I once had to design an equipment with a switch with a very variable contact
resistance. I made it work successfully by ensuring a small dc current
passed thro the contacts on closure and this was enough to break down the
surface film.
I've often wondered if this could be applied to relays looking for sub uV
signals to make them more tolerant to ageing: in QSK, 1M ops is not a big
number.
David
G3UNA
----- Original Message -----
From: "Tom W8JI" <w8ji@w8ji.com>
To: <amps@contesting.com>; "Bill Fuqua" <wlfuqu00@uky.edu>
Sent: Tuesday, July 10, 2007 10:58 PM
Subject: Re: [Amps] 200 Watt Fast Relay
>> Here is a problem I have with relay specifications.
>> Usually, for weak
>> signal applications we use gold plated contact switches
>> and relays. Since
>> most relays or switches are normally exposed to air,
>> oxidation can form and
>> weak signals can't always be conducted between them.
>
> Unfortunately you can use any plating you like and a
> percentage of relays will eventually mess up if it has
> exposure to "air".
>
> The most common problem for sealed relays (not vacuum, just
> enclosed) is contamination caused by the materials in the
> relay. It's a tiny layer just a few molecules thick.
>
> That's why the contacts have to wipe, or have a small amount
> of current when closing.
>
> Vacuum relays cure that problem.
>
> 73 Tom
>
>
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