Small HV relay >5kV?

use of a GDT with a common relay would most likely be cheaper in your case.

Jamie

A gas discharge tube would shunt the 5kv to ground or somewhere else on the board which under no circumstance can happen. It must be open, no current while the 5kV is applied.

semi-silly suggestion: 5 relays in series with 10M across each

NT

The GR6FNA218 is a 5k SPST relay that can do PC board mount and has a

Jamie

The classic source is Kilovac, but they're expensive.

How about a string of small SSRs?

One gathers that this is an EKG or something that has to survive defibrillators or hospittal spec Tesla coils or something.

Cheers

Phil Hobbs

Look for the reeds by themselves; price seems to be a lot lower.

GDT: Geometric dimensioning and tolerancing? Global Descriptor Table? Global Dairy Trade?

No; they all move at different times - which will put the full stress on one of them = *ZZzap!*

Turn-on and turnoff time differentials are a lot better than mechanical, but the differentials can kill them.

Smells of EKG afraid of defibrillation pulses.

We did it 40 years ago with gas discharge tubes in first stage and zener / diode networks in second stage. The patient will get burns from the defibrillation anyway, so the current to the protection devices does not matter.

It's not an ECG but yes, it is to allow defibrillation. The unit is fully self-protected but this is for patient safety. Ideally you do not want any kind of ever so slight conductive path from one area of a patient to another.

Even if not necessarily required sometimes such extra measures are the right thing to do.

However, then I'd have to make and place a coil. Should be a self-contained unit. I have a question into Standex/Meder, to see if any of their smaller KT series can be certed 5kV when open.

It's not silly at all but then I might as well us the big fat Meder HE12.

Thanks, Jamie. I'll check on pricing and who sells it but this would be about as big as the 7.5kV Meder HE12 (which runs $30-40).

Big and expensive is out for this design. I found one coll-looking HV-relay and froze when chekcing the price. 500 bucks! Although one never knows these days. In December I had a crown put on a tooth for $800. Now my old dentist retired and the new one quoted $1200 for the next one I need (and that's with a discount). Does not include the root canal. Ouch.

Can't do, it has to be totally non-conductive when open. No bleeders, nothing.

Hi Joerg

Some reed relay manufacturers also sell reeds and coils separately, for applications like multiple (customer-selected, possibly different) reeds installed in one coil.

You may be able to find a coil with a large enough inside diameter to accommodate some additional isolation (or use a small coil positioned over the middle of the reed far from the ends) and then use this reed:

It's rated to 7.5 kV and might even be surface-mountable (note the wide flat 2.5 mm ends) if you can provide some tension relief and get a coil that "sits inside" a board cutout.

Dimitrij

P.S. You mentioned that you are protecting a patient interface. In that case, most likely you will have more than one line to disconnect. If space is really at a premium, what about a custom-made coil on a flat multi-reed coilformer. That way you could set the distance between the reeds of the different lines to exactly meet the minimum clearances.

Cross-section like this:

coil ---------------------------------------------------------- / ------------------------------------------------------ \ / / \ \ | | A B C D | | \ \ / / \ ------------------------------------------------------ / ----------------------------------------------------------

A, B, C, D: reeds (each in its own glass), looking from the ends "into the coil"

l_min: minimum required clearance for line-to-line isolation

Regards Dimitrij

On this one we only need to cut one line. The whole thing is isolated and only two lines so that takes any risk away.

I am looking for something that can just be plopped onto the board.