Is it safe to stick my multimeter probes in the wall socket ?

[ptricks]

The deaths associated with electric shock are mainly not from the electricity , it is from the reaction to the electricity. What is the first thing you do when you get shocked ? You jerk back your hand or whatever is contacting the power. If you are on a ladder changing a light bulb and get shocked, you jerk back, you fall off the ladder. Or you are working on something small, not really dangerous, you get shocked jerk back and hit your elbow on something hard, doesn't kill you but injures you more than the shock alone did.

[ejeffrey]

Certainly things like falling off a ladder can kill you even if the shock doesn't, but 115 or 230 VAC can certainly kill you by electrocution, and saying anything that implies otherwise is just reckless, stupid, and wrong.  There are many factors that affect electrocution danger like the condition of your skin, your heart health, and what path the current has to take to ground, but never just dismiss the risk.

[Psi]

He never implied 115 or 230 VAC cannot kill.

All he implied was that deaths/injuries from incidents involving an electrical shock are more often from other factors than the shock itself.
Which could be true since not all shocks approach the current needed to kill but can still give you a big fright and result in a fall or injury.

[vk6zgo]

No argument that these precautions are necessary when working on high-energy circuits. I'm aware that vaporization is a perfectly normal failure mode for metal tools when working on large battery banks. But assume you use suitable probes and DMM and plug the probes into a wall socket. What would it involve to get these kinds of failures? Depending on the plug your country uses, it's barely more dangerous than plugging in a real plug: make sure you keep your fingers away from the metal parts.

The great thing about Australian standard sockets (GPOs),apart from the fact that they are all switched,is that standard DMM probes can be plugged into them,& will be retained in the socket.(Tough titty to all you non-Oz people! )

It then becomes easy:

Make sure you are connected to the volts inputs on your DMM,switch the thing to AC Volts,place the meter on a convenient surface,if you are really paranoid,then switch on the GPO.

Now read the voltage---Easy! caveman can do!!

[psycho0815]

No argument that these precautions are necessary when working on high-energy circuits. I'm aware that vaporization is a perfectly normal failure mode for metal tools when working on large battery banks. But assume you use suitable probes and DMM and plug the probes into a wall socket. What would it involve to get these kinds of failures? Depending on the plug your country uses, it's barely more dangerous than plugging in a real plug: make sure you keep your fingers away from the metal parts.

The great thing about Australian standard sockets (GPOs),apart from the fact that they are all switched,is that standard DMM probes can be plugged into them,& will be retained in the socket.(Tough titty to all you non-Oz people! )

It then becomes easy:

Make sure you are connected to the volts inputs on your DMM,switch the thing to AC Volts,place the meter on a convenient surface,if you are really paranoid,then switch on the GPO.

Now read the voltage---Easy! caveman can do!!

I'm pretty sure you could fit standard 4mm bananaplugs into an german schuko-plug, that would give you a solid hands-free connection. Most of them aren't switched though, so you win.

[G7PSK]

The UK also has shuttered and switched power socket that you can put your probes into and they stay there.

[T4P]

Sockets in UK have a fantastic invention mostly no other sockets have : A Switch.
That said, you can prepare yourself if something big is coming but the BS1363 sockets themselves have really huge conductors and great plug retention system, it takes effort to yank a plug out by accident and if it does, a weak wire will snap instantly
Well it's also quite hard to accidentally poke something into the live and neutral terminals ... you can't, at least without pushing a chisel screwdriver into the earth terminal

[dr_p]

I remember when I probed 220V mains for the first time: thorough test cables inspection, triple checked the 500V AC range, two sets of gloves  %-B, rubber sole shoes. Nearly wet my pants when I saw the reading on the LCD. 

[jeroen74]

A long time ago, somewhere in the eighties, when I was still a kid and quite ignorant, I was in the workshop of my father's computer shop, and I decided to measure how many amps the mains could deliver.

So I stuck the probes of the IIRC, Fluke 77, into the nearest socket I could find, a bang... and everything went dark, the whole shop, the whole street. Somehow a fuse in a distribution cabinet in the street failed, not just a local breaker. My father did not appreciate my little experiment

[LAZLOT]

Check Dave's Blogs on cheap multimeter's... He has a lot to say re: safety of some of the cheap Chinese units- food for thought. I have five m-m's, only one of which I trust with high power. I have previously checked line-voltage (in Aus. it's 240V, with less current potential, but same power overall) with cheap m-m's with no ill effects. BUT be ABSOLUTELY CERTAIN you have the m-m set correctly- i.e AC Volts in the right range setting, depending on the m-m. Different m-m's have different range maximums. The safest way is to start at the highest setting (750 volt?)- or whatever your m-m has, then work down to increase resolution, stopping before you go too far! Also, you should ensure the red lead goes to the active terminal for maximum safety. BOTTOM LINE... DON'T do it until an electrician has shown you how to do it and keep safe, AND checked your m-m! Frayed lead's, poor quality leads (my oldest m-m leads have smooth handles with no way to stop your fingers sliding down onto the probe tips), or a dodgy m-m are just a few of the potential hazards. View ep's. 6.1&2, 10.1&2, 66, 91 and esp. 94-and some tutorials, not mentioned here, but, again GET PROFESSIONAL ADVICE FIRST!

[Monkeh]

in Aus. it's 240V, with less current potential, but same power overall

Less current potential than what?

[LAZLOT]

Quote from: LAZLOT on Today at 04:47:33 PM

    in Aus. it's 240V, with less current potential, but same power overall


Less current potential than what?  - From Monkeh

Getting a bit late here, and I'm noodling up my terms... What I should have said was -we have higher wattage items, but same power overall; i.e. same current (compared to England's 120 Volts).  Eg; Aus 240V @ 2400W=10A, GB 120V @ 1200W=10A. Pls excuse my dylsexia!

[Monkeh]

Quote from: LAZLOT on Today at 04:47:33 PM

    in Aus. it's 240V, with less current potential, but same power overall


Less current potential than what?  - From Monkeh

Getting a bit late here, and I'm noodling up my terms... What I should have said was -we have higher wattage items, but same power overall; i.e. same current (compared to England's 120 Volts).  Eg; Aus 240V @ 2400W=10A, GB 120V @ 1200W=10A. Pls excuse my dylsexia!

Uhm.. The UK operates on 240VAC 50Hz. The reason you operate on 240VAC 50Hz is.. well, because we do. That's actually why most of the world uses 240VAC 50Hz or near enough..

And power is measured in watts, not amps.

[SeanB]

I think you mean USA, not GB.

The problem with mains is that the potential current is incredibly high. A 16A socket outlet ( or 10A, 15A or whatever is the local socket) generally is fed by a cable with a resistance in the order of milliohms. Typically 0.2 to 0.3 ohms resistance for a typical socket outlet. The supply point to the house can have a cable resistance of under 100 milliohms, and the supply network typically can be considered to be zero or pretty close to it.

Thus you have the potential to have short circuit currents in the order of 1000A for a typical socket for the time it takes the protective device to react and open the circuit. Thus the need for 1kA rated fuses in power distribution in the home, and for a class 3 meter to have 1ka rated fuses.

If you are measuring at the point of supply you have the potential short circuit current being higher, 10kA or more until the protection opens. Thus the class 4 fuses being rated for 10kA. Your supply fuses are rated for 20kA breaking typically, and are large and expensive ceramic blocks. They have to be big to withstand the pressure from the failing element inside. The linesmen typically wear blast shields and blast aprons when putting these into the panel when replacing them, as they can let go explosively.

If you are measuring at the upstream side you need training, and a meter certified to be used on these lines. These typically have fused leads as well, as the internal fuses may be inadequate.

[Monkeh]

1kA and 20kA? What is this, the 50s?

Fault currents are often much higher than 1kA. Where they're low you need supplementary protection to prevent fire before the normal protective devices can operate.

[T4P]

1kA only? It would be fine if your substation transformer is roughly about 240kW but it's not in my case ... it's roughly about 2.4MW

Linesman wear Arc Flash PPEs for a reason when going anywhere near fuseboards or switchboards ... if anything happens it's not them getting blown into pieces/burnt into crisps

[SeanB]

1kA at the plug outlet. All bets are off at the breaker box, the meter point or the substation. An assumption is that there will be no faults within 3m of the distribution panel, which is used to calculate the breaking capacity of breakers. Here you get a residential breaker that is 2.5kA rated, but newer ones are 3kA. Light commercial come in 5 and 10kA ratings, with a common breaker range from 5A to 80A for non specialised loads. If it is hard wired then you can go up to a 100A breaker with 15ka rating. Transformers still have fuses, as they are more reliable, and always fail open circuit. At work I have a little 250kVA substation that provides power, and an unused backfeed to the 2MVA transformer 50m away. Connected but no fuses, the Metro would have to come and place the 3 800A fuses to use it, though both poles of the fuse holder are live to show cable damage, using 200A fuses at the other end. The 11kV cable has had a few incidents involving pickaxes, but the protection relays did work to cut the power, or the 11kV line fuses did the same on the ring.

[Monkeh]

1kA at the plug outlet.

Sorry, that won't cut it.

All bets are off at the breaker box, the meter point or the substation.

What's this betting about, then? It's easily calculated and tested.

An assumption is that there will be no faults within 3m of the distribution panel, which is used to calculate the breaking capacity of breakers.

Uuuhhm, that's a ridiculous assumption.

Here you get a residential breaker that is 2.5kA rated, but newer ones are 3kA.

So very 70s.

[SeanB]

Not in the UK............

Most fires are caused by exploding paraffin stoves and illegal wiring, not from home wiring.

[Monkeh]

Not in the UK............

Most fires are caused by exploding paraffin stoves and illegal wiring, not from home wiring.

Laws of physics are the same everywhere, and no matter where you are, it's generally considered a good idea to get with the times.

[G7PSK]

I get the impression that some people on here are scared shitless by the mains. As long as reasonable precautions are taken there is no reason to be scared of a few hundred volts in a system nor of high amps for that matter. The highest amperage that I have worked with is ten thousand, quite interesting as when switched the field in the conductor would make 200 KG of steel jump.

[Psi]

As long as reasonable precautions are taken there is no reason to be scared of a few hundred volts

Even with all the precautions taken, people should still be a little scared of it and should definitely respect it.
The moment ya start to be causal about it is the moment you make a mistake.

It's pretty much the same as handling a loaded gun. It has the capacity to injure or kill you.
Except that the trigger is potentially any metal object.

[nixxon]

If this compares to aviation pilots, the safest people are either the newly graduated or the senior workers. Worst off are the ones that are neither rookies, nor seniors. These are the ones that believe they are the best of the untouchables...

[G7PSK]

I meant to put caution to be used, but it is caution not fear, if you are afraid that is when it is most likely you will make a mistake.

[jeroen74]

I once accidentally touched a fully charged photoflash capacitor (330uF@380V). That will teach you some respect. My whole arm hurt for two days.