Mega-Ohm protection resistor in ESD protection equipment

[Pha5e]

Mega-Ohm resistor in ESD protection equipment

Could someone please explain why ESD (anti-static) protection leads, adaptors, plugs have a mega-ohm resistor in series?

I recall someone mentioning that it is to prevent an electric shock if the cable were to accidentally be connected to live mains?

 

[betwixt]

That's correct.

The high value resistor can pass enough curent to ensure a static charge is leaked away safely to ground but limits it enough that if the user accidentally came into contact with a live mains or other high voltage source, the current would be low enough not to cause harm.

Consider what would happen if the resistor was not there and for example, the user wore a wrist strap connected directly to ground then they touched a live connection with their other hand. Their body would provide an easy path from hand to hand for current to flow and injury would result.

Brian.