Why was i electrocuted?

[treez]

How an ESD mat should operate:
multilayer:
* the top layer is relatively high ohmic. It prevents high current flow when a PCB is placed on the mat with line voltage applied. --> no smoke
It also reduces ESD currents due to its high impedance.
* then there is a higher conductive layer. It is used to lead ESD currents to the earth connection. It also keeps areas of high potential small on the top layer (this prevents you from being electrocuted).
--> both layers help to keep ESD damage low: Low currents, relatively fast voltage decay, small areas, currents fed to GND.
* Maybe there is an additional layer (at the bottom) between this higher conductive layer and the desktop surface. It depends on the mat.

Thanks, we really don’t care about the danger of being electrocuted through a conductive ESD mat…..we will just be careful….the highly conductive ESD mats are far cheaper so we want to use them.
Our highly conductive ESD mat has a metal push-on connector to a yellow earthing plug, and the lead to this yellow plug has a high resistance of 2 Megohms…so there is the high resistance needed…and we simply wont be able to get high current flowing in our conductive esd mat because the 2meg resistance to earth in the lead of the earthing plug will stop this?……….as you know, all current flows in loops, and since the loop of current that contains our conductive esd mat contains 2 meg of resistance, then we simply won’t get high currents when highly charged esd festered objects touch it. Surely you agree?

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https://www.farnell.com/datasheets/...MI6vvDrJ6J1wIVEBIbCh2irgg_EAQYASABEgIQxvD_BwE

...the above is a bona fide esd mat an is only 10kohms per square metre........i dont think this product woudl be for sale if it was unsuitable?

 

[KlausST]

Hi,

I have to repeat:

You talk about 10kOhms/square meter as if it is highly conductive. But ofr small electrodes - or other connection points - it is relatively high ohmic.

Thanks, we really don’t care about the danger of being electrocuted through a conductive ESD mat

But the headline says so.

and we simply wont be able to get high current flowing in our conductive esd mat because the 2meg resistance to earth in the lead of the earthing plug will stop this?

Only true if there is just a single point of connetion to the ESD mat. But usually there are several connetions on the SED mat on the same time.
* A human touching the mat - maybe by accident.
* several points of a bare PCB that is placed onto the mat.
* the sodering iron
* a scope probe lying around
* a connector of an earthe power supply .. or just the cables...
* and earthed metal case standing on the mat
* some USB device - or onle a USB connector
all these form current loops where the 2MOhms to earth is not involved. --> The 2MOhms doesn´t limit the current.

Klaus

 

[Kajunbee]

My question and I believe @cmitra already touched on this. If you use a highly conductive mat with high resistance on the ground wouldn't the large area of the mat act like and uncharged capacitor. Meaning there would be a moment of high current until the mat and board equalized and then the charge would slowly bleed down through the resistor.

 

[KlausST]

Hi,

@Kajunbee: Very true.
Capacitor --> high peak currents --> low ESD protection

Klaus

 

[c_mitra]

...the above is a bona fide esd mat an is only 10kohms per square metre

Certainly not a bonafide ESD mat: the unit should have been only 10K Ohms (not Ohm/square meter)

It will certainly provide psychological protection.

(when I saw the link and the units mentioned, I was rather confused and was forced to look up)