Where can I buy North America version of grounding plug?

[eeguy]

Hi,

I want to ground myself before using electronics components. I have an anti-static wrist strip already but no source for grounding. I am looking for something like this item to be used in Canada. Any suggestion on where to buy it?
 
https://shop.paperchain.net/anti-static--noshock-esd-grounding-plug---various-connections---1-x-10mm-stud-and-2-x-4mm-socket--uk/pi/PCV50064--49835-1.html

[timelessbeing]

Can't you just cut off a power cord?

[Ian.M]

Take a rewirable NEMA 6-15p plug,  insulate the Line and Neutral terminals inside it so the ground wire cant contact them if it comes loose, and connect the ground to a small box containing 2x full size 1/4W 560K resistor in series (for your safety) between the incoming ground, and a couple of 10mm press-studs (available from any good marine chandler or canvas-work shop), 4mm sockets, or whatever other  connector your ESD grounding accessories use.  You could also skip the NEMA 6-15p plug and instead, fit a IEC C14 inlet on the small box (L and N insulated as before) and simply plug it in with an ordinary PC power cord.

Its also worth fitting a 'hard ground' screw terminal post that can take 4mm plugs, connected direct to the ground wire for occasions when you need to ground equipment chassis etc.  *NEVER* use a 'hard ground' for personal grounding as it increases the risk if you get a shock.

[eeguy]

I touched the computer case a few times and got some kind of electric shocks. Do I have to worry? Somebody mentioned that I should plug the power cord from the power supply to the electric outlet, have the power supply of the computer off, connect the anti static wrist strip to the unpainted metal frame of the computer case before installing/uninstalling the components. However, my case came fully painted. I think the power supply is the same. So it means even I connect the wrist strip clip to the case, I don't get grounded. What suggestion do you have?

[Gregg]

I have an older model (made in USA) outlet strip that the metal case is screwed together.  I simply put a green binding post near one end and connected it to the ground wire.  Older outlet strips are often available in thrift stores and yard sales for next to nothing.
Also the standard North American three prong 120 volt plug is a NEMA 5-15P. 

[eeguy]

Is it dangerous to touch the "supposed" to be ground on the wall outlet? Will I get killed sticking a metal in that hole? I am living in a condo in Canada. Don't know if those previous owners have done anything to the wall outlets. The former one surely fooled around with various things in the unit before I moved in.

[GreyWoolfe]

I took a cheap 3 prong replacement plug from Home Depot and removed the line and neutral terminals.  I attached the ground point wire to the ground pin using a banana plug and jack and plugged into an unused outlet.  Maybe that would work for you.  I have a 2 outlet ground point that snaps onto the 10 mm stud on my ESD mat.

[timelessbeing]

I touched the computer case a few times and got some kind of electric shocks. Do I have to worry?

You should be worried that your body is generating a lot of static electricity. You want it to jump to the case, but if it happens so frequently then you definitely want to wear the strap.

However, my case came fully painted.

I've never seen a case that is painted on the inside. Even if it is, there must be some unpainted screws.

Is it dangerous to touch the "supposed" to be ground on the wall outlet?

No it's safe. Otherwise everything in your house would be live.

[Ian.M]

Is it dangerous to touch the "supposed" to be ground on the wall outlet?

No it's safe. Otherwise everything in your house would be live.

That's only true if the outlet in question is properly wired and grounded.  If its on a GFCI protected circuit, the chance of it being dangerous is vanishingly small, but if you are in an older property without whole-house GFCI protection, and there is a break in the ground between the outlet and the panel feeding it, the combined ground  leakage current of all other devices on the circuit may add up to enough to be dangerous if you become part of the ground path. e.g. by touching the outlet ground with your other hand on a water pipe. 

If in doubt, check the ground integrity.  A socket tester will tell you its probably grounded OK, but if you want to be absolutely certain you need to check the ground resistance is within the limits set by the NEC, using a sufficiently high test current to fuse any weak connections that would be likely to fail under fault conditions.  That's a specialised test, best left to a professional electrician, who will have the appropriate test equipment.

[timelessbeing]

the combined ground  leakage current of all other devices on the circuit may add up to enough to be dangerous

What are the chances of this? Wouldn't that require some spectacular failure?

[james_s]

Touching the ground terminal in the outlet is the same as touching the metal housing of any grounded appliance plugged into the outlet. If there is any doubt you should test your outlet to make sure it's wired correctly and properly grounded. This is true whether you want to ground a wrist strap to it or just plug something into it.

[Ian.M]

the combined ground  leakage current of all other devices on the circuit may add up to enough to be dangerous

What are the chances of this? Wouldn't that require some spectacular failure?

The chance is pretty small, but no actual fault (other than the upstream open ground) is required.  All it needs is a *LOT* of PCs or similar equipment with grounded SMPSUs on the circuit.  However if there is a second fault and no GFCI, then everything 'grounded' on the circuit may already be live, with no one realising until some unlucky sod gets electrocuted.

If the O.P. is getting shocks off the PC chassis, and its plugged into a supposedly grounded outlet, the question that must be asked is: Do you ever get a second shock if you touch it again without otherwise moving around?  If the answer is yes, it may not be ESD, so isolate the circuit at the breaker and call in a professional electrician.

[TheNewLab]

Just cutting off a 3 wire grounded plug, using a resistor on the ground wire is the simplest. In my case, I just cut into the ground wire of a computer cord. 500K resistor extended to a 1M connector box for straps and anything else needing connection.
I went ahead and kept the rest of the cord running it to a 2 wire polarized connector I had and spliced into the computer cord. So long as the ground wire is safely isolated, with a resistor to protect yourself you are fine.

most straps have 1M resistors, but you still want a small resistor at the point of splicing into the ground (as stated above)..just to be safe.

[timelessbeing]

All it needs is a *LOT* of PCs or similar equipment with grounded SMPSUs on the circuit.

How many?

if there is a second fault and no GFCI, then everything 'grounded' on the circuit may already be live, with no one realising until some unlucky sod gets electrocuted.

Right, so if there's a fault AND if there's no gfci AND if the ground circuit isn't actually grounded...

If it were a problem, then you couldn't have anything with exposed grounded chassis (microwave, stove, PC etc...). Essentially, we can call it "safe". And it should be, because it is exists preceisely to protect you from faults.

[Ian.M]

The max leakage current permitted for grounded IT equipment is 3.5mA.  A single workstation consisting of a PC, monitor and printer, could therefore leak over 10mA to ground, enough for a significant shock.   A home office with a couple of PCs, or a PC and a multimedia center will probably leak over 10mA to ground. 

To get lethal levels of leakage current, you more or less have to have an appliance suffering from partial insulation breakdown.  Heating, cooking, refrigeration and washing appliances are particularly liable to faults of this nature.  Without GFCI protection, such faults typically go undetected so long as the ground connection remains intact, until the insulation 'cooks' enough to fully breakdown and blow the fuse or trip the breaker.  Therefore on a non-GFCI-protected circuit, a open ground fault can immediately present a lethal hazard.

If you value your and your family's lives, fit GFCI protection on *every* circuit feeding socket outlets!

[timelessbeing]

A single workstation consisting of a PC, monitor and printer, could therefore leak over 10mA to ground, enough for a significant shock. 

Sorry but this doesn't make any sense.
I have several such devices (more than you describe) connected in my office, and they certainly do not give me "significant shocks". There would have to be close to 100V just to penetrate your skin (in addition to an open ground circuit).

If you value your and your family's lives, fit GFCI protection on *every* circuit feeding socket outlets!

In North America this simply isn't common practice, and families aren't dying.

Your claim that touching household ground is dangerous, is nonsense.

[Ian.M]

You cant get a shock from the ground leakage current of grounded equipment  if the ground conductor is intact all the way back to the panel and the grounding rod.  3.5mA is the worst case limit (in most 230V countries), and with a 120V supply + equipment having less than the permitted leakage current its probably <1mA per item.   If it was more, nuisance tripping would be an even worse problem than it is due to your NEC calling for class A GFCIs for personnel protection with trip current in the range 4 to 6 mA.  That's fine for a single or duplex outlet but risks nuisance tripping if you feed more outlets off it.   

IMHO that's self-defeating on the part of the NEC as it discourages the use of GFCI protection on circuits that don't require it by code due to the expense of fitting individual GFCi outlets to avoid the nuisance tripping problem.

The rest of the world typically use GFCIs in the 10 to 30 mA range, often combined with an over-current circuit breaker, to feed a whole circuit, and in developed countries, there is an increasing trend to protect *ALL* domestic circuits.  There's a slightly higher shock risk due to the higher trip current, but that's mitigated by the much higher probability that an outlet will be GFCI protected.

[eeguy]

the combined ground  leakage current of all other devices on the circuit may add up to enough to be dangerous

What are the chances of this? Wouldn't that require some spectacular failure?

The chance is pretty small, but no actual fault (other than the upstream open ground) is required.  All it needs is a *LOT* of PCs or similar equipment with grounded SMPSUs on the circuit.  However if there is a second fault and no GFCI, then everything 'grounded' on the circuit may already be live, with no one realising until some unlucky sod gets electrocuted.

If the O.P. is getting shocks off the PC chassis, and its plugged into a supposedly grounded outlet, the question that must be asked is: Do you ever get a second shock if you touch it again without otherwise moving around?  If the answer is yes, it may not be ESD, so isolate the circuit at the breaker and call in a professional electrician.

I touched the case about 10 times (don't remember if the computer was on or not). Half of the time I got such shocks. I also got shock one time I touched the heatsink when the machine was on. I asked the case manufacturer a week ago. They are still investigating the course but no definite answer yet. So, I suspect may be the outlet is not properly grounded or there is something wrong with the power supply. I asked the power supply company Corsair but they have no comment.

Case manufacturer told me that there is no unpainted metal part of the case.

My area is about -15c to -30c this week. The shocks happened when  the temp was about 5 to -10c.

[Richard Crowley]

https://www.amazon.com/StaticTek-Adapter-Universal-Connection-Unbreakable/dp/B071J61CSV

[Ian.M]

Start by unplugging the PC from the wall and checking continuity from a screw on the PC PSU to the ground pin of the plug on its power lead.  If its got continuity, the next step is to go to the hardware store to get an outlet tester, and check the outlet.  If it doesn't pass (see tester instructions) go round your house testing all the three pin outlets, mark those that fail, then you need to consult an electrician.   

The electricity supply company's responsibility ends at the meter - if they are delivering power that meets the standards that far, anything past that point is the responsibility of the homeowner, so don't expect much from the supply company s helpline other than "Call a licenced electrician"

[eeguy]

Thanks Richard and Ian for the suggestions. Just performed continunity tests by connecting one probe of the tester to the ground pin of the power cord of the PSU and the other probe to the point of test. Here is the results:

1. Beep sounded when the other probe touched any of the screws that connect the power supply to the case. Does that mean if I connect one end of the wrist strip to one of the screws, I will be grounded?

2. No beep sound when the other probe touched the screws that connect the motherboard to the computer case. (How they ground the motherboard then? Via wires that connect usb ports from the case to the motherboard?)

3. No beep sound when the other probe touched the surface of the computer case.

4. No beep sound when the other probe touched the surface of the PSU.


In this case, for convenience, is it still better to buy one or two StaticTek adapter(s)? Besides building computer, I will build some electronic circuits at home as well.

My electric outlet is like the one shown in the StaticTek product page. Before I did the tests, I was thinking of:

1. Buy one StaticTek Adapter and connect it to the wrist strap
https://www.startech.com/ca/Computer-Parts/System-Build/Anti-Static/Anti-Static-Wrist-Strap~SWS100

2. Buy another StaticTek Adapter and connect it to the matt
https://www.startech.com/ca/Computer-Parts/System-Build/Anti-Static/24x27in-Beige-Desktop-Anti-Static-Mat~M3013

Can I assume for sure that those two 3-pin sockets are connected to the same ground? If they are not, I may introduce a potential different in grounds which is not good.

[Ian.M]

The tray the motherboard is mounted on should be grounded, and motherboard screw holes that have a silver coloured ground pad round them should be screwed down to a metal standoff pillar so those screws should be grounded.  However paint is an insulator so it is likely your PSU doesn't ground properly to the case.    Fortunately the 0V wiring coming from the PSU and going to the motherboard and drives is normally internally grounded in the PSU and that will be grounding your motherboard.  Check continuity between the PSU screw you tested to earlier, and a black wire on a spare drive power connector (old style connector not SATA power connector) to confirm that.

Fixing your PC's internal chassis grounding problems could be quite tedious.  It will probably involve a lot of work scraping away tiny circles of paint under screw heads, and/or fitting serrated washers under the screw heads.

I wouldn't trust there not to be a potential difference between two outlet grounds unless they are on the same faceplate or power strip.  However ESD grounding almost invariably has high value series resistors, and potential differences in grounding systems are typically very small, so with no low impedance path between the two grounding plugs other than the ground wiring in the wall, there are no significant risks to you or to equipment.   Before putting multiple grounding plugs into service, plug them in and check the resistance between their ESD grounding connectors is double that between a single plug's ESD grounding connector and its ground pin.  If there is no resistance between the connector and the pin you *MUST* use ESD leads with a built-in safety resistor.   

Whether or not your outlets are grounded at all or to the same ground can only be definitely resolved by resistance measurements with the breaker(s) in the panel feeding them off, between them, and a ground point in the panel and a temporary test ground rod.   Doing such tests properly requires a good working knowledge of your electrical regulations (US National Electrical Code), and specialised test equipment which is why calling a qualified electrician is recommended if you don't have previous experience and training in performing NEC compliant electrical work.   A rough check can be made with an ordinary multimeter, but if there is a pre-existing fault, dangerous voltages may be present on supposed grounds so be careful and test for voltage difference before doing any resistance checks.  A socket tester is useful as a quick and cheap check that anyone can make that shows you if Line, Neutral and Ground are present at a socket and wired to the correct pins, but it wont find connections that have a higher than normal resistance e.g. due to a loose terminal screw, wirenut or backstab connector + oxidisation on the wire end.

[timelessbeing]

My area is about -15c to -30c this week. The shocks happened when  the temp was about 5 to -10c.

Cold temps make the air dry and it's easier to build up static electricity on your body.

1. Beep sounded when the other probe touched any of the screws

"Beep" means that whatever your probe tips are touching is electrically connected, therefore the screw is grounded. Tighten the screw down onto a piece of wire connected to your strap and you'll be fine.

The electricity supply company's responsibility ends at the meter

Corsair is a PC component manufacturer, not an municipal utility provider.

[eeguy]

The tray the motherboard is mounted on should be grounded, and motherboard screw holes that have a silver coloured ground pad round them should be screwed down to a metal standoff pillar so those screws should be grounded.  However paint is an insulator so it is likely your PSU doesn't ground properly to the case.    Fortunately the 0V wiring coming from the PSU and going to the motherboard and drives is normally internally grounded in the PSU and that will be grounding your motherboard.  Check continuity between the PSU screw you tested to earlier, and a black wire on a spare drive power connector (old style connector not SATA power connector) to confirm that.

Fixing your PC's internal chassis grounding problems could be quite tedious.  It will probably involve a lot of work scraping away tiny circles of paint under screw heads, and/or fitting serrated washers under the screw heads.

I wouldn't trust there not to be a potential difference between two outlet grounds unless they are on the same faceplate or power strip.  However ESD grounding almost invariably has high value series resistors, and potential differences in grounding systems are typically very small, so with no low impedance path between the two grounding plugs other than the ground wiring in the wall, there are no significant risks to you or to equipment.   Before putting multiple grounding plugs into service, plug them in and check the resistance between their ESD grounding connectors is double that between a single plug's ESD grounding connector and its ground pin.  If there is no resistance between the connector and the pin you *MUST* use ESD leads with a built-in safety resistor.   

Whether or not your outlets are grounded at all or to the same ground can only be definitely resolved by resistance measurements with the breaker(s) in the panel feeding them off, between them, and a ground point in the panel and a temporary test ground rod.   Doing such tests properly requires a good working knowledge of your electrical regulations (US National Electrical Code), and specialised test equipment which is why calling a qualified electrician is recommended if you don't have previous experience and training in performing NEC compliant electrical work.   A rough check can be made with an ordinary multimeter, but if there is a pre-existing fault, dangerous voltages may be present on supposed grounds so be careful and test for voltage difference before doing any resistance checks.  A socket tester is useful as a quick and cheap check that anyone can make that shows you if Line, Neutral and Ground are present at a socket and wired to the correct pins, but it wont find connections that have a higher than normal resistance e.g. due to a loose terminal screw, wirenut or backstab connector + oxidisation on the wire end.

Thanks. Is this the device to test if the 3 holes in each socket are wired correctly as expected?

https://www.kleintools.com/catalog/electrical-testers/gfci-receptacle-tester

[Ian.M]

Yes, that will do the job and vastly reduce the risk of you geting a nasty surprise.

That's a luxury socket tester as it also has the ability to test if the circuit's GFCI protected.   You could get away with a basic no buttons 'three lights' one, but its nice to have the GFCI  test button, so if you are happy with the price, go for it.   IMHO every homeowner who's not dangerously DIY-incompetent should have one.

The electricity supply company's responsibility ends at the meter

Corsair is a PC component manufacturer, not an municipal utility provider.

   
I don't expect to recognise the names of N.A. local utility companies and aren't in the PC building biz, so that flew right past me!

[eeguy]

Thanks. But that alone cannot test if the two ground holes are connected. Based on what I read in this thread, it seems that I have to open the socket which could be dangerous?

[Ian.M]

That tester shows a different light pattern if the ground is not present.  It wont tell you if the ground resistance is as low as it should be, but will detect gross wiring errors and open circuits.  If both sockets test OK, I'd have no hesitation using them with ESD grounding adaptors.  If however you need a guaranteed low impedance ground for any reason, further testing with better measuring equment would be required.

[james_s]

Testing the ground impedance is reasonably easy, just wire up an incandescent bulb between hot and ground, if it lights full brightness then the ground is almost certainly in good shape.

[Richard Crowley]

Testing the ground impedance is reasonably easy, just wire up an incandescent bulb between hot and ground, if it lights full brightness then the ground is almost certainly in good shape.

And if it trips your RCD or GFCI, then that protection is working properly as well.   

[eeguy]

The tray the motherboard is mounted on should be grounded, and motherboard screw holes that have a silver coloured ground pad round them should be screwed down to a metal standoff pillar so those screws should be grounded.  However paint is an insulator so it is likely your PSU doesn't ground properly to the case.    Fortunately the 0V wiring coming from the PSU and going to the motherboard and drives is normally internally grounded in the PSU and that will be grounding your motherboard.  Check continuity between the PSU screw you tested to earlier, and a black wire on a spare drive power connector (old style connector not SATA power connector) to confirm that.

Fixing your PC's internal chassis grounding problems could be quite tedious.  It will probably involve a lot of work scraping away tiny circles of paint under screw heads, and/or fitting serrated washers under the screw heads.

I wouldn't trust there not to be a potential difference between two outlet grounds unless they are on the same faceplate or power strip.  However ESD grounding almost invariably has high value series resistors, and potential differences in grounding systems are typically very small, so with no low impedance path between the two grounding plugs other than the ground wiring in the wall, there are no significant risks to you or to equipment.   Before putting multiple grounding plugs into service, plug them in and check the resistance between their ESD grounding connectors is double that between a single plug's ESD grounding connector and its ground pin.  If there is no resistance between the connector and the pin you *MUST* use ESD leads with a built-in safety resistor.   

Whether or not your outlets are grounded at all or to the same ground can only be definitely resolved by resistance measurements with the breaker(s) in the panel feeding them off, between them, and a ground point in the panel and a temporary test ground rod.   Doing such tests properly requires a good working knowledge of your electrical regulations (US National Electrical Code), and specialised test equipment which is why calling a qualified electrician is recommended if you don't have previous experience and training in performing NEC compliant electrical work.   A rough check can be made with an ordinary multimeter, but if there is a pre-existing fault, dangerous voltages may be present on supposed grounds so be careful and test for voltage difference before doing any resistance checks.  A socket tester is useful as a quick and cheap check that anyone can make that shows you if Line, Neutral and Ground are present at a socket and wired to the correct pins, but it wont find connections that have a higher than normal resistance e.g. due to a loose terminal screw, wirenut or backstab connector + oxidisation on the wire end.

Thanks. Is this the device to test if the 3 holes in each socket are wired correctly as expected?

https://www.kleintools.com/catalog/electrical-testers/gfci-receptacle-tester

Just tested the two sockets using this device. The orange LED in the middle and on the right were on at the same time. According to the table, it meant "Fault=Correct", "Explaination: Receptacle is wired correctly".  When I pressed the black button in the middle of the device, the GFCI LED was on for both sockets. So, it is safe to use the "StaticTek Banana Jack Outlet Plug Adapter" Richard posted in Post#18 on these two sockets?

In order to see if the two grounds of the two sockets are the same, can I just plug each probe of a multimeter into each ground and measure the voltage (zero if they are connected) or just test continuity (beep if they are connect)?

[Ian.M]

'Fault'='Correct' is the indication it gives when it detects a correctly wired, grounded socket.

It has a separate indication for 'no ground', which is permitted for three pin sockets under the US NEC but *ONLY* if the socket is labelled as such and is GFCI protected.

N.B. it cant detect if Neutral and Ground are swapped on a non-GFCI protected circuit, as those wires should be at the same potential (give or take a few volts). 

The 'Test' button applies a small test leakage current >6mA between Line and Ground.  If the socket is GFCI protected and the GFCI is working, when you push 'Test' the GFCI should trip almost immediately, and cut the power faster than you can react.   If the GFCI LED stays on when you hold 'Test', either there's no GFCI, or its bad.

You can check voltage between the two socket grounds, but I wouldn't advise checking continuity unless you have killed power to both sockets by tripping the breakers in the panel.  A continuity test may be ambiguous anyway as its US practice for Neutral and Ground to be bonded together in the master panel, and if not, are bonded together somewhere in the neighbourhood by the supply company.

[eeguy]

'Fault'='Correct' is the indication it gives when it detects a correctly wired, grounded socket.

It has a separate indication for 'no ground', which is permitted for three pin sockets under the US NEC but *ONLY* if the socket is labelled as such and is GFCI protected.

N.B. it cant detect if Neutral and Ground are swapped on a non-GFCI protected circuit, as those wires should be at the same potential (give or take a few volts). 

The 'Test' button applies a small test leakage current >6mA between Line and Ground.  If the socket is GFCI protected and the GFCI is working, when you push 'Test' the GFCI should trip almost immediately, and cut the power faster than you can react.   If the GFCI LED stays on when you hold 'Test', either there's no GFCI, or its bad.

You can check voltage between the two socket grounds, but I wouldn't advise checking continuity unless you have killed power to both sockets by tripping the breakers in the panel.  A continuity test may be ambiguous anyway as its US practice for Neutral and Ground to be bonded together in the master panel, and if not, are bonded together somewhere in the neighbourhood by the supply company.

Just tested again. For both sockets, the GFCI LED stayed on as long as I presssed the middle black button of the device.

[Ian.M]

So the sockets aren't GFCI protected.   If you are ever working on a mains PSU circuit, or other mains control circuit you should therefore use a plug-in GFCI  feed the device you are testing (D.U.T.).  If you are testing or using SMPSUs that may be of dubious far east origins, I would also recommend a GFCI, even if you never open their cases.  Get one and use it - its far cheaper than a funeral!

From the point of view of ESD grounding, the test iindicates you can use both sockets. The built-in safety resistor that is supposed to be present in all ESD grounding accessories will prevent any hazard or other issues if there is ever a small potential difference between their grounds. 

However, I wouldn't trust them if you need two devices to have the same low impedance mains ground as you don't know how big the ground loop is - it could go right back to the panel, or in a large apartment building, right back to the utility company's transformer! Therefore, if you need your D.U.T. to have a common ground with your test equipment, feed everything from a good quality socket strip plugged into *ONE* of the outlets to minimise the ground loop size.  This typically apples for  scopes, signal generators, PSUs with grounded output and PC based USB connected test equipment, as any significant ground differential can cause $expen$ive$ damage.  If you are setting up a permanent workbench with mounted socket strips fed from separate wall outlets, bond all their grounds together at the bench with heavy wire or braid when you fit them to mitigate this issue.

One nasty 'gotya' is mains powered soldering irons and many soldering stations typically have the tip directly grounded without a safety resistor as the leakage current through the element insulation when hot may be too high to permit including one.  If you use the soldering iron on the D.U.T. without disconnecting other grounds to it, and they are plugged into different wall sockets, if there is a large ground loop, induced transients may be enough to blow sensitive semiconductors on your board!

[eeguy]

If I just install and uninstall components on the PC and make electronics circuits for school projects at home, do I need GFCI?

Just to clarify, is it fine if I just use ONE StaticTek Banana Jack Outlet Plug Adapter in the following cases:

1. Connect it between the Startech's anti-static mat and the electric outlet. Can make PC and electronics circuits on the mat for school projects at home.
2. Connect it to between the Startech's anti-static wrist strap and the electric outlet during components installation/uninstallation on PC.

However, it is NOT good if:

3. I have the power cord of the PC plugged into one socket of the wall (even the PC is turned off) while I have the Startech's anti-static wrist strap connected to another socket vai the StaticTek Banana Jack Outlet Plug Adapter. This is because it means I connect two grounds indirectly through the system (myself and the computer).

Am I correct?

[Ian.M]

The ESD grounding adapter should have a safety resistor of approx. 1 meg between its mains ground pin and its ESD grounding connector.  Confirm its got one using your DMM.  If it has that, (or if the leads you use with it have an inline safety resistor) its safe even in a different mains outlet to the equipment as long as both outlets test as having ground connected.

If you *NEVER* work on any PSU or mains powered device with any exposed mains connections inside it,  never buy cheap far-east wallwarts, USB chargers or mains powered test  equipment or tools and never work on AT era and earlier PCs which typically had mains connected to the front panel power switch, a plug-in GFCI will do little to improve your safety.  However it could save your life if you are ever trying to troubleshoot a device with a  counterfeit wallwart.

[eeguy]

The ESD grounding adapter should have a safety resistor of approx. 1 meg between its mains ground pin and its ESD grounding connector.  Confirm its got one using your DMM.  If it has that, (or if the leads you use with it have an inline safety resistor) its safe even in a different mains outlet to the equipment as long as both outlets test as having ground connected.

If you *NEVER* work on any PSU or mains powered device with any exposed mains connections inside it,  never buy cheap far-east wallwarts, USB chargers or mains powered test  equipment or tools and never work on AT era and earlier PCs which typically had mains connected to the front panel power switch, a plug-in GFCI will do little to improve your safety.  However it could save your life if you are ever trying to troubleshoot a device with a  counterfeit wallwart.

By "ESD grounding adapter", are you referring to "StaticTek Banana Jack Outlet Plug Adapter"? The manufacturer told me that:

"there is no resistor in the ground adapter. It is directly connected to the ground connection on an outlet."

They also mentioned: "in a normal configuration the outlet is grounded through a bus bar that has to be physically removed if the ground is not used. Normally and outlet would share the same ground connection to earth ground and any other outlet in the area would share the same connection."

Note that they used "normal" twice so I guess unless we open the outlet and test, we can't tell for sure.

[Ian.M]

Yuk.     What you never want to happen is for a wrist strap to directly connect to ground without a safety resistor, otherwise the chances of electrocution if you touch a live conductor with the other had are *MUCH* higher.  If all ESD kit has integrated safety resistors, that cant happen.  Its not a good idea to rely on a single safety resistor, because the wrist strap and its lead both wear out with use and age, and when you replace one of them, you may accidentally get a counterfeit with no resistor.


As the StaticTek manufacturer have said it doesn't have a resistor, the leads you use with it *MUST* have a 1 Meg internal resistor, and you'd be best off making up an short Y adaptor to allow both the mat and the wrist strap leads to connect to the same StaticTek grounding plug to minimise the risk of a potential difference between them.  Alternatively,  if the mat's got two studs, you could use one to ground it to the StaticTek and the other for your wrist strap lead.  I'd want the StaticTek to either be plugged into a duplex outlet with the other one feeding your bench, or plugged into a good quality socket strip feeding the other gear on your bench, that you have personally checked is wired correctly.  In fact if you are wiring the socket strip yourself or its rewirable, you could skip buying the StaticTek, and make your own ESD grounding connector box for it as I described in my first reply, freeing up an outlet on the socket strip.

[Gregg]

FYI, never assume your building is wired correctly.  Here is something I found a couple of months ago in a house I am selling as executor of an estate.  I strung new green wires from the main ground bus in the electrical panel to each outlet and wired them all with a real ground.  Note how the short green wire connects the neutral to the terminal that is supposed to be grounded.

[timelessbeing]

Wow look at that textile sheathed wire. Must be an old installation that originally had a two pronged outlet.

Apparently this is still permitted in existing installations
https://en.wikipedia.org/wiki/Bootleg_ground

[james_s]

Looks like 1950s, I still see quite a bit of that stuff, it's the predecessor to modern Romex.

[Gregg]

Close guess on 1950's wiring, the house was built in 1942.  That crap makes knob and tube look good!     I used heat shrink on all of the wires as the rubber under the braid was breaking away and the cotton braid wasn't in good shape; then I used pigtails to the new receptacles to not disturb the existing any more than necessary.  If it had been my own house, I would have rewired everything and added 4x as many outlets.  I found this problem when I went to install GFCI receptacles.  I did add 6 new circuits in the kitchen and laundry room.  The service had been upgraded, but not the existing wire runs. 

[Nusa]

Bootleg grounds (connecting neutral and ground prongs at the outlet) has never been legal on 3 prong generic outlets. The old exception mentioned in wikipedia applied only to certain permanently wired and appliance outlets. When you find such things, they should either be fixed to have proper grounds, reverted to two-prong outlets (still no ground, but they're grandfathered as legal), or have a gfci outlet installed.

As an aside, knob and tube wiring as originally installed is generally very safe, so long as it's hasn't been disturbed inside walls or ceilings or incorrectly spliced with more modern wiring. Sadly, there are a lot of idiots out there that modify it without knowing what they're doing.

[eeguy]

Yuk.     What you never want to happen is for a wrist strap to directly connect to ground without a safety resistor, otherwise the chances of electrocution if you touch a live conductor with the other had are *MUCH* higher.  If all ESD kit has integrated safety resistors, that cant happen.  Its not a good idea to rely on a single safety resistor, because the wrist strap and its lead both wear out with use and age, and when you replace one of them, you may accidentally get a counterfeit with no resistor.


As the StaticTek manufacturer have said it doesn't have a resistor, the leads you use with it *MUST* have a 1 Meg internal resistor, and you'd be best off making up an short Y adaptor to allow both the mat and the wrist strap leads to connect to the same StaticTek grounding plug to minimise the risk of a potential difference between them.  Alternatively,  if the mat's got two studs, you could use one to ground it to the StaticTek and the other for your wrist strap lead.  I'd want the StaticTek to either be plugged into a duplex outlet with the other one feeding your bench, or plugged into a good quality socket strip feeding the other gear on your bench, that you have personally checked is wired correctly.  In fact if you are wiring the socket strip yourself or its rewirable, you could skip buying the StaticTek, and make your own ESD grounding connector box for it as I described in my first reply, freeing up an outlet on the socket strip.

Thanks. I have an idea. Could you please check if this will work?

I have a surge protector. How about connecting this surge protector to a normal electric wall outlet. Then, since the ground of the sockets in the surge protector should be connected (are they?), just plug the two StaticTek Banana Jet Outlet Plug adapters to two of those sockets in the surge protector. Then, connect the Startech wrist strip to one StaticTek Banan Jet outlet Plug adapter and the Startech mat to another StaticTek Banana Jet outlet plug adapter. This allows the mat and the wrist strip to share the same ground. If I make a PC rather than build electronics circuits, I just connect the power cord of the PC to the same surge protector. This allows the PC, the wrist strip and the mat to share the same ground. Will it work?

[Richard Crowley]

Most consumer "surge protectors" are a cheap $2 plastic power strip with a "one-time" 73-cent MOV across neutral to hot.
The green-wire, round-pin ground terminal should be hard-wired from the input plug all the way through to the last output receptable.
There should be absolutely no difference between a cheap power strip and a rip-off expensive "surge protector".
Or even if you have a "real" $200 surge-protector, the grounds are hard-wired all the way through everywhere.

Of course, the more different gadgets, plugs, receptacles, etc. you go through the reliability is necessarily reduced, perhaps by only a small, insignificant, but non-zero amount.

BONUS MATERIAL:  Consumer "surge protectors" RANT:
I never use consumer "surge protectors".  Whatever minuscule "protection" they offer is not worth the significant premium price.
Even if they did protect you from some moderate surge, the chances are that the incident blew out the MOV.
So now you think you are protected, but you have no way of knowing.  IMHO cheap consumer plastic "surge protectors" are rip-off junk.
And they offer no protection at all from a really significant surge.

End of RANT.

[Ian.M]

As long as you've checked ground continuity of the surge protected socket strip, from the outlets right back to its plug, and you plug it into a wall outlet that is grounded (as confirmed by your outlet tester, in a property that has passed an electrical inspection and hasn't had any rewiring or other major electrical work done since the inspection - see Gregg's horror photo above!), then,*IF* the Startech leads for the mat and wrist strap contain safety resistors (which they should have, check with your DMM),  yes that's fine and is better than many alternatives.

However, I'm with Richard on surge protectors.   MOVs (used to shunt the surge) are effectively consumable items but there's no provision to easily replace them.  A cheap surge protector may fail to disconnect its MOVs when they wear out and fail which, if its got a plastic case,  could burn your house down! 

[eeguy]

Thanks. I asked Startech Tech Support if there is a safety resistor in their wrist strap and matt, their reply was: "Unfortunately we do not have the information that you are requesting on hand, We have the electrical resistance of the mat, would that be helpful?" They don't even know the answer to such question. Isn't that strange?

For the electrical resistance of the mat, they stated:

"Surface Resistance 10e8  ~ 10e10 ohm
RTG Resistance 10e8  ~ 10e10 ohm
RTT Resistance 10e8  ~ 10e10 ohm"

[Ian.M]

The mat is inherently safe.  You'd have to make contact with a large metal area very close to its grounding snap to get a resistance under 1Meg. For the leads, just measure them end to end with your DMM on resistance.

[eeguy]

Thanks. Am I correct that as long as the mat is grounded, it is saver to put the motherboard or other electronics circuits on the mat rather than on a piece of paper or just on the wooden desk? Usually I just put the motherboard on the cartoon box and insert the RAM, CPU and heatsink. Given that I have that mat, perhaps I just use it?

[Ian.M]

Its a good idea to work on the mat, especially when opening or configuring PC components.

Painted, plastic coated or plastic PC cases may not make good enough contact to effectively ground to the mat.  If you want to be certain,  connect a clip lead between bare metal on the case and your ESD ground.    That also frees up space on the mat  as you can then put the PC off to the side.

[eeguy]

How come when I tested for connectivity of the wrist strap by connecting one probe of a multi-meter to the big metal of the wrist strap (the area that touches my wrist) and the other probe to the banana plug of the wrist strap, there was no beep sound?

[Bratster]

How come when I tested for connectivity of the wrist strap by connecting one probe of a multi-meter to the big metal of the wrist strap (the area that touches my wrist) and the other probe to the banana plug of the wrist strap, there was no beep sound?

there should be approximately 1 mega ohm of resistance.

If you had a low resistance path on The wristband to ground that would endanger the person is attached to if they touch something live.

Having the high resistance is enough to dissipate the static electricity, without causing electric shock danger to the user if they grab something live.

Sent from my Fi Moto x4 using Tapatalk

[Richard Crowley]

How come when I tested for connectivity of the wrist strap by connecting one probe of a multi-meter to the big metal of the wrist strap (the area that touches my wrist) and the other probe to the banana plug of the wrist strap, there was no beep sound?

The "beep sound" is only a crude indicator of "continuity".  Where "continuity" is likely defined as a MUCH MUCH lower resistance than anything that should be found in a proper ESD protection scheme. 

It is not valid to use the "continuity beeper" when analyzing/measuring high-impedance circuits as yours should be.  It would be an interesting experiment to get a high-value potentiometer (perhaps 100K?) and experiment to see how low the resistance has to be before your "continuity beeper" senses continuity.  I would expect it to be 100x or perhaps 1000x lower than anything that would be safe in an ESD circuit.

It is a good thing that your continuity beeper does not sound.  If it did, you would be in danger of electrocution because your circuit is much too low resistance.