Author Topic: Help! Total beginner- Just recieved my new UNI-T multimeter and I've killed it  (Read 22463 times)

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Offline Sorry State

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I'm a real beginner. I treated myself to a UNI-T UT61D (as reviewed in the $100 test). So I started using it, I tested a 9V battery for Volts and Amps and that worked fine. Then I thought I'd test an agricultural eclectic fence. At first I had the red and black cables on the same piece of eclectic fence wire no great result so then I kept one cable on the electric fence and I touched the other cable to a non-electrified metal sheep wire fence under the eclectic fence. 

There was a slight click from the arc of the electric fence being short circuited (which is normal if you touch the fence with anything that will conduct.) Except the Multimeter has gone dead.

In the manual it has a way of testing to check if the fuses are blown, except it requires the display to work. But mine is just dead.

Could an electric fence really kill a Cat III 1000v multimeter? I am so p*ssed off right now.
Any help appreciated
 

Offline Time

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aren't electric fences on the order of 10,000 V?
-Time
 

Offline DJPhil

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I haven't heard of a fence lower than 2kV, and that was a tiny unit meant to wire 30 feet of flower patch to keep dogs out. The farms around here that I've been to use 10kV fences for livestock fencing.
It's most likely your fuse, but the voltage is high enough that it may have arced across traces in the case. Even if the fuse is toast the meter should power up. I'd pull the fuses and the leads out, swap the battery, and see if it turns on. If not I'd suspect that the voltage arced inside and fried something sensitive. Is it still under warranty?

I wish you luck. :)
 

Offline Kiriakos-GR

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That's a crazy story ... that's how it sounds to me at list ...

You should pay a visit at the Nearest Church, light up about 50 candles , and Glory the Lord ..

This multimeter saved your life ... keep it as souvenir for ever.

There is special tools for voltages above the 1000V mark.
They called as High voltage probes.

Now you know ...  :)
 


« Last Edit: October 20, 2010, 02:35:18 pm by Kiriakos-GR »
 

Offline Mechatrommer

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so whats the verdict on the Uni-T? should a descent meter survive this? should we ask Dave to re-test Fluke beyond its limit? if the fence is 10KV, then thats a 10 times abuse test... wait...
i re-watched my saved Dave's 4KV DMM Blow. I'm not sure how much energy the fence got. But by right, there is possibility of DMM explosion. Luckily your just went dead silently. ;)
opening the case and post the picture here to see whats happened inside will interests me.
« Last Edit: October 20, 2010, 02:36:35 pm by shafri »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Strube09

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Yep,

If you don't have warranty (bought it used) then it is time to open it up!
 

Offline dds

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I am so p*ssed off right now.
Any help appreciated


You should write email to factory and thank them for a good product ;)
 

Offline Kiriakos-GR

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so whats the verdict on the Uni-T?

Died like a hero ..  

should a descent meter survive this?

The guinness world records, does not know any common DMM that passed this test  :D

http://www.guinnessworldrecords.com/

http://www.guinnessworldrecords.com/search/default.aspx?q=multimeter
« Last Edit: October 20, 2010, 02:49:53 pm by Kiriakos-GR »
 

Offline Time

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Just to clear some things up:

Electric fences aren't meant to kill you.  High voltage will sting like hell but not really cause any damage if there isn't much current behind it.  Its high voltage DC that you should fear.  Imagine a mile of electric fence charged to 30 kV DC.  Just the thought of that scares the day lights out of me.  There would just be dead animals strewn about that length of fence.  If someone comes along and touches their leg between the 'electrode' wires, the stray parasitic capacitance alone would be enough to deliver a burst of charge that could very well blow your leg off.  Whats on electric fence lines are short HV pulses that come every second or so. The meter didn't protect him because there wasn't anything to be protected from.  He should thank the electric fence company for making a fence thats not going to cook his unsuspecting dogs or livestock. :)


I have seen cows that have desensitized themselves to shock lean on extremely strong agricultural electrical fences with no problems.
-Time
 

Offline Mechatrommer

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If you don't have warranty (bought it used) then it is time to open it up!
even if its new. i think he broke the warranty already by violating the rules and regulation, to operate the DMM within its limit.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Kiriakos-GR

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If you don't have warranty (bought it used) then it is time to open it up!
even if its new. i think he broke the warranty already by violating the rules and regulation, to operate the DMM within its limit.


Totally agree ..

Silicone IC's does not respond as cows does ..


.
« Last Edit: October 20, 2010, 04:08:12 pm by Kiriakos-GR »
 

Offline Sorry State

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Wow, you guys reply quickly.

You can touch the fence with your hand and it gives a nasty little sting but its nowhere near dangerous.

I opened up the unit and temporarily replaced the 1A fuse with a 5A and the 10A with a 13A (its all I have at the moment) and a new battery but there was no signs of life.

There is no sign of damage inside, from what I can see.

I can't believe a simple agricultural electric fence could kill a multimeter. I'm astonished...astonished.

I'm going off somewhere quiet to cry.
 

Offline Kiriakos-GR

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I can't believe a simple agricultural electric fence could kill a multimeter. I'm astonished...astonished.

There is nothing simple to it ... you should had ask any older near by , so to take some advice !!
  
I'm going off somewhere quiet to cry.

There is no need for that ...  

We all have kill our first multimeter ...  :D
I bet that the second will live for ever ...
And If you get the same model , you will have some spare parts too.
Extra display and  housing plus leads , from the dead one ..  ;)
« Last Edit: October 20, 2010, 04:19:21 pm by Kiriakos-GR »
 

Offline Bored@Work

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So I started using it, I tested a 9V battery for ... Amps and that worked fine.

I call bullshit.
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Offline Sorry State

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So I started using it, I tested a 9V battery for ... Amps and that worked fine.

I call bullshit.

Explain?
 

Offline Mechatrommer

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So I started using it, I tested a 9V battery for ... Amps and that worked fine.
I call bullshit.
when reading that line, i thought that was what killing the DMM. yea! bullshit. how do you measure 9V in amp? thats how i kill my 1st MM ;)

edited: ammendment pls... there is possibility today's DMM can accept excess current (given that non excess voltage). mine was analog cheapy and killed by car's battery, not 9V. after 2 posts below, 4Amp max for 9V, then its may not be bullshit i think ;) sorry!
« Last Edit: October 20, 2010, 05:27:47 pm by shafri »
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Offline allanw

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It's just measuring the short circuit current of the battery. Nothing fishy about that...
 

Offline JohnS_AZ

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I don't know. I read somewhere that a dead short across a new alkaline 9V battery can provide around 4 amps, albeit for a very short amount of time. I presume a used 9V would be far far less. His meter MIGHT autorange to accept it. I know that my trusty olf Fluke 77 wouldn't on the low current scale (300ma).
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Offline Sorry State

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I don't know what the "bullshit" remark was for. As it says in the Subject headline I'm a total beginner. I touched the two probes to the terminals of the 9V battery and select Volts and then selected amps. I had to mess around with a couple cable position but I got a reading. Is that impossible? Wheres the conspiracy in that?
 

Offline allanw

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Right, it's not the best thing to try on the fused low current amp jack, but there's nothing wrong with trying it on the amps jack. It doesn't really have anything to do with how the multimeter died when applied to high voltage.

edit: to shafri's edit: a car battery is designed to provide a humongous amount of "cold cranking" current. Something like 500A+. A short across the battery will definitely kill whatever you used to short it with.
« Last Edit: October 20, 2010, 05:31:42 pm by allanw »
 

Offline Mechatrommer

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my last post ammended, sorry for my "premature thinking" ;)
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline saturation

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Sorry to read, Sorry State, as a last resort you might be able to return it to the vendor or maker for a warranty replacement, and say its just died.  Good luck!  You've nothing to lose.  I presume its brand new and still under full warranty.


I'm a real beginner. I treated myself to a UNI-T UT61D (as reviewed in the $100 test). So I started using it, I tested a 9V battery for Volts and Amps and that worked fine. Then I thought I'd test an agricultural eclectic fence. At first I had the red and black cables on the same piece of eclectic fence wire no great result so then I kept one cable on the electric fence and I touched the other cable to a non-electrified metal sheep wire fence under the eclectic fence. 

There was a slight click from the arc of the electric fence being short circuited (which is normal if you touch the fence with anything that will conduct.) Except the Multimeter has gone dead.

In the manual it has a way of testing to check if the fuses are blown, except it requires the display to work. But mine is just dead.

Could an electric fence really kill a Cat III 1000v multimeter? I am so p*ssed off right now.
Any help appreciated
Best Wishes,

 Saturation
 

Offline Bored@Work

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I don't know what the "bullshit" remark was for.

For lying to us (telling us bullshit, making up a story, also known as trolling). Or you are doing bullshit so carelessly that you should be lucky to be alive. Then consider the broken meter to be kind of an idiot tax you paid for being careless and giving a dam about what you are doing. And don't get me started on replacing the fuses with stronger ones. Really ...

Finally, don't give me that shit about being a beginner. This is no excuse for being stupid or for lying to us.
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Offline Strube09

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Calm down boredatwork... what is so unbelievable about what he said? Seems a bit rude to be discouraging people from the forum or the world of electronics.

You can short a 9V battery across a current shunt... probably didn't get more than a few amps anyways... at most he might have blown the fuse... but as he said it didn’t die until he used it on the fence which is very likely is what killed it.

Strube
 

Offline Sorry State

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I don't know what the "bullshit" remark was for.

For lying to us (telling us bullshit, making up a story, also known as trolling). Or you are doing bullshit so carelessly that you should be lucky to be alive. Then consider the broken meter to be kind of an idiot tax you paid for being careless and giving a dam about what you are doing. And don't get me started on replacing the fuses with stronger ones. Really ...

Finally, don't give me that shit about being a beginner. This is no excuse for being stupid or for lying to us.


(1) How am I lying to you? Why would any one make this up to 'troll'
(2) How is testing a 9v battery for voltage and amps so careless that I should be lucky to be alive
(3) How is testing an agricultural electric fence for voltage  so careless that I should be lucky to be alive. I've been touching that electric fence since I was a kid
(4) I just put the stronger fuses in to see if I could get the display to come alive... like I said they were temporary.

Me Stupid? I think my efforts today prove that. Lying to you? No

But thanks for your help. Appreciate it
« Last Edit: October 20, 2010, 06:21:53 pm by Sorry State »
 

Offline Simon

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time to cool it maybe, if you think the discussion is such a waste of time simply stop replying.

Testing a batteries "amps" cannot be done, because you are shorting it, I think it's often done I did it too on my first meter, if you do it with a big battery yes at least your fuses will blow.

The fence wont deliver much power but that sort of voltage will jump through the air and parts made with sensitive CMOS technology will just be killed off by even a small current
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Offline Sorry State

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The fence wont deliver much power
That's exactly what I had figured seeing as touching is 'the recommended use' of the fence.


but that sort of voltage will jump through the air

Now that I don't understand at all. I presumed the fuses would have protected any delicate CMOS technology. i don't understand how the fuses failed to protect the thing.
 

Offline allanw

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The fuses are only there to limit the current when measuring amps. There's nothing like an easily replacable fuse to protect the circuitry from high voltages.

The multimeter can probably be fixed if they won't take it for warranty. There's input protection circuitry that might be replacable.
 

Offline Strube09

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fuses are current limiting devices. We know that the fence will limit the current (As not to cook your cow leaning against it).

The voltage if great enough can arc across a blown fuse. Also they the voltage may have worked itself into a cmos IC that won't hand this kind of voltage.

To protect against voltage most inputs have MOV (metal oxide varistors) or some other voltage protection devices (Tyristors Zeners...). However even those have their limits.

 

Offline Bored@Work

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It is about taking responsibility for your own actions and cutting your losses, instead of telling bullshit and blaming everyone except your own stupidity.

And I am disgusted by some commenters suggesting the criminal act of defrauding the seller by simply returning the instrument under warranty. No, that isn't clever or cool. It is plain and simple fraud.
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Offline Simon

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I forget the figure but a spark or arc will occur if there are "x" amount of volts per cm, the fuses are useless against high voltage and the voltage could jump from PCB track to PCB track until it got into something delicate and blew it. you don't need much current to blow a cmos IC, a few mA at 10'000 vots will certainly send it to IC heaven, but your fuse will not blow at a few mA as it is meant to blow at a little over the max the meter can take
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Offline Sorry State

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To protect against voltage most inputs have MOV (metal oxide varistors) or some other voltage protection devices (Tyristors Zeners...).

They don't sound like (amateur) user replaceable parts?
 

Offline Simon

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It is about taking responsibility for your own actions and cutting your losses, instead of telling bullshit and blaming everyone except your own stupidity.

And I am disgusted by some commenters suggesting the criminal act of defrauding the seller by simply returning the instrument under warranty. No, that isn't clever or cool. It is plain and simple fraud.

agreed, the warranty should not cover this as the instrument was used outside of it's specifications, lesson learnt ? good, don't do it again
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Offline Sorry State

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It is about taking responsibility for your own actions and cutting your losses, instead of telling bullshit and blaming everyone except your own stupidity.

A couple of posts ago you were claiming my post was all lies, now you believe it? Haven't blamed anyone but myself.

Helpful as always. Cheers.
 

Offline Strube09

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To protect against voltage most inputs have MOV (metal oxide varistors) or some other voltage protection devices (Tyristors Zeners...).

They don't sound like (amateur) user replaceable parts?

These types of devices (provided they are not bad) are intended to automatically reset once the fault is cleared.  I am not sure the UNI has these on the inputs as they should have reset and your device would have powered back up... sound like it has gotten into the main controller of the unit.

I think you are probably out of luck.... but always keep it for parts you may need to replace the display on a future unit.
 

Offline Time

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Yep, 33,000 V/cm is the breakdown field strength of air at standard temperature and pressure.  So if you put 33,000 volts across a 1 cm gap it will breakdown.  Inside of a multimeter the field strengths between traces needed to breakdown are even less because the arcs can track along the surfaces, known as surface flashover.  Even further complicating the situation and raising the probability of breakdown are the points inside the meter where air, metal, and dielectric meet.  These points are called triple points and provide dense amounts of free electrons under HV excitation which can initiate a surface flashover event, making it even easier to break the device.

Gas discharge processes like surface flashover and volume discharge are somewhat chaotic and slow processes, so under pulsed excitation it takes larger field strengths for them to occur compared to a DC excitation.  This is why he probably doesn't see any visible carbon tracking (burns) from the failure because the pulses from the fence probably just blew up the first solid state device they ran into, internally.
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Offline Sorry State

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but always keep it for parts you may need to replace the display on a future unit.


No, I don't think I'm going to get another one. I've gone right off the idea of a multimeter. :(
 

Offline Kiriakos-GR

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No, I don't think I'm going to get another one. I've gone right off the idea of a multimeter. :(

I think, that this is an good idea for now ...  If you ever get some training in the years to come ,
about becoming electrician or in electronics , at that time you will be more wise to handle such matters..

But I like to thank you , for a good reason .... suddenly you reminded to all of us, where we can find "True high voltage "  ,  because some they get confused with the Mains ( voltage on your wall plug) , and they considered it as master danger , for the multimeter's !!  

Take care ..   ;)  
And stay away of the electricity .. as all wise people do.  

 

« Last Edit: October 20, 2010, 08:19:21 pm by Kiriakos-GR »
 

Offline Strube09

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I disagree with Kiriakos. I think you should get a new meter and you should get back to experimenting. The only thing I would say is stay away from mains and other high voltage high amperage circuits until you get some better understanding.

I think it is important to never discourage curiosity. Where would this world be today if people just told you that unless you have training then you should just stay away?

I say if you are curious about electronics and electricity pick up a basic electronics book and a new meter and get to experimenting.

No, I don't think I'm going to get another one. I've gone right off the idea of a multimeter. :(

I think, that this is an good idea for now ...  If you ever get some training in the years to come ,
about becoming electrician or in electronics , at that time you will be more wise to handle such matters..

But I like to thank you , for a good reason .... suddenly you reminded to all of us, where we can find "True high voltage "  ,  because some they get confused with the Mains ( voltage on your wall plug) , and they considered it as master danger , for the multimeter's !!  

Take care ..   ;)  
And stay away of the electricity .. as all wise people do.  

 


 

Offline Nermash

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My advice would be to get a new meter, stick with 9v battery and nothing above, and try to read up on the basics of voltage, current, and move on from there. And best advice I've read here before in someone's post: always use your best instrument first - your brain!
If you persist, soon you will know what happened to your meter and why it happened :)
Never stop experimenting, just use common sense question before you plug something in "Can it kill me, injure me or just cost me money?"
 

Offline Mechatrommer

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looking back at the original post, came to this line...
"Could an electric fence really kill a Cat III 1000v multimeter? I am so p*ssed off right now."

then who you are pissed off at? the uni-t? the fence? or yourself? if you are me, then i will choose pissed off at myself for not learning more before doing stuffs. ;) i believe you are not talking bullshit here, just expressing your experience (just as what i've experienced long ago). Cheers. ;)

so after you "painful scar' cool down, when you are ready to continue the quest of EE, you may get another DMM, and be prepared to study beforehand whats the DMM can do or not, how to measure amperage correctly etc. Dave's $100 shootout video alone will not do any good. It implied a sound knowledge at hand. You are quite luxurious though getting $100 DMM as you first and eventually killed it as most of us here did. Mine was a $3 AMM ;D So next time, maybe you'll get $300 DMM as your serious DMM ;), BUT... there is a big "BUT"... only when the time comes, NOT tommorow ;) (Mine currently is the Uni-T 71A, still in the $100 range, so i'm too a beginner! :D)

ps: it will be a nice experiment though to see how much high V the fence got. you may start getting the life-neutral/earth wires close together (using alligator clips cable perharps?). So if the figure is right, 10KV fence at 33KV/cm air dielectric. you should see an arc jump (spark) across wires through air at about distance 0.3cm (3mm). on the big scale, its the lightning you saw between clouds and earth. and also, probably thats what was happening in your dmm circuitry or even on the broken fuse. i've seen clearly this kind of nasty spark bypassing a resistor in electronics circuit. and i always ask my brothers/friends to earth their body before fiddling with my stuffs, i tell them, they can electrocute the circuit (static), not the other way around people usually understand it. so i think u should earth yourself after doing the fence experiment before doing any other EE related job.

well, mumble jumble here... got nothing to do at work ;)
« Last Edit: October 21, 2010, 12:38:49 am by shafri »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Kiriakos-GR

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I disagree with Kiriakos. I think you should get a new meter and you should get back to experimenting. The only thing I would say is stay away from mains and other high voltage high amperage circuits until you get some better understanding.

I think it is important to never discourage curiosity. Where would this world be today if people just told you that unless you have training then you should just stay away?

I say if you are curious about electronics and electricity pick up a basic electronics book and a new meter and get to experimenting.


No matter if you liked my advice or not ,  some things its a matter of age ..
One green tomato no matter how much red paint some one will use on it, its no good for salad ..

Ask first the age of the person that you give advices to ..

Thanks.
« Last Edit: October 21, 2010, 12:47:46 am by Kiriakos-GR »
 

Offline Sorry State

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For what its worth I found out that the output voltage of the electric fence is 7,500 volts at approximately 2mA.

Anyway I'd like to thank you guys for helping me and providing feedback. While I have some rudimentary understanding of electronics  (I  specifically choose the 9v battery and the electric fence to experiment on as there was no danger whatsoever to me)  I had no idea that an agricultural electric fence had such a high voltage.

Thanks again.
 

Offline Mechatrommer

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7.5K x 2m = 15W. is it enuf to make us pain? seems small to me. i think if its like, 1000W (just for a moment) then it will feel something :D how much does it take to stop the heartbeat? or the safe margin for the body to take? just a thought.
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Offline Zero999

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The fence will also produce the power in pulses so the power will be much lower, probably 100s of mW.

I'd recommend buying a new meter and using it for low voltage, low energy sources (i.e. a small 9V battery, mains adaptor, not a car battery or the mains) but learn more (especially electrical safety) it before doing anything with it. By the way mains is not high voltage, it's low voltage. High voltage is generally any voltage high enough to cause significant arcing between conductors, typically anything above 600V or 1500VDC depending on which standards you're into, anything below that is low voltage.

Extra low voltage (ELV under 120VDC or 50VAC) is low risk and is unlikely to cause death although it will shock you, anything under 60VDC or 25VAC is generally considered harmless unless you're really wet, in which case no voltage is completely safe, although under 12VAC or 30VDC is unlikely to cause a lethal shock to even wet skin. Generally DC voltages are safer than mains frequency AC because the peak voltage is lower and the body responds differently to DC than AC. Higher frequency AC (above 20kHz or so) is generally safer than both DC and low frequency AC because it doesn't shock, although it can cause deep burns.

In informal use people often talk about low voltage as being on the lower end of ELV, typically below 60VDC or 30VAC and high voltage being anything above that but it's good to know the proper definitions. It's important to know that even really low voltages can be hazardous if the source has a low impedance (i.e. a car battery) because a large current can flow which can cause severe burns and batteries can explode. This is why I prefer the term low voltage, low energy source to denote sources of electricity which pose minimal risk.

I blew my first DVM too by trying to measure the output voltage of a DC fluorescent tube ballast without the tube connected. Fortunately the meter wasn't rendered totally useless and still worked on the DC settings. In the end I gave it to a friend who only wanted to use it to measure the DC voltage on
 

Offline Simon

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7.5K x 2m = 15W. is it enuf to make us pain? seems small to me. i think if its like, 1000W (just for a moment) then it will feel something :D how much does it take to stop the heartbeat? or the safe margin for the body to take? just a thought.

it's not about power (watts) it's about the voltage and amperage. 7'500V will blow most IC's if applied to any pin even at uA it will just cause semiconductor junctions to break down. cmos chips use nA or uA for each transistor in the chip, so 2mA @ 7.5 KV will be plenty to blow the circuitry on any IC pin
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Offline Mechatrommer

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it's not about power (watts) it's about the voltage and amperage. 7'500V will blow most IC's if applied to any pin even at uA it will just cause semiconductor junctions to break down. cmos chips use nA or uA for each transistor in the chip, so 2mA @ 7.5 KV will be plenty to blow the circuitry on any IC pin
hehe! i was not so clear, sorry... i mean to human or animal, not the chip. for the chip, i know even our own static (high V with insignificant A) may cause it to damage. ;)
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Kiriakos-GR

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Well this multimeter will do  5KV ,  for 10KV use two multimeter s,  in series ..    :D   :D   :D


 

Offline saturation

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Some kV items sold in the consumer market:

piezo electric lighters or igniters for gas ovens

dog collar trainers

Tazer guns

electronic bug killers
Best Wishes,

 Saturation
 

Offline Time

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Inside a conventional microwave oven there is a 2 kV AC transformer.  Part this out, add a diode, add some HV caps, and finally a HV SCR and have fun "blowin' shit up". 

Be careful not to kill yourself.
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Offline Fraser

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That last comment made me shiver... I know you may have been kidding but...........

Anyone who is not familiar with the workings of the Microwave oven..... PLEASE do not use it or it's parts in experiments unless/until you learn about the correct safety procedures and take precautions.

I still break into a sweat when working on RADAR magnetrons and Microwave Ovens PSU's. There are absolutely no second chances if you get across the transformer HT winding or smoothing capacitor. The HT will happily punch straight through a set of old (degraded)  or inadequate test leads and I am personally aware of two deaths in the UK as a result. If you get it wrong on the HT supply, you die, no maybe about it. The reason is simple.... microwave ovens power high energy magnetrons using HT voltages at deadly currents. The HT capacitor will store enormous amounts of energy (in terms of Joules) and, if allowed to, release it into a victims body tissues at HT voltage and unrestricted current...... your heart will beat no more. Remember, it is the current that actually kills .... you just need a high enough voltage to set up conduction.

For those reading this with knowledge of the voltages and currents inside a microwave oven you will already know the dangers, but I beg those without the knowledge to not experiment or tinker with these things internals.  

And finally.... Anyone who thinks 110V is 'safe' just check out the domestic accident electrocution figures for the USA.... 110V ac can still kill if across your chest (arm to arm). We don't mess around with the light weight stuff here in the UK, we go the whole hog and use 240V ac to ensure quality conduction through peoples bodies ! It's a form of natural selection....  Also known as the Darwin effect for which a victim may win one of the famous Darwin Awards.

Sorry, a bit of a heavy posting but with good reason.
« Last Edit: October 21, 2010, 08:17:14 pm by Aurora »
 

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Offline Simon

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I am a firm beleiver in natural selection  :D
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Offline djsb

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Yep, 33,000 V/cm is the breakdown field strength of air at standard temperature and pressure.  So if you put 33,000 volts across a 1 cm gap it will breakdown.  Inside of a multimeter the field strengths between traces needed to breakdown are even less because the arcs can track along the surfaces, known as surface flashover.  Even further complicating the situation and raising the probability of breakdown are the points inside the meter where air, metal, and dielectric meet.  These points are called triple points and provide dense amounts of free electrons under HV excitation which can initiate a surface flashover event, making it even easier to break the device.

Gas discharge processes like surface flashover and volume discharge are somewhat chaotic and slow processes, so under pulsed excitation it takes larger field strengths for them to occur compared to a DC excitation.  This is why he probably doesn't see any visible carbon tracking (burns) from the failure because the pulses from the fence probably just blew up the first solid state device they ran into, internally.

Are there any references or other sources of information on high voltages? It could be useful so people can do their own research and become more informed on what to expect.

David
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Offline saturation

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http://en.wikipedia.org/wiki/High_voltage

It has all the basic elements for anyone to read more after.

Yep, 33,000 V/cm is the breakdown field strength of air at standard temperature and pressure.  So if you put 33,000 volts across a 1 cm gap it will breakdown.  Inside of a multimeter the field strengths between traces needed to breakdown are even less because the arcs can track along the surfaces, known as surface flashover.  Even further complicating the situation and raising the probability of breakdown are the points inside the meter where air, metal, and dielectric meet.  These points are called triple points and provide dense amounts of free electrons under HV excitation which can initiate a surface flashover event, making it even easier to break the device.

Gas discharge processes like surface flashover and volume discharge are somewhat chaotic and slow processes, so under pulsed excitation it takes larger field strengths for them to occur compared to a DC excitation.  This is why he probably doesn't see any visible carbon tracking (burns) from the failure because the pulses from the fence probably just blew up the first solid state device they ran into, internally.

Are there any references or other sources of information on high voltages? It could be useful so people can do their own research and become more informed on what to expect.


Best Wishes,

 Saturation
 

Offline Time

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Honestly, I can't think of any readily available online sources that address high voltage safety other than what one could find by just googling it.  Most of what I know comes from my time with my practical work and schooling (expensive text books :( ).  I spent a few years studying plasma discharge physics and just kind of picked up the know how through tinkering and exposure to high voltage, high energy systems (the kind used to generate plasma discharges).  I have been shocked many times over by something as low as the mains (I don't even know how many times, getting mains shocked is barely noticeable sometimes - its just a gradual tingle) to as much as 70 kV in my hand (definitely notice this as voltage of this magnitude will make a large pop sound and stings worse than any other sting I have ever felt).

The best advice I have for anyone handling anything live or charged is use one hand to touch the system.  A gloved hand, preferably.  i.e. If you are dealing with a large system don't lean over the chasis and support your weight on it with one hand and reach into the device with another.  Since the chasis is normally the reference potential for the dangerous voltages, your wandering hand suddenly becomes a lightning rod with your heart as the load.  If you use 2 hands than you can risk the current going across your chest and through your heart.  Using one hand is not even fail safe though. It takes very little current across the heart to kill you.  You can take much more current through less significant appendages and only receive painful burns or shock.  Though if its a large enough system it could very well dismember whatever its discharged through (yikes).  Another good rule is never lose your fear with what you are dealing with and relax when handling dangerous or live systems.  A lot of people in this kind of work become desensitized to the danger from their day to day dealings with these kinds of systems and relax causing them to become unattentive and careless.

-Time
 

Offline Kiriakos-GR

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Honestly, I can't think of any readily available online sources that address high voltage safety other than what one could find by just googling it. 


I have not find either on-line training for any true profession , soooo  they it must teach all those at those large white square buildings called as technical schools and universities .   ;)
 

Offline PetrosA

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About 20-30 mA is all the heart can take. Class A GFCI (personnel) protection in the US is designed to shut off at ~5 mA. RCD protection in EU countries doesn't kick in till about 30 mA and is only designed to protect equipment.

Even I've made dumb mistakes before. I used my Agilent once to check the output of a HID socket not thinking that without a bulb in it and running, the ignitor was outputting 4 kV pulses. The Agilent survived, my pride was humbled ;) Interestingly, the Agilent wouldn't give a voltage reading on the pulse and the display flashed all kinds of numbers while a Fluke settled down at an incorrect 200V reading.
« Last Edit: October 22, 2010, 03:43:39 am by PetrosA »
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Offline Simon

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well in the EU a 30mA RCD is supposed to be the life saver, I think it takes 30mA to turn off fastest but will still kick off with lower currents taking more time to do so. 100mA is for equipment protection only and that's what some dick head put in my house before i bought it.
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Offline Jon Chandler

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My first meter was a $7 analog meter from RadioShack.  Amazing that the arcing from connecting it across a 750 VAC high voltage supply for a tube circuit in ohms mode can be seen through the case.  The burned electronics smell was overpowering too!

At least that was a cheaper lesson.
 

Offline Zero999

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For those reading this with knowledge of the voltages and currents inside a microwave oven you will already know the dangers, but I beg those without the knowledge to not experiment or tinker with these things internals.  
Yes, a microwave oven is certainly the most dangerous household appliance. People often go one about supposedly deadly 25kV old CRT TV tubes which are really quite low risk, the low voltage (300V to 600V) stored in other capacitors around the TV set is the real hazard.

Quote
And finally.... Anyone who thinks 110V is 'safe' just check out the domestic accident electrocution figures for the USA.... 110V ac can still kill if across your chest (arm to arm).
I think this is directed at my remark about voltages below 50VAC or 120VDC being classed as extra low voltage which is fairly low risk. I think you missed the fact I said 120VDC not 120VAC 50Hz or 60Hz which is much more dangerous. Of course 50VAC or 120VDC can kill as well, it's just unlikely so appliances designed to work from such voltages are designated as class 3 so don't need to conform to the same standards as those connected to low voltage mains power.

Don't forget that AC is really 1.414 times the RMS voltage and the human body is more sensitive to 50/60Hz AC than it is to steady DC, so from the US mains you're really receiving a 170V shock not a 120VAC shock and the changing current is interfering with your heartbeat more than steady DC.
 

Offline Kiriakos-GR

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Don't forget that AC is really 1.414 times the RMS voltage and the human body is more sensitive to 50/60Hz AC than it is to steady DC, so from the US mains you're really receiving a 170V shock not a 120VAC shock and the changing current is interfering with your heartbeat more than steady DC.

I need to see the scaned page of the book that says such things ..
 

alm

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Edit: Never mind, poor reading on my part.
« Last Edit: October 22, 2010, 02:20:20 pm by alm »
 

Offline gonnafail

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Well the 1.41 times the RMS voltage is definitely correct. I cannot comment on the human body being more sensitive to AC than DC but its plausible in my opinion.
A quick google search gave me multiple sources that stated the same saying anywhere from 5 to 10 times more sensitive to AC. Sometimes a google search can be faster than a post calling someone out.
 

Offline allanw

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alm

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I cannot comment on the human body being more sensitive to AC than DC but its plausible in my opinion.
Agreed. More current will flow (reactive impedance is likely to be lower at 50/60Hz than resistive impedance), and it's in the same order of magnitude as the heartbeat. Can't imagine that it's hard to find references in medical journals about electrocution with DC and 50/60Hz if anyone is so inclined.
 

Offline Fraser

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 Hero999,

Thanks for the comment... please be assured my comment was not aimed specifically at your statement... it was really highlighting what I have heard many times from people who believe the 110/120VAC mains system is 'safe' or 'safer' whereas they believe the UK's 240VAC system is dangerous... an interesting concept that I personally would not wish to test on myself  ;) I was trained to respect all voltages, but for differing reasons.

An example of which was a colleague who decided to investigate an oil leak on his car. Whilst delving around the engine he managed to get his stainless steel watch strap across the starter motor solenoid terminals. 12V at hundreds of AMPS flowed through it instantly turning it into a heating element. He reported that the pain was excruciating and the smell ghastly as the watch strap melted itself into his wrist. Imagine… the strap links and release catch had welded together so it was not removable and was red hot until he could get to water :(  He still bears the scar to remind him of his mistake.

I think it has already been said here.... before people start 'playing' with test kit on live circuits they should know the possible risks and consequences in order to stay safe. I am certainly not perfect  ;D I managed to get some pretty nasty 240VAC belts on my hands whilst live working on mains powered CRO's, amplifiers and the like. The 240VAC shocks made my arm ache for some time after, but the 100 to 300 VDC valve anode shocks I also experienced just stung a bit. I was a teenager at the time so learnt my lesson well before being released on the professional world.
« Last Edit: October 22, 2010, 06:23:40 pm by Aurora »
 

Offline Zero999

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I need to see the scaned page of the book that says such things ..
Better still, I can provide a link to a good book on Google:

http://books.google.co.uk/books?id=B0aPhJn0YcAC&pg=PA963&lpg=PA963&dq=let-go+current+shock&source=bl&ots=eELpQzCycv&sig=xMzkz9AeJWLghhYrWU7B4Sa4VS4&hl=en&ei=SejpSajnJcONjAf64LibCg&sa=X&oi=book_result&ct=result&resnum=5#v=onepage&q=let-go%20current%20shock&f=false

Here are some more links:
http://www.pat-testing.info/electric-shock.htm
http://www.esdjournal.com/techpapr/elechazd/ehaz.htm
http://www.health24.com/medical/Condition_centres/777-792-2557-2577,15144.asp

Agreed. More current will flow (reactive impedance is likely to be lower at 50/60Hz than resistive impedance), and it's in the same order of magnitude as the heartbeat. Can't imagine that it's hard to find references in medical journals about electrocution with DC and 50/60Hz if anyone is so inclined.
Actually it's got nothing to do with the reactive impedance, the human body is a poor conductor so the resistance will be the dominant component of the impedance.

One myth I encounter often is that high frequency AC is less dangerous because of the skin effect which is not true because the human body is a poor conductor so the skin depth is very deep. If the skin effect offered considerable protection then a microwave oven would only heat meat on the surface, like a grill but in reality it penetrates quite deeply.

Thanks for the comment... please be assured my comment was not aimed specifically at your statement... it was really highlighting what I have heard many times from people who believe the 110/120VAC mains system is 'safe' or 'safer' whereas they believe the UK's 240VAC system is dangerous... an interesting concept that I personally would not wish to test on myself  ;) I was trained to respect all voltages, but for differing reasons.

I agree. I think part of the problem is that in the UK 110VAC is used on building sites for safety reasons and is classed as reduced voltage. The reason why the 110VAC used in the UK is safer than that used in the US is because in the UK it's derived from a centre tapped transformer or two phases of a three phase transformer so the maximum voltage with respect to earth is 55V (single phase) or 63.5V (threes phase), in the US 110V is 110F with respect to earth so is much more dangerous.
 

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Agreed. More current will flow (reactive impedance is likely to be lower at 50/60Hz than resistive impedance), and it's in the same order of magnitude as the heartbeat. Can't imagine that it's hard to find references in medical journals about electrocution with DC and 50/60Hz if anyone is so inclined.
Actually it's got nothing to do with the reactive impedance, the human body is a poor conductor so the resistance will be the dominant component of the impedance.
Your point that impedance at DC and 60Hz is the same may be valid, I couldn't find a proper reference in the few minutes I had available (the Google Books link doesn't work anymore, and the other links didn't mention impedance), but I don't see how your argument supports this. The ideal capacitor has an infinite DC resistance, but depending on capacitance, may have a low reactive impedance. PTFE is a pretty poor conductor, but that doesn't mean that it will dominate the impedance in a PTFE capacitor with an AC signal applied.

Also, the human (dry) skin is a pretty poor conductor, the rest of the body is not as far as I know, and is often considered a good conductor compared to the skin in models of the human body.

One myth I encounter often is that high frequency AC is less dangerous because of the skin effect which is not true because the human body is a poor conductor so the skin depth is very deep. If the skin effect offered considerable protection then a microwave oven would only heat meat on the surface, like a grill but in reality it penetrates quite deeply.
I don't follow this argument either. A microwave oven is about absorption of an electrical field, it's not the induced currents that are dangerous, but the energy (heat). With RF burns, the opposite is the case: the heat is generated by the current, since the body doesn't absorb most of the RF spectrum very well.
 

Offline Time

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One myth I encounter often is that high frequency AC is less dangerous because of the skin effect which is not true because the human body is a poor conductor so the skin depth is very deep. If the skin effect offered considerable protection then a microwave oven would only heat meat on the surface, like a grill but in reality it penetrates quite deeply.


Ehhhhh, I can't disagree with this statement but the physicist in me is not sure the microwave oven analogy is a good one.  Yes, the skin depth is deeper on a more resistive element but in some cases when the magnetic permeability of something is high enough than the skin depth is shallow.  Consider iron vs. copper in this case.  Iron is more resistive than copper but is a terrible high frequency conductor because of its magnetic properties.  The higher the permeability of something the longer it takes the magnetic field from the current to penetrate the material.  This limits the current flow to the 'skin' of the conductor.

A convential microwave oven heats materials by producing microwaves at frequencies that cause molecular bond structures to harmonically resonate with the oscillating electric field component of the microwaves.  This frequency is usually optimized around the OH in H20 since water is present in all foods.  A good conducting material will heat or cause sparks because the electrons in the material are easily influenced by the field and allowed to move inside the conductor to oppose the influence of the e-field (more so, no electric field can exist in a conductor which gives rise to some complicated boundary conditions in the case of EM theory which I dont know how to describe without differential equations).

Yes, microwave energy does not penetrate a good conductor and yes it penetrates a poor conductor more thoroughly but the governing phenomenon is different than what gives rise to the skin effect.  I don't know if any of that even makes sense.  I have already rambled a lot on this thread.

edit:

In regards to alms post below, tissue is a dielectric just as PTFE.  Dielectrics and insulating materials behave differently than materials with any considerable amount of bulk conductivity.
« Last Edit: October 22, 2010, 07:54:56 pm by Time »
-Time
 

Offline Zero999

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Your point that impedance at DC and 60Hz is the same may be valid, I couldn't find a proper reference in the few minutes I had available (the Google Books link doesn't work anymore, and the other links didn't mention impedance), but I don't see how your argument supports this. The ideal capacitor has an infinite DC resistance, but depending on capacitance, may have a low reactive impedance. PTFE is a pretty poor conductor, but that doesn't mean that it will dominate the impedance in a PTFE capacitor with an AC signal applied.

Also, the human (dry) skin is a pretty poor conductor, the rest of the body is not as far as I know, and is often considered a good conductor compared to the skin in models of the human body.
I wasn't intending to back up my argument regarding impedance of the human body, just reinforcing what I was saying about the effects of AC vs DC current on the human body being the reason why power frequency AC is more dangerous than DC.

You're right about the impedance of dry skin increasing the reactive component, but if the skin is dry not much current will flow at 50/60Hz because the capacitance will be really low, probably under 100pF. I don't have any information on the permittivity of human skin but I doubt it's high enough to make the capacitance high enough to allow a significant current to flow, if it was it would be used to make capacitors :D. At higher frequencies, it's true a significant current can flow due to capacitive coupling but at those frequencies the nerves won't be sensitive to shock so it's low risk. Besides, at low frequencies the insulating properties of the skin have to be compromised anyway to allow a harmful current to flow and damp or carbonised skin will have very poor dielectric properties.

Quote
I don't follow this argument either. A microwave oven is about absorption of an electrical field, it's not the induced currents that are dangerous, but the energy (heat). With RF burns, the opposite is the case: the heat is generated by the current, since the body doesn't absorb most of the RF spectrum very well.
You're right there to but if the skin depth of flesh was very shallow the radiation wouldn't penetrate the surface so it would work like a grill.

Ehhhhh, I can't disagree with this statement but the physicist in me is not sure the microwave oven analogy is a good one.  Yes, the skin depth is deeper on a more resistive element but in some cases when the magnetic permeability of something is high enough than the skin depth is shallow.  Consider iron vs. copper in this case.  Iron is more resistive than copper but is a terrible high frequency conductor because of its magnetic properties.  The higher the permeability of something the longer it takes the magnetic field from the current to penetrate the material.  This limits the current flow to the 'skin' of the conductor.
Human flesh has a low permeability so I don't see what your point is there.

Quote
A convential microwave oven heats materials by producing microwaves at frequencies that cause molecular bond structures to harmonically resonate with the oscillating electric field component of the microwaves.  This frequency is usually optimized around the OH in H20 since water is present in all foods.  A good conducting material will heat or cause sparks because the electrons in the material are easily influenced by the field and allowed to move inside the conductor to oppose the influence of the e-field (more so, no electric field can exist in a conductor which gives rise to some complicated boundary conditions in the case of EM theory which I dont know how to describe without differential equations).

Yes, microwave energy does not penetrate a good conductor and yes it penetrates a poor conductor more thoroughly but the governing phenomenon is different than what gives rise to the skin effect.  I don't know if any of that even makes sense.  I have already rambled a lot on this thread.
That's another myth, the frequency of microwave radiation has nothing to do with the resonance of water and everything to do with the skin depth and dimensions of a microwave oven. Liquid water has no strong resonant peaks because any resonance is damped by the hydrogen bonds fixing each molecule to its neighbour. Only gaseous water has strong resonant modes because the molecules are free enough to move and the 2.45GHz used in a microwave oven is an order of a magnitude too low to excite any resonance.

http://amasci.com/weird/microwave/voltage3.html
http://www.zyra.org.uk/microw.htm

« Last Edit: October 22, 2010, 08:31:26 pm by Hero999 »
 

Offline Time

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Ehhhhh, I can't disagree with this statement but the physicist in me is not sure the microwave oven analogy is a good one.  Yes, the skin depth is deeper on a more resistive element but in some cases when the magnetic permeability of something is high enough than the skin depth is shallow.  Consider iron vs. copper in this case.  Iron is more resistive than copper but is a terrible high frequency conductor because of its magnetic properties.  The higher the permeability of something the longer it takes the magnetic field from the current to penetrate the material.  This limits the current flow to the 'skin' of the conductor.
Human flesh has a low permeability so I don't see what your point is there.

Quote
A convential microwave oven heats materials by producing microwaves at frequencies that cause molecular bond structures to harmonically resonate with the oscillating electric field component of the microwaves.  This frequency is usually optimized around the OH in H20 since water is present in all foods.  A good conducting material will heat or cause sparks because the electrons in the material are easily influenced by the field and allowed to move inside the conductor to oppose the influence of the e-field (more so, no electric field can exist in a conductor which gives rise to some complicated boundary conditions in the case of EM theory which I dont know how to describe without differential equations).

Yes, microwave energy does not penetrate a good conductor and yes it penetrates a poor conductor more thoroughly but the governing phenomenon is different than what gives rise to the skin effect.  I don't know if any of that even makes sense.  I have already rambled a lot on this thread.
That's another myth, the frequency of microwave radiation has nothing to do with the resonance of water and everything to do with the skin depth and dimensions of a microwave oven. Liquid water has no strong resonant peaks because any resonance is damped by the hydrogen bonds fixing each molecule to its neighbour. Only gaseous water has strong resonant modes because the molecules are free enough to move and the 2.45GHz used in a microwave oven is an order of a magnitude too low to excite any resonance.

http://amasci.com/weird/microwave/voltage3.html
http://www.zyra.org.uk/microw.htm



The point was not refuting your argument against its occurence in tissue.  I was just explaining the phenomenon and than going on to explain why its not the same as what is occuring in microwave heating.  

Oxygen is inherently very electronegative so its presence in a molecule usually causes a net charge distribution across the molecule.  Any bond with a charge distribution will move in some manner under the influence of a field , of course.  Anything with movement will have an inertia or momentum and momentum transfer with surrounding molecules (thermal transfer) and because of this a frequency (or range of frequencies) can be optimized for the most ideal energy transfer from these movements.  By resonating and harmonic I was not refering to spectroscopic data and peaks like the literature you presented refers to (nice mickey mouse color schemes, by the way :P ).  Anyhow, all your sources even go to say "microwaves work because they shake water up" and shaking water up has nothing to do with the skin effect.  Skin effect refers to electron flow.  Microwave heating in a non-conducting material has nothing to do with electron flow.
« Last Edit: October 22, 2010, 09:21:24 pm by Time »
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Offline Time

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http://www.martin.chaplin.btinternet.co.uk/microwave.html

Excellent link.  It was a citation in your first source, Hero.

The electromagnetic penetration portion might be more what you are refering to.  Dielectric loss tangents are not the same as skin effect.  The loss factor which is dependent upon relative dielectric constant which is largely governed by water, especially in food.
« Last Edit: October 22, 2010, 09:16:18 pm by Time »
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Offline Simon

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I used to have a 24V AC/DC power supply i made from salvaged parts from a TV, at 24VDC I could feel nothing, at 24VAC I could feel a tingle in my fingers
https://www.simonselectronics.co.uk/shop
Varied stock of test instruments and components including EEVblog gear and Wurth Elektronik Books.
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Offline Zero999

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Skin effect refers to electron flow.  Microwave heating in a non-conducting material has nothing to do with electron flow.
Yes, indeed non conductive fats can be heated in a microwave.

Nice links by the way, I'll remember next time I have this discussion. :D

I used to have a 24V AC/DC power supply i made from salvaged parts from a TV, at 24VDC I could feel nothing, at 24VAC I could feel a tingle in my fingers
I'm not surprised, the IEE regulations state that in dry areas, all voltages above 25VAC need to be insulated but DC voltages up to 60VDC don't need to be insulated.
 

Offline Time

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Skin effect refers to electron flow.  Microwave heating in a non-conducting material has nothing to do with electron flow.
Yes, indeed non conductive fats can be heated in a microwave.

Nice links by the way, I'll remember next time I have this discussion. :D


Yep.  They can be heated because of their hydroxyl groups (OH attached to some other organic compound).  I was going to make this point to further my OH bond claim but I decided not to bring organic chem to a physics discussion on an electrical engineering forum.  Its just a coincidence that the link I posted down below mentions it directly in a footnote.
-Time
 

Offline Kiriakos-GR

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Handbook of psychophysiology  !!!

 ;D  ;D  ;D    oh my what the people are reading this days ...

Yes talking for Mars , with out to have even get there , its an easy task ..
 

Offline Hypernova

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Man this thread takes me back to something incredibly retarded I did when I was a teen with MORE POWER stamped all over me brain.

Cliffs:

1) Boy finds broken microwave  :D
2) Boy extracts the transformer out of said microwave.  ;D
3) Boy hooks up low side to the mains.  ???
4) Boy tries to measure the voltage on the other end.  :o

It's a damn miracle how I didn't die right then and there that day. Only my multimeter blew. Ironically it was an award from Dick Smith from my high school electronic class for something I built.
 

Offline Kiriakos-GR

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Well,  from my prospective , 
by trying  to get-rid all "your own"  responsibility ( nothing personal)  about safety , on to an instrument that was build to be used by people with common experience about such matters ..   

Makes my brain to explode .. simple as that .  :) 
 

Offline david77

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Just wanted to say something about RCD's. They do not switch off slower at a smaller leakage current!
A 30mA RCD kicks in at about 25-30mA leakage, depending on make.
In most EU countries a 30mA RCD is only required in new installations, there are still millions of homes
without RCD protection. I love the RCD in my workshop, it has saved me from some nasty bites.
You can get them with 10mA IdeltaN, too, if you want to play it safe. Some electricians I know recommend
a dedicated 10mA RCD for bathrooms.

The problem is "normal" people don't understand what a RCD does, and that it is different to fuses or MCB's.
Add to that the cost of 40-50 EUR and the cost of installation and you can imagine how many people have
one installed...
 

Offline Fraser

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A little off the topic but I thought I'd chuck it into the conversation.....

Just like the saying regarding ladders.... it's not the falling that hurts it's the stopping when you hit the ground  ;D

People have been seriously injured and even killed when they have been testing a non lethal voltage/current combination whilst working at height... they get a good shock that startles them, they lose balance and fall.... the fall distance and what they hit influences the severity of the incident  :(

Another accident that I was told of whilst at Maritime college was an when a ships RO dropping a high vacuum RADAR CRT after accidentally touching the Anode feed hole....  Implosion followed along with plenty of flying shards of glass.... nasty ! No serious injury but still not a great situation to find yourself in.

The moral of the tale..... a lethal accident is not always caused by a lethal stimulus.
« Last Edit: October 24, 2010, 06:04:09 pm by Aurora »
 

Offline Mechatrommer

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The moral of the tale..... a lethal accident is not always caused by a lethal stimulus.
good point! but still, the stimulus is the one who started it, no matter how "unlethal" it is ;)
ps: a woman will drop the glass when a mouse just passing by.
« Last Edit: October 24, 2010, 01:25:35 pm by shafri »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline PetrosA

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Looking over some statistics for the US, at the start of the 20th century, 50% of electricians were killed by electric shocks at work. Today, the main cause of death is falling off of ladders, and a lot fewer are dying at work.
I miss my home I miss my porch, porch
 

Offline Fraser

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I'm fortunate to be qualified to work on many types of electronic and mechanical equipment but I know when to call in a specialist .... I hate working atop ladders and leave my TV aerial installations and roof repairs to those who do it as a daily job. I have worked on ships masthead Radar scanners and HF/VHF aerials but HSE provides plenty of anti fall countermeasures in those scenarios. Such are not normally present when doing 'domestic' DIY etc. A very wise aerial rigger once told me that I would fall because of holding on too tight ! He was right, you need to be relaxed and disciplined when working atop 100 foot aerial masts that are swaying in the wind :o

You still hear of people being paralysed or worse, killed, whilst trying to save a few pounds doing DIY aerial erection on their house roof. I know my limits and GBP100 or so is cheap compared to serious injury or worse.
 

Offline PetrosA

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I miss my home I miss my porch, porch
 

Offline Mechatrommer

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so the keyword is still valid i think... "Safety First"
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Kiriakos-GR

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so the keyword is still valid i think... "Safety First"

Yes for the DMM , that's why I got the 28II   ;D   ;D   ;D
if we fall together, it will survive and tell what had happened ..    :D




.
« Last Edit: October 24, 2010, 11:49:00 pm by Kiriakos-GR »
 

Offline Fraser

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That video made me feel quite queezy !

I hope they get paid well and I wouldn't want to be their life insurer  :D

The High Steel workers who assemble the girders for skyscrapers are another group of gentlemen for whom I have the greatest of respect. They also find it easier to free climb and one told me that he considered a safety strap an added danger as it got in the way !

Great video. thanks
« Last Edit: October 24, 2010, 04:56:32 pm by Aurora »
 

Offline Mechatrommer

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That video made me feel quite queezy !
they should wear parachute! for three purposes. 1) accidentally fallen 2) quick way to go down 3) having fun of parachuting.

They also find it easier to free climb and one told me that he considered a safety strap an added danger as it got in the way !
yea right, added danger! when u wear the strap and got fall down, u probably got a broken rib due to hit to the wall or something and feel the pain. without the strap, u'll just drop blacked!
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline saturation

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I wonder what happens if you have to go to the bathroom?    :-[

OK for the guy on top, but what for the companion guy below?  :o

That video made me feel quite queezy !

I hope they get paid well and I wouldn't want to be their life insurer  :D

The High Steel workers who assemble the girders for skyscrapers are another group of gentlemen for whom I have the greatest of respect. They also find it easier to free climb and one told me that he considered a safety strap an added danger as it got in the way !

Great video. thanks
Best Wishes,

 Saturation
 

Offline Zero999

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Make your own welding gear. :D
 

Offline Fraser

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Quote
I wonder what happens if you have to go to the bathroom? 

You take a bottle of Coke with you, drink it and then you have an empty bottle for 'other' uses  :D

The crane operators in Hong Kong used to do that but one day one of them must have forgotten as yellow rain started to fall not far from where I was standing and it was a lovely sunny day  :o
 

Offline Kiriakos-GR

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Make your own welding gear. :D

Yes and its an smart idea too , this is an hand made transformer .
« Last Edit: October 24, 2010, 11:55:07 pm by Kiriakos-GR »
 

Offline .o:0|O|0:o.

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Climbing a 1768 Ft Radio Tower!

A great view, fresh air, exercise and no room for errors. Couldn't they have some system whereby they are permanently attached the last stretch of the climb? Some sort of a strap and belt system in addition to the cord and carabiner (maybe a parachute for back-up)?
 
.o:0|O|0:o.
 

Offline Kiriakos-GR

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They get payed by five times more than the average monthly payment,
this keeps them in good shape , they do not need parachute .
 

Offline Mechatrommer

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...they do not need parachute .
sure! they just do.... or die. nothing in between.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Zero999

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What good would a parachute do?
 

Offline .o:0|O|0:o.

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It would give them a non-zero chance of survival if they fell over. Provided it didn't increase their chances of falling over. That the risk doesn't warrant a paracute is a seperate matter.

My comment about perhaps having a parachute with them was only half serious, but if you are referring to the relatively low altitude, BASE jumpers do this sort of thing for the thrill all the time and from much lower as well: http://en.wikipedia.org/wiki/BASE_jumping .

.o:0|O|0:o.
 

Offline Mechatrommer

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What good would a parachute do?
the same as safety strap does... to annoy them. well... thats a kid answer, if you want the serious answer, then.... it a safety measure in case of fell over, they can pull out the chute open so they can go down slowly and safely. and in case of the "charge suckers" fail (flower shaped on the antenna) and cannot avoid thunderstorm, then there is option for quick way down alive. they should be trained in military paratrooper first before qualifying for this kind of job, but thats is only when i become a prime minister :P. Why prime minister? because he can make any decision he want, in US its called Mr President. And sometime people dont be thankful when a rule is enforced on them. Its for the good of them, and they say its annoying. Cheers ;)
« Last Edit: October 25, 2010, 11:49:13 pm by shafri »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Zero999

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the same as safety strap does... to annoy them. well... thats a kid answer, if you want the serious answer, then.... it a safety measure in case of fell over, they can pull out the chute open so they can go down slowly and safely.
You'd have to be very high up for that to happen, parachutes take long enough to open that if you're not high enough, you'll hit the ground before it opens. There also might not be enough room for it, if you're up a mast, it wion't.
 

Offline Time

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I wonder if the OP has come back to see this thread grow to 100 replies.
-Time
 

Offline Kiriakos-GR

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He got it very heavy that the DMM died from the fence.

But we all, when we was that young , did crazy things.
I call those,as experiments of the young hood.

Lets hope that if he gets an second one , he will read the instructions first !!

 
 

Offline marianoapp

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the same as safety strap does... to annoy them. well... thats a kid answer, if you want the serious answer, then.... it a safety measure in case of fell over, they can pull out the chute open so they can go down slowly and safely.
You'd have to be very high up for that to happen, parachutes take long enough to open that if you're not high enough, you'll hit the ground before it opens. There also might not be enough room for it, if you're up a mast, it wion't.

700 meters or so is the recommended minimum altitude to open a parachute, but of course you can open it much lower and still survive.
Anyway opening a parachute while falling down gives you no guarantees, since you have to do it in a precise way to avoid getting tangled with the tower.


I used to be a skydiver, but it became to expensive to fast :-\
 

Offline dimlow

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Bla, no need for a parachute, it wont hurt when you hit the ground.
 

Offline Mechatrommer

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700 meters or so is the recommended minimum altitude to open a parachute, but of course you can open it much lower and still survive.
Anyway opening a parachute while falling down gives you no guarantees, since you have to do it in a precise way to avoid getting tangled with the tower.
I used to be a skydiver, but it became to expensive to fast :-\
i heard a base jumpers have opened parachute at height less than 400 meters and they still have more room for error (i saw a video once). but i think the 700m recommended is for very high jumping such as skydiver (tens of thousand feet of drop) where you have build up a very fast free fall speed at 700m. just my 2cnt, i never/havent do skydive.

being getting tangled, is one of the more likely problem. but it can still provide option for quick way down. o well, i was just giving a crazy idea, the chute may as well annoy the climber just as the strap does :-\ since looking at the video is very spooky esp on the very top of the antenna tower where you just stand on a very small base with no really hard metal to hold on, i can see just a small metal "pipe", but i think that one is like going to break. and there are two guys climbing it and the one is maintaining the first person's bag, IIRC. if one is going down, i think the other one will be, too.
« Last Edit: October 27, 2010, 03:22:33 am by shafri »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Mechatrommer

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Bla, no need for a parachute, it wont hurt when you hit the ground.
very true! :D
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 


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