Technical relationship advice

[Laserman532]

Rings are not only electrical or a reflective problem. I was walking out of a department store one time and hooked my ring on the edge of the square thing you open the door with, and I swear to god I felt it rip my finger tendon all the way up to my shoulder (if that is possible) If you know what I am talking about, I think my finger stretched about 1.5 inches or more, hurt like hell

Oh Congratulations on engagement!

[mikkojay]

Hi Heroic,
Congratulations! This one is out there(oops, just noticed it was mentioned up there^) but hey, its non-conductive:

So is there going to be a wicked laser wedding reception or what?
-Mike

[loopee]

there's always carbon fiber

Carbon Fibre is actually conductive, that's why you need to be cautious with fishing rods around power lines.

Congratulations on the engagement

[heroic]

Thanks everyone for your suggestions!

We've decided we want matching rings, which kinda compresses the choice a bit (she's not as techy as I am... but then again who is?) but we've seen jade rings which look nice and combine several nice properties. They are non-conductive, polycrystalline so they won't form sharp edges if they shatter, look great, won't wear out, and don't tarnish. Plus, everyone likes unearthly green minerals except Superman, and that guy sucks anyway.

So is there going to be a wicked laser wedding reception or what?
-Mike

Sadly due to the backwards nature of the US political process, we're going to have to go to Canada to get married, which rather puts a crimp on our plans for family gatherings and/or receptions; I for one don't envy repeating the process of importing the laser to the USA. (Before anyone asks why we're not doing the Californian domestic partner thing- check out the difference in rights and portability between the two.)

There will definitely be a party at some point afterwards though. 8)

[Jem]

Hi Heroic

Can I just add my congratulations to both your partner and yourself. I hope you have a wondeful life together filled with love and affection

On the Jade rings... My Dad used to be a gemstone dealer, he sourced and had manufactured quite a few jade rings for people. Some of them were absolutely stunning with beautiful intricate carving on them. I guess what i'm trying to say is that you don't just have to restrict yourself to a plain band . I know my dad had them manufactured in Idar Oberstein (well, a little village called Kirschweiler to be exact) in Germany which is pretty much acknowledged as the quality gemstone cutting capital of the world. Perhaps you could find a gemstone dealer who has contacts there and have something designed just for you. Having said that, this was back in the 70's and early 80's. I know that there's some nice Jade carvings coming out of China right now, but you need to be a bit selective with the Chinese Jade to ensure you don't get ripped off.

Cheers

Jem

[White-Light]

Yes, the ring gets very hot and amputates one's digit.

The PSUs I work with are rated at hundreds of amps and source impedances are very low as a result.

If you're running hundreds of amps I'd think you're going to be dead along time before your finger melts off!!

Jade is a good suggestion. Just check the conductivity!

As an alternative, why not have 2 rings? A dress one for going out with the wife and a symbolic insulated one for home / work? If you only ever wear the dress one for special occasions eg dinners out its unlikely you'll have it on by accident when heading off to work.

[p1t8ull]

If you're running hundreds of amps you're going to be dead along time before your finger melts off!!

Not at 5/12/24v you 'aint...

Mmmmm... I love that smell of cookin' finger in the mornin' SMPS

[heroic]

If you're running hundreds of amps I'd think you're going to be dead along time before your finger melts off!!

The resistance of a human being is about 1 kohm. The supplies I work with are generally around a volt or two (that's why they use such insanely huge currents). I=V/R. This voltage cannot therefore push a physiologically significant current through a human body.

The problem, therefore, is when a conductive object is in intimate contact with tissues that may be damaged by it suddenly heating itself to hundreds of degrees. Since resistive heating power is given by P=I^2*R, and I is large, a hundred milliohms of metallic ring will abruptly melt itself if I should short, say, a PC motherboard's CPU core supply (capable of delivering hundreds of amps peak) over it. The heating effect of shorting the same supply with my fleshy human body is negligible, since a couple of volts divided by thousands of ohms equals sweet FA.

I handle these things with my bare hands all the time, and the worst injury I've managed was when I managed to whack the end off my finger on a spinning fan; on the other hand I managed to obliterate the end of a screwdriver totally when it slipped off a heatsink screw and landed on the output FET of a Vcore switcher. (It also wiped out the motherboard, but the processors and RAM were fine- how about that!?) Flying gobs of incandescent metal, the works!

Please don't ask what I was doing taking the heatsink off a running CPU. It was for science, I promise you...

-J.,
not a good teacher of lab safety practices

[White-Light]

Not at 5/12/24v you 'aint...

Mmmmm... I love that smell of cookin' finger in the mornin' SMPS

You're not far off. Supplies as low as 32 volts have been known to be lethal with high currents.

It only takes as little as 300-500ma with DC to pass directly through the heart to induce ventricular fibrillation.

[buffo]

You're not far off. Supplies as low as 32 volts have been known to be lethal with high currents. It only takes as little as 300-500ma with DC to pass directly through the heart to induce ventricular fibrillation.

Close... It actually only takes about 100 ma across the heart to induce V-fib. But your estimate of minimum fatal voltage is right on the money. Minimum body resistance is generally considered to be 300 ohms. Sure, it's normally at least an order of magnitude higher, but under the most perfect conditions of blood electrolyte level and skin conductivity, it is possible to have a body resistance of just 300 ohms.

Thus, to get .1 amps, you need just 30 volts. That's why 30 volts is considered the minimum fatal voltage. (Had this crap drilled into my head when I was in the Navy, and again when I went through EMT training.)

Speaking from personal experience, I can tell you that the 66 volts you have a on a POTS line will give you one hell of a shock if your hands are the slightest bit sweaty. I reached into a computer case to swap a jumper and got shocked. I knew the computer was off, so I was quite puzzled. When it happened again, I yanked the cord out of the wall and checked the molex connectors with a multimeter for any residual DC before proceeding.

The *third* time it bit me, I finally figured out that the modem was still connected to the phone jack, and the isolation transformer on the input had exposed terminals that were brushing against my hand when I reached inside the case! Who would have thought?

Oh yeah, and ring voltage is much higher... 90 + volts. So you can be killed by a phone line, if everything is going right. (or wrong, I suppose...)

Heroic:

Congratulations on your engagement. I second the idea of wearing your ring around your neck on a necklace. My mother has worn her ring like that ever since my father passed away. Although I must admit that a jade ring would be mighty pretty too!

Adam