Anti-Static Grounding - how?
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I've seen a lot of "anti-hazard" warnings here and there for our K2 building process. Various outfits sell anti-static pads, wrist straps, wrist straps with series megohm protection - but none ever mention where these devices are supposed to pick up a reliable earth ground? Or don't they need one? I don't think one can rely on their house wiring to find a reliable un-connected earth ground. ...building K2 # 5422, control board finished and Front Panel on desk in a pile of parts. :) Tnx 73's Fred N3CSY 3/21 __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: Anti-Static Grounding - how?
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Fred, N3CSY wrote:
Various outfits sell anti-static pads, wrist straps, wrist straps with series megohm protection - but none ever mention where these devices are supposed to pick up a reliable earth ground? Or don't they need one? I don't think one can rely on their house wiring to find a reliable un-connected earth ground. ----------------------------------- I use the power mains safety ground. All of the electronics lab benches I've used in various companies rely on the mains ground. If you are unsure of your mains ground, you can buy a very inexpensive outlet tester at most hardware stores. It'll tell you whether your outlet safety ground is connected and whether the outlet is wired correctly. The latter can be important if you have any two-wire equipment that does not use the safety ground. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Anti-Static Grounding - how?
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What you are seeking rather than an earth ground, is to tie the commons of
the equipment you are working upon, and yourself, suitably protected by the wrist strap internal resistor, to the same point, and thus voltage potential. You are trying to have everything at the same potential before you reach toward a board with a conductive tool and provide a discharge point for any accumulated static on one side or the other. The objective is to bleed off any static charge you bring on your body, clothes, etc., to the work table, to the static mat and to the common bus of the circuit board, chassis, or whatever is sitting on the pad. In other words, it matters not if the pad and you and the equipment float at some voltage, as long as you all become tied together so as to be at the SAME voltage. That is why you do not see any specific instruction to tie the mat to an earth rod. If you walk up to the work area and thus buildup a charge from walking along; as soon as you strap on the resistive wrist strap tying you to the other equipment, you dissipate the charge thru the resistor or induce the same charge to whatever you are working upon. The earth itself does not have any magical property to effectively nullify static; rather, you attempt to spread the charge evenly among all conductive elements involved in your workbench. Sometimes earthing thru a rod might aid in keeping the bench from rising up in charge itself, but the risk of that is tied to such issues as is there a steady wind blowing across metal surfaces, or is the air around the bench very dry and cool, thus facilitating static charge accumulation. -Stuart K5KVH _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Anti-Static Grounding - how?
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In reply to this post by Fred (FL)
Indeed, some house grounds have induced voltages in having long runs back to
any ground point; and might not be the safest thing to tie your static mat to as a "ground" point. "Ground" in AC systems may have imbalance phase currents and be much different from a zero voltage point. It shouldn't ideally, but the real world resistances of wiring carrying heavy current my make it so. -Stuart K5KVH _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Anti-Static Grounding - how?
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In reply to this post by Fred (FL)
They don't need one.
The idea is to keep you, your tools, the equipment your working on and your PSU, antenna, test equipment etc at the same potential. It doesn't matter what that potential. Your mains electricity supply ground is certainly sufficient as most things will already be connected to it. F and J wrote: > I've seen a lot of "anti-hazard" warnings here and > there for our K2 building process. Various outfits > sell anti-static pads, wrist straps, wrist straps > with series megohm protection - but none ever > mention where these devices are supposed to pick > up a reliable earth ground? Or don't they > need one? I don't think one can rely on their > house wiring to find a reliable un-connected earth > ground. > > ...building K2 # 5422, control board finished and > Front Panel on desk in a pile of parts. :) > > Tnx 73's > Fred N3CSY > 3/21 > > > > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Stuart Rohre
That 1 meg resistor not only causes a slow discharge of any static buildup
on you it also protects you. You could easily get a good zap by connecting yourself with a solid wire to what you think is "ground." Don’t think that you can save money by hooking up a test lead to your wrist watch band and ground. I got a good jolt when I was a kid (many years ago) from a "grounded" drill that was plugged into a "grounded" outlet in my barn. The power line had the Hot, Neutral and Ground BUT there was no local ground rod in the barn. At first we thought that the Hot wire had shorted to the case. As luck would have it the fuse panel ground had gotten mowed off below the meter, the only ground for the house and barn, and the utility crew forget to ground the transformer after an accident some months earlier. There was enough voltage to light a bulb, over 90 volts, between the "ground" wire and earth. Rich, KE0X ----------- Indeed, some house grounds have induced voltages in having long runs back to any ground point; and might not be the safest thing to tie your static mat to as a "ground" point. "Ground" in AC systems may have imbalance phase currents and be much different from a zero voltage point. It shouldn't ideally, but the real world resistances of wiring carrying heavy current my make it so. -Stuart K5KVH -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.6/286 - Release Date: 3/20/2006 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Fred (FL)
That 1 meg resistor not only causes a slow discharge of any static buildup on you it also protects you. You could easily get a good zap by connecting yourself with a solid wire to what you think is "ground." Don’t think that you can save money by hooking up a test lead to your wrist watch band and ground. I got a good jolt when I was a kid (many years ago) from a "grounded" drill that was plugged into a "grounded" outlet in my barn. The power line had the Hot, Neutral and Ground BUT there was no local ground rod in the barn. At first we thought that the Hot wire had shorted to the case. As luck would have it the fuse panel ground had gotten mowed off below the meter, the only ground for the house and barn, and the utility crew forget to ground the transformer after an accident some months earlier. There was enough voltage to light a bulb, over 90 volts, between the "ground" wire and earth. Rich, KE0X ----------- Indeed, some house grounds have induced voltages in having long runs back to any ground point; and might not be the safest thing to tie your static mat to as a "ground" point. "Ground" in AC systems may have imbalance phase currents and be much different from a zero voltage point. It shouldn't ideally, but the real world resistances of wiring carrying heavy current my make it so. -Stuart K5KVH -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.6/286 - Release Date: 3/20/2006 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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