How I can trust the earth on the sockets? - Page 1
Forum section: electronics / beginners

author: 3rj4
author_rank: Regular Contributor
timestamp: July 13, 2020, 08:35:40 am
content: I live in a small, slightly older apartment building and, I want to build an electronics workstation. I have already used a voltage tester to check that the power outlet is working correctly. However, I am wondering how I can trust the earth on the sockets. My understanding is that this can't be checked using a voltage tester or multimeter, right? So how can I be sure that it is safe for me to use the power outlet for my ESD equipment? My understanding is that, if there is something wrong with the earth on the sockets, then this creates a very dangerous situation for me, since I'd be attached to it by the wrist strap, right?Would my only choice be to call an electrician to check?I'm new to all of this and concerned about safety, so I would really appreciate advice.

author: Ian.M
author_rank: Super Contributor
timestamp: July 13, 2020, 10:10:28 am
content: Do you touch your metal bodied kitchen appliances? If so, you are already trusting your apartment's ground wiring.However for peace of mind, the first step is to go round your whole apartment with a basic three indicator lights socket tester*looking for any sockets with major problems. Then, if you are 100% confident you know the difference between a live wire and a ground wire, you could turn off your mains isolating switch at the breaker panel, and while the circuits are de-energised, measure resistance from the grounds at the sockets you are concerned about back to an externally accessible ground at the breaker panel. If you don't mind bending the rules, while the power's off you can take a peek inside the socket back-boxes to check that the ground is on a separate wire, not strapped to Neutral by some total drongo. If you do find a problem, put the covers back, call an electrician to check the circuit(s) and, as you are in Australia, don't admit you've looked at it yourself!Also all reputable ESD protection gear has built-in safety resistors, typically 1Meg to limit the current to a non-hazardous level if you touch a live circuit while wearing it. If you buy the cheapest crap you can find on EvilBAY, YMMV!* e.g.https://www.bunnings.com.au/deta-power-outlet-tester-plug_p4420488or any similar.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: July 13, 2020, 10:17:43 am
content: What has led you to believe you cannot trust the earth on the sockets?

author: RK_aus_S
author_rank: Contributor
timestamp: July 13, 2020, 11:39:46 am
content: I don't live in Australia, so I'm not sure if my comment is useful here.I live in Switzerland and it is a requirement here that an approved electrician checks the sockets every 20 years. This test was carried out with a Megger (mega-ohm meter) / Insulation Tester under higher voltage (1000V). The entire household was previously disconnected from the grid. In addition, I was advised to unplug all sensitive (electrostatic) devices from the socket. The resistance between phase, neutral and earth was measured. Of course, it was also checked whether all sockets have an intact earth condition (reference in the basement).Regards

author: 3rj4
author_rank: Regular Contributor
timestamp: July 13, 2020, 06:19:37 pm
content: Quote from: Ian.M on July 13, 2020, 10:10:28 amQuote from: Ed.Kloonk on July 13, 2020, 10:17:43 amCan I please pm you both?

author: ejeffrey
author_rank: Super Contributor
timestamp: July 13, 2020, 06:34:49 pm
content: Note that ESD wrist straps *should* have a large value (typically 1 meg) and ideally high voltage rated resistor inside them. You can test this with your hand held DMM. So assuming the resistor doesn't arc over or otherwise fail it shouldn't be a safety hazard even if connected to the live wire.However, as mentioned by Ian.M, your metal chassis electronics will almost always be connected to the grounded conductor without any sort of limiting resistor. If it somehow failed hot (rather than just open circuit), all that equipment would have a dangerously live chassis, and if connected to anything with a properly grounded chassis would immediately short out.

author: Bud
author_rank: Super Contributor
timestamp: July 13, 2020, 06:34:55 pm
content: Quote from: RK_aus_S on July 13, 2020, 11:39:46 amWho is responsible for tracking the 20 year period? The homeowner? The utility company? Else?

author: Ian.M
author_rank: Super Contributor
timestamp: July 13, 2020, 06:44:35 pm
content: Quote from: 3rj4 on July 13, 2020, 06:19:37 pmNope. Anything I have to say for free goes on the forum, where it gets peer reviewed and is available to all future readers. I *REALLY* don't want to know any 'secret' that might make PMing me desirable to you, nor am I willing (or even qualified), to offer private paid electrical consultancy to an Australian resident.Ed can speak for himself . . .

author: 3rj4
author_rank: Regular Contributor
timestamp: July 13, 2020, 06:49:48 pm
content: Quote from: Ian.M on July 13, 2020, 06:44:35 pmIt's nothing like that, but I understand. Thishttps://electronics.stackexchange.com/a/510070/207355is where I got the information regarding trusting the earth on the socket. Do you think the answerer's fears are overblown? Reading their answer is what made me concerned.

author: Ian.M
author_rank: Super Contributor
timestamp: July 13, 2020, 07:05:29 pm
content: Quote from: ejeffrey on July 13, 2020, 06:34:49 pmYes, and I specifically gave in the kitchen as the example location, as IMHO the maximum shock hazard from a live case*appliance is there due to the higher probability that you will also be on a wet floor or in contact with actually grounded metalwork (e.g. the kitchen sink).If you've got a failed 'hot' protective ground conductor at your bench, your scope probe is almost certainly far more dangerous than your ESD wrist-strap.* Lets avoid the term 'live chassis' for metal case failed 'hot' as back in the day, TVs and radios existed with intentionally live chassis, with user safety (such as it was for that era) provided by the insulating case and controls and isolated aerial and headphone jacks.

author: Renate
author_rank: Super Contributor
timestamp: July 13, 2020, 07:10:53 pm
content: Quote from: Ed.Kloonk on July 13, 2020, 10:17:43 amLet's put it the other way, whywouldyou trust the earth on your sockets?If you have the slightest qualms, test it yourself.

author: 3rj4
author_rank: Regular Contributor
timestamp: July 13, 2020, 07:18:43 pm
content: Quote from: Renate on July 13, 2020, 07:10:53 pmI had no qualms until I read thishttps://electronics.stackexchange.com/a/510070/207355answer. How would one test it themselves? As I said, I already used the power outlet tester (as shown herehttps://www.bunnings.com.au/deta-power-outlet-tester-plug_p4420488by Ian), which indicated that everything was fine.

author: themadhippy
author_rank: Super Contributor
timestamp: July 13, 2020, 07:20:16 pm
content: If you want a reliable electrical earth dont rely on water pipes,radiators or any other random lump of metal.you can get a plug in socket tester that will give an indication as to whether theirs an earth or not,however to do it properly you need a proper tester funnily enough called an earth loop impedance tester .Quotethats for testing the insulation resistance not earth impedance

author: 3rj4
author_rank: Regular Contributor
timestamp: July 13, 2020, 07:31:44 pm
content: Quote from: themadhippy on July 13, 2020, 07:20:16 pmIs thishttps://www.aegis.net.au/products/electrical-testers/cz20054what you are referring to? Can I not check the same thing using a multimeter?

author: Zero999
author_rank: Super Contributor
timestamp: July 13, 2020, 07:35:19 pm
content: An ESD earth/ground connection doesn't have to have as lower resistance, as one which is required for safety. It's actually recommended to have a relatively high impedance, over 1M, for safety reasons. If you're wearing an ESD protective strap, which for the purposes of this exercise is the only electrical path between you and earth, the 1M resistor will limit the current to a harmless 230µA, if you touch a 240V conductor. It's also a good idea to limit the current of electrostatic discharges, which will cause less damage when dissipated slowly vs very quickly.You don't actually need a good path to the mains earth for ESD protection. In one of the benches where I used to work, a large strip of copper foil glued to the wall served as an earth connection, with around 10M of resistance to mains earth. I presume this was done because the bench bizarrely didn't have any mains sockets, as it was used for assembly, i.e. plugging ICs in boards and connectors, rather than soldering.Of course a decent earth connection is required for safety. A suitable ohmmeter needs to be used to test whether it's safe or not. From memory, it uses a fairly high current and the impedance needs to be low enough to ensure the main circuit breaker will disconnect the circuit very quickly and the voltage on the earth connection remains below 50V, if there's a short to earth. If you're asking how to do this, then you should seek a qualified electrician, because if you were capable of doing it safely, you wouldn't need to ask.

author: 3rj4
author_rank: Regular Contributor
timestamp: July 13, 2020, 07:49:23 pm
content: Quote from: Zero999 on July 13, 2020, 07:35:19 pmSo are you implying thishttps://electronics.stackexchange.com/a/510070/207355answer is being alarmist, and that I should be fine with just my wrist strap and its 1M resistor?I'm new to electronics, so some of the stuff you're all saying is going over my head. I just want to know whether thishttps://electronics.stackexchange.com/a/510070/207355answer is cause for me to worry. I'm just looking to set up my first electronics workstation.

author: Ian.M
author_rank: Super Contributor
timestamp: July 13, 2020, 08:32:17 pm
content: Quote from: 3rj4 on July 13, 2020, 06:49:48 pmIts all about the odds, the consequences of a fault and the probability of it endangering you. As most people are bad at assessing risk vs odds, and even more don't have the knowledge to reasonably assess electrical risks there is a lot of fear and uncertainty going around.Its worse than you think - If the odds stack up against you, a bad ground can even make agarden tap a lethal shock hazard. (Yes, that's in Australia and fairly recent)Also, and this is particularly relevent to apartment buildings, if there's a break in the protective ground conductor to your apartment, outside it or before your breaker panel, each device or appliance with a three wire cord can (and probably will) contribute a significant leakage current from Line to your faulty ground conductor and thus to the case of any three wire metal cased appliances. Its only somewhere between a fraction of a mA and a couple of mA per device, but it adds up to dangerous levels rather quickly, if you and neighbours above you on the same grounding conductor have significant numbers of plug-in appliances and devices and fitted appliances. That's a potentially lethal single fault broken ground, not the double fault of a broken ground + a short Line to ground that would be required for a previously safe individual appliance or branch circuit to become an instant shock hazardIf the building is competently and legally maintained, and there's a reasonably recent electrical inspection certificate, the odds are very good that a wall socket that passes the DIY test possible for anyone with a simple three indicator tester is *NOT* going to electrocute you. OTOH if the building management is shady and one of the occupants since the last electrical inspection was an intellectually challenged mad DIYer, or there's any other indications of pre-existing electrical problems, a full electrical inspection by a fully qualified and licenced electrician is cheaper than getting yourself fitted for a pine box.However any reputable brand of personal or bench ESD protection is *VANISHINGLY* unlikely to be implicated in putting you in that pine box, as each accessory will have its own built-in safety resistor or integral distributed resistance, so odds are there will be two or three 1 Meg resistors in series limiting your touch current (via the ESD protection) to at most a couple of mA, safe for all except a very few patients on some types of pacemaker.

author: 3rj4
author_rank: Regular Contributor
timestamp: July 13, 2020, 08:51:23 pm
content: Quote from: Ian.M on July 13, 2020, 08:32:17 pmThanks for the reply.Yes, I remember hearing about the terrible garden tap incident with the young girl a few years ago. Fortunately, nothing like that has happened here.1. The apartment building is only 3 stories, with myself on the third floor.2. The apartment building is managed by a professional management company that regularly communicates with us regarding any maintenance, etc.3. Both the ESD bench mount and the ESD wrist strap have a 1M resistor built into them.4. The socket tester indicated that the outlets were working correctly.5. I have never had any electrical problems, such as getting shocked or anything of the sort, even during thunderstorms (which do happen occasionally, especially now during the winter).6. My apartment electrical system is such that, if I turn on too many appliances at the same time (like the air conditioner, laundry machine, microwave, kettle, and other small appliances such as computers, etc.), which I sometimes accidentally do, the power to my specific apartment is automatically cut off (excluding the lights), and I then have to step outside and flick the switch back on. I am assuming that this is an indication of a correctly working and well-devised electrical system for my apartment?Furthermore, once I'm confident in my knowledge of multimeter use, I will check the power outlets using the multimeter as well (as shown here).My wrist strap will be connected to the bench mount fixture, and the bench mount fixture will be connected to the mains via thishttps://www.oritech.com.au/clipsal-esd-earth-plug.html(also shown herehttps://www.clipsal.com/products/detail?CatNo=463SAS&tab-document-1=0) plug.Given all of this, it seems to me that it is likely that everything is working correctly and it would be safe for me to go ahead and continue with my electronics journey. Does this sound fine to you?

author: themadhippy
author_rank: Super Contributor
timestamp: July 13, 2020, 09:05:14 pm
content: QuoteI recon damien should put his screw driver down and pick up some books

author: Bud
author_rank: Super Contributor
timestamp: July 13, 2020, 09:24:09 pm
content: That youtuber should go to jail for having his meter in such horrible filthy condition. When i see things like this it will tell me a lot about the owner.

author: 3rj4
author_rank: Regular Contributor
timestamp: July 13, 2020, 09:36:30 pm
content: Quote from: Bud on July 13, 2020, 09:24:09 pmOut of curiosity, how does one go about cleaning such a device?

author: AlfBaz
author_rank: Super Contributor
timestamp: July 13, 2020, 10:12:54 pm
content: Quote from: Bud on July 13, 2020, 09:24:09 pmYes it tells me that the guy is a proper electrician that uses his meter out in the field. If it were clean I wouldn't trust a thing he saidHaving said that, haven't watched the video so who knows.Top left slot is active, top right is neutral and the bottom vertical slot is earthWith a meter active to neutral and then active to earth should give you your nominal 240VThat will indicate that you MEN link is good and the earth wire is connected all the way back to your Distribution Board.Any active fault to an appliance's metal case that's connected to the earth pin should trip whatever protection is in place, hopefully an RCD but depending on the age of the building, it's most like just a circuit breaker or possibly a fuse.In the case of the latter 2 your relying on a low impedance fault that will draw enough current to trip the CB. Clearly not ideal and often the reason a lot of people complain of getting "tingelleing" sensations when touching some appliances, usually electric stoves.Unfortunately many kitchen sinks are not earthed and the water pipes are now days plumbed in PVC pipes so checking earth continuity to one of these often proves fruitless with a resistance in the kilo ohm rangeIf you have access to your appartment's DB board then by all means, open it up and see if RCDs are used. If not and you would like the extra protection you can swap out your outlet with one that has a builtin RCD. If your not comfortable doing that then buy one of those orange boxes you see on construction sites and use that

author: 3rj4
author_rank: Regular Contributor
timestamp: July 13, 2020, 10:24:33 pm
content: Quote from: AlfBaz on July 13, 2020, 10:12:54 pmIs this what you're looking for? I can see that there are a number of "RCD" written.

author: Ian.M
author_rank: Super Contributor
timestamp: July 13, 2020, 10:51:13 pm
content: Quote from: 3rj4 on July 13, 2020, 09:36:30 pmCarefully! If the outer rubber boot is removable, which is usually the case, you can remove it and hand-wash it with hot soapy water, scrubbing any persistent stains with a pink(non-scratch) panscourer. The meter itself can be wiped down with a little foam cleaner on a piece of kitchen towel, being careful not to have the kitchen towel wet enough for foam or moisture to squeeze out into any case joint or opening. The leads can be cleaned by pulling them through a generous amount of foam cleaner on a kitchen towel taking care *NOT* to stretch them. If particularly manky you may need to pull them through foam cleaner on that pink panscourer first. As you are cleaning the leads, inspect them for any damage, and if you find even slightly nicked insulation or any cracks at all, they *MUST* be replaced before using that meter on any circuit above 50V. Allow everything to totally dry, preferably overnight, before putting it back into service.However, I'm with AlfBaz - there isn't time in the day for a field engineer/technician to keep their tools and test equipment surgically clean if the job specs don't call for that. If they are being used in the field they will get mucky, and you try to wipe the worst off before putting them away. You'll be lucky if you get an hour a month at the end of the day to clean and reorganise your toolbag and its contents, and replenish your small stock of 'just in case' consumables. Overly clean tools and equipment indicates either someone who works in an industry that requires 'cleanroom' standards, or an amateur with too much time on their hands and nothing better to do with it!Also, remember that video shows an American probing 120V mains. 240V mains is considerably more dangerous, and the minimum safety rules even fifty years ago were: Keep one hand with its thumb in your waist-band or pocket, so you only use *ONE* hand for probing so you can't get a shock across your chest, and make sure you are aware of the position of all nearby grounded objects and aren't at risk of contact with them, so you cant get a shock through your body. Treat all concrete or unmade/unfinished floors as a grounded object so wear rubber soled shoes (not black rubber - it may use conductive carbon black filler) or if you cant work standing, put down a thick plastic or rubber insulating mat.Most of the time, probing the mains like that wont tell you much that the three indicator light socket tester didn't, and if you want to check the voltages, its much better to use a plug-in mains lead terminated at a choc-bloc screw terminal block long enough to get your test leads into side by side, so you can make the meter connections before plugging it in (and unplug it before changing them), and take the voltage measurements at your bench without having to touch an energised circuit. Any concerns that the plug-in mains lead may introduce uncertainty can be eliminated by checking each wire and that each goes to the correct pin, using your meter on continuity, *BEFORE* first plugging it in.TLDR: Don't mess with measuring Mains voltages unless you absolutely have to and know how to do so as safely as possible.

author: ejeffrey
author_rank: Super Contributor
timestamp: July 13, 2020, 11:02:25 pm
content: Quote from: 3rj4 on July 13, 2020, 07:49:23 pmYes. And misguided. Even if your ground is miswired running a separate ground stake or connecting to copper pipes will -- if anything -- make the situation worse. Lets say you have a safety ground terminal that is either live or is floating and subject to several milliamps of ground leakage from attached devices. That ground will be connected to exposed metal in many places such as your computer case, oscilloscope BNC jacks, and power supply ground terminals. If that is the only exposed metal you still won't get shocked because you need a potential difference. However, if you go run a wire outside to some extra ground stake and then strap that to your wrist, now you have a potential difference between your wiring safety ground and the "earth ground" and you can get shocked. It is probably no surprise that the accident with the garden tap happened outside where the victim was presumably standing on the earth possibly with bare and wet feet. If you bring in an outside ground from any source onto your workbench you want to connect it to your local safety ground connection so that any sort of fault like is discussed will trip an RCD or circuit breaker, or in the case of leakage currents too small to trip the RCD, be dissipated to minimize the potential difference between any exposed conductors. Again, not super relevant to wrist straps by themselves as they should have integral current limiting resistors.

author: AlfBaz
author_rank: Super Contributor
timestamp: July 13, 2020, 11:05:41 pm
content: Yep. The labeling is a bit confusing so just to check, trip the one labeled light/main switch and see if you loose power on the outlets you want to use.

author: themadhippy
author_rank: Super Contributor
timestamp: July 13, 2020, 11:16:53 pm
content: One design flaw of many of the plug in testers is they show a good circuit with only 2 of the 3 indicators lit.unless you test the tester before and after every use you cant be 100% certain of the results.The better testers indicate all is good by illuminating all 3 indicators.Out of curiosity how many people test there volt meter before and after checking if a supply is safe to work on?

author: AlfBaz
author_rank: Super Contributor
timestamp: July 13, 2020, 11:36:09 pm
content: Quote from: themadhippy on July 13, 2020, 11:16:53 pmIt depends on the level of sphincter contraction. The greater the contraction the greater the level of care

author: wizard69
author_rank: Super Contributor
timestamp: July 14, 2020, 03:45:46 am
content: The posting you referenced leaves a lot to be desired, in part it is garbage.First the age of a building does impact its wiring, the ground and even if there is a ground installed. The Safety of a buildings electrical system can easily be inspected and if you are concerned frankly you should learn to do the minimal yourself.Second any ground can fail that is why testing and inspection make sense. For example the original author claimed that driving a ground rod into the ground outside of the hose is a good solution. It may be perfectly fine in one location and fail miserably in another. Soil conditions weather and age all impact how well a driven ground rod will work. Someplace on the net there was a rather elaborate write up on how to get those driven ground rods to work properly. Likewise water pipes might not be ideal either as there has been a fairly large scale change to synthetic materials there.In simple terms if grounding is important to you take the time to understand electrical systems and how to test those systems. After all home wiring is just another form of electronics. Highly regulated but not impossible to understand. Ultimately if you are involved in electronics you will not want to rely upon others when it comes to safety.Quote from: 3rj4 on July 13, 2020, 06:49:48 pm

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 14, 2020, 04:14:56 am
content: One possible way without spending a fortune. Make a fixture with safety in mind and probe points. A properly rated 1M or 100k ohm resistor. Connect one end to earth wire, one end to hot live, measure potential of both end with dmm. If showing mains voltage level, there is current flowing, earth should be good. Earth potential will be the nominal mains voltage in your country, subtract with shown dmm reading.. if less than few volt, earth side is safe. Break or earth wiring impedance is within acceptable level.. but that depend on how stable the installation is. Ymmv.

author: tkamiya
author_rank: Super Contributor
timestamp: July 14, 2020, 07:06:51 am
content: I am a licensed electrician. I've seen far too many cases of improperly wired ground that unless I did the work, I don't trust the outlet. Typical multi-meter cannot be used to test an outlet. Input impedance is way too high that "phantom voltage" (via magnetic and capacitive coupling) becomes a problem. Fluke has a version specially made for electricians that has lower impedance.A only reasonably sure way to test it is to go to a main distribution panel, and measure resistance between the grounding point and the ground prong. Of course this should be done with someone with experience, and preferably a proper certification.Aside from that, your local home improvement center should have an outlet tester with few lights. It will give you a reasonable assurance that it is connected properly (or not). But does it grantee it? I won't bet my life on it.

author: Zero999
author_rank: Super Contributor
timestamp: July 14, 2020, 03:27:35 pm
content: Quote from: Ian.M on July 13, 2020, 10:51:13 pmThat's fine if it's just your meter/test leads and you only use them at home, or in a situation where no one's going to use it on the mains, but I must stress you shouldn't take it to work like that. If someone else uses it on the mains and is injured, you will be liable. If I saw a some test leads in an unsafe condition where I work, I'd chop them up into pieces and put them in the scrap cable bin, even if they weren't mine! An unsafe meter would have its test leads, battery and fuse removed, the dial covered in duck/gaffer tape, a label attached stating it's unsafe and shouldn't be used and disposed of in the electronic recycling bin.

author: Renate
author_rank: Super Contributor
timestamp: July 14, 2020, 03:40:58 pm
content: Quote from: Zero999 on July 14, 2020, 03:27:35 pmThat's right from a safety point, but it's also right from a sanity point.If you have a VGA cable and one end is slightly wonky, chop the darn thing off so somebody else (or you) won't waste time with it.

author: Ian.M
author_rank: Super Contributor
timestamp: July 14, 2020, 06:50:43 pm
content: Unfortunately its all too easy to damage good quality modern test leads - silicone insulation may be heat resistant but it is a lot softer and rips more easily than the old-fashioned PVC, and the probes and plugs are almost invariably moulded on so aren't rewirable.I must emphasise that Zero999 is right: Damaged leads *SHOULD* be cut up immediately in a workplace, makerspace, or formal educational environment, but if one tells an impoverished maker hobbyist who's never going to go over the 30V from their bench PSU that, they'll probably laugh at you and ignore all your other advice. If you do decide to risk keeping damaged test leads, *PLEASE* tag them 'Damaged: 50V MAX' and keep them in a locked draw to stop numpties killing them self with them!I have bad memories of replacing plugs on VGA cables, in the days when monitors had wired in cables . . . . It was always preferable to find a 'near enough' replacement cable from a scrap monitor and fiddle with the pin order of the PCB end till it matched, and transplant the cord grip rather than having to solder the center row of a DE-15 plug, then get everything to fit in a metal DE back shell!

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 14, 2020, 07:10:14 pm
content: Quote from: Zero999 on July 14, 2020, 03:27:35 pmmake sure you have replacement cable ready for them...

author: Ian.M
author_rank: Super Contributor
timestamp: July 14, 2020, 07:24:54 pm
content: That idiot had better pray he never meets someone wearing the $3000Shure KSE1500electrostatic earbuds, as if he does, he's probably going to end up in A&E getting his nose reconstructed!

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 14, 2020, 07:35:42 pm
content: then this is more sane idiot... check 10:36, he wont cut anything equal or higher than the replacement cable...at least these bunch of jobless filled the net to teach us what to do when we cut other peoples cable..

author: Zero999
author_rank: Super Contributor
timestamp: July 14, 2020, 07:55:37 pm
content: Quote from: Mechatrommer on July 14, 2020, 07:10:14 pmFunny video, but no, not for meter cables which I've destroyed because they were dangerous. They can thank me for saving their life and I'm pretty sure the company would buy a replacement, if they complained to a manager.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: July 14, 2020, 10:16:54 pm
content: I was going to say cut something else off so they can't breed. Then I saw the flaw in my thinking in regards to who got the headphones cut the most.

author: John B
author_rank: Frequent Contributor
timestamp: July 15, 2020, 02:57:29 am
content: https://www.eevblog.com/forum/chat/girl-in-critical-condition-after-fault-earth-electric-shock/I did have a re-read of this thread to get my head around the fault conditions. So for however unlikely the fault is, it's not unreasonable to give the house a thorough inspection to spot even slightly fishy readings.Am I right in thinking the crux of the issue is a difference in potential between the "ground" wire circuit in the house and the actual physical earth? So all the metal appliances etc inside the house are connected with low resistance/impedance wire, but that circuit is bonded to the ground through an earth stake at minimum, and maybe some metal pipework, both of which have significant resistance to the ground?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 15, 2020, 03:36:25 am
content: I'm going to add my voice to saying the link is overly alarmist.I have observed each of the conditions described. Starting with the dorms at my university. But to my knowledge no one was killed or injured in spite of the hundreds or thousands of careless young people that cycled through them. The reason is that two conditions are required to cause a hazard. You need to have a moderate (few thousand ohm) connection to one of the wires. And you need a similarly low resistance connection to ground. The combination of two relatively unlikely events is very unlikely (though it does happen given the millions of people using electricity around the world.) Normal life activities, including soldering with a wrist ground, rarely cause both of these conditions.I agree with others that you can not prove that the wiring is totally correct or safe with simple multimeter or tester checks. But you can easily check for an unusually high level of hazard simply by observing the voltage between ground and the neutral and hot wire. Use old school safety tricks (one hand in pocket, one hand handles one probe at a time). Think about the risks of sticking a probe into a socket and don't do it if you don't understand them and believe you have them under control. If there is less than a volt between neutral and ground, and the nominal voltage is seen between neutral and hot and between ground and hot you are probably not at serious risk. This simple test can give false positives which can be reduced by connecting an appropriate 30 kohm resistor between the multimeter inputs. An additional check would be to measure voltage between the ground lead and earth potential, but as mentioned above earth potential is not easily found.Finally the suggestions in the attached link for correcting problems range from problematic to dangerously wrong. If you find something that causes serious concern it is time to engage someone who knows what they are doing.

author: pickle9000
author_rank: Super Contributor
timestamp: July 15, 2020, 04:23:34 am
content: Just curious does Australia have gfci power bars? In Canada they are pretty common on worksites.

author: Ian.M
author_rank: Super Contributor
timestamp: July 15, 2020, 05:01:57 am
content: Yes.From AlfBaz'sReply #21above.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: July 15, 2020, 05:08:48 am
content: Tools like this:https://www.barefoothealing.com.au/p/australian-socket-tester/STAU

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 15, 2020, 05:31:23 am
content: What is earth's potential is less important, (esp for high rise dwellers). Whats important is what is your feet's potential, thats what will decide kill or not kill. I've seen both floated neutral and gnd line and even got shocked from floated neutral. I've given enough thought about it and made the suggestion on my 1st reply.. and confirmed by some youtubes videos where people can touch KV safely if their feet as well.. though i'm not a certified electrician to be paid nor to give any credible advice. another cheap life saving device and light enough to bring anywhere anytime.. it uses your feet as decision maker.. so to get a valid reading, make sure your feet is wet enough (coupled with hot to gnd or hot to neutral test i mentioned, i believe this is how the 2 lights tester works). men are afraid of what they dont understand. Ymmv.edit.. the one hand trick is not a guarantee to safety, if you get gripped the line with one hand, you can be dead as well, but the occurence of the one testing the line with their palm is very rare, but its not impossible.

author: tszaboo
author_rank: Super Contributor
timestamp: July 15, 2020, 07:06:19 am
content: Step 1: Buy a socket testerStep 2: Test each sockets. Test the RDC, while not doing super important BIOS updates on your PC and ironing.Step 3: Remove 1 typical socket, to take a look inside, on how the cables look like. If you see any wierdness, like aluminium cables, rotten isolation, dead mice, etc... thenStep 4: call an electrician. They charge you less money than doctors.

author: SL4P
author_rank: Super Contributor
timestamp: July 19, 2020, 07:58:42 am
content: If your socket tester indicates all is well, the simplest second test for me would be to measure resistance from the socket earth pin to a known metal water pipe that can physically be traced to physical ground.Once you have a known good earth, you can test between others and that good one.This can be done with power off to avoid any nasty existing wiring errors.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 19, 2020, 08:07:29 am
content: Always GFCI aka RCD. No excuses in 2020.Having working, properly done Protective Earth connections remove some risks, and add some others.GFCI is a near-silver bullet that protects from both types of risks, without requiring earthing connection. The remaining risk types are very rare.

author: rstofer
author_rank: Super Contributor
timestamp: July 20, 2020, 05:13:45 pm
content: You have used the same tester that a typical Building Inspector would use for approving an installation.https://www.bunnings.com.au/deta-power-outlet-tester-plug_p4420488Around here it would be similar to this:https://www.amazon.com/Sperry-Instruments-GFI6302-Receptacle-Professional/dp/B000RUL2UUI don't see worrying about made up possibilities posited on the Interwebs. If you're worried about grounding, you're going to hate the BNC connectors on your scope. They will be connected directly to earth ground. So will that dangling alligator clip on the probe.

author: tooki
author_rank: Super Contributor
timestamp: July 20, 2020, 08:41:46 pm
content: Quote from: 3rj4 on July 13, 2020, 09:36:30 pmI can attest to the Fluke rubber holsters being safe to clean with dish liquid and warm water, as well as with isopropyl. Those two things will get off most grime. Neither one alone gets everything. I’ve been using those two to progressively wash every old Fluke 87 that comes across my desk at work. (It’s a training center, so it’s a pool of a couple of dozen meters.)