How dangerous is 4000V? - Page 1
Forum section: electronics / beginners

author: Aldo22
author_rank: Super Contributor
timestamp: July 18, 2025, 10:33:33 am
content: Yes, that's a clickbait title ;-)I bought a "TKDMR 0-4000V Voltage Withstand Capability Test and Voltage Discharge 2-in-1 Tester".I realize that with a maximum of 5mA (realistically probably 2mA) the danger to life is not quite so huge.I am interested to know how to use it sensibly.On the AE product page you can see a picture of how it is operated with gloves and a pen.On all the Youtube videos I've seen, I don't recognize any difference in the safety precautions compared to a 5V device.for example:https://youtu.be/_yXQITTtXZQ?t=497What is reasonable?

author: Zenith
author_rank: Frequent Contributor
timestamp: July 18, 2025, 10:59:49 am
content: Well there's 4000V and 4000V and they are not all the same. For instance a 4000V shock from touching a car on a hot day, which would occasion the use of profane language, is very different from a 4000V shock from a few hundred car batteries connected together, when you wouldn't get the chance to swear.I'd have thought for this to be on the market, you ought to be able to use it without resorting to hands off techniques. A nip from the business end might be unpleasant. The gloves and pen in the picture don't look like approved high voltage PPE.One of the biggest dangers with shocks from spark plugs, scope tubes etc, is the involuntary reflex, causing hands to contact moving or hot parts, or you to be thrown off balance and landing on something dangerous.

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 18, 2025, 11:39:56 am
content: Static eliminator often is around 6000V and less than 5mA current. People do touch them by accident and got shock. Never heard it kills anyone but I have seen one guy got shock so he fell into a gaylord He didn't get hurt either.

author: Grandchuck
author_rank: Super Contributor
timestamp: July 18, 2025, 11:42:01 am
content: When testing a capacitor, could additional danger be possible?

author: Gyro
author_rank: Super Contributor
timestamp: July 18, 2025, 11:46:24 am
content: Yes, when high voltage testing with a low current tester, it's the capacitor (depending on size, obviously) that is the dangerous element. A big capacitor could cause nasty burns or, I suppose, fatal under the wrong conditions.P.S. I got so fed up with getting shocks from SMPS transformer primary - secondary pins (parasitic capacitance) after testing with my 10kV tester that I added a discharge probe.

author: m k
author_rank: Super Contributor
timestamp: July 18, 2025, 12:41:00 pm
content: Back in the day measuring a live analog part of CRT circuit made you cautious quite fast.The closer to high voltage your measuring spot is the closer a need of turning it off first also is.The reason is exactly that secondary reaction.Longer tip will help, but it will rise other issues.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: July 18, 2025, 01:25:08 pm
content: Quote from: BeBuLamar on July 18, 2025, 11:39:56 amForgive me BeBuLamar, but can you tell me what a 'gaylord' is ? Uncle Google is being deceptive.Thanks BeBu

author: m k
author_rank: Super Contributor
timestamp: July 18, 2025, 01:35:44 pm
content: My guess is a certain type of a box.

author: mikerj
author_rank: Super Contributor
timestamp: July 18, 2025, 01:48:51 pm
content: Quote from: BILLPOD on July 18, 2025, 01:25:08 pmIt's a word I haven't heard since my school playground days, and it had nothing to do with high voltage!

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 18, 2025, 05:07:41 pm
content: Quote from: BILLPOD on July 18, 2025, 01:25:08 pmThe gaylord is a cardboard box quite large. See the linkhttps://www.oxbox.com/products/4048-stock-triple-wall-pallet-box/?gad_source=1&gad_campaignid=20953599287&gbraid=0AAAAAD4XRYvDdRs27rNB-SG82n8wTAUJy&gclid=CjwKCAjw4efDBhATEiwAaDBpbry2J1dj0qKh_0NJczEGyVo0vz2BDcYwKSJPueW6bVxivl4SvUx4ahoCFHYQAvD_BwEAt the time the gaylord was used to store the raw polystyrene material used to make the styrofoam cups. It's an empty one they put next the the styrofoam cup production line. The static eliminator was used to prevent the static would make the cups stick together and even to the conveyor they used to convey the cups away. The static eliminator shocked him and his reaction caused him to fall into the gaylord. It's not funny but it was funny.

author: metrologist
author_rank: Super Contributor
timestamp: July 18, 2025, 05:24:43 pm
content: I recall in HS physics, the instructor brought in a 90kV alkaline battery and a 2-liter bottle size capacitor.De demonstrated the touching of the two battery terminals was only mildly uncomfortable.He then proceeded to connect the 90kV battery to the capacitor and after some minutes, there began to glow a neon bulb he had as an indicator of charge.Then he proceeded to lecture of the dangers while finishing by shorting the capacitor with a bar of steel. The loud pop and subsequent rain of molten metal bits was impressive.

author: edavid
author_rank: Super Contributor
timestamp: July 18, 2025, 05:27:47 pm
content: Fun fact - they were named after the Gaylord Container Corporation:https://en.wikipedia.org/wiki/Gaylord_Container_CorporationI wonder if the nickname will die out now that the company is long gone.Getting back to OP's question, I don't see what the gloves and pen are supposed to do. Just keep one hand in your pocket or at least well away from the tester (as usual when dealing with unsafe voltage).

author: edavid
author_rank: Super Contributor
timestamp: July 18, 2025, 05:29:18 pm
content: Quote from: metrologist on July 18, 2025, 05:24:43 pmI think you made a typo there. A 60000 cell battery would be something to see. Even 900V seems implausible. How would a high school have the budget for such a thing?

author: David Hess
author_rank: Super Contributor
timestamp: July 18, 2025, 05:43:13 pm
content: I have been literally knocked across a room from a capacitor bank charged to 1000 volts, but uncomfortably survived much higher voltages that had little charge.

author: TimFox
author_rank: Super Contributor
timestamp: July 18, 2025, 05:55:02 pm
content: Quote from: edavid on July 18, 2025, 05:29:18 pm90 V “B batteries” (usually Zn-C) used to be a thing, and the long-gone 300 V batteries were handy for physics labs (e.g. bias for ionization chambers) without power-supply ripple.

author: calzap
author_rank: Frequent Contributor
timestamp: July 18, 2025, 05:57:51 pm
content: Quote from: Grandchuck on July 18, 2025, 11:42:01 amOK. I'll bite.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 18, 2025, 06:22:26 pm
content: Quote from: calzap on July 18, 2025, 05:57:51 pmI think your username says it all here.[linked video was not available to me ("Playback on other websites has been disabled by the video owner")]

author: metrologist
author_rank: Super Contributor
timestamp: July 18, 2025, 06:33:12 pm
content: Quote from: edavid on July 18, 2025, 05:29:18 pmThe closest thing I can find now is a vintage Eveready camera flash battery. As I recall, it was a sliced bread sandwich size battery in a white box with red graphics and lettering, like the vintage Eveready branding - not that exciting. I recall he could make the capacitor arc an inch or so.He was an active working physicist so that gear was his personal equipment. He wasn't having us come up to play with the stuff so I just took his word for it.

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: July 18, 2025, 10:07:21 pm
content: Quote from: Aldo22 on July 18, 2025, 10:33:33 amI have been thinking of purchasing a similar device for a while.Have you found it useful for hobby-grade use?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 18, 2025, 10:13:05 pm
content: I also bought one of these testers a while back, and I like it very much.If you touch the wires during test it just tickles a bit because the current is so low.You can easily try this but touching the output and then slowly turn up the output voltage while holding the test knob. At "low current setting" (1/4 open) the voltage just stops at 50V because of leakage through my thumb.Quote from: Grandchuck on July 18, 2025, 11:42:01 amYes, charging a (biggish) capacitor makes it a whole different story. The capacitor collects energy and can release it in a high current burst. This can create a lot of noise, burn holes in your skin or worse. I once destroyed my DMM probes by accidentally shorting out the capacitors from a big audio amplifier. That made a blinding flash, a lot of noise and the tip of the DMM probe was a bit shorter and blackened. And that was just from an audio amplifier (around 80V 80mF or so)Just now I did a test on an electrolytic capacitor, rating 220uF, 385VAt 1/4 of the current setting, it charged the capacitor to 73V. (and I got bored) After discharge (with a 10k power resistor) I did a second test at the maximum current and it charged the capacitor to 300V in 15s (That was the max voltage I set on the tester). And I'm not going to test a 220uF charged to 300V with my fingers.Quote from: UnijunctionTransistor on July 18, 2025, 10:07:21 pmYes, definitely confirmative!With this tester I have confirmed that 2SC5200 BJT's I bought were fake (It went into avalanche at 150V) and you can use this thing as a poor man's Hi-Pot tester, or charge capacitors, let them sit for a while to test their leakage, and quite a lot of other tests.There are quite a lot of variants of this thing, with small differences. I bought one with banana bushings so I can use regular test leads. Some have the green pluggable screw connectors. The display may have a different color and the printed texts vary. There may be other differences too. The panel meter on my version even has auto ranging. at low voltages it has a 100mV resolution, that's nice for testing zener diodes. (The photograph posted here also has a dot in the "000.0" display.) I just tested a 15V zener diode, the panel says 14.2V, while my Brymen says 14.078V.Mine version also has a Li-ion bag in it, and a hard power off switch (the little black stub at the bottom) and it has an USB-C port for charging the battery. I have it now for one or two years. I may have charged the battery once when it arrived (I forgot) but that would have been the only time I charged it.Mine version also has a black front panel with the name "Longxian Xingua" on it and "Type: XH37-504" on the back.

author: coppercone2
author_rank: Super Contributor
timestamp: July 18, 2025, 11:00:29 pm
content: When you start getting absurd with the layer count its usually called a 'pile' not a battery. I believe you can get quite a voltage by just stacking thin plates up.https://en.wikipedia.org/wiki/Zamboni_pilePortable ones for tubes exist in the 20kV range. Like tactical. So 80kV is probobly possible with some benchtop equipment.

author: coppercone2
author_rank: Super Contributor
timestamp: July 18, 2025, 11:11:43 pm
content: So to get 80kV, you would need 100000 layers.How thin can you make a piece of paper? If your cells are 0.02mm, then ~2 meters = 80kVThey really made this more then like 20kV?I mean I guess you can. Not sure when it starts to fail.https://lampes-et-tubes.info/ic/ic009.php?l=fI had this thought that it would be funny if someone made some fancy magazine that happened to use materials as 'ink' that can work as a battery, and then say someone stacked up a pile of magazines to the ceiling and a pipe leaked, with every page forming a battery because they had metal foils on every page.

author: golden_labels
author_rank: Super Contributor
timestamp: July 19, 2025, 12:23:08 am
content: Aldo22, I hope you do realize that you may expect replies that are hardly above guesses. Without knowing how exactly the device works, only very generic predictions may be made.The post you linkedincludes a manual indicating it’s DC and that’s all we know. This is very little, given how complicated electric safety landscape is.Don’t put yourself whereDUTgoes and you should be fine. That means: don’t grab metal bare parts of the leads with opposite hands.With DC the risks are very different than with AC. Most notably it can’t cause persisting muscle contraction. It may give a solid and very unpleasant kick, burns, or pain. As anybody touching power supply input capacitors or a charged CRT learned the hard way. But it is scarcely directly lethal. But if that charging pulse we see on the trace goes to 100 V under load, the story gets very different.I mentioned that electric safety landscape is compicated. Here is a nice example, from Styropyro. Don’t try this at home: he’s a professional(1)and a crazy person. Mostly the latter. But he explores some interesting areas of that landscape. Enough to give a feel of how unexpected it may be:To extend on that, let me add some trivia. 100 mA is considered the threshold for heart fibrillation. What is often skipped, is that it’s the arm-to-arm value. For other paths the thresholds are different. For leg-to-leg it is… unknown. It can’t be experimentally tested, because the current would need to be so high the subject would have their legs cooked long before any useful effect is observed. And then there is the entire probabilistic part of the subject, which later extends into the difference between real values and those indicated as safe limits. This is why BigClive could quite safely conduct his famous experiment in which he grabbed a live wire to check the effects.(1)Means: he makes money from posting such videos on YouTube.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 19, 2025, 02:40:17 am
content: Just did another test. I put a 100k resistor over the terminals, turned up the voltage (left knob) and then adjusted the current.With the current potentiometer I can adjust between 6V and 330V, so that is 3.3mA max (The scale around the poteniometer goes from 50uA to 5mA, so it's a bit off, but good enough).I did open the thing just after I bought it. There is (of course) a small SMPS inside, and the feedback ladder is with a whole bunch of SMT resistors in series.Anybody interested in a few pictures?

author: Aldo22
author_rank: Super Contributor
timestamp: July 19, 2025, 08:17:34 am
content: Thanks for all the answers! Very interesting!Quote from: golden_labels on July 19, 2025, 12:23:08 amI had a look at this with my ZT-225.Since the pulse is about 100Hz, the DMM should give a correct RMS value of the VAC part.I see 11VRMS at 1000VDC (no load), which should not be a problem.Under load, the voltage breaks down anyway. I tested with a 1kΩ resistor.The oscilloscope might be more informative (peaks), but I don't have 100x probes and I'm not quite sure what it can withstand.

author: Psi
author_rank: Super Contributor
timestamp: July 19, 2025, 08:26:26 am
content: Current limited high-voltage supplies can be safe when the current is low enough.But as soon as you add a capacitor into the mix the safety goes out the window.A capacitor that can store a deadly amount of energy is not very large phystically.

author: tooki
author_rank: Super Contributor
timestamp: July 19, 2025, 10:43:31 am
content: Quote from: Analog Kid on July 18, 2025, 06:22:26 pmIn the gray box, there’s a “Watch on YouTube” link that opens the video in a separate tab where you can watch it.

author: Aldo22
author_rank: Super Contributor
timestamp: July 19, 2025, 11:21:35 am
content: Apparently you can damage similar devices by deliberately creating an arc:https://www.eevblog.com/forum/reviews/completely-non-sketchy-mini-high-voltage-transistor-tester-(emeco)/msg5932088/#msg5932088

author: BILLPOD
author_rank: Frequent Contributor
timestamp: July 19, 2025, 01:12:10 pm
content: Good Morning BeBu, A cardboard box would have been my last guess. Thank you for increasing my vocabulary.

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: July 19, 2025, 03:23:44 pm
content: Quote from: Doctorandus_P on July 19, 2025, 02:40:17 amI am always interested in tear-downs.

author: Aldo22
author_rank: Super Contributor
timestamp: July 19, 2025, 03:27:21 pm
content: Quote from: UnijunctionTransistor on July 19, 2025, 03:23:44 pmhttps://youtu.be/_yXQITTtXZQ?t=749

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 19, 2025, 05:25:58 pm
content: Mine is similar, but not quite the same. See pictures.For the panel meter, Notice the 15 3M resistors in series. The 3kV8 goes directly to this PCB. On the PCB there is a second voltage divider, also with 3M resistor.@13:36 Mine has 3 separate LED's instead of an RGB led.@14:02 Also an 3SD1804 on mine version.@14:22 I don't have the gap in the PCB, and no HV fet, My version also only has two banana bushes@14:40 two rows of 3 diodes in series each time, then a capacitor, and again 3 diodes in series, but it does not look like a crotch craft multiplier.@15:20 Back of the PCB is empty too.@15:52 LTC4056 Li-Ion chargerhttps://www.analog.com/en/products/ltc4056-4.2.html@16:11 The 14 pin IC is an 324 (LM324 clone)@16:11 U3 on the left a small SMPS IC, Code B628 It generates 6V66.Near the Banana bushings, I have 5 sections (in series) of a 10M resistor with two 10nF capacitors parallel.When the test button is pushed, the circuit is audible, it hums at a very low frequency (Pulses of 10Hz or so) to around 5kHz at the maximum voltage setting.

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: July 20, 2025, 02:36:31 pm
content: When a simple, low cost, well designed (*) test equipment is developed in a crowded lab in Shenzen, and becomes successful, you can bet that several “unlicensed second sources” will suddenly appear. The reverse-engineers working in another crowded Shenzen lab will change the circuit slightly or employ different components which better suits their availability.But it remains essentially the same basic concept.(*) I am not saying they are perfect or provide high performance. Only that for the price point, they offer good value.

author: David Hess
author_rank: Super Contributor
timestamp: July 23, 2025, 08:45:30 pm
content: Quote from: UnijunctionTransistor on July 20, 2025, 02:36:31 pmDoesn't that apply no matter where it was developed, and especially if production was outsourced to China?