Thinking about getting myself a welder, but...

[Jesse masterson]

Thanks for support, I never meant to act like a know it all , that wasn't my intention and if I came across that way I'm sorry,however I stand by all I said and I do know you can die from dc also just not quite as dangerous by the way if you want the truth look it up on the net ac current causes defibbulating of the heart which causes the heart to go into cardiac arrest dc current has a different effect on the heart that isn't as fatal but dc will be more likely to burn you you are 11 times more likely of cardiac arrest with ac

 

[Soundguy]

This is long and a little technical, but may help to clear things up:

Ohm's Law (again!) : ELECTRICAL SAFETY

James K0UA

That's right james.. and as most of us Ham's or ET/EE know:

.. when the term 'ac' voltage is thrown out.. lets look at what that really is.

standard use of the term 'ac' volts here is an RMS measurement.. that's root mean squre, for you non engineer types. that's essentially a measuring nomenclature so that you can compair work perfromed between a dc source and an ac source. now here's the kicker.

ok.. so you have lets say.. 240vdc as your supply..a nd lets compair that to the average household dryer plug... 240vac (RMS )

so what does that really look like. first of all.. ac is a waveform.. a sine wave. in measuring on an osciloscope, you would get a peak to peak measurement ( peak to peak is another measurement just as RMS is ). peak to peak measures from the top of the wave from on the positive side to the bottom of the waveform on the negative side, center being 0 potential. now.. how do we get from peak to peak.. which is what is really happening at that plug, to what our RMS meter reads ... first... we HALVE the value.. and then that is termed. 'PEAK' voltage.

still.. gets better.. after we have halved the peak to peak, to arrive at peak... then we hit it with another reduction.. we multiply by .707 to get our RMS value that's right.. the ac voltage at your dryer plug, for nomenclature .. has gone thru a halving, then another near 30% reduction... 678.95vac Pk-PK = 240vac rms

ps.. this hold true for sine waves.. not other waveforms.. etc ( square, sawtooth..e tc.. )

73's

 

[deereman75]

That's right james.. and as most of us Ham's or ET/EE know:

.. when the term 'ac' voltage is thrown out.. lets look at what that really is.

standard use of the term 'ac' volts here is an RMS measurement.. that's root mean squre, for you non engineer types. that's essentially a measuring nomenclature so that you can compair work perfromed between a dc source and an ac source. now here's the kicker.

ok.. so you have lets say.. 240vdc as your supply..a nd lets compair that to the average household dryer plug... 240vac (RMS )

so what does that really look like. first of all.. ac is a waveform.. a sine wave. in measuring on an osciloscope, you would get a peak to peak measurement ( peak to peak is another measurement just as RMS is ). peak to peak measures from the top of the wave from on the positive side to the bottom of the waveform on the negative side, center being 0 potential. now.. how do we get from peak to peak.. which is what is really happening at that plug, to what our RMS meter reads ... first... we HALVE the value.. and then that is termed. 'PEAK' voltage.

still.. gets better.. after we have halved the peak to peak, to arrive at peak... then we hit it with another reduction.. we multiply by .707 to get our RMS value that's right.. the ac voltage at your dryer plug, for nomenclature .. has gone thru a halving, then another near 30% reduction... 678.95vac Pk-PK = 240vac rms

ps.. this hold true for sine waves.. not other waveforms.. etc ( square, sawtooth..e tc.. )

73's

You lost me :confused2: EDIT: I read it a few more times, I think I get it.

 

[Soundguy]

it's simple measuring and quantative nomenclature.

yer dryer plug, looked at on a oscope provides over 678vac whereas if you had 19 12v car batteries ( nominal 12.6vdc ) in series you would read 240vdc on that same oscope. the average 'joe' doesn't realize that ac measurements commonly seen in and around are RMS measurements...

soundguy

 

[dynasim]

The interested ought to google the fatality quote to put this discussion in context.

The article does not say what the source of the shock is, and it is a translated article.

From my perspective, OSHA is draconian about extension cords for a reason. It is far more likely that the fatality in question was caused by a bad source connection than by a shock from welding, but there is no way for any of us to know.

Chris

 

[k0ua]

it's simple measuring and quantative nomenclature.

yer dryer plug, looked at on a oscope provides over 678vac whereas if you had 19 12v car batteries ( nominal 12.6vdc ) in series you would read 240vdc on that same oscope. the average 'joe' doesn't realize that ac measurements commonly seen in and around are RMS measurements...

soundguy

Only problem is when you start talking Peak to Peak and RMS measurements, peoples eyes glaze over. But a few minutes with a calibrated oscilloscope in front of them and some waveforms to measure would make it pretty clear. Of course then we can start talking about higher frequency AC waveforms. And skin effect, RF burns and on and on . But the bottom line is if you become part of the circuit, any circuit.. it ain't a good thing I have been there and done that, and didn't like it much at all. Stay safe out there.

James K0UA

 

[Soundguy]

unfortunately so.

some people are more interested in parroting a statistic than verifying it, or actually understanding some of the underpinnings.. etc..

 

[greasemonkeyok]

One way to demonstrate the meaning of RMS is to put a rectifier in series with a 600v capacitor on a 240v outlet, and watch the voltage across the capacitor rise to well over 240v.

 

[yomax4]

It's nice to see how the wave forms act when watching them while messing with a modern Tig unit with variable wave form and Hz adjustments. I have never been shocked by any welder but I have often wondered why. I have held a part in the air and welded on it without in being grounded to a table as well as guiding the stick with one hand while holding the stinger in the other. Both seem like they could bite you if conditions are right.

 

[Soundguy]

One way to demonstrate the meaning of RMS is to put a rectifier in series with a 600v capacitor on a 240v outlet, and watch the voltage across the capacitor rise to well over 240v.

a real industrial grade meter, perhaps with graphing an oscope capabilities where you can switch between rms and other measurement modes, and / or see the wave form, along with freq counting.. etc... that's another good way.. especially if it has data hold and / or pc hookup.