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I would like to know how to properly use an antistatic wrist strap. By antistatic wrist strap I mean a band with a wire attached to it, with a metal clip on the end of the wire.

From what I read about them they really do help prevent harmful static discharge. However, it isn't clear to me what to connect the wrist strap to. Obviously one end goes around the wrist, the other is clipped to the ground. But what exactly is the ground? Does it work to connect it to:

  1. ... the case of the pc, while the power plug is still connected to the case, but the switch on the back of the PC is off. To me this seems risky, since it's difficult to guarantee the components of the PC are truly powered down.
  2. ... the case of the PC while the case is NOT connected to anything. There is no grounding to the actual earth in this case.
  3. ... the plumbing in my house, meaning radiators or metal piping. This doesn't seem like the ideal grounding to me, since the static charge on the plumbing could still differ from the charge of the computer case. Right?
  4. ... any large metal object, not connected to anything. It would just lose static to the air over a large surface area?

In all these cases I would of course not connect to a painted surface, since the paint might isolate rather than conduct the static electricity.

Additionally, is one wrist strap sufficient when working with both hands? Does the wristband drain the static on my other hand as well? (Sometimes a component is stuck, and may require two hands to pull it out.)

And what do I ground myself to when I am working on separate electronic components? For example; cleaning my graphics card while it is not in my computer case?

And finally, does a good anti-static wrist strap need a resistor? And if so, how much resistance should it offer?

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    It isn't required (seriously) if you're working in a good stable environment. – AStopher Sep 20 '15 at 7:09
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    In all the years that I've been fondling various computer components, I've never once worn one of these contraptions, have always mocked others for even suggesting it, and have never once observed or been accused of any destruction that was caused by this attitude. Anybody who gets super serious about this doesn't want to admit that this part of the job is just playing with glorified lego blocks. – user72945 Sep 20 '15 at 12:35
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    To those saying it isn't required, ok. But please back that statement up. Cause some people say it is, some people say it isn't. I am considering to work in a computer hardware shop, and I would like to be informed. If I am going work on the PC's of others, I rather be save than sorry. Even if the odds and stakes are low, it isn't very professional to go about things the wrong way. I rather at least know how to do it properly. For the record, I have worked on my PC countless times, and never used a wrist strap, but I would still like to know how to use one. – Static Storm Sep 20 '15 at 21:28
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    @TechnikEmpire: I just touch the unpainted metal near the power supply while the computer's still plugged in before touching components inside, just in case. I wouldn't futz with a grounding strap. – Peter Cordes Sep 21 '15 at 3:41
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    @StaticStorm "But please back that statement up." - it is a discussion fallacy, I'm afraid. Simplifying a bit, burden of proof only makes sense on people claiming there is something, for example a need. Proving there isn't is usually impossible. There is a thought experiment called orbital teapot. you can't prove there is no teapot orbiting Pluto, right? You can't prove that anti-teapot shielding is not needed on space probes there. But you probably feel this idea is ridiculous to begin with. People claiming that teapot is there might be asked for proof, but not the other way around. – Mołot Sep 21 '15 at 22:54
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To really answer this question, you need an understanding of both electric potential and house wiring.

All objects have an electric potential, sort of like the "pressure" caused by the electrons inside them. When two objects have different electric potentials, we say there's a "potential difference" or a "voltage" between them. When these two objects touch, the electrons will flow from the higher potential to the lower potential, similar to how fluids flow from high pressure to low pressure.

Hydraulic analogy
(image source)

This happens every time two objects touch. Usually you won't feel anything because the potential difference is so low (or the resistance so high), but occasionally the shock is large enough to feel. Potential differences of 10,000+ volts are common due to the triboelectric effect. Note that electrical components can be damaged by shocks that are too small to feel.

So, to prevent yourself from shocking the motherboard, you just need to make sure you're at the same electric potential, without causing a shock to do that.

Will connecting the strap to the motherboard work?

Yes, but I wouldn't recommend it.

It works without shocking the motherboard because the wrist-straps are specifically designed to equalize potential slowly. However, motherboards are delicate, and strap-clamps are not. There are wires literally painted onto the motherboard, which could be easily scratched off by a clamp. Also there's no particularly good place to clamp onto.

If you want to work on a lone motherboard, you should use an anti-static mat, which "connects" to the motherboard by touching its bottom

Anti-static mat
(image source)

Will connecting to the case work?

Yes, this is the recommended solution.

As long as the motherboard is screwed into the case, the two will be electrically connected by the screws. This is why all motherboards have metal rings where the screws connect (and why you should not use painted-screws).

Motherboard case connectors
(image source)

This is true whether or not the case is connected to Earth-ground (ie. plugged into a three-prong outlet).

I usually don't pay much attention to whether the PC is plugged in or not when I'm working on one, other than to make sure the power-supply is off. However, if you're working on multiple computers at once, I'd recommended plugging them all in to ensure they all stay at the same potential.

Will connecting to metal pipes, radiators, or the ground on an outlet work?

Yes, but it's not ideal.

As long as the computer is plugged into a three-prong outlet, the motherboard and case will be electrically connected to the ground wire from the outlet (why?). Any house-pipes are also supposed to be grounded, and so will be electrically-connected to the motherboard.

Ground across meter
(Ensuring pipes stay grounded in the presence of a water meter. Image source)

However, there's a few reasons this isn't ideal:

  1. It requires the computer to be plugged into the wall, which is inconvenient and increases the possibility of mistakes. If your strap is plugged into the wall but the computer isn't, you are not grounded to the computer!
  2. It assumes the house-wiring is correct and up-to-date, which is sadly often not the case, especially in older homes or (previous) homes of amateur DIY-electricians.
  3. It assumes the grounding circuit hasn't broken (if a pipe bonding wire came loose, you would probably never know it).
  4. Even if everything is wired and working correctly, it's still possible for a potential difference to build up between electrically-distant pieces of hardware. Wires have resistance too, after all.

Because of all this, I would only recommend connecting to pipes or the ground outlet if for some reason you absolutely cannot connect to the case.

Will connecting to any large metal object work?

No!

If this large metal object is not connected to anything, there's no reason to believe it will have the same electrical potential as the motherboard. Doing this is the same as grounding to nothing at all.

Is one wrist strap sufficient when working with both hands?

Yes.

There's enough oil, moisture, and salt on the surface of our skin to make it a half-decent conductor of electricity.

I used to work at a circuit-board manufacturer - they were extremely paranoid about static electricity. Every surface, including the floor, had to be at ground-potential. We had to wear anti-static coats, and our shoes needed to be conductive (or wear conductive shoe-straps). Even there, the workers only used one wrist-strap.

PCB manufacturing
(Not where I worked, but with similar outfits. Image source)

What do I ground to when I am working on separate components?

Place them on an anti-static mat and ground to that.

Your concern is making sure you and the components all stay at the same potential. This happens automatically when you touch the anti-static bags the components are in (the bags have a moderate resistance, so the potential equalizes slowly. One second should be enough time). From there, you should place the components on an anti-static mat, and ground your wrist-strap to the mat. From then on, you and everything on the mat will have the same potential. When you're done, make sure to place them back in their anti-static bags.

If you are working across multiple anti-static mats, you should ground them all to the house-ground, simply because is it a convenient, easily-accessible reference potential.

  • It's not just surface conduction that equalizes potential across your body. Your skin is moderately conductive, and the inside of your body is effectively salt water. If you're working on multiple things, can't you just touch the outside of their cases to ground them all safely? The problem with ESD causing damage is when it all goes into one data line or something. Even if you get a shock from touching the case, not enough current will move through any single transistor to cause any damage. The total charge that moves does so through all paths to ground at once. – Peter Cordes Sep 21 '15 at 3:48
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    I didn't mean sequentially. I was thinking, hold onto one while you touch the others, then maybe repeat the process. If you have more capacitance to ground than the objects, your voltage won't change much, and the objects will all approach each other in voltage w.r.t. ground. Fair point about generating static while working, though. I guess it's possible to build up enough charge between letting go of the object and touching it again to actual cause a damage-inducing discharge, esp. if you aren't working on it continuously. Anyway, touching the case before working is better than nothing – Peter Cordes Sep 21 '15 at 4:05
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    You mention clipping to motherboards is a bad idea, since they are delicate. If this is the only option though, then putting clip onto the plated screw holes from the edge of the board is best. This space intentionally has no delicate traces around. – tehwalris Sep 21 '15 at 14:17
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    Would working on anti-static bag (while touching it) help if you have no anti-static mat around? I have a big anti-static bag as a left over from my motherboard, and I don't open up my PC often enough to justify buying a mat. – Dumitru Sep 22 '15 at 7:03
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    @Dumitru: Ideally it should be a static-dissipative bag (metal-lined, silvery-grey) and not just an anti-static bag (transparent pink). But the grounding to the board should still be done. – Ignacio Vazquez-Abrams Sep 22 '15 at 9:42
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The ideal situation is to connect to the ground on an electronic device that is plugged in but turned off. Other grounds, such as radiators or plumbing, are a decent second choice. Professionals sometimes use an adapter that disconnects the hot and neutral leads and connects only the ground. For typical PCs, it's perfectly reasonable to just make sure the power supply switch is off.

If all else fails, you can connect it to your computer case even with it not connected to anything. At least that way there be no static discharge between your hand and the case.

While you connect the strap to your wrist, the charge over your entire body will be equal. So it will remove static charge from your entire body. Your wrists are already connected to each another through your skin.

A static wrist strap should have a resistor to ensure that it can't become a conduit for a potentially fatal, line voltage shock. One million ohms is typical. This still permits static to drain but prevents typical voltages from being able to push enough current to shock you.

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    Connecting it to things other then the case may not be such a good idea - particularly if the computer is unplugged or does not have a ground connection - you are best to connect it to the case - so that even if you have a floating earth, at least you and the case are at the same potential. – davidgo Sep 20 '15 at 1:07
  • you answered almost all my questions perfectly. However, what to do when I am working with a separate electronic component such as a circuit board or a graphics card outside the case? Does a wrist strap still work if the component itself is not grounded? Or would I need an anti-static mat? – Static Storm Sep 20 '15 at 1:10
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    @DarioOO No, static won't kill you. Accidentally touching a live wire while you have the (resistor-less) strap on the other hand will. The resistor is there to limit the current to something less fatal. – matega Sep 20 '15 at 12:57
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    @DarioOO You could because a short to ground could cause the ground line to no longer be at ground level, depending on how much resistance there is between the ground line and real earth. For example, your knee could touch a metal desk that's grounded through one device while your hand is grounded through the ground strap. If either ground experiences a short to the line (say your computer shorts line to ground), current could flow between the two grounds ... and you! But the bigger risk is what matega said. – David Schwartz Sep 20 '15 at 18:52
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    @DavidSchwartz Grounding to Earth ground is really only necessary when working over a large area (like at a circuit-board factory). When working on a single computer, grounding directly to the case is actually preferable (see my answer for details). – BlueRaja - Danny Pflughoeft Sep 20 '15 at 20:56
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CompTIA recommends that you have a properly grounded ESD mat. This is ideal if you are working on cleaning some of your components. If that is not practical for you, try to find an antistatic bag and sit the component on top of it while cleaning. I save those bags any time I buy electronics because they are quite handy. This may go without saying: pick up the component by only the metal plates. If it has no plate (RAM or system board), pick it up by the edges farthest away from the transistors and conducting metals.

There are standards defining appropriate ESD protection, namely ANSI/ESD S6.1, which aims for equal potential. When you are wearing one strap grounded, it does not necessarily mean that your other limbs have equal potential. The body does not have equal potential in all of its limbs even after grounding. As an example, you could drag your feet across carpet, touch the computer case with both hands, and still have an imbalance. In my time working in hardware, we used ESD floor mats and ESD desk mats grounded like you see below.

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How to properly use an antistatic wrist strap when working on a desktop PC?

An anti-static wrist strap is one part of a good anti-static solution. Alone it will help, but it doesn't resolve all the static problems you might encounter.

First you need a work surface that is also anti-static to place all the components on. Then you connect the strap to the work surface, or a grounding point that also grounds the work surface. This way you, the work surface, and everything you place on it is at the same potential. It isn't an issue of eliminating potential, it's an issue of matching potential slowly so that large damaging static discharges don't occur.

If you have an anti-static surface, such as an anti-static table mat, connect it to the ground lug of an outlet (the screw on the outlet cover is grounded) or use a special outlet adapter that connects the wire to the ground of the outlet. Follow the manufacturer's instructions and local code for this ground point. Note that there will be a resistor in this connection, usually 1M ohm.

Connect the wrist strap to the mat, and attach the wrist strap to yourself. This will also have a 1M ohm resistor in it. These resisters allow the potentials to equalize slowly without sparks, while also protecting the user against possible electrical hazards if one of the wires shorts to AC or another dangerous voltage source.

Once you and the mat are properly set up, you may start unboxing the products, and assembling the computer on top of the anti-static mat.

If you don't have an anti-static mat, you might consider cutting open the anti-static bag the motherboard comes in, resting the computer case on a portion of it, and clipping the wrist strap to the case. This is far from ideal, but you and the components will come to the same potential quickly and safely without damaging static discharges.

Lastly, to those who insist on claiming that anti-static protection is useless, please understand that most discharges are harmless, and that those discharges that do damage often don't destroy the product, they merely damage it. The damage may not be detectable in normal use, or it may appear as an infrequent, but frustrating, bug, freeze, glitch, etc. So you may have in fact assembled dozens of PCs without proper protection and had no problems you could attribute to your lack of protection - but you or your clients may also have been dealing with minor, infrequent problems and simply living with them because you can't easily find the problem. It's your choice, but you are spreading bad information when you claim that anti-static policies and procedures have no benefits. To me, it's not worth the time and frustration later when I can spend a little time and effort during the build to completely eliminate the possibility at build time.

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I would recommend using antistatic measures. One company I know making hi-tech lab gear stopped using antistatic workspaces. For 2 years everything was fine, then they noticed increasing failures.

It seems the static discharges rarely cause an actual failure but they can weaken the device internal structure causing more failures as time goes on.

They went back to using antistatic measures and failure rates returned to normal

  • This answer doesn't really add anything. The entire thread is about how to do it, not whether to do it. Several of the answers, including the accepted one, discuss antistatic measures beyond just the wrist strap. On a forum, it's common to pile on with related stuff. SU's Q&A format relies on answers being solutions to what was asked in the question. – fixer1234 Sep 23 '15 at 22:14
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My electrostatic strap comes with a dummy wall plug that has only the earth pin. I simply plug it into the mains, sort of.

enter image description here

If you can find one of these, or just the plug to go on the end, you're sorted.

  • That is, IF it is best to ground myself to electrical earth, rather than the case itself. But thanks for the advise. – Static Storm Sep 20 '15 at 21:34
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    @StaticStorm: I'm certainly no expert. But I would have thought it's best to earth everything, no? – Lightness Races in Orbit Sep 20 '15 at 21:35
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    @StaticStorm - You want to ground yourself, to electrical earth, since that means ground would be 0 Ohms. Which is the entire point of grounding yourself. Indeed putting the case on a grounding mat, and connecting it to the same ground, would be ideal. – Ramhound Sep 21 '15 at 1:15
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I thought this video might give some answers: https://www.youtube.com/watch?v=by4PB3WtdLo&feature=youtu.be

  • Links to YouTube videos are not helpful. Your answer should exist here, in text, not on a third-party website or in a video. – Ramhound Mar 21 '16 at 19:55

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