Safety: testing Electrical outlets

[The Dude]

It's funny how things change. Back in my early gigging days, we thought getting shocked by the mic while playing guitar was just an annoyance. Often, you'd just throw a windscreen over the mic and play on. Or, just be sure not to get close enough to touch it. We never realized the actual danger. Getting a zap from a mic was a relatively common occurrence back when buildings had no grounded outlets and amps had two wire mains cables. That's just how things were and nobody thought much of it. Thankfully, we now know better!

[Bill Moore]

Back in the 60's, being the drummer, it was my job to rotate amplifier plugs to match the PA. The drill was to hold your guitar, and brush the back of your hand across the mic, no tingle, good to go!

[Chuck H]

The commonality of getting shocked by typically bad AC terminal stage wiring at clubs, often due to low budget DIY club owners, is the reason I got the nickname "Sizzlin' Chuck". I'd have prefered it was for my playing but insiders knew the real story

[x-pro]

Your network voltage is only 110V. Just tickles and caresses.
What if 220V?

[R.G.]

Your network voltage is only 110V. Just tickles and caresses.
What if 220V?

It's not the volts that kill you, it's the current. Currents at 50-60Hz cause "can't let go" muscle clamping at about 15-20ma or above. Skin resistance varies with how dry the skin is, from 100k ohms or more for very dry skin, down to 1000 ohms for wet, sweaty skin. 15ma into 1000 ohms is only 15Vac. 220 versus 110 is largely immaterial unless you have some specific, critical skin condition - or are just unlucky.
Here is a reference to learn more about the issues: https://pmc.ncbi.nlm.nih.gov/articles/PMC2763825/

[Helmholtz]

https://en.wikipedia.org/wiki/Extra-low_voltage

[Chuck H]

It's not the volts that kill you, it's the current. Currents at 50-60Hz cause "can't let go" muscle clamping at about 15-20ma or above. Skin resistance varies with how dry the skin is, from 100k ohms or more for very dry skin, down to 1000 ohms for wet, sweaty skin. 15ma into 1000 ohms is only 15Vac. 220 versus 110 is largely immaterial unless you have some specific, critical skin condition - or are just unlucky.
Here is a reference to learn more about the issues: https://pmc.ncbi.nlm.nih.gov/articles/PMC2763825/

I almost covered this but decided to let it go. Still glad you brought it up though because it was stuck in my craw

[Chuck H]

https://en.wikipedia.org/wiki/Extra-low_voltage

I could have told of this from experience having been hit by automotive ignition systems. Great link and something everyone needs to know.

[Helmholtz]

220 versus 110 is largely immaterial unless you have some specific, critical skin condition - or are just unlucky.

Yes, it's body current.
But everything else being the same (particularly body resistance and voltage source impedance) a higher voltage will drive a higher current, so must be considered more dangerous.
I think that's what x-pro meant.

[g1]

https://en.wikipedia.org/wiki/Extra-low_voltage

I could have told of this from experience having been hit by automotive ignition systems. Great link and something everyone needs to know.

Can you expand more on what you are referring to? Automotive 12V systems are pretty harmless unless you pierce skin. The sparkplug stuff on the other side of the coil is high voltage.

[Bill Moore]

High voltage, but of course very low amperage, not unlike the HV circuits in our guitar amps!

[Chuck H]

Can you expand more on what you are referring to? Automotive 12V systems are pretty harmless unless you pierce skin. The sparkplug stuff on the other side of the coil is high voltage.

Only that in my youth as a motorhead (before learning anything about electronics as a teen) I was hit a couple of times by a spark plug coil. So not 12V but higher (as the ignition system would be). Only observing that even in lower voltage systems there can be issues. This was a knee jerk response so it didn't actually apply as I'd intended. I originally wanted to support the idea that lower voltage at higher current can be analogous in danger to higher voltage at lower current. But my example did fail in this case.

[g1]

Well, a good caution that even something that seems harmless enough due to low voltage, can still turn around and bite you!

[Helmholtz]

I originally wanted to support the idea that lower voltage at higher current can be analogous in danger to higher voltage at lower current.

As the body impedance limits the body current, a low voltage cannot cause a high body current.
According to the link I posted earlier, an AC voltage below 50V (or DCV below 120V) is considered safe regarding shock.
50Hz body impedance drops with increasing voltage.
Official numbers are 8k@125V and 3.8k@200V measured between dry hands.
So body currents of 16mA@125V and 53mA@ 200V.
I'd say our mains voltage is much more dangerous than yours.

[g1]

Official numbers are 8k@125V and 3.8k@200V measured between dry hands.

This is what I meant about 12V being dangerous if skin is pierced. Most of how we think about shock is under the assumption of normal dry skin resistance.