Electronics > Projects, Designs, and Technical Stuff
Open HV Probe 40kV
ArthurDent:
I am somewhat baffled at the endless discussion of possible failure modes of different plastics, methods of construction, or maintenance issues that could cause injury or death while no one seems to be paying any attention to how this safety issue has been solved for decades.
As I said in post #34, the simple safety solution is to have a complete ground potential between you and the HV resistor built into the probe handle. Below is a drawing of the Tektronix 6015 HV probe showing the grounded tube they used around the end of the HV resistor. In the video link it shows the same idea in a Fluke probe of having the closest thing to the HV be a grounded shield and not your hand at minute 3:10.
tggzzz:
--- Quote from: ArthurDent on April 22, 2019, 11:24:48 pm ---I am somewhat baffled at the endless discussion of possible failure modes of different plastics, methods of construction, or maintenance issues that could cause injury or death while no one seems to be paying any attention to how this safety issue has been solved for decades.
As I said in post #34, the simple safety solution is to have a complete ground potential between you and the HV resistor built into the probe handle. Below is a drawing of the Tektronix 6015 HV probe showing the grounded tube they used around the end of the HV resistor.
--- End quote ---
Appropriate materials and appropriate construction are not mutually incompatible.
Do you need both or is either sufficient on its own?
Personally, in this case I think both are highly desirable - I wouldn't want to rely on either alone.
ArthurDent:
tggzzz - "Appropriate materials and appropriate construction are not mutually incompatible."
I don't see anything wrong with any of the plastics used and I didn't mentioned that as a problem. What I am confused about is how the safety issue is being ignored when it has been solved ages ago. Everything can possibly fail, I just don't want that failure to take me with it.
beanflying:
Sigh, the Spaghetti monster paid me a visit overnight :palm:
On the plus side all the threads work well as do the PCB slots. The modded inner tube now takes four layers of spiral wrapped Kapton and would probably take a fifth.
Re the outer shield it is certainly possible to make rolled copper sheet then soldered is the obvious one or you could design around a standard hard drawn Copper pipe size. The downside to it is in terms of usability as the probe diameter will need to be increased making it awkward in more cases. The Scope test point I needed to measure last week was already fairly tight and only 2kV so I could have butchered something up to get it done.
I see no reason not to use the base handle and lower sections and then screw a different tip section to it. It may actually be of benefit to do that in the case of the higher frequency version to add some noise shielding as well?
If we can move on a little:
PLA and ABS are both good insulators - PERIOD !
PLA as some sort of magic water sponge is BS and it doesn't breakdown rapidly even when immersed in water without microbiological activity as well.
PLA as a rapidly Bio-Degradable Plastic in open Air is BS unless someone finds me ACTUAL SCIENTIFIC EVIDENCE to prove otherwise?
Dirt Contaminants and Grime are the enemy so the probe outer needs to be easily cleanable (smooth) so an Epoxy Coating should be added to the 3DP surface.
Operator Safety is paramount as it always was. Lets work to improve it where possible.
beanflying:
--- Quote from: ArthurDent on April 23, 2019, 12:01:56 am ---tggzzz - "Appropriate materials and appropriate construction are not mutually incompatible."
I don't see anything wrong with any of the plastics used and I didn't mentioned that as a problem. What I am confused about is how the safety issue is being ignored when it has been solved ages ago. Everything can possibly fail, I just don't want that failure to take me with it.
--- End quote ---
Just slowed the video right down you linked and took a screen cap. Some of the commentary about spark gaps and the circuit is wrong and the parts he tried to reference simply hook over the shield on the barrel section as shown. The question if someone that has one can check is how far into the barrel on the Fluke does the shield go? Also the LV end of the Resistors is back right at the operators hand
In the case of the Resistors I am looking at and the layout of my design it sees that point 65-70mm up into the barrel.
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