When possible, we have always used GFI for 120V based table top production and test equipment.  This is
accomplished by having a GFI breaker for the production benches.  I understand that GFI for 240/480  is
either unreliable or unavailable.  We had an old Contact Systems CS-400 that was 120V but could never
GFI the line because something (good filtering - leaky power supply caps?) would keep tripping the
breaker.

Gary Camac

Guy Ramsey wrote:

> The only danger I see is injection of unwanted potential into the mat. A GFI
> (Ground Fault Interrupt) on the equipment circuit would eliminate that
> possibility and is a good practice anyway. "Common" ground in some old
> factories may have significant voltage potential. The GFI will trip under
> those conditions, drive maintenance crazy for a little while, but it will
> prevent EOS damage caused by the conditions that your old policy attempts to
> prevent.
>
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]]On Behalf Of Jim Jenkins
> > Sent: Thursday, May 30, 2002 2:26 PM
> > To: [log in to unmask]
> > Subject: [TN] ESD and equipment isolation
> >
> >
> > Hi everybody,
> >
> > One of our internal specifications states that processing
> > equipment needs to
> > be "electrically isolated" from the static dissipative mat.  We are
> > interpreting this to mean that if the equipment has a metal case it is not
> > allowed to be in contact with the mat.  There has been some
> > controversy over
> > this, because we have whole areas and labs that have test equipment and
> > other items that do not have the little feet on the bottom and
> > make contact
> > with the mat.
> >
> > We have people arguing on both sides here.  Some say that the contact
> > provides a direct path to ground taking out the resistance needed to slow
> > down the discharge.  I say that the dissipative (rather than conductive)
> > nature of the mat provides the necessary resistance.  That is why
> > resistors
> > are no longer required in ESD specifications.
> >
> > Others say that the equipment can inject electrical energy through the mat
> > into the ESDS devices.
> >
> > What do you all think?
> >
> > Thanks,
> >
> > Jim Jenkins
> >
> > [log in to unmask]
> >
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