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BobKoblish
User Rank
Bronze
ESD zapping terminals
BobKoblish   9/8/2014 2:03:07 PM
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Some decades ago we computerized the admissions department at a series of entertainment venues. The initial installations were in coastal Florida, where the humidity was high and we had no problems.

At a newer site in New Jersey the installation was in the cold weather and the terminals were resetting at random. We eventually figured out that the tellers' uniforms were rubbing up a static charge as they shifted on their stools, then the terminal would get zapped as they touched it to process the next patron. The fix was to install a conductive plastic cover over the seat cushion. We also removed the rubber tips from the stools' metal legs so that the stool would ground itself to the masonry floor.

In retrospect, attaching a length of sash chain to the bottom rung of the stool might have worked as well to ground the legs. But it might have created a tripping hazard.

 

 

BobKoblish
User Rank
Bronze
Re: One static charge after another
BobKoblish   9/8/2014 11:18:23 AM
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I've experienced this just walking across an epoxy-painted concrete floor in tennis shoes.

tekochip
User Rank
Platinum
Re: One static charge after another
tekochip   8/8/2014 7:16:28 PM
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All true, you have to ground the aircraft before fueling.  Imagine a spark like that being drawn from the fuel hose into an empty tank.

J. Williams
User Rank
Platinum
Re: One static charge after another
J. Williams   8/8/2014 6:16:20 PM
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That was most likely due to the static charge built up on the skin of your aircraft just from airflow.  Rotary wing aircraft are particularly susceptible to this issue.  Don't they always have you ground the skin before you put fuel in your plane?  I'm not a pilot, but I have spent more than a few hours coming and going off of vaious flight lines, usually hauling a ruck. 

tekochip
User Rank
Platinum
Re: One static charge after another
tekochip   8/8/2014 4:29:45 PM
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One night after a flight I was pushing the aircraft back and when the towbar got close to the nose gear I drew a good 1" spark and a dandy SNAP.


rhayashi
User Rank
Silver
ZAPPED!
rhayashi   8/7/2014 7:29:15 PM
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I had a Medical instrument the was reported to reboot in a Swedish operating room that had very bad static charge issues. We could not duplicate the problem with a local unit, so the aquired the Swedish unit. I could not get it to fail with my sparky stick. The only clue was it happened when it was set for full volume. The volume control was for a anoying vacume level warbler sound. (so I always set it to minimun) I finnaly tried it at full volume. As it turns out the volume control pot set at maximum allowed a spark into the A/D which latched up the CPU, While a low volume setting sent the spark into ground.

dbues
User Rank
Gold
Re: ESD discharge
dbues   7/1/2013 8:50:11 AM
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Frank,

Good idea to pull the batteries.  Didn't work, though.  Not sure what the right way would be to discharge the alleged capacitor.  I might try to remove the batteries and then short the DC + and - together.  Otherwise, I'll have to take a look inside.

Dwight

J. Williams
User Rank
Platinum
Re: One static charge after another
J. Williams   6/17/2013 5:34:42 PM
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Yes, the carts at my local Sam's Club replicate four little Van De Graaf generators with the wire basket and frame working as a top load.  The whack I get from the cart is quite startling.

Cadman-LT
User Rank
Platinum
Everyone
Cadman-LT   6/17/2013 5:03:35 AM
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I would have to guess that almost everyone has had this happen to them at some point in time. I sure have.

Larry M
User Rank
Platinum
Re: Painful excersize
Larry M   6/13/2013 8:58:42 AM
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g-whiz wrote: " I was electrically isolated, in intimate contact with a hard rubber belt, moving and rubbing against another surface."

The other name for this particular apparatus is "Van de Graff generator." They can generate up to 5 million volts. See the Wikipedia article for more details.

 

 

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