Proper Anti-Static Strap Usage?

[ATITek]

I own a basic anti-static wrist strap with an alligator clip. Just like this one:

http://www.newegg.com/Product/Product.aspx?Item=N82E16899261005&cm_re=strap-_-99-261-005-_-Product

My question is the proper use of it. I have heard of the following two ways:

1. Connect it to the bare metal part of your computer chassis and UNPLUG the computer from the wall. [This equalizes your potential with the computer and eliminates chance of any anti-static zaps, but does not ground you to earth]

2. Connect it to the bare metal part of your computer chassis and leave your computer PLUGGED-IN with the power switch on your PSU off and surge protector switch off. [Grounds you to earth via the chassis]

I am about to do allot of work in my machine and want to do this the correct way. I feel uncomfortable having any PC plugged into a wall outlet [switches off or not] when I am working in it. I searched the web last night and people seem to be split on what is safer and what works

Do you REALLY need to have the PC plugged into the wall or not?

 

[engiNURD]

No, you just need to be at the same potential as the case and your components, so there's no discharge. However, if there is a discharge, it would be best if it had a path to ground rather than to your components. I work with a bunch of ESD sensitive IC's, so I always have a path to ground when building computers, but thats just me. Also, remember that ESD can have a latent effect, so you may not even know if you damaged something with ESD until its too late. Therefore, my recommendation would be to plug it into the wall, assuming your wall socket is properly grounded.

 

[gimp]

Also, remember that ESD can have a latent effect, so you may not even know if you damaged something with ESD until its too late.

so true.

I killed a sound card with ESD, and there wasn't even a "zap"
it just didn't work upon reinstalling it.

 

[ATITek]

No, you just need to be at the same potential as the case and your components, so there's no discharge. However, if there is a discharge, it would be best if it had a path to ground rather than to your components. I work with a bunch of ESD sensitive IC's, so I always have a path to ground when building computers, but thats just me. Also, remember that ESD can have a latent effect, so you may not even know if you damaged something with ESD until its too late. Therefore, my recommendation would be to plug it into the wall, assuming your wall socket is properly grounded.

So if I worked in my computer without being able to plug it into the wall w/ the wrist strap attached to the case then I still have protection?

I have had a zap go into the frame of the case from my hand without the PC being plugged in. I would hope the case absorbed it and it did not strike any other components. The side panel was off when it happened.

 

[ATITek]

Bump for further clarification.

Is there anyway to test for latent damage that will show signs of that?

 

[PM650]

Bump for further clarification.

Is there anyway to test for latent damage that will show signs of that?

Unless you designed whatever you're handling, the only way you'll know is to put it in and see if it works. Modern LSI/VLSI components often have ESD-diverting mechanisms built-in to provide inherent protection, although this only works so well (a large enough voltage would still cause damage).

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