Re: gEDA-user: Contact reliability

[Bert Douglas <bertd@xxxxxxxxxxxxx>]

Karel Kulhavy wrote:

> On Wed, Jan 19, 2005 at 01:36:21PM -0600, Bert Douglas wrote:
>
> > Karel Kulhavy wrote:
> >
> >
> > > On Wed, Jan 19, 2005 at 01:01:51PM -0600, Bert Douglas wrote:
> > >
> > >
> > > > The way that you guarrantee contact reliability is by forcing current to 
> > > > flow, every time the contact points are moved.  This causes microscopic 
> > > > welds.
> > >
> > >
> > > But when I have 10Mhz broadband signals with 700mVpp amplitude I probably
> > > can't weld them together. Or is there some trick even for this situation?
> > Somehow you have to force a DC current of perhaps a few amperes.  This 
> > only needs to be done for a short period of time.  Less than 1 second.
>
>
> And what is the voltage at which even the thickest layer of oxides is guaranteed
> to break through?

A good question, but difficult to answer.  You will have to conduct 
experiments.

But, as I understand your application, this contact will be opened only 
during maintenance.  So a human will be nearby.  The human can verify 
that the new contact is successful.

On the same topic, one of the reasons that telephone wiring is so 
reliable is because of the relatively large current during "ringing".