continuity tester

So, AC line cord with a light bulb (or bank of 'em) in series with probes?

This will be an on-demand automated self-test of a box with about 300 relays inside. A pecularity of the architecture is that, with minor finagling, we have test access to all the relays.

The customer would like it if they could self-test our box before and after using the overall test system, and include the BIST reports in the final test reports to their customers.

We considered some sort of AC-coupled RF thing, but that doesn't wet the contacts.

Some sort of cap-coupled pulsed AC thing might work. Flyback? Sense on the primary side?

Something like this. Honking test pulse.

And then again, |:| maybe not

Piotr Wyderski posted here, I think earlier this year, a way of contact sensing across a transformer barrier. I seem to remember it could distinguish between 68 ohms and a true contact closure.

piglet

That's a really BIG peculiarity! Just exactly how is it configured?

It's confidential, but imagine a large number of nodes that can each be switched to a small number of busses. We can test the relays through the busses. The nodes could have anything connected to them, so we need an isolated continuity tester.

Bit of luck, actually.

Would thinking along the lines of a multiple drill press help at all?

Hi John, A good challenge. 300 test targets, so cost could be an issue? I like the first sketch. Good solid DC test current & I-limiting. Use a current high enough to detect an out-of-spec contact R. (Or if stuck closed). How often would the BIST be done? Any risk the test might degrade the contacts? Maybe ramp up the test current, instead of a step.

I'm curious why you went with mechanical relays instead of SSRs given need for high-rel. I don't expect an answer tho' ;-)

regards, RS