling associate,Nominal Animal, used before. It’s not clever. It’s not technical. It’s just the same pathetic trolling.If you're not a paid troll, but were simply drawn into this behavior by others who are, take a moment to reflect: what relevance do your posts, such as "this person is always wrong and therefore not to be trusted", have to the actual topic of measuring mains voltage? Even setting aside the obvious fallacy of such reasoning, just consider: how is this related to the technical subject under discussion?Why bring personal assumptions and off-topic commentary into a technical thread? What purpose does this noise serve, other than derailing the discussion?Do you even understand the difference between a technical discussion and personal attacks? Learn it.If you actually want to contribute to a technical conversation, focus on the topic. Say what exactly you disagree with, or what you don’t understand. Stop flooding the forum with your narcissistic, off-topic rants about who’s "always wrong" and who you believe you’re allowed to insult.Just stop that bullshit. Thanks.Quote from: tooki on June 15, 2025, 11:13:51 amI haven’t posted anything incorrect. If you believe that an official statement from a regulatory authority is wrong and that your interpretation of something you found on Wikipedia and internet is more accurate you are free to submit an official inquiry to that regulator. Explain to them that they’re mistaken because of what you read online.Who knows, perhaps they’ll revise their position based on your "insightful" comments.Once again, this is not my personal opinion - I just mentioned an official statement from a regulatory body. You responded by claiming it’s incorrect, then immediately shifted to personal attacks with childish claims like “you’re incompetent because you’re always wrong”.That’s not how technical discussions work.Quote from: tooki on June 15, 2025, 11:13:51 amDisagreements are a natural part of technical discussions - what matters is how they’re handled.I mentioned to a current official regulatory source. If you believe there’s a discrepancy based on older documents, that’s a valid point for clarification and could be worth discussing if approached constructively.However, dismissing the current official regulatory position and responding with personal attacks, while insisting that others are always wrong and never listen, is not constructive.Moreover, you do not live in Ukraine, and from your comments, it’s clear you have little or no understanding of the actual situation here. Yet you’re attempting to lecture someone who does live here on what is supposedly happening in their own country based on non-official secondhand internet sources with dubious origin.If your goal is genuine technical discussion, drop the arrogance, stop the personal attacks, and focus on technical questions. Otherwise, you're not contributing you're just trolling and undermining the discussion.To understand how a professional discussion is conducted: if you disagree with a statement made by a regulatory authority, you could simply state that you disagree based on information you found in unofficial online sources suggesting that the transition to 230 V may have started prior to 2025.Framed this way, your position would be professional and valid for discussion and free of personal attacks. Instead, you chose to present your opinion with unwarranted certainty and condescension, as if you alone decide what is correct and used that as justification for insulting others. That’s not how professional or respectful dialogue works.Regarding the actual situation on the ground - as a local resident, I’ve been monitoring mains voltage with precise true-rms DMM for a long time and can provide some clarity. Yes, the legal transition toward 230 V has been ongoing for years and still didn't finished, but in practice, the average voltage remained around 220 V, with peak levels rarely exceeding 235 V. Usually 220V at daytime with drops to 205V and 230V at night time. There was a very gradual upward drift in the upper fluctuation limit, but it was slow and stable.After the war began in 2022, the upper limit started rising more noticeably. Currently, nighttime voltages can reach 250 V or higher - something that never occurred before.As for the official announcement regarding the full transition to 230 V, it has not yet come into legal force. Therefore, it’s difficult to say whether this will have any measurable impact on actual grid voltages. We'll only be able to assess that after July 1, 2025. However, such a transition may have a negative impact on end users, as the majority of older appliances were designed for 220 V operation.PS: As you can see, I strive to maintain a professional discussion focused strictly on technical matters. The firm tone in my responses to you arises when the conversation shifts away from the technical subject and toward personal attacks. It seems that you have an assumption that discrediting your opponent personally somehow validates your arguments - but that is not the case. Regardless of how you characterize your counterpart or assert they are wrong, it does not change the core of the issue.Just think about it - will the answer to 2 + 2 change if you call your opponent incompetent and always wrong and continue to insult him? Or does such an assumption rather point to serious issues with your logic and perception of reality?Resorting to personal attacks only demonstrates your inability to engage in a professional dialogue, technically it just shows your incompetency - nothing more.

author: shapirus
author_rank: Super Contributor
timestamp: June 15, 2025, 08:11:05 pm
content: Quote from: radiolistener on June 12, 2025, 02:29:51 pmFrom what I can see, both the so-called journalists and the government regulatory website are (re)posting the same bullshit, initially produced by some keyboard-operating monkey that we have no shortage of, which is nothing new.The old standard, "ДСТУ EN 50160:2014", which became effective, if I'm not mistaken, in 2014, already specified 230 V (+10%/-10%, with some exceptions) single-phase voltage for the low-voltage network. It's super easy to check, PDFs are freely available, e.g.:https://chernihivoblenergo.com.ua/files/consumer/law_docs/%D0%94%D0%A1%D0%A2%D0%A3%20EN%2050160-2014-1.pdfBefore that one, again if I'm not mistaken, we were on 220 V.I couldn't find the text of the new standard, "ДСТУ EN 50160:2023", which became effective this year and replaced the old one. It doesn't seem to be available free of charge, or maybe I failed at searching. I couldn't find a diff between the two, either.Quote from: radiolistener on June 15, 2025, 05:52:30 pmAs you can see, they are not to be trusted unless what they publish is crosschecked and confirmed to be true.I wish this would be the only known instance of such incompetence on their part...

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 15, 2025, 08:20:56 pm
content: Man, calm down, please. :-) It doesn't matter if it is 220 or 230 VAC, really. Let's waste our energy onto something useful.

author: shapirus
author_rank: Super Contributor
timestamp: June 15, 2025, 08:27:48 pm
content: Quote from: tggzzz on June 10, 2025, 09:01:02 pmIt won't be typical to find an antediluvian scope like this nowadays, let alone procure an additional front panel for the same, or similar, model to build such a contraption.Modern scopes typically don't have metal parts on the front panel except for the BNC shields, which are easy to isolate using rubber caps.It's time to find a new picture.

author: tggzzz
author_rank: Super Contributor
timestamp: June 15, 2025, 08:38:48 pm
content: Quote from: shapirus on June 15, 2025, 08:27:48 pmThat completely depends on the specific scope.Please do supply an alternative picture thatviscerally rams homethe point of what is necessary if you float a scope.Until you can do that,...

author: TimFox
author_rank: Super Contributor
timestamp: June 15, 2025, 08:49:55 pm
content: In that picture, note that the BNC shells are totally inaccessible from the added front panel.

author: shapirus
author_rank: Super Contributor
timestamp: June 15, 2025, 08:59:21 pm
content: Quote from: tggzzz on June 15, 2025, 08:38:48 pmI'm afraid I won't be bothered to go searching for a picture.I see your point, of course, and in fact the picture I commented on can be legit in some circumstances. There are still many old scopes with metal chassis and controls in use.So let us generalise: if you need to float a scope and there is a possibility of non-earth potential becoming present on the scope ground, then, besides other safety measures, make sure that you cannot touch any metal part on the scope. Methods of achieving this vary depending on what specific scope you're working with.Scaring people away with "don't float your scope or you'll be killed" will not work. Educating and explaining the risks and how things work exactly will (normally). Bad things happen because of receiving an electric shock, not because of floating a scope. Receiving an electric shock can be avoided by knowing how it can be received and taking the necessary precautions.People will try to float their scopes despite being told not to, so telling them not to is useless. But explaining how to do it safely might work.

author: TimFox
author_rank: Super Contributor
timestamp: June 15, 2025, 09:02:57 pm
content: Or explaining the problem and urging them not to take the risk, especially in > 220 V countries.

author: radiolistener
author_rank: Super Contributor
timestamp: June 15, 2025, 09:27:56 pm
content: Quote from: shapirus on June 15, 2025, 08:11:05 pmYou're correct that the standard ДСТУ EN 50160:2014 specifies 230 V as the nominal voltage for low-voltage networks. However, this standard also includes a national note which clearly states:QuoteIn English:QuoteThis indicates that Ukraine is in a transition period, where 220 V is still the official regulatory nominal voltage. The move to 230 V is planned, but still not applied even today, the new 230 V standard is set to take effect on July 1, 2025.So at this point (on June 16, 2025), 220 V remains the current official standard.Will the actual voltage in the grid change significantly after July 1, 2025 - we'll see soon. In practice, though, the transition to the new standard has already been happening gradually throughout the war period. At this point, daytime voltage typically sits around 225 V, nighttime around 245 V, with an average close to 235 V, which is already slightly above 230 V.So, in essence, the grid network has already aligned quite closely with the future standard, even before its official legal enforcement.The downside of the new standard taking effect is that the upper permissible voltage limit will increase, effectively allowing higher voltages in the grid. This may lead to premature failure of older equipment designed for 220 V operation.

author: tggzzz
author_rank: Super Contributor
timestamp: June 15, 2025, 09:40:25 pm
content: Quote from: shapirus on June 15, 2025, 08:59:21 pmNo one technique will work with everybody. Most people will respond to one technique - but not everybody.Photos complement words; some people respond more to one, some to the other.Telling or scaring people too often provokes the reaction "yes, but that won't happen to me". There are too many examples of that in this forum, and arguably even in this thread.Demonstration is difficult, especially remotely. I taught my daughter to have a visceral appreciation of electricity by getting her to touch an electric fence. I explained in advance what would happen, and ensured she would touch it with the back of her hand - not her fingertips which might contract and grip it.Her seeing someone die skiing and being in charge of aircraft that have "departed from controlled flight". Has also been salutary.

author: radiolistener
author_rank: Super Contributor
timestamp: June 15, 2025, 10:09:01 pm
content: Quote from: shapirus on June 15, 2025, 08:59:21 pmIt seems like an electric shock might actually be one of the most effective teachers.I still remember my first lesson - I was six years old and tried to "charge" a battery by plugging it into the mains using a cord from an old electric iron. The worst part wasn't even the shock itself - it was the fact that I was holding the battery in my hand when it happened. As soon as the current hit, my muscles seized up from the voltage, and I couldn’t let go or throw it away. It took a serious effort to overcome that paralysis and pull the plug while my muscles were locked up and I could barely move. I vividly remember the sense - my entire body tensed up and was trembling at a 50 Hz rhythm, completely beyond my control. In that moment, I was unable to react or move effectively. I don't even recall exactly how I managed to unplug the cord - I just remember desperately trying to let go of the battery, while my muscles stubbornly kept a tight grip on it. It could have ended much worse. What struck me most at the time was that the electric shock occurred even through the cardboard casing of the battery.That gave me quite a scare, but clearly not enough to keep me away for good. Years later, despite fully understanding the risks of working with mains voltage, I still managed to get shocked while taking measurements - due to a careless mistake. And, to be honest, that wasn’t the only time.These days, I triple-check everything before probing anything connected to the mains. Experience may be a harsh teacher, but it sure leaves a lasting impression.

author: TimFox
author_rank: Super Contributor
timestamp: June 15, 2025, 10:23:10 pm
content: Yes: a big problem with electrical contact to the hands is that the muscles immediately contract to grip the electrode.

author: shapirus
author_rank: Super Contributor
timestamp: June 16, 2025, 06:25:17 am
content: Quote from: TimFox on June 15, 2025, 10:23:10 pmThat's why one of the safety measures (in addition to isolation etc.) when working with mains voltage should be to always have a second person present who will be able to cut power when that happens.