Correct use of anti-static wrist straps

November 13, 2012 at 00:47:55
Specs: Windows XP, i7 6GB
My problem is that all forums (this one included) contain threads that contradict each other and almost all contain no indication as to the basis of why the opinion expressed is correct.
Nor do almost all of these threads contain information relevant to the significantly different exercise of removing a component, or touching a component already inside a PC, versus taking a new component out of its packet (or from another PC) and then installing it in the PC in question.
Granted, if you are going to remove a component from inside a PC (not attached to earth), the component, yourself and the chassis will all be at the same potential if you are touching the chassis with the other hand or attached to the chassis with a wrist strap. No problem; now remove any component to your heart's content.
But what if you are about to insert a new component?
It will have come to you in an anti-static bag and no doubt was placed inside that bag in an enviroment at earth potential at it's point of manufacture.
So, if you are at chassis potential of a PC that perhaps has been disconnected from its power cable and perhaps moved from one place to another since then, or has accumlated a charge courtesy of you touching it, are you and the chassis necessarily now at the same potential as the "static free" component you are about to remove from it's bag?
What about if you have removed a component from another PC and had it lying somewhere on the bench top and now you go to pick it up?
And lastly, just because a component was put in a bag at earth potential in say Taiwan, is it necessary at the same earth potential as a grounded PC on theother side of the world that you are now working with?
So what's the answer to working correctly? Wrist strap connected to chassis, with chassis plugged in to a power point that is not turned on? Or Chassis unplugged?
Anf how do we ensure that a new component has been brought to the same potential as it's new PC home, without the very act of bringing it to the same potential causing it to malfunction?

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#1
November 13, 2012 at 01:05:56
I just touch the chassis before handling cards or components. In thirty-odd years of playing with computer equipment I've never damaged anything through static discharge.

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#2
November 13, 2012 at 02:25:32
Thanks ijack. Appreciate your reply and your experience in making it. However, this is the sort of answer that can be seen in so many other threads. I.e. "this is what I have done and it works for me". But it does not really answer the questions I have posed. You will also see similar questions on any number of other forums and indeed on this site.
But unfortunately, there are so many other people who have answered that they have had, or have it on good reason to believe in, static discharge problems when merely touching the chassis of an ungrounded PC.
Do we have anyone out there who can provide a qualified answer regarding whether the PC should be connected to earth (i.e. plugged in but not turned on, or not plugged in).
I should have added also that I am asking in the context of the average user (or repair man on site) where purpose built service environments or grounded work surfaces will not be available.
Do we need to be more careful about wrist straps when inserting a new component vs removing an existing component after first touching the chassis to equalise potentials?
Do ground potentials vary over large distances around the earth? If so, is it likely that a component placed in an anti-static bag on one side of the world will be at a different earth potential when removed from its bag on the other ide of the world?
Is it likely that a component removed from one PC could be at a different potential to the PC you are about to put it into? If so, in both these latter cases, how do you safely get the potential of this about-to-be-installed component to the same potential as your PC, without zapping it in the process?

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#3
November 13, 2012 at 03:48:42
You probably need to review ESD Fundamentals - http://www.esda.org/esd_fundamental... - and follow the other links on that site.

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Related Solutions

#4
November 13, 2012 at 04:50:09
If the power supply in the computer has an On/Off switch then leave the power cord connected to the AC but turn off the switch. This condition will keep the computer case grounded and ijack's suggestion will protect the hardware.

Power strips should also have ground continuity even when the switch is in the off position. Both scenarios assume you are plugging into a properly grounded receptacle.


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