HV Cable routing dilema

Jun 01, 2017 9 Replies
S

Hello:



I have a question regarding what would be the proper routing for the ground cable in a fixture I've made. The fixture's purpose is to measure the ripple that's present in the output of a high voltage supply (up to 3000V, but it's used at 1500V).



The voltage is isolated by a ultravolt model 40TF-ACV&DCD which gives



1:1 for ac and 1000:1 for dc. The input of the ultravolt is two unshielded HV cables. The output of the power supply under test and the input to the plastic box is HV coaxial connectors.

Question: I have to go from shielded to unshielded inside my plastic box, one part of me says to route the ground as short as possible to the ground of the ultrabox, the other part says that I should keep the ground next to the unshielded wires to avoid discontinuities.



Both paths are depicted in the next two pictures:



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So.. which one is the proper way?



Best Regards



Steve Sousa


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J

Doesn't matter.

John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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G

I can't see how it would matter much either way. (But I haven't done much HV) What's the maximum frequency? If you cared about noise getting in you could put it in a metal box. (or is that a no-no?)

George H.

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J

What did that Ultravolt thing cost?

John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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M

My preference would be to use a short braid for the ground like in the first pic. If the HV wires do leak it would not affect the measurements as much. Plus if there is an arc the braid makes a low impedance path. Ground both inputs too, looks like one (left) is floating.

And Deja vu.

Cheers

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S

It's specified to 10MHz but -3dB is 20MHz

I believe so, it also avoids problems with negative suplies. Even the Ultravolt thing doesn't ground it's chassis directly. It goes through a 100k resistor.

Best Regards Steve

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S

1670 eur in 2015 130 for two cables with those connectors.

Best Regards Steve

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S

My concern has to do with the frequency response/noise sensitivity (it's a plastic box) rather than with HV itself. Do you still think it doesn't matter?

Best Regards Steve

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J

Not knowing your system requirements, anything could matter. If you are concerned about a little noise on the HV, you'll need a superb HV supply and a metal box. I'd expect that routing of the common wire would be inconsequential.

You did it both ways. Did it make any difference?

John Larkin Highland Technology, Inc lunatic fringe electronics
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J

Yikes! There must be a few dollars worth of parts inside.

John Larkin Highland Technology, Inc lunatic fringe electronics
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