Few questions about grounding yourself

proto-man · 01-30-2009, 12:03 AM

Hi,

I've got a simple few questions about grounding yourself when working inside the computer. I've heard that one must touch the metal case on the computer, but:

1. Must the computer have the power cable connected to it?

2. If not, must the computer be on the ground, or can it be on a higher platform like a table? Of course, the table would technically be "connected" to the ground but what if the material of the table (wood) is not very conductive of static electricity.

3. How often do we need to touch the metal case?

4. Does grounding work by touching any metal object?

Basic questions, but ones to which I never really had an answer. Hope you can help.

**grimx133** · 01-30-2009, 01:26 AM

1 - The power cable should not be connected, any time you work inside the case, the computer needs to be unplugged. You should also hit the power button a few times to discharge capacitors.

2 - Doesn't matter where the computer is, depends on what I have to do and how lazy I am, I either move to a better location where I'm more comfortable, or do whatever I have to do wherever it happens to be. Kind of hard on the back when it's under the kitchen table though.

3- Often. I'm usually leaning a forearm on the case, added bonus to that, it steadies my hands. At least the hand that has the magnifying glass in it.

4 - No. Static discharge happens when two things have a different level of potential energy. Nature wants that energy to be equal. So it does so, unfortunately that can cause a spark as the gap between the objects is almost bridged. Depends on how large the difference in potential is. So, you need to touch the case metal frame itself in a spot that is not prone to static damage, that way if there is anything, it doesn't get to any sensitive components.

Hope that makes sense.

proto-man · 01-30-2009, 02:30 PM

I mentioned the part about the power cable because I heard that you should connect the power cable so that it acts as a grounding terminal (since it has a ground pin) and that you should turn off the power button to cut off electricity.

I do understand somewhat the concepts of grounding (the earth has a slightly positive charge and so any electrons will travel there if they are provided a path). If you don't connect the power cable, and you have the computer on a table, where is the direct path to the ground?

I'm not quite sure I understand your response to question 4.

Quote:

So, you need to touch the case metal frame itself in a spot that is not prone to static damage, that way if there is anything, it doesn't get to any sensitive components.

So you're saying that the metal just acts as a dummy object where you allow all your static discharge to take place. The metal takes the hit, but the parts don't? But where does the grounding part come in this then.

I think this is turning into a Science question, but I'm sure someone could clarify this for me.

DavidHB · 01-30-2009, 03:39 PM

If you've disconnected and discharged as grimx says, I don't think it can do any harm to re-connect the power lead (with the power off) to earth the chassis, provided that you have a properly wired electrical installation and a good connection to earth. If your consumer unit has ECLBs rather than old fashioned fuses, and they don't trip, you are probably OK. At least that is true in the UK (220/240 volt supply, so less current than 110 volt systems).

The disadvantage of this, as I have found, is that the power cord can be a real constraint when re-positioning the case to fit and connect components. These days, I don't connect the cord, but rely on the fact that the (relatively) large mass and conductive nature of the metal chassis will be enough to discharge any static build up when I touch it. In the fairly humid climate of the UK, I don't seem to get much static build-up in any case.

In practice, as I think grimx was hinting, access and visibility are bigger issues than static. Do your build where you can get at everything, and where the light is good. Use a torch to see into the case; I use one of those wind-up torches, so the battery doesn't give out at the wrong moment. grimx's magnifying glass may also be a good idea, though I don't need one, as I'm short-sighted.

If your installation is at all complex, consider building and testing offline. My two desktops share the monitor etc. through a KVM switch. This is not a good test environment, so I have an old monitor, and a cheap keyboard, mouse etc. which I use for testing new builds and mods before connecting the machine back into the system. This spare kit also travels with me when I visit friends to help them with their builds. I am actually writing this on a machine which is offline (i.e. on the dining room table) so I can do an extended test of the video card, which was giving me problems in the KVM environment.

Hope this helps.

David

**wrench97** · 01-30-2009, 06:12 PM

FYI "Use a torch to see into the case; I use one of those wind-up torches, so the battery doesn't give out at the wrong moment."

British for Flashlight not to be confused with a Torch that has a Flame as in the US:)

DavidHB · 01-31-2009, 03:55 AM

Quote:

Originally Posted by wrench97

FYI British for Flashlight not to be confused with a Torch that has a Flame as in the US:)

"Two nations divided by a common language" ...

David

proto-man · 01-31-2009, 09:35 AM

Thanks for your replies guys. I still don't think I completely understand the workings of grounding but I think I know enough for the practical use of discharging myself.

01-30-2009, 12:03 AM	#1 (permalink)
proto-man Registered User Join Date: Jan 2009 Posts: 3 OS: Linux Fedora	Few questions about grounding yourself Hi, I've got a simple few questions about grounding yourself when working inside the computer. I've heard that one must touch the metal case on the computer, but: 1. Must the computer have the power cable connected to it? 2. If not, must the computer be on the ground, or can it be on a higher platform like a table? Of course, the table would technically be "connected" to the ground but what if the material of the table (wood) is not very conductive of static electricity. 3. How often do we need to touch the metal case? 4. Does grounding work by touching any metal object? Basic questions, but ones to which I never really had an answer. Hope you can help.

01-30-2009, 01:26 AM	#2 (permalink)
grimx133 Mentor Hardware Team Join Date: Jan 2008 Location: Canada eh Posts: 3,137 OS: xp mce sp2, xp pro sp2, windows 7 beta My System	Re: Few questions about grounding yourself 1 - The power cable should not be connected, any time you work inside the case, the computer needs to be unplugged. You should also hit the power button a few times to discharge capacitors. 2 - Doesn't matter where the computer is, depends on what I have to do and how lazy I am, I either move to a better location where I'm more comfortable, or do whatever I have to do wherever it happens to be. Kind of hard on the back when it's under the kitchen table though. 3- Often. I'm usually leaning a forearm on the case, added bonus to that, it steadies my hands. At least the hand that has the magnifying glass in it. 4 - No. Static discharge happens when two things have a different level of potential energy. Nature wants that energy to be equal. So it does so, unfortunately that can cause a spark as the gap between the objects is almost bridged. Depends on how large the difference in potential is. So, you need to touch the case metal frame itself in a spot that is not prone to static damage, that way if there is anything, it doesn't get to any sensitive components. Hope that makes sense. __________________ Last edited by grimx133; 01-30-2009 at 01:32 AM.

01-30-2009, 03:39 PM	#4 (permalink)
DavidHB Registered User Join Date: Jan 2009 Location: UK Posts: 151 OS: Vista x64 SP1; XP Pro; Ubuntu 8.10	Re: Few questions about grounding yourself If you've disconnected and discharged as grimx says, I don't think it can do any harm to re-connect the power lead (with the power off) to earth the chassis, provided that you have a properly wired electrical installation and a good connection to earth. If your consumer unit has ECLBs rather than old fashioned fuses, and they don't trip, you are probably OK. At least that is true in the UK (220/240 volt supply, so less current than 110 volt systems). The disadvantage of this, as I have found, is that the power cord can be a real constraint when re-positioning the case to fit and connect components. These days, I don't connect the cord, but rely on the fact that the (relatively) large mass and conductive nature of the metal chassis will be enough to discharge any static build up when I touch it. In the fairly humid climate of the UK, I don't seem to get much static build-up in any case. In practice, as I think grimx was hinting, access and visibility are bigger issues than static. Do your build where you can get at everything, and where the light is good. Use a torch to see into the case; I use one of those wind-up torches, so the battery doesn't give out at the wrong moment. grimx's magnifying glass may also be a good idea, though I don't need one, as I'm short-sighted. If your installation is at all complex, consider building and testing offline. My two desktops share the monitor etc. through a KVM switch. This is not a good test environment, so I have an old monitor, and a cheap keyboard, mouse etc. which I use for testing new builds and mods before connecting the machine back into the system. This spare kit also travels with me when I visit friends to help them with their builds. I am actually writing this on a machine which is offline (i.e. on the dining room table) so I can do an extended test of the video card, which was giving me problems in the KVM environment. Hope this helps. David

01-30-2009, 06:12 PM	#5 (permalink)
wrench97 Moderator, Hardware Team Join Date: May 2008 Location: S.E. Pennsylvania Posts: 18,450 OS: Win7	Re: Few questions about grounding yourself FYI "Use a torch to see into the case; I use one of those wind-up torches, so the battery doesn't give out at the wrong moment." British for Flashlight not to be confused with a Torch that has a Flame as in the US:) __________________ Power Supply and Selection

01-31-2009, 09:35 AM	#7 (permalink)
proto-man Registered User Join Date: Jan 2009 Posts: 3 OS: Linux Fedora	Re: Few questions about grounding yourself Thanks for your replies guys. I still don't think I completely understand the workings of grounding but I think I know enough for the practical use of discharging myself.