Bob Engelhardt wrote:

Michael A. Terrell wrote:
Do you expect each set of contacts to have the eaxact same resitance?

I don't know, should I? I guess that's an question that might be
answered here. My intuition is that they would be "close enough".

Bob


If they are not equal, you have different current in each set of
contacts. It might be "Close Enough" in a fresh production switch, but
it will change as the switch ages. At some point the imbalance can be
enough to cause excessive current to flow trough one set of contacts,
welding them, or causing them to overheat and destroy the switch. I've
seen it too many times to ever do it myself. Every time the switch is
used, it expects a small spark to clean the contacts. Always switching
under no load makes them deteriorate even faster. There are two types
of switch contacts. Power and low level signal. The low level
mechanically wipe, or use a pair of knife edges at right angles to apply
a lot of pressure so they don't need any current to stay clean. He
others are simple, flat faces that touch in pairs. The do no open or
close perfectly, and a double pole switch doesn't operate at exactly the
same time, due to mechanical tolerances, and even how squarely you
operate the switch.


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