# Electrocution by Mic



## blademaster (Dec 7, 2005)

Hey Guys I heard a few weeks ago about a Texan Pastor that got eletrcouted when either a mic fell into the water or he touched it. I'm wondering what you're guys opinion is on pssible causes as well as whether or not the shure Beta 58 handheld wireless mics could cause the same thing if they were to fall into the water. (i.e. how many amps does a 9v put out at a non-used full current drain)


----------



## CHScrew (Dec 7, 2005)

I think that I heard about that too. I forget exactily how it happened but I know that it did. But I don't know how bad it was though. Did it do damage or was it just a little shock?


----------



## AVGuyAndy (Dec 7, 2005)

First off, to answer the question "Did it do damge?"...the guy died, so yes, it did damage.

Second, this incident was not caused by phantom power, or power from a wireless mic. In fact, it was a wired mic which he touched. 

Third, the guy was standing in a pool of water. The mic did not fall into the water, he simply touched it. 

Before the incident, the heater in the pool was not working properly, and it was replaced, or repaired or something, and the guy who wired it, didn't do it well. 

The moral of the stroy, make sure your gear is wired properly, and grounded. NEVER use a ground lift adapter if you have a noise problem. Using a ground lift adapter will kill you.


----------



## blademaster (Dec 7, 2005)

thanks Andy. how about the other question. If i use a wireless handheld that takes a 9v will the battery getting shortcircuited have the amps to kill a man


----------



## AVGuyAndy (Dec 7, 2005)

Nope, not even close.


----------



## blademaster (Dec 7, 2005)

off hand do u know how many amps it does produce being shortcircuited


----------



## jumpjet (Dec 8, 2005)

Typically with no resistance, the amps will just increase to the maximum output of the battery. Ohms law: E= IR, if R is 0, no matter what voltage is, I can go from 0-infinity. That being said, There is a power limitation based on the power equation. P=IE. Without the amount of power neccesary, you will run out of amps. It only takes a tiny bit of current to send the heart into fibrulations(sp) so be careful!


----------



## Radman (Dec 9, 2005)

That's right, it only takes around 50 milliamps to be fatal, and the fatility is not directly related to voltage.

Also, never use a multimeter to try and measure the amperage of a battery, something will most likely explode. The amperage rating of a component is what it draws, and the amperage rating of a circuit is the maximum amperage it is designed to withstand. A multimeter measures the amperage being drawn by a component.


----------



## Mayhem (Dec 11, 2005)

blademaster said:


> thanks Andy. how about the other question. If i use a wireless handheld that takes a 9v will the battery getting shortcircuited have the amps to kill a man



Think about it - ever tested a 9V battery by touching the terminals to your tongue? Well that is what shorting it out feels like.

One of the most important factors in electrocution is resistance. When your skin is dry the resistance is high, when it is wet, the resistance is lower. Those of you that have worked on, or grew up on a farm will know the difference in getting bitten by the electric fence in summer as opposed to winter!

The other important factor is the ampage (as radman pointed out).

The 12V ignition coils on some cars actually carry a warning sticker as the amperage that they generate is enough to cause a serious (potentially fatal) shock.

I got a shock a few months ago from a 240V 16A breaker that had a break in the insulator and suffered nothing more than muscle contractions for the duration of the shock (it actually took a few seconds for me to work out what was happening) and then some general arm soreness for a few hours after. Fortunately, I was sitting on a wooden work bench at the time and my hands were dry.

I would have to check on the 50mA rating, as I suspect that would be current going directly into the heart (via pacing wires or intra-operatively). I do know that the number of joules used in an open defibrillator is approximately 10% of that delivered externally (with conductive gel pads).


----------



## Radman (Dec 12, 2005)

30mA across the human heart kills.

Kindof related.


----------



## Mayhem (Dec 12, 2005)

Interesting reading and supports my comment about resistance of the human body. Interesting that you note 30mA but I could only find reference to 90mA in the calculation put forward here. 100mA appears to be the listed minimum threshold in this and other references.

Another that I found was: http://www.elec-toolbox.com/Safety/safety.htm which provided a good description of how a GFCI (RCD) works. It also cites a similar lethal current.

Most of the RCDs that are available here are 35mA rated but you can get them up to 100mA so it would seem strange that these devices would not break the circuit until a lethal current was detected.

If you look at his calculation for a 9V battery and the average human having a resistance of 500K, you can calculate the required voltage battery required to produce the 100mA shock that is considered to be fatal.

x = 100mA and 9V = 0.018mA (18 microampares)
Thus, x = (100 x 9)/0.018 which equals 50,000
Therefore, you would require a 50,000V shock to be fatal. I think that most stun guns that the police use are 20,000 to 50,000V

To check, E=IR so 50,000V=I x 500,000ohms
I=50,000V/500,000ohms, which equals 0.1A (100mA)

Whilst the math is correct on paper, something doesn’t seem correct to me and I am sure it is more complicated that this. The ability of a power source to actually be capable of delivering the current has to be a factor. I believe that low voltage DC welders have killed people due to the reduced skin resistance form perspiration and the high current at which they operate. 

I have not yet been able to find out the current generated by a defibrillator but I know that 300J to 360J are the standard ‘shocks’ that are delivered during a cardiac arrest. 

Regardless of this fact however is the importance of electrical safety as whilst this debate is interesting, I wonder if people will simply think, “That couldn’t possibly deliver enough current to kill me” when we should be thinking that any electrical device has the potential to cause us harm (even death).


----------



## Radman (Dec 12, 2005)

According to my latest findings, there is yet another factor involved in this "mystery": the very fabric of time itself! (OK, maybe not the "fabric" part, but the time part, yes.)

According to this, it takes 1-3 seconds of shock to start fibrillations, which whould then easily explain such high amperages in GFCI's (RCD's), as I believed they are designed to cut off current within a few thousandths of a second. This would be plenty soon enough to avoid fibrillations under most circumstances.

Another interesting thing is that I remember seeing on the Science Channel (I'm that nerdy) that as a result of earth's magnetic field, there is a constant electrical charge in the air of several thousand volts. It just has such little amperage that it goes completely unnoticed. However, as this is static electricity (I think) I'm not sure exactly how it plays into this discussion. 

And with that I submit my findings to the board for your approval. (I'm a scientist today.)


----------



## jumpjet (Dec 13, 2005)

It could have something to do with thermal runaway, as the electrical energy heats up your tissue, it could lower the resistance, allowing more current through...

In re: the darwin awards thing.

I really don't think the human body only puts up 100 ohms of resistance. I mean...I could be wrong, but that just sounds FAR too low...


----------



## Radman (Dec 13, 2005)

jumpjet said:


> It could have something to do with thermal runaway, as the electrical energy heats up your tissue, it could lower the resistance, allowing more current through...
> 
> In re: the darwin awards thing.
> 
> I really don't think the human body only puts up 100 ohms of resistance. I mean...I could be wrong, but that just sounds FAR too low...



If you read closely it says 100 ohms if you take out the skin, as in through a wonderfully conductive liquid that goes to every part of the body: blood.


----------



## Chris15 (Dec 14, 2005)

Mayhem said:


> Most of the RCDs that are available here are 35mA rated but you can get them up to 100mA so it would seem strange that these devices would not break the circuit until a lethal current was detected.



Actually most RCDs in Australia are 30mA. Those used in hospitals etc are rated to 10mA since persons in those places are more likely to be ill and so less able to sustain the shock. The 100mA units were not designed for protection to human, rather to protect equipment in fault situations. In some cases a main switch in a switchboard will incorporate a 100mA RCD. This is based on what an electrician told me. I believe that where Australians regulations require 30mA RCDs, New Zealand rules mandate 10mA.


----------



## Mayhem (Dec 14, 2005)

Chris15 said:


> Actually most RCDs in Australia are 30mA. Those used in hospitals etc are rated to 10mA since persons in those places are more likely to be ill and so less able to sustain the shock. The 100mA units were not designed for protection to human, rather to protect equipment in fault situations. In some cases a main switch in a switchboard will incorporate a 100mA RCD. This is based on what an electrician told me. I believe that where Australians regulations require 30mA RCDs, New Zealand rules mandate 10mA.



Yes you are quite correct and that was a typo on my part. Australian RCDs are available in 10 mA, 15 mA, 30 mA and 100 mA.


----------



## jumpjet (Dec 14, 2005)

> If you read closely


I read that, I still think it's low.


----------



## Radman (Dec 15, 2005)

NIOSH explains it all.


----------



## Mayhem (Dec 15, 2005)

Nice find Ryan. I think everyone should have a read of that.


----------



## RonaldBeal (Dec 19, 2005)

While I don't know all of the details of this particular incident, I suspect a RCD on the audio gear would not have helped. It sounds like the Heater had a short to the water tank. The person becomes the path to ground through the sound system. A RCD on the audio gear would not have tripped, and additionally, if a RCD or circuit breaker was open, it would not interrupt the path to ground.
A ground lift on the audio gear may actually have saved his life, by not giving the current a path to ground (Still not reccomended practice!)

Ultimately, the (I suspect) faulty heater DOES need a RCD (or GFCI in the US), and how many of us inspect EVERY peice of eletrical gear we come close to?


----------



## blademaster (Dec 21, 2005)

Mayhem said:


> [Think about it - ever tested a 9V battery by touching the terminals to your tongue? Well that is what shorting it out feels like.



Well yes that is it being short circuited but does it change in the fact that you are now in a much larger body of water than whats on youre tongue thats covering nearly half your body


----------



## Mayhem (Dec 21, 2005)

Drop one in the bath tub!

Seriously - NO, it wouldn't make any difference.


----------



## Sinorm (Jan 14, 2006)

*What Actually Happened*

Here is an article describing exactly what went wrong:

http://www.mikeholt.com/files/PDF/Tragedy_Strikes_Texas_Church.PDF

Basically, the sound system was wired correctly, but there was a problem with the heater in the bapistry. The wired microphone simply acted as a ground, allowing the charge to flow and leading to his death.


----------



## blademaster (Jan 14, 2006)

Awesome guys i just wanted to make very sure so that my pastor doesn't freak out. thanks sinorm for the page


----------



## AVGuyAndy (Jan 14, 2006)

If you are thinking what I think you are thinking, it STILL isn't safe to use a wired mic in water. Use a wireless.


----------



## mbenonis (Jan 15, 2006)

This is a good place to remind everyone that it is unsafe to cut the ground on devices that are are introducing hum into a system. Many uneducated sound technicians think that cutting the ground on a piece of equipment that is humming is a magical cure which will reduce or eliminate hum in their system. However, the ground is there for a reason - to prevent you from getting shocked if a wire inside breaks. So, the moral of the story again: NEVER CUT THE GROUND ON ANYTHING!

OK, I'll step off of my soap box now.


----------



## Mayhem (Jan 15, 2006)

Mike – there is no such think as a soap box when it comes to preaching safety. It is something that cannot be overstated.


----------



## blademaster (Jan 23, 2006)

AVGuyAndy said:


> If you are thinking what I think you are thinking, it STILL isn't safe to use a wired mic in water. Use a wireless.



Im not that crazy. I know what the dangers are of it especially now and generally i would prefer to use a wireless even without those dangers due to a wired has the inheirant evil of people tripping over cords


----------

