ORIGINAL MESSAGE:
On Sun, 8 Aug 2010 11:45:35 +0100, "David Cutter"
<d.cutter@ntlworld.com> wrote:
>That begs a question I've often puzzled over: how does a contact rated at
>10A cope with uV level signals, particularly after the gold flash has gone ?
REPLY:
A properly designed relay will have a slight wiping action when it
closes. If you look carefully, you will see the contact close and then
move sideways a few thousands of an inch. The idea is that will wipe
the contact clean.
IMO, the best relays for small signals are made with contacts that
conduct even when oxidized. Rhodium is one such metal. Silver is a
second choice. Silver oxide is a conductor but in areas with high air
pollution, silver sulfide can form and that is not a conductor.
Hermetically sealing a relay helps too.
73, Bill W6WRT
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