Remove rings, watches...advise. Reason ?

[carlossan]

Hi,

I was wondering if somebody knew the reasons as why almost all equipment's manuals suggests to remove rings, watches, and any metal objects in general before working in or close to the power supply.

The only reason I can think of is to avoid for example a wrist watch to make a short circuit. Are there other reasons -I know that is reason enough, but I was just wondering if there were others-?

Thanks,

Carlos

 

[cdogg]

My guess is the risk that part of an object you're wearing could touch the inside of the power supply (by sliding past the cover through one of the vent slots). Though not likely, it's a possibility.

However, the cover of the power supply is fairly safe. It's the capacitors on the inside which store a lot of electricity for long periods of time, even when the power supply is left unplugged.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[maultier]

Electrical energy will always take the path of least resistance. In some cases that means it'll jump to a watch, a ring or other metal object and pursue a path to ground. If that path makes its way through vital body parts, you have more than a short circuit to worry about. The guidelines are not so much to protect equipment as to protect the person working on the equipment. In addition, rings, necklaces, watches etc can get snagged and cause injury when you're trying to pull away from a piece of gear. Always observe safety precaustions when working on live gear. If the gear doesn't have to be up, take it down and work on it off line.
If it absolutely has to be up, you must be extremely safety conscious and be aware of your environment.

 

[edfair]

Human skin won't conduct enough to damage the outputs of PC type power supplies , or you. Watches and rings will conduct enough to damage them. And the high currents through both of those can heat the metals hot enough to brand you.

In my days of installing telephone equipment there were installers missing ring fingers. Seems that when you took a hit of ringing voltage and jerked your hand out of the crossconnect bay and snagged a ring the finger came off with it or did enough damage that the repair was to remove the damaged part.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[kmcferrin]

All of the above are good reasons, but I've got another. I don't know what metals your jewelry are made out of, but I found out the hard way that the bits and pieces inside a PC case are much harder and sharper than my wedding ring, which now has several dings and scratches in it. Ever since that I have always taken off my rings and watches.

 

[IPTnewbie]

becuz SILVER and GOLD are the best conductors on earth. next to copper

I love gooooooooooold.

 

[gbaughma]

I, too, have had similar mishaps because of wearing my wedding band.

I remember going over to a friend's shop (electronics repair)... he was soldering on a VCR mainboard... he asked if I'd hold it elevated a little for him.

My ring shorted a couple of traces, and the whole thing went up in smoke, ruining all his work.

He was... to say the least... not happy.



Just my 2¢

"When I die, I want people to say 'There was a wise man' instead of 'Finally, his mouth is shut!'" --Me
--Greg

http://parallel.tzo.com

 

[RICHINMINN]

Just some additional information to IPTNewbie's response:
Silver, copper, and gold are the three best-conducting metals, in that order.

When comparing their conductivities, if copper's is set to 100% as the standard of comparison, silver's conductivity is 108.40%, while gold's is 70%. Next in line is pure aluminum at 61%.

Check out

http://www.eddy-current.com/condres.htm

to see how a couple hundred different elements and alloys compare.

Rich (in Minn.)

 

[Auger282]

you never know when somethings going to jump out of a capacitor and bite you....

 

[LawnBoy]

In my days of installing telephone equipment there were installers missing ring fingers.

Yep, I saw it happen once.

 

[TrojanSquirrel]

I'd never given that a second thought and have always worn both my watch and gold ring when inside mine and others PCs including the fitting of the psu.....

I'll prob change my technique now!

I'm not certain about the voltages within a psu, but I know that for a microwave oven the power supply holds up to 4000 volts within and the capacitor can hold this charge for quite some time after the supply cas been cut. Therefore every electrical store I went to wouldn't sell me a fuse for one as it was possible I could kill myself!

Regards,

Rob

http://www.transcom.net

 

[edfair]

there is no way you could contact anything dangerous inside the sealed PSU with a ring or watch. The dangerous area is the bottom of the printed circuit card and it is mounted to the side that has no air holes.
Not nearly as stiff a jolt, only 350 volts or so but still no fun. There are older systems with power supplies where you can pull the card easily and defective supplies can hold the charge for days.

Ed Fair
Give the wrong symptoms, get the wrong solutions.