sealing/whetting current

John Larkin is frightened by stuff he doesn't understand, he understands surprisingly little, and where he thinks he understands stuff he has been known to get it wrong.

Reed relays aren't unreliable. They were invented by the telecom industry to make more reliable telephone exchanges.

The thermocouple voltages between copper and the iron alloy of the reed are significant, but if you are careful about your thermal design they aren't usually horrible.

The minimal amount of mercury in a mercury-wetted reed might be toxic, if you broke the reed, but the whole point about reed relays is that the glass encapsulation is vacuum tight.

Latching reeds aren't power hungry.

Reeds and regular telecom relays are both magnetic field sensitive - they both relay on magnetic forces to get the contacts together or to separate them - so it's a bit silly to complain about the sensitivity to ambient magnetic fields.

I always think of whetting a knife on a stone. Does dhrying a knife dull the blade?

George h.

I think of dhrystones more in terms of computers. Come to think of it, the subject is pretty dull.

I have no control over the external dry contact given to us. But I bet there's no mercury-whetted relays in a 3ph 1000A ATS.

So I need to think defensively over what I work with.

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Probably no mercury-wetted reed relay, but there are other kinds of relays that do rely on mercury to make and break contact in higher-current situations.

Thinking a bit harder, and doing a bit more background reading, would seem to be called for. Asking the customer what they have in mind might be a good start.

It's a wonder the 1AESS worked at all....

They get a ATS with aux. dry contact outputs, with the generator. Hardly likely they can negotiate over what ilk they are, in a UL-listed device, much that they will.

We use their dry contacts. I started this thread to see if anyone had more specific knowledge on the topic.

I have repaired electromechnical devices (minidisc player) that had small s witches to sense the position of the loading device. They were connected t o a micro and very little current flowed through the switches. Over time, the switches were intermittent.

I added 0.1uF across the switches and the problem resolved.

A small spark can be a good thing.