[time-nuts] Conducting Bench Top Material

[Bill Hawkins]

My first job was in a blasting cap plant in 1960. There were
military devices so sensitive they could be set off by turning
on a nearby fluorescent desk lamp.

I learned that the human body has a capacitance of 400 pico F.
Getting up from a chair could raise a couple of kilovolts. We
walked on conductive rubber floors wearing conductive rubber
shoes. Bench tops were conductive rubber. Nobody had thought of
the wrist strap yet.

In those days, rubber was made conductive with carbon black. It
was almost as effective as a pencil at marking things. If the
anti-static material is not black, maybe it won't be a marking
hazard.

A megohm and 400 pF has a time constant of 400 microseconds, but
you do get the kilovolt spike. The wrist strap looks really good
as long as your motion is the only source of static electricity.
It keeps your body from ever reaching kilovolt potentials.

Bill Hawkins


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Scott Burris
Sent: Monday, January 25, 2010 2:11 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Conducting Bench Top Material

So looking at ESD mat material at Digikey, there appears to be a  
bewildering array of choices.  Elastomer, rubber, vinyl,  
thermoplastic, laminate, foam rubber, and polyethelene.

Any guidelines about what to choose?

Scott