Electronics > Projects, Designs, and Technical Stuff
Open HV Probe 40kV
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joeqsmith:

--- Quote from: beanflying on May 04, 2019, 02:38:17 am ---Life has been in the way.

Will assemble the Divider insert and take some pics of it as I have all the bits needed. The Probe front end itself is now epoxy coated and I have a few more Rolls of Black so I will reprint the handle end as I have tweaked some of it internally.

--- End quote ---

Abandoned your efforts?  I would sill like to see a few pictures of the coated parts.
Kosmic:
I did some non-scientific electrical tests with a PLA filament. Connected 1.2 cm of filament to my Genrad 1644. Tested a 1Kv on the Tera Ohms range. The filament was
beforehand washed with IPA and gloves were used for manipulations.

- At room temperature I was reading 1000 TOhm (pretty much the limit of the instrument)
- Now heating the filament at 100C at almost no effect.
- Heating at 200C I saw a very little drop in resistance.
- Now at 300C for some time the filament was starting to melt and resistance dropped to something like 750 TOhm.

I was expecting a drastic change of electrical characteristics at high temperature but in the end, it was pretty moderate.
Kosmic:
In comparison, with a similar piece of PTFE I can't detect any resistance (infinite) and heat do not really affect the results.
trobbins:
I was a bit surprised that some simplified testing of the solid insulation resistance of significant sections of a probe didn't appear until post #115. But even that 5kVdc test, as shown by the photo, appears to be poorly configured.  Testing should I suggest be about wrapping foil around one surface region, and the other relevant surface region - whether that be for checking creepage as well as bulk resistance as shown, or by making an internal surface that coats the inner tubing, or about covering the entire handle region.   Foil wrapping was the standard technique for testing PD and breakdown of telephone handsets in days of yore - certainly for Telstra and EPR issues.

I would think the advantage of 3D printing would be more towards a lower kV probe, but with designed-in shielding to allow experimentation for flat compensation out to kHz plus range, as that is where the commercial probes get expensive for DIYers.  Designing in protective earth tubing, and even an additional redundant earthed handle would similarly seem to be worthwhile, plus some compartment allowance for compensation parts and additional protection parts such as MOVs to shunt any fault to redundant protective earths.
tautech:

--- Quote from: trobbins on December 11, 2019, 04:24:34 am ---...............
Designing in protective earth tubing, and even an additional redundant earthed handle would similarly seem to be worthwhile, plus some compartment allowance for compensation parts and additional protection parts such as MOVs to shunt any fault to redundant protective earths.

--- End quote ---
Yet if someones scope is inadvertently floated due to a poor or NO mains earth there would be no protective gain.
Better to use the foil wrap test you suggested and so prove there is no HV leakage.
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