Author Topic: Anti-static wristband newbie.  (Read 1676 times)

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Offline giovimonto

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Anti-static wristband newbie.
« on: January 27, 2016, 04:26:21 am »
Why there is a 1M? resistor in an anti-static wristband?
Shouldn't the current be able to quickly leave my body?
 

Offline bitslice

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Re: Anti-static wristband newbie.
« Reply #1 on: January 27, 2016, 04:31:25 am »
Zaps are unpleasant, dissipating it more slowly is preferred.

Besides, it is just there to stop the static building up, not dumping a potential out of nowhere

And it's handy to be able to measure a defined value when testing to see if the strap is still functional
« Last Edit: January 27, 2016, 04:37:34 am by bitslice »
 

Online Ian.M

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Re: Anti-static wristband newbie.
« Reply #2 on: January 27, 2016, 04:49:27 am »
More to the point, its there for your safety.  Shock currents in excess of 10mA through the skin are generally regarded as hazardous. Assuming you aren't working on anything above 360V (the bus voltage in a EU SMPSU under high mains conditions), the 1Meg resistor will limit the current to 0.36mA, which is extremely unlikely to cause any injury.
 

Offline bitslice

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Re: Anti-static wristband newbie.
« Reply #3 on: January 27, 2016, 05:17:23 am »
^
Isn't that assuming the person isn't earthed by some other route?

I'd assume the bench RCB would deal with any ground current issue, but yeh, fair point.
 

Online Ian.M

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Re: Anti-static wristband newbie.
« Reply #4 on: January 27, 2016, 05:24:21 am »
If you are earthed by another route, the wrist strap manufacturer isn't liable
 

Offline c4757p

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Re: Anti-static wristband newbie.
« Reply #5 on: January 27, 2016, 05:50:40 am »
It is not only there for your safety, it is absolutely essential to the operation of the wristband. The term ESD exists for a reason. Electrostatic discharge - it's not the voltage/charge that's a problem, it's the current that flows when you discharge it. If you were solidly grounded, and touched a part that had picked up charge, you'd discharge it very quickly and kill it.
No longer active here - try the IRC channel if you just can't be without me :)
 

Online Ian.M

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Re: Anti-static wristband newbie.
« Reply #6 on: January 27, 2016, 06:09:03 am »
I beg to differ slightly.  Due to the human body's capacitance to ground, you can still kill a highly charged, very ESD sensitive device just by touching it, even with a 1Meg resistor in your wrist strap.   It does however decrease the risk for less sensitive devices.
 

Offline c4757p

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Re: Anti-static wristband newbie.
« Reply #7 on: January 27, 2016, 08:13:34 am »
Well, yes, I never said it was perfect...
No longer active here - try the IRC channel if you just can't be without me :)
 

Offline xwarp

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Re: Anti-static wristband newbie.
« Reply #8 on: February 04, 2016, 09:38:04 pm »
I prefer applying ESD as if I were doing an EKG........ :-DD
 


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