grounding straps

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v6a1a4
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grounding straps

Post by v6a1a4 » Thu Nov 18, 2004 8:01 pm

Hello, I'm setting up an electronics workbench and want to properly install a grounding strap. Is attaching my wrist grounding strap through a 1 Meg resister to house ground good enough?<p>Cheers, James

Bernius1
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Re: grounding straps

Post by Bernius1 » Fri Nov 19, 2004 3:02 am

I wouldn't hook myself through a sweaty wristband to a grounded water pipe. Probably because my 110V circuit to my shop area is improperly grounded, and shows 74V to the gas line (though not to its own ground). YES I'VE GOTTA FIX IT , AND SOON !!! But I want to be sure that it's only a break in the conduit first, and not a sign of really bad wiring, or a differential between phases and their grounding. (Sounds stupid, but most errors are!) So just ground yourself to your immediate work area.
Can't we end all posts with a comical quip?

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Dave Dixon
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Re: grounding straps

Post by Dave Dixon » Fri Nov 19, 2004 5:03 am

James,
If you are setting up a shack/shop, I would suggest sinking a copper rod into actual earth ground. We go 8 feet here at work, but 3-4 feet should suffice. Then we run #6 GA unshielded
copper wire from it to a location under our benches where it can be "clipped" onto for our anti-static stations. Nothing beats an actual earth ground... especially for antenna connections!
Good luck, and stay safe (Check for voltage between earth and house conduit).
Dave N0QOF<p>[ November 19, 2004: Message edited by: Dave Dixon ]</p>

bridgen
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Re: grounding straps

Post by bridgen » Fri Nov 19, 2004 10:11 am

A wrist strap is for the protection of static-sensitive components.

It should be connected through the 1M resistor, as you correctly state, but to the conductive work-mat on which the sensitive parts are placed. <p>The point of it is to make sure that you are at the same potential as the work-piece (the bits you will be working on) so it doesn't matter at all whether it, and you, is connected to earth (the planet on which we live) or not.<p>[ November 19, 2004: Message edited by: David Bridgen ]</p>

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Dave Dixon
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Re: grounding straps

Post by Dave Dixon » Fri Nov 19, 2004 12:00 pm

David,
I understand your point about potential, and your reasoning that if the item is on the static mat that no electrostatic discharge will occur between yourself and the item, if you are connected to the mat (through said resistance). I'm not comfortable with having a static station at an unknown potential (relative to "Ground").
"That's the way we have always done it" is no good excuse for anything.... But every specification I have (MIL-STD's, DOD stds, EOS/ESD Ass., Customer standards, and various textbooks) call for every ESD workstation - even portable ones - to have a proper ground (I assume for safety reasons).
I am looking forward to further input/discussion on your point of view - as well as hearing from others on the forum.
Respectfully,
Dave - ESD Program Manager/Engineering Technician
Aero-Mach Labs Inc.<p>[ November 19, 2004: Message edited by: Dave Dixon ]</p>

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jwax
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Re: grounding straps

Post by jwax » Fri Nov 19, 2004 12:11 pm

One Meg from wrist strap to bench mat, then bench mat(s) to earth ground. Give that charge a place to go! ;)

v6a1a4
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Re: grounding straps

Post by v6a1a4 » Fri Nov 19, 2004 8:16 pm

Thanks for all your input.<p>Cheers, James

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Re: grounding straps

Post by bridgen » Sat Nov 20, 2004 12:27 pm

Hello Dave (Dixon). <p>The point of my post was, as you have grasped, to try to explain the reason for the conductive connection between the work and the person. <p>This seems to escape a great number of people, who, I must assume, just don't understand what is going on. <p>They are surprised to hear (whether they believe it or not is another matter) that once you are conductively connected to the work it matters not, insofar as the wellbeing of the work is concerned, if you connect yourself, and therefore the work, to earth, or even elevate yourself to some thousands of volts different to earth. <p>Connecting things to earth all over the place is another kettle of fish, and is for your protection, not that of the work.<p>I don't, and never have, advocate ignoring sensible safety legislation but one thing you say in your posting <p>" ..... even portable ones - to have a proper ground (I assume for safety reasons)....."<p>does bring home to me (again) that some legislation simply isn't sensible, and that assumptions, some of which can be dangerous in the extreme, are made. <p>We see this every day in politics as well as in industry. Non-specialist people trying, oh so inadequately, to do a specialist job and make specialist decisions. But I begin to digress. <p>Apropos legislation, I am a firm believer in the adage that "rules and regulations are for the obedience of fools and the guidance of wise men", but I am taking the digression even further afield ......<p>My regards to you.<p>[ November 20, 2004: Message edited by: David Bridgen ]<p>[ November 20, 2004: Message edited by: David Bridgen ]<p>[ November 20, 2004: Message edited by: David Bridgen ]</p>

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