ESD Grounding Mat Cable

[rstor22]

I purchased the following ESD Grounding Mat cable:

http://www.ebay.com/itm/261170719303?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Originally I planned to connect one end of the cable to my mat and the other end to my ESD grounding point snap connector:

http://www.ebay.com/itm/261217237976?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Afterwards I realized that the snap connector on the grounding point is only used to park the cable of your ESD wrist strap when not in use and does not have a direct path to ground (as opposed to the banana plug connectors on the grounding point).

I would like to cut the 10mm snap to snap cable at one end and add a 4mm banana plug on that end (so I can plug it into the grounding point). As the cable has a 10meg ohm resistor, I am unsure where the resistor would be located so I can cut accordingly. Is there a standard placement of the 10meg ohm resistors in such a cable (e.g. at one end or in the middle)?

[nanofrog]

Not a good idea to daisy chain your mat to your common point via a connector IMHO (must pay attention to what's going on with the resistance for safety's sake, as well as run the risk of the connector coming off if bumped/yanked hard enough).

As per the resistor in the cable, it's typically between the connector and wire, so in the injection molded plastic in this case.

The following should help clarify matters:

• 3M's How to Install an ESD Workstation (pdf)
• FUNDAMENTALS OF ESD (pdf)
• How to Design an Esd Workstation (Stationary Personnel Mandatory Recommendations should suffice)

[rstor22]

 Thank you. I will connect the mat directly to the electrical ground rather than the bench common ground point.

I was reading here:

http://documents.desco.com/pdf/tb-2000.pdf
" ANSI/ESD S6.1 recommends that a non-resistor ground cord be used to ground worksurfaces and
floor mats. However, cord may have a 1 megohm resistor for non ESD puropses.  "

So if I am correct in understanding, there would be no harm to use a 1 meg ohm resistor between the mat and ground?

[nanofrog]

Thank you. I will connect the mat directly to the electrical ground rather than the bench common ground point.

I was reading here:

http://documents.desco.com/pdf/tb-2000.pdf
" ANSI/ESD S6.1 recommends that a non-resistor ground cord be used to ground worksurfaces and
floor mats. However, cord may have a 1 megohm resistor for non ESD puropses.  "

So if I am correct in understanding, there would be no harm to use a 1 meg ohm resistor between the mat and ground?

If the mat and wrist strap are wired correctly, no harm using a 1M resistor (assumes the wrist strap = 1M).  Most kits actually include common point wires with a 1M resistor in them, and the wrist straps have their own 1M resistor (example of what you typically get in a kit).

BTW green w/ yellow stripe wire = no resistor; black wire = 1M resistor for ESD ground wiring. If the resistance is anything else, red is supposed to be used to indicate a non-standard value.

2 layer rubber ESD mats aren't exactly cheap by most people's standards, but they're worth it IMHO. And if you're lucky, you might be able to find what you need as a closeout (example, if in the US). There's also a seller on eBay (US & CAN) that sells them more reasonably than other sources' regular prices (can do custom sizes if needed & has lots of options <color, textured or smooth, kit or just mat, ...>). FWIW, I've bought from both sources with no issues.

Also, if you go into your user profile and set your country, your nations flag will display under your userID. Saves lots of questions as to where you're located, as it's necessary for posting relevant links. 

[rstor22]

Thanks nanofrog, I've updated my profile. It was some of your other posts that convinced me to buy from canvu0_0. I ended up purchasing my mat from this seller a couple months ago. Everything was great except the stud (upper) detached from the lower part (I believe it is the ones that are pressed on with a tool) not the ones with the spiky ends. I'll probably get these screw on one ones:

http://media.digikey.com/photos/Desco%20Photos/09864.jpg

I am trying to decide on the wrist strap to get. I was looking at Desco straps and read the following on their site
"Note: Metal expansion bracelet style wrist cuffs may trap moisture underneath and can be more effective for people with dry skin." [ESD Handbook TR20.20 section 5.3.2.4.3]"

In one of your previous posts you mentioned that you purchased the following:

http://www.all-spec.com/products/09205.html

I was thinking about getting these on eBay:

http://www.ebay.com/itm/ESD-Safe-Anti-Static-Wrist-Strap-6ft-Ground-cord-METAL-WRISTBAND-10MM-/261170230460?pt=LH_DefaultDomain_0&hash=item3ccef574bc

Is there any significant advantage of spending the extra money and buying the Desco brand ones? I see that the Desco snaps are machined and the one on eBay is pressed however I don't think this alone would be worth the extra cost...

Also, I recall reading  that it is not recommended to wear metal jewelry or watches when working on live electronics. Though the one on eBay mentions that the upper surface is coated with insulated paint, is this sufficient ?

[nanofrog]

Thanks nanofrog, I've updated my profile. It was some of your other posts that convinced me to buy from canvu0_0. I ended up purchasing my mat from this seller a couple months ago. Everything was great except the stud (upper) detached from the lower part (I believe it is the ones that are pressed on with a tool) not the ones with the spiky ends. I'll probably get these screw on one ones:

http://media.digikey.com/photos/Desco%20Photos/09864.jpg

Sad to hear about the connector coming off. The mat I purchased from him came with a 4 prong type I had to install myself. Not a fan of this type, but they do work.

So like you, I was drawn to that Desco screw type you linked, and they're great to use IME.  Easy to install, and they've stayed put for me (I'm not kicking the ground wire though). Not cheap if that's all you get due to shipping, but they make great filler items on orders if you can do it that way.

I was thinking about getting these on eBay:

http://www.ebay.com/itm/ESD-Safe-Anti-Static-Wrist-Strap-6ft-Ground-cord-METAL-WRISTBAND-10MM-/261170230460?pt=LH_DefaultDomain_0&hash=item3ccef574bc

Is there any significant advantage of spending the extra money and buying the Desco brand ones? I see that the Desco snaps are machined and the one on eBay is pressed however I don't think this alone would be worth the extra cost...

IME, the wrist straps I've gotten from unknown sources tend to be child sized. I'm over 6ft tall, so they tend not to fit properly, if at all (usually don't have enough strap to latch down in the buckle).

Desco offers different sizes for their wrist bands, and the large I linked fits. The machined sockets have better electrical contact (intermittent contact is a problem this helps to solve), and can be worth having. 3M also offers decent quality ESD products. Do note the different quality levels, as they have multiples to meet different budgets (even disposable meant for field service).

I use an ESD workstation monitor (Desco Jewel Continuous Workstation Monitor) I got off of eBay for a very good price (I'm fond of used gear that's been well cared for, and especially NOS  ). This particular unit connects directly to the 10mm snap connector on the mat itself, so it eliminates a wire.

Found a Desco 19228 on eBay that would be worth trying to get (about to expire w/ no bids, so it may get relisted).

They also have much better ground wires to the wrist straps (heavier, not as likely to come off IME).

Though the one on eBay mentions that the upper surface is coated with insulated paint, is this sufficient ?

So long as you don't scrape it against things that will wear through it, Yes. And if you get some scuffs and scrapes, you can touch it up with some Testors model paint or something. 

Another trick, is to attach it to your bicep (Dave did this in the uCurrent video where he assembled one on camera IIRC). Frees up your hands, and you don't drag it across anything.