[Elecraft] K3 ESD

[Don Wilhelm]

  Fred,

Your statement of connecting to an equipotential plane is a good one, 
but your concern about spikes and inductive reactance back to the 
"planet" should not be a concern.  It IS important that all items in the 
protected area be connected to the SAME point on this safety ground.  
Connecting one ESD prevention device to one green-wire ground, and 
connecting yet another device to yet another receptacle's green wire 
ground will cause a difference in potential between those two points on 
the green-wire ground.

The same principles apply to installations like commercial broadcast 
stations which must remain in operation throughout a lightning storm.  
The solution is to keep everything in the station at the same potential 
through the use of a "grounding window" - which is the single point to 
which *everything* in the station is connected.  In the event of a 
strike, it does not matter whether that grounding point raises to 
several thousand volts - everything connected to that point will also 
rise in potential by that same amount.  It is the potential *difference* 
of those items that are connected to that single point that is kept to a 
minimum.  It takes a potential *difference* to cause harm or damage.

It is similar with ESD protection, but on a much smaller scale.  Do not 
connect your wrist strap to one receptacle ground screw and your 
anti-static mat to yet another.  Connect them all to the same point.  
Failure to do so destroys the design of your anti-static setup.  And 
that is the reason that many anti-static mats have a connector where you 
can attach your wrist strap - use it to keep everything at the same 
potential.

73,
Don W3FPR

On 12/18/2010 6:19 PM, Fred Jensen wrote:
> Connecting your equipotential plane to the planet is a mixed bag.  If
> the connection is direct and big, it's probably fine.  If other things
> use it and might put significant current spikes into it, you might want
> to reconsider.  It's sometimes surprising the amount of noise pulses
> that can wander around on the "green wire" in a normal residence.  If
> your house is wired to code, it's connected to the neutral and the
> planet at the main electrical entrance [only], which could mean quite a
> bit of wire to your shack and lots of inductive reactance in it for very
> fast pulses.
>