Our church also has a walk-in baptismal font. The celebrant some times gets in the font with an adult candidate to be baptized. The celebrant is wearing a wireless microphone which is battery powered. I have learned it only takes milliamperes to electrocute. Is wearing the wireless microphone unsafe? Thank you, Doug Harrison
Waco, Tx
- Thread starter dharrison
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Re: Waco, Tx
It takes no more than 100 milliamps to electrocute a person. It would seem obvious that the power source within a wireless microphone cannot sustain that amount of current through the resistance of a human body long enough to cause any injury. But we cannot trust our instincts, and cannot believe the "obvious."
If you haven't already done so, I suggest you read this thread.
It takes no more than 100 milliamps to electrocute a person. It would seem obvious that the power source within a wireless microphone cannot sustain that amount of current through the resistance of a human body long enough to cause any injury. But we cannot trust our instincts, and cannot believe the "obvious."
If you haven't already done so, I suggest you read this thread.
hbiss
EC, Westchester, New York NEC: 2014
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Re: Waco, Tx
No not at all, as long as it's wireless there is no danger. I would be seriously concerned though if there were a cable.
I would be concerned about where the pool is located and what electrical devices and metallic objects surround it. I believe such a baptismal font constitutes a pool and should comply with the NEC as such particularly with respect to its proximity to electrical devices such as switches, receptacles, lights, cords, bonding, etc.
-Hal
-Hal
No not at all, as long as it's wireless there is no danger. I would be seriously concerned though if there were a cable.
I would be concerned about where the pool is located and what electrical devices and metallic objects surround it. I believe such a baptismal font constitutes a pool and should comply with the NEC as such particularly with respect to its proximity to electrical devices such as switches, receptacles, lights, cords, bonding, etc.
-Hal
-Hal
petersonra
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Re: Waco, Tx
the wireless microphone is certainly safer, probably by at least an order of magnitude than one with a cord on it conencted to a source of 120V power.
whether it is "safe" is something else altogether.
the wireless microphone is certainly safer, probably by at least an order of magnitude than one with a cord on it conencted to a source of 120V power.
whether it is "safe" is something else altogether.
hbiss
EC, Westchester, New York NEC: 2014
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Re: Waco, Tx
Peter, let's not get carried away here to the point of being ridiculous because of some tragic incident. Put the blame where it belongs.
Wireless mikes are perfectly safe unless you beat someone over the head with them. Same goes for cell phones and mp3 players. Ever had someone electrocuted by one even when they were submerged in water?
-Hal
Peter, let's not get carried away here to the point of being ridiculous because of some tragic incident. Put the blame where it belongs.
Wireless mikes are perfectly safe unless you beat someone over the head with them. Same goes for cell phones and mp3 players. Ever had someone electrocuted by one even when they were submerged in water?
-Hal
petersonra
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Re: Waco, Tx
Whether they are "safe" to use in water is not a judgement I feel qualifed to make. What are your qualifications to make that judgement?
Re: Waco, Tx
I see no way that a wireless mike or any other battery powered device could be a danger. The body must become part of a current path for any danger to exist. If you immerse the unit in water, small currents might exist around it, but I can't see them as being dangerous.
[ November 04, 2005, 02:52 PM: Message edited by: rattus ]
I see no way that a wireless mike or any other battery powered device could be a danger. The body must become part of a current path for any danger to exist. If you immerse the unit in water, small currents might exist around it, but I can't see them as being dangerous.
[ November 04, 2005, 02:52 PM: Message edited by: rattus ]
petersonra
Senior Member
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Re: Waco, Tx
I agree with your opinion that a wireless mike is "safe" if immersed in water. However, I do not feel qualified to make this judgement.
- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: Waco, Tx
Let's take a quick look at the physics behind the issue. We all know that the current that a power source will supply will be equal to the voltage it puts out divided by the resistance of the circuit path. We also know that 100 milliamps is enough to cause a fatal shock, and an even lower current might suffice in worst case conditions. We all know that the resistance of a human body varies widely from person to person and from moment to moment. Finally, we all recognize that a body immersed in water will have a lower resistance than the same body would have if it were dry.
One example I have used in training classes assumes a body resistance of 300 ohms. To get a 100 milliamp current through that body would only take a voltage source of 30 volts. So I am willing to guess that a car battery could give a serious, if not fatal, shock.
But let's look at the wireless microphone. A quick (i.e., not at all thorough) Internet search led me to expect the mike to have a power source no stronger than a single 9 volt battery. You could postulate a body resistance of 90 ohms when the person is immersed in water, and thus calculate a current of 100 milliamps. You could then conclude that this 9 volt battery might give a fatal shock.
Here's what you would be missing. For the 9 volt battery to give a serious, or even fatal, shock, it would have to be able to hold a constant output voltage for a significant period of time. Whatever chemical properties cause the battery to create a voltage in the first place would have to be strong enough to keep pushing out current, regardless of how much current was being drawn and for how long that current was being drawn. A common 9 volt battery will not be up to that challenge. Its internal resistance would come into play, and there would be a large voltage drop internal to the battery. Thus, by the time the voltage made its way to the battery terminals, there would not longer be 9 volts to pass on to the rest of the circuit.
By contrast, look at the source of power that would drive current through a 120 volt circuit. You have all the generators in perhaps a multi-stage region connected together, all of them creating the "push" behind every utility transformer that supplies every household. You can draw all the current you want from a 120 volt outlet. Until the moment that some breaker trips or some fuse blows or some wire burns up, the basic power source, the generators, will keep pushing out current.
That is why a 120 volt power source is more dangerous than a low voltage battery system. It's not just the voltage level. It's the fact that the 120 volt source will keep pushing out current, whereas the small battery will not be able to keep pushing out current.
Look at the difference in this way. Suppose you want to make another person wet (with his permission, of course). </font>
Let's take a quick look at the physics behind the issue. We all know that the current that a power source will supply will be equal to the voltage it puts out divided by the resistance of the circuit path. We also know that 100 milliamps is enough to cause a fatal shock, and an even lower current might suffice in worst case conditions. We all know that the resistance of a human body varies widely from person to person and from moment to moment. Finally, we all recognize that a body immersed in water will have a lower resistance than the same body would have if it were dry.
One example I have used in training classes assumes a body resistance of 300 ohms. To get a 100 milliamp current through that body would only take a voltage source of 30 volts. So I am willing to guess that a car battery could give a serious, if not fatal, shock.
But let's look at the wireless microphone. A quick (i.e., not at all thorough) Internet search led me to expect the mike to have a power source no stronger than a single 9 volt battery. You could postulate a body resistance of 90 ohms when the person is immersed in water, and thus calculate a current of 100 milliamps. You could then conclude that this 9 volt battery might give a fatal shock.
Here's what you would be missing. For the 9 volt battery to give a serious, or even fatal, shock, it would have to be able to hold a constant output voltage for a significant period of time. Whatever chemical properties cause the battery to create a voltage in the first place would have to be strong enough to keep pushing out current, regardless of how much current was being drawn and for how long that current was being drawn. A common 9 volt battery will not be up to that challenge. Its internal resistance would come into play, and there would be a large voltage drop internal to the battery. Thus, by the time the voltage made its way to the battery terminals, there would not longer be 9 volts to pass on to the rest of the circuit.
By contrast, look at the source of power that would drive current through a 120 volt circuit. You have all the generators in perhaps a multi-stage region connected together, all of them creating the "push" behind every utility transformer that supplies every household. You can draw all the current you want from a 120 volt outlet. Until the moment that some breaker trips or some fuse blows or some wire burns up, the basic power source, the generators, will keep pushing out current.
That is why a 120 volt power source is more dangerous than a low voltage battery system. It's not just the voltage level. It's the fact that the 120 volt source will keep pushing out current, whereas the small battery will not be able to keep pushing out current.
Look at the difference in this way. Suppose you want to make another person wet (with his permission, of course). </font>
- <font size="2" face="Verdana, Helvetica, sans-serif">First, you hit the person in the face with a bucket full of water. The bucket will soon be empty, and you will not be able to make the person more wet. That is like the battery running out of the energy needed to keep the current flowing.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Next, you use a garden hose. No matter how long you hold the hose on the other person, the water will keep flowing, and keep getting the person more wet. That is like a 120 volt circuit that can continue to supply current until something finally trips or fails or disconnects the circuit.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Finally, let's look at the shock potential of a 480 volt, or 4160 volt, or 765,000 volt source. This is like hitting the person in the face with a large (very large) wave of water that has the force of the entire ocean behind it.</font>
- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: Waco, Tx
His name is Bob. "Peter" is part of his last name.
hbiss
EC, Westchester, New York NEC: 2014
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- Hawthorne, New York NEC: 2014
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Re: Waco, Tx
His name is Bob. "Peter" is part of his last name.
Yeah I knew that, just in a hurry. Sorry Bob.
Maybe it would be a good idea for everybody to use their real names around here like you Charlie.
-Hal
[ November 04, 2005, 01:26 PM: Message edited by: hbiss ]
His name is Bob. "Peter" is part of his last name.
Yeah I knew that, just in a hurry. Sorry Bob.
Maybe it would be a good idea for everybody to use their real names around here like you Charlie.
-Hal
[ November 04, 2005, 01:26 PM: Message edited by: hbiss ]
Re: Waco, Tx
Well, Rattus is my real name, or nickname. My brothers called me Rat, so I have Latinized it to Rattus.
C.B. I think the real issue here is that any energy source has to be coupled to the body for any danger to exist. Large currents in the water can do just that when the body becomes a parallel path. My memory tells me that only about 1 milliamp is enough to kill.
Well, Rattus is my real name, or nickname. My brothers called me Rat, so I have Latinized it to Rattus.
C.B. I think the real issue here is that any energy source has to be coupled to the body for any danger to exist. Large currents in the water can do just that when the body becomes a parallel path. My memory tells me that only about 1 milliamp is enough to kill.
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- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: Waco, Tx
I don't recall the source of this table. But I think it is reasonable summary of the effects of current on a human body.
</font>
I don't recall the source of this table. But I think it is reasonable summary of the effects of current on a human body.
</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">1 milliamp = Perception level. Just a faint tingle.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">5 milliamps = Slight shock felt; not painful but disturbing. Average individual can let go. However, strong involuntary reactions to shocks in this range can lead to injuries (e.g., falling from ladders).</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">25 milliamps = Painful shock, muscular control is lost.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">100 milliamps = Extreme pain, respiratory arrest, severe muscular contractions. Individual cannot let go. Death is possible.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">1 amp = Ventricular fibrillation. Muscular contraction and nerve damage occurs. Death is most likely.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">10 amps = Severe burns. Cardiac arrest. Probable death.</font>
petersonra
Senior Member
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- Northern illinois
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Re: Waco, Tx
it is my real name. peterson r a
hbiss
EC, Westchester, New York NEC: 2014
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- Hawthorne, New York NEC: 2014
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Re: Waco, Tx
I belong to another board that gave everybody 1 month to change their "handle" to their first and last names. The administrator's reasoning was that everybody there is a professional and the board shouldn't look like an internet chat room.
-Hal
I belong to another board that gave everybody 1 month to change their "handle" to their first and last names. The administrator's reasoning was that everybody there is a professional and the board shouldn't look like an internet chat room.
-Hal
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Re: Waco, Tx
Hmmm, funny thing is when I go to my profile here it won't let me edit my name even if I wanted to.
-Hal
Hmmm, funny thing is when I go to my profile here it won't let me edit my name even if I wanted to.
-Hal
Re: Waco, Tx
See
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/shock.html
for the source of C.B.'s table.
See
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/shock.html
for the source of C.B.'s table.
Re: Waco, Tx
A current of 1mA AC is at the threshold of sensation for currents through the body such as from one hand to the other. However, a fraction of a milliAmp through the heart muscle is enough to cause fibrillation. This is according to the Merck Manual. They also say that AC is more dangerous than DC--just like Edison said! This could be because the peak currents are higher than the RMS currents.
A current of 1mA AC is at the threshold of sensation for currents through the body such as from one hand to the other. However, a fraction of a milliAmp through the heart muscle is enough to cause fibrillation. This is according to the Merck Manual. They also say that AC is more dangerous than DC--just like Edison said! This could be because the peak currents are higher than the RMS currents.
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