The Shocking Truth About ESD

Category: Hardware

I have warned readers to beware of static electricity – electrostatic discharge or ESD, in geek speak. Today, I’m going to explain in some detail what ESD is, what it can do to electronic devices, and how protect against this common hazard. Read on…!

What is Electrostatic Discharge?

I must confess that one of my favorite childhood pranks was shuffling around on a shag rug, and then touching my finger to a friend's earlobe. That's the low-tech definition of ESD. And maybe that's why I had to eventually make friends with computers. But I digress...

ESD is a high voltage, low amperage electrical current that flows suddenly and briefly between two objects when the make contact or come very close to each other. Voltage is the difference in electrical charge between two points. Amperage is the rate of flow of an electrical current. So an ESD involves a transfer of electrical charge from an object that has a lot of it to one that has much less, but at a relatively slow rate and for a very brief period.

Electrostatic Discharge

The upshot of an ESD is that its high voltage is literally shocking, but its brevity and low amperage transfer too little electrical energy to seriously harm a human being. But it can produce hilarious YouTube videos like this one .

However, electronic components are much smaller and more sensitive to ESD than humans. Tiny transistors, resistors, capacitors, etc., are designed for very precise voltages and amperages. Zap them with an ESD that is wildly outside of their operating parameters and visible holes will be burned in them. Lightning is a very large ESD, and a lightning bolt can start a forest fire.

ESD starts with a buildup of electrons on an object, creating a large voltage (difference in charges) between it and other objects. Typically, rubbing two different materials together will transfer some electrons to one of them. Some materials acquire electrons more easily than others. (Sneakers on a shag rug, for example.)

Are You High Voltage?

Studies have found that a typically clothed human body can build up charges (called “electrostatic potential”) of between 500 and 2,500 volts during a workday - far more than the mere 25 volts it takes to damage electronic components, yet below humans’ perception level. Many plastics, especially Styrofoam, have even higher electrostatic potential. Keep disposable coffee cups and other plastic items at least four inches away from electronic devices.

Even rubbing air molecules together rapidly builds up electrostatic potential, which is why blowing or vacuuming dirt out of a keyboard or computer can be hazardous. If you use “canned air,” use a brand made of “anti-static” gases that do not acquire electrons easily.

There is no way to prevent buildups of electrostatic potentials in all the objects, especially people, that come into contact with electronic devices. But we can make the ESD take a path that avoids the sensitive components inside.

People can ground themselves to avoid zapping their electronic devices. Electronics assembly, testing, and repair workers often wear wristbands that keep them constantly grounded via a wire attached to a nearby electron sink. Anti-static floor mats beneath one’s chair come with grounding wires that are attached to electron sinks; they’re a good idea, too.

Touching an electron sink before touching an electronic device will discharge your electrostatic potential; it’s a good thing to do each time you sit down at the computer. In practical terms, tapping an object that has a metal chassis and is plugged into a properly grounded outlet should do the trick.

Don't Try THIS at Home

Do not attach a wire to your computer’s chassis and then attach the other end to the grounding wire of an electrical outlet, a solution that seems obvious but is actually quite dangerous. AC current flowing through the nearby “hot” wires in the wall can induce an AC current in your grounding wire through electromagnetic induction. That current can flow through your computer to fry you as well as the machine!

Mobile devices that people carry on their persons will gradually acquire the same electrostatic potential that their owners have. An ESD happens only when there is a difference in potentials between objects, as our hapless friend in the video above demonstrates. So you need not worry about the phone in your pocket or the laptop in your shoulder bag.

As mentioned above, the electrostatic potential of the human body is normally imperceptible, even when it discharges. Just because you don’t feel “static shocks” or see little blue sparks is no assurance that you aren’t jolting your computer with enough ESD to damage it. So take precautions even if you don’t see or feel any ESD.

Your thoughts on this topic are welcome. Post your comment or question below...

 
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Most recent comments on "The Shocking Truth About ESD"

(See all 25 comments for this article.)

Posted by:

Joseph Palmere
20 Apr 2015

Bob,
Having worked in designing and testing Integrated
Circuits, you are so right in outlining this hazard. I remembered to always wear my wrist band and to make sure it was well grounded.


Posted by:

Jan
20 Apr 2015

Thanks for a short, but comprehensive and easily understandable explanation of ESD. Jan


Posted by:

Troy
20 Apr 2015

Having worked as an Electrician for several years I know for a fact that this statement is false "Do not attach a wire to your computer’s chassis and then attach the other end to the grounding wire of an electrical outlet, a solution that seems obvious but is actually quite dangerous." any computer that has a third grounding lug on its cord does exactly this! That grounding lug is connected straight to the case inside the computer.


Posted by:

Frank
20 Apr 2015

What you didn't mention is that the extra dry conditions here in the West, due to lack of rain has created a condition that is more conducive to static discharges. And by the way you can tell that the humidity is low by your nose. And because my nose unusually large I have a distinct advantage over others. I am that no one will be envious.


Posted by:

Dan
20 Apr 2015

I have encountered problems with computers related to the sudden zap of ESD - lost data and sudden blue or black screens. My solution was to place a grounding strip (similar to the wrist band) at the spot under the ledge of my desk where I grab it to pull my chair into position when I first sit down. This strip is just connected to the heat ducting of my furnace system. This automatically removes my charge painlessly and has protected my computers for many years now.


Posted by:

Robert Kemper
20 Apr 2015

Thanks Bob, for that very thorough and informative
article about ESD and the danger related to modern day electronics equipment.


Posted by:

Lee Hamilton
20 Apr 2015

Don’t try to go to the plumbing store for an electron sink. Sink here refers to a ground, typically an “earth” ground with a resistor in series leading to a banana jack mounted near your test station.

You connect the wrist strap to yourself, and plug the banana plug into the ground sink. To do the job right, you should have a tester to make sure that you are properly connected. You plug the banana jack into the tester, and touch a test point on the tester. If you are connected properly the tester will signal an ok, usually audible and visual. If not, there are conductive lotions that can be rubbed on your wrist to aid the connection. This was a necessity on several dry days. A proper workstation would also have an ESD mat connected to the ground sink, usually with a banana plug for your wrist strap cable.

In an industry setting a special grounded floor and heel straps can serve the same purpose, but still need testing to make sure that they are actually grounding.

Note that an untested wrist strap can be worthless. I once worked in a lab with over 20 other software engineers that were performing embedded work that included plugging memory chips into boards and boards into chassis, and emulators into CPU sockets after removing the CPUs. There were a handful of wrist straps floating around the lab, and ground sinks installed every 6 feet or so. I decided to test one, then all of the straps. The majority were open circuits, only two were functioning. That probably explains why some equipment was failing and PROMS that would no longer program. Quickly ordered enough for everyone that handled boards to have a wrist strap and cord and a few extras for the lab and provided instructions on testing at least daily. (Should be tested after attaching to your self before using, and retesting if removed and re attached, e.g. after lunch.) Unless they found another testing station, I don’t think anyone else bothered to test unless I said something as there were few entries from the software team in the log.

If you don’t have a proper setup, the poor man alternative is to grab an exposed part of a metal chassis that you will be working on. Grab it constantly or at least frequently so that you are at the same potential as the equipment that you are working on. If a board or other equipment needs to be removed, use an antistatic ESD bag for boards (save some for reuse); antistatic foam or tubes for chips. Grab the storage container while grounded before moving equipment. Putting bare equipment particularly chips and boards, on a table or desk, particularly on papers, is a recipe for needing replacements.

As an aside. I used to work on stage crew in high school. We would form a chain of 3 or 4 people, shuffle our feed on the carpet, then take a key and touch a metal object. We could get sparks over an inch long. (They really hurt without the key.)


Posted by:

Lee Hamilton
20 Apr 2015

Re Troy 20 Apr 15 "...I know for a fact that this statement is false "Do not attach a wire to your computer’s chassis and then attach the other end to the grounding wire of an electrical outlet, a solution that seems obvious but is actually quite dangerous." any computer that has a third grounding lug on its cord does exactly this! That grounding lug is connected straight to the case inside the computer."

In my early years I worked for an advanced research lab. The grounded chassis were a problem with ground loop currents, probably because there were several electrical panels that controlled the many outlets in the lab. Each ground plug had to be removed and the chassis connected to a common earth ground buried in the parking lot.

If the chassis is already grounded through the cord, don't connect another ground to the chassis.


Posted by:

Bill Boogaart
21 Apr 2015

I can recall when small electronic PBXs became popular we ended up replacing many of them until the technicians learned to properly use antistatic straps before taking off the cover to work on the insides of them. We even had training courses for techs to attend to learn about the damage ESD can cause, damage that might not even be apparent until much later.


Posted by:

Peter
21 Apr 2015

With regards to "repair workers often wear wristbands that keep them constantly grounded via a wire attached to a nearby electron sink", and the comment posted by Mike:

The idea of a low-resistance connection between the worker and the machine frame (i.e. the frame that is connected to ground when the machine is plugged in), is to eliminate the voltage potential between the worker and the machine. If there is no voltage potential between them, then there can be no electrostatic discharge in either direction.

The statement "No one should ground themselves while working around any electrical equipment unless they are using a wrist band specifically designed for this purpose" is also somewhat unclear. You must ground to the same ground as the equipment, otherwise you risk creating a phenomenon known as ground current. Basically it means that two different places on earth, even a few yards apart, are at different voltage potentials and are constantly changing as per ambient conditions, thus generating current through the circuit which passes through the person and the equipment.

Last but not least, some equipment uses a configuration known as a "Faraday cage", where the machine frame and case are actually electrified at a low voltage so as to prevent electrons and other particles from entering the space within the machine. This is more prevalent on main frames, and the wrist band must be used when working on the internals of such machines so as to eliminate voltage potentials.

Why don't birds get electrocuted on high wires? They just aren't grounded!

Cheers


Posted by:

Humbug7
21 Apr 2015

For Troy and Mike...I read this as a caution against using a jury-rigged grounding solution instead of the wrist-strap/sink mechanism mentioned. I think it's assumed if you've got your computer case open and are working on the components inside, you usually (I know, "not always!") have it unplugged. I heard somewhere that having an electronic device plugged in still doesn't provide adequate protection against ESD if you're working on the innards...anyone with more electrical knowledge have anything to say?

A note also: this is why many gas pumps have a caution against using cell phones while dispensing gas and why you shouldn't get into your car while gas is dispensing and then back out to put the nozzle back...you can theoretically generate enough ESD to ignite the fuel vapor.


Posted by:

HA
21 Apr 2015

Too bad, I am envious.


Posted by:

terry
21 Apr 2015

thanks Bob for reminding me about shuffling around on a shag rug, and then touching my finger to a friend's earlobe. we did that as kids, and rubbing the balloon and putting it "magically" on the wall. thanks for the sweet memories.


Posted by:

Patty
22 Apr 2015

FYI, it's not just computers. While dusting my TV, I got a static electricity shock and in the process fried the power switch. The TV was never able to be turned on again.


Posted by:

Marian
23 Apr 2015

I had an ipod Touch for a couple years and I had 6 electrical shock incidents that I never could figure out and I am not sure that anyone I told ever believed me. They have knocked the ipod out of my hand and the earbuds out of my ears and the jolt in my ears and head every time was awful. There was never anything consistant...I was inside, outside, on cement, on grass, different earbuds, different clothes, sometimes it was in my hand and sometimes in my pocket or purse. The only constants were the iTouch and that I have a pacemaker. Doctors couldn't believe the pacemaker had anything to do with it.

I lost the iTouch last year and replaced it in October with a Samsung Galaxy. I have used both earbuds and Bluetooth headphones with it and have not had an shock incident so far.

I would be interested to know if anyone else has had a problem with a mobile device.


Posted by:

Donald
23 Apr 2015

Some IBM Techs use the anti static wrist band on the nozzle of their vacuum cleaner to drain away static.


Posted by:

Earle
24 Apr 2015

I prefer a mat to the confinement of a wrist strap. My computers are in a study, where the entrance panels to the house are located. I have an alligator clip in the entrance panel permanently attached to the equipment ground bar in the panel. On the other end is a snap which will snap into the mat or a wrist strap. I might add, the house being older, the common and equipment grounds were the same until a tree fell across our power line. Now, the equipment grounds go all the way back to the utility company, at a total cost of around 9K (most paid by insurance). It's a PITA when I have to use my backfeed generator during extended outages, because I have to completely break the common and the equipment grounds to avoid electrocuting some poor utility worker...


Posted by:

Carol Keck
24 Apr 2015

I have blown out a stereo speaker and my car's amp just by using them. I also feel a strong shock sometimes from blankets, doorknobs, etc. In the dark, I can see quite the reactions. If you know, are some people generating more static electricity than others? I think I experience this much more often than others.

I assume I can allay this somewhat by touching a non-electronic metal surface first, but I don't often think of this, especially when getting in bed. :)


Posted by:

Michael L. McQuown
11 May 2015

At my last job, someone wiped out a $60,000.00 machine by vacuuming its insides with a vacuum cleaner that didn't have a grounded plug.


Posted by:

Quaid
02 Aug 2015

Thank you for the shocking article :)


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