EEVblog > News/Suggestions/Help

'Anti-Static' white coats

(1/3) > >>

Thermal Runaway:
At my place of work, everyone has to wear a white coat if they're on the shop floor.  Now, I've always questioned the reasoning behind this, and to be honest I reckon the only reason we're really forced to wear these on the shop floor is because management think it looks more professional when they have customers walking around if everyone is dressed in a white coat.  That's all well and good, but I just wish they'd come clean and tell us that's the reason.  Instead, they insist upon justifying the white coats for ESD reasons.  Are they really any good for this purpose? Well, I don't actually know.  But one day...

I was invited to an ESD training session.  During the training session we were shown an instrument that basically measured static charge, and then we were asked to rub our clothes together and take measurements to prove that our clothes were generating a significant charge.
And I accept that they were - this was already apparent to me because I've noticed it when pulling off jumpers and such like - some of my jumpers can really generate quite a significant charge.  In the night time you can actually see the mini-lightning effect that is generated!

But... what does my white coat generate, I wonder? It's *supposed* to be an anti-static coat, which I take to mean that it won't generate any static charge itself (although whether it shields against static generated by your clothes underneath it is another matter).  But I rubbed my white coat together with itself, and the instrument was still measuring quite a significant charge.  Not as much as on some people's jumpers (particularly the Ladies fluffy jumpers), but it seemed to me that it was significant enough to totally bust the idea (Adam Savage style) that wearing white coats protects equipment on the shop floor from static charges generated by a person's clothes rubbing together.  It's far more likely that our static foot-straps that we also have to wear, are conducting any charge away.  I'm just not convinced by the whole white coat thing.

So what do you say Dave? Is the white coat thing a valid method for preventing static build up on your clothes or what? I wanted to take my test one step further by rubbing my jumper together with itself, underneath the white coat, and seeing if the coat actually provided any kind of shielding against it or not.  But the general consensus amongst the group was that I should stop mucking about with my silly experiments and let the trainer get on with it, so that's what I did.

Perhaps the EEVblog can provide a definitive answer?

Brian

desolatordan:
There are about 3 EEVblog episodes relating to this topic.

http://www.eevblog.com/2009/07/26/eevblog-20-the-unusual-oscilloscope-phenomenon/
http://www.eevblog.com/2009/07/28/eevblog-21-the-unusual-oscilloscope-phenomenon-part3/

I remember Dave donning a lab coat for a demonstration like this, but I can't seem to find the episode.

EEVblog:

--- Quote from: desolatordan on January 30, 2010, 08:49:17 pm ---There are about 3 EEVblog episodes relating to this topic.

http://www.eevblog.com/2009/07/26/eevblog-20-the-unusual-oscilloscope-phenomenon/
http://www.eevblog.com/2009/07/28/eevblog-21-the-unusual-oscilloscope-phenomenon-part3/

I remember Dave donning a lab coat for a demonstration like this, but I can't seem to find the episode.

--- End quote ---

It's here:
http://www.eevblog.com/2009/04/12/eevblog-3-anti-static-myths-busted/

But with hindsight I should have busted much more than the one myth about "anti-static" bags.

As you've seen in my oscilloscope phenomenon video, the anti-static coat and wrist strap didn't do much under those conditions.
Good anti-stat coats have carbon fibers to help better disperse any static buildup generated, and the material is coated in an anti-static chemical which I believe does wear off with time. So if the material didn't build up a charge ever, there would be no need for the carbon fibre threads.
"Anti-static" means that the material is supposed to be incapable of holding a charge, not necessarily incapable of building up a charge for a brief period under all conditions.

To do static protection properly you need the whole gamut of protection. Ionizer, wrist strap, floor mat, proper chair, desk mat, coat, shielding packaging, sprays etc. It's all about minimization, not necessarily total elimination.

A more in-depth look at all this might make an interesting blog...

Dave.

Ferroto:
Just grab a large metallic grounded object, such as the chassis of a PC (not the painted part, the unpainted part inside). Honestly, I have never lost anything due to ESD, I'm starting to think it's total BS.

GeekGirl:

--- Quote from: Ferroto on January 31, 2010, 03:42:55 am ---Just grab a large metallic grounded object, such as the chassis of a PC (not the painted part, the unpainted part inside). Honestly, I have never lost anything due to ESD, I'm starting to think it's total BS.

--- End quote ---

Ummm, how long have you been doing electronics ?

When I used to board stuff (did it for 1 year to make some cash) one of the people fitting chips to sockets did not use a static strap, EVERY board worked, but 6-12 months latter FAILED with very strange problems. We ended up having to REPLACE EVERY chip in EVERY product this guy had installed. This was back in the MID 90's.

Yes these days chips are better at withstanding static, BUT DO NOT RELY on this.

Static in high speed logic or high impedance is VERY REAL.

Regards,

Kat.

PS I refrained from swearing, as I have seen many times how real static is.

Navigation

[0] Message Index

[#] Next page