ECN Forum Forums General Topics of the Trade General Discussion Area Transformers: mind-boggling, mysterious beasts

Spark,
I've got some bad news for you buddy. You're DEAD! Not only that, you've been dead for quite some time if the Fluke can't see some R across you. But before we start calling your next of kin, is there any chance that you have your meter on "diode check", instead of "ohms" or inadvertantly gotten into a manual, low resistance range? For now, let's stipulate that you are among the living. I haven't checked out Winnie's link yet but let's consider why it doesn't seem too credible. A modern DMM will usually have an imput impedance of about 10 million ohms. You would probably be hard pressed to find one with less than a million ohms. This is a good thing because we wish to measure a circuit without influencing it. To consider the possibility of a DMM being a shock hazzard, we have to think of it as a 9 volt power supply with a source impedance of 10 million ohms. Our unknown voltage is Vdead (Vd). Our poor victim's resistance is Rdead( Rd),(maybe we should use URdead). Total resistance (Rt)= Rsource (Rs) + Rdead (Rd). We can use voltage divider equations to note that Vt/Vd = Rt/Rd. If you happened to look like 100,000 ohms of resistance, you would plug & chug & come up with 9/Vd = 10,100,000/100,000. Vd = 0.089 volts in this case. Your current is 8.9^-7 A. So my gut feeling is that the only way that a DMM set to R is going to kill someone, is if Jet Li is using it.

Why don't you try taking a 9 volt battery and putting yourself in series with your Fluke on DC uA across it. Then if you can get a hold of a Simpson 260 or other analog meter that has its input R expressed in thousands of ohms per volt(R depends on voltage scale that you use), try this. Measure your battery voltage with the analog volt meter and your DMM. Now put a 1M resistor in series with the battery and measure between the other terminal and the free end of the resistor. Quite a difference between the 2 readings now, right? That's because, "All the world's a voltage divider."
Joe


[This message has been edited by JoeTestingEngr (edited 12-24-2005).]

Sorry folks, got suckered by the second page.
Joe
By the way, I-wire posted before I did and I agree with him completely.

While it is non-conclusive, the body's structure is non-conducive to being non-conductive. Since further speculation is non-constructive, I'll just say MERRY CHRISTMAS!!!

[This message has been edited by JoeTestingEngr (edited 12-24-2005).]

Winnie posted:
Joe, there is a story (urban legend? I have no proof, here is a Darwin Awards reference http://www.darwinawards.com/darwin/darwin1999-50.html ) of someone electrocuting themselves with a 9V source using a multimeter to measure body resistance.

Yikes! I just went to the link and see how it might be possible. He used a VOM and flunked his bloodborne pathogen practical test. I just asked my fellow Testing Engineers to test themselves with a hi-z DMM. I didn't ask them to become my blood brothers and sisters.
Joe

I'm using a Fluke 336.

http://us.fluke.com/usen/products/specifications.htm?cs_id=30405(FlukeProducts)&category=ELW(FlukeProducts)

Hey Spark,
Everything makes sense now and you don't have to worry about hanging out with my friend, "Dave the reptile" That is sort of a special purpose, stuck in the middle meter, that you have there. It will probably serve you very well as an electrician. If you want to do the kind of mad scientist, disturbed mind, experiments, that I tend to come up with, the 70 & 80 series of their meters work better. Yours won't indicate resistances higher than 6000 ohms and low currents. You'll probably want to pick up another meter, down the road, to delve into experiments such as these.
Joe

I don't how true that story is......

I was in the AF in '84, and heard the same story, but it was a trainee in the AF.


Dnk....

[This message has been edited by Dnkldorf (edited 12-24-2005).]

Has there ever been a study done on humans being shocked? Certainly somebody must have done that kind of thing long ago. I've seen those machines with two brass handles, you're supposed to hold the handles and the machine shocks you with more and more intensity until you either let go or somehow "win" - I guess it maxes out at some predetermined point. Sounds dangerous to me, since from one hand to the other, it goes through your heart. I wonder if there was ever an experiment to see how much voltage it takes to "shock" somebody, if the voltage was fed through a variac. Where does a person start feeling a tingle? Where does a person start feeling shocked? Where does a person get jolted and burned? Killed? Was there ever a study done where people might know something about this?

Iwire, to answer your question, my Fluke 336 meter gives you continuity and ohms on one setting. It also does AC volts, DC volts, AC amps and DC amps with an amp clamp. 600 volts, 600 amps.

I thought I had a decent meter. It's better than the ones I've seen on the job. Joe was kind enough to let me know that it's a middle-of-the-roader on the grand scheme of things. Basically I'm trying to take a de-tuned four stroke enduro out to Carlsbad.

Joe, thanks for your help. What meters would you recommend for someone with a sick mind?

I see, 70 & 80 series...I'll look for that.

Thanks!

Quote:
" I wonder if there was ever an experiment to see how much voltage it takes to "shock" somebody"

If you ever want to really be sickened by human greed, go study the competition between Edison and Westinghouse in the beginning days of electricity. Edison, promoting DC, went to extraordinary means to prove how deadly Westinghouse's AC was. This involved "scientific" studies in the torture of dogs and anything else they could electrocute to prove how deadly AC was. I believe there was even a film of them electrocuting an elephant.
I wouldn't swear to it, but I believe the first criminal execution involving the electric chair also stemmed from this feud.

If you can imagine a "scientist" shocking a dog repeatedly while gradually increasing the voltage until the animal finally died, then you have an idea of how sick some individuals are.



[This message has been edited by WFO (edited 12-24-2005).]