Trimpots for more than 500V?

Folks,

Need a trimpot in the 1M range, small. SMT would be nice but T/H is ok.

5-10 turns would also be nice. The tiny ones are often spec'd at 100V or less and the longer ones like this at 400V:

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400V is a tad marginal in this case. Does anyone know of such a trim potmeter >500V? The search machines at places like Digikey don't have a column for the voltage rating.
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Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg
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I see four different, contradictory, voltage ratings on that thing. Does Bourns have such things as applications engineers any more? I'd be tempted to call and ask; I suspect the 400V rating is either boilerplate or whatever they're testing to, or why would they bother with a 500V insulation resistance and a 1000V dielectric resistance?

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www.wescottdesign.com
Reply to
Tim Wescott

I"m not sure why you say 400V; this series is rated for 0.75W, and the higher resistance ranges should be fine

v**2/R < 0.75 V < SQRT(0.75 * R)

500 < SQRT(0.75 * R) whenever R > 334kOhm
Reply to
whit3rd

The voltage rating is another constraint that must be simultaneously satisfied. Otherwise you could put 2.3kV on a 22M '1/4-W' resistor.

If you're talking about CYA statements that put a blessing on the use of the pot, I can commiserate but not help much**.. finding mains rated knob pots, for example, is quite limiting. One major former application of these (CRTs) has vanished 'overnight' in a poof of glittering phosphor..

For example, the Bourns 3386-HV2 and HV3 are now obsolete (1kV and

600V ratings respectively)- they were aimed at focus adjustment.

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If you're interested in actual capability.. inside the 'long' multiturn pots there is a multi-fingered wiper that bridges between the thick film element and a parallel conductive strip. The spacing of those strips on the substrate is key- it potentially has the full voltage across it.

**If you don't mind a slightly oddball supplier, I suggest checking out Piher @
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.. they probably have something that is rated to do the job.

--sp

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Best regards,  
Spehro Pefhany 
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Reply to
Spehro Pefhany

Yes, it's a bit vague. Usually you can only use the lower value and that's a bit tight in my case. But I can (and will) specify that it'll only be touched with a plastic alignment tools like the Bernstein kit.

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Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

That's the problem. It's about arc-over and things like that, has nothing to do with resistance. Even a lower resistance range can theoreticallly be pulsed to very high voltages but there comes a BZZZT

*POP* point.

In the not always so good old days of CRTs this was never a problem. And it goes on. I also need a HV transformer for this project and one can already count the years when CCFL transformers will go lalaland because monitor backlighting is now very quickly migrating to LED. But with magnetic one still has could custom builders who don't charge an arm and a leg. Not so for trimpots.

That would be almost ideal but since they did not mention "For new designs please consider ..." it seems the market for this stuff has shriveled to the point where it is no longer profitable to make potmeters for it.

Thanks, will try. Piher is still mainstream I think. Just haven't found anything suitable from them either at the distributors but a call to them is a good idea. I found email not to be such a great support tool anymore since many companies starting outsourcing.

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Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

Do you really need an adjustment over the full zero to 500V range? ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

Den tirsdag den 15. december 2015 kl. 17.38.55 UTC+1 skrev Jim Thompson:

yeh was thinking the same thing, would think sticking a few hundred k in series should do it

-Lasse

Reply to
Lasse Langwadt Christensen

Worse, from about 300V or 700V versus ground. So in case somebody reaches in with an insulated shaft screwdriver (against advice) that sat at the usual zero charge there should not be a microscopic discharge event when a metal spindle or the like is touched.

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Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

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