Electronics > Projects, Designs, and Technical Stuff

Open HV Probe 40kV

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vk6zgo:

--- Quote from: The Soulman on April 25, 2019, 09:33:58 am ---
--- Quote from: beanflying on April 25, 2019, 07:29:50 am ---It is really simple SHOW ME EVIDENCE of the material or process not being suitable.

--- End quote ---

Engineers are used to it being the other way around.

--- End quote ---

Maybe in modern times, but Engineers were, in the past, very much in the forefront of finding what materials were most suitable for such use.
This was mainly using real world tests, so most of the evidence of "what works" comes from as much empirical testing, as from any knowledge supplied by the manufacturers of the materials.

vk6zgo:

--- Quote from: joeqsmith on April 25, 2019, 06:08:02 pm ---Some time ago, we had bought some sort of plastic to machine some parts from.   These parts were used in a high voltage application.   Once they were made and installed, we noticed that the system was having a problem.  The new plastic parts were presenting a decent load.   I pulled the remaining raw stock and sure enough, it was fairly conductive at DC.   The properties of the plastic chosen wouldn't have suggest it would behave this way.  In the end, we bought another slab of the same material and it was fine.   I never took the time to dig into why that one lot had a problem.  Something in the mix.   I can only think of one case like that in my entire career.     

Most of the commercial probes similar to what is being shown will state in their manuals that they are for CAT I only.  For my own personal use, pretty much everything it CAT I and very low energy.  Fairly low risk for the most part and certainly something I am willing to accept.

Back to the scheduled program...

--- End quote ---

There are many interesting properties of various materials, which sometimes seem counter intuitive.

An FM transmitter broke a porcelain standoff insulator in the driver stage.
The real part was forever away in Norway, so I dug around & found a piece of what looked exactly like  PTFE, & fashioned a new one.

Turning the Tx on, it came up OK, but after a few minutes dropped in power markedly.
On investigation, the insulator now looked like a "Cocoa Pop".
Whatever it was, it wasn't PTFE!

At home, later, I found a suitable porcelain insulator in a box of some National HRO receiver parts, so the beast was returned to service.
(A short interval for vintage Radio fans to burn me in effigy! ;D).

Cad plated steel screws usually don't fare well in RF environments,(both MF & VHF), & there are reports  of Nylon getting quite hot in the same environments.

beanflying:

--- Quote from: vk6zgo on April 26, 2019, 03:58:19 am ---
--- Quote from: The Soulman on April 25, 2019, 09:33:58 am ---
--- Quote from: beanflying on April 25, 2019, 07:29:50 am ---It is really simple SHOW ME EVIDENCE of the material or process not being suitable.

--- End quote ---

Engineers are used to it being the other way around.

--- End quote ---

Maybe in modern times, but Engineers were, in the past, very much in the forefront of finding what materials were most suitable for such use.
This was mainly using real world tests, so most of the evidence of "what works" comes from as much empirical testing, as from any knowledge supplied by the manufacturers of the materials.

--- End quote ---

Some of us also went through the Victorian Technical School system before it was Kennetted  :horse: so we learned a large bunch of practical hands on Engineering method as well as Maths and Science before getting to Uni. ;)

vk6zgo:

--- Quote from: beanflying on April 26, 2019, 04:35:29 am ---
--- Quote from: vk6zgo on April 26, 2019, 03:58:19 am ---
--- Quote from: The Soulman on April 25, 2019, 09:33:58 am ---
--- Quote from: beanflying on April 25, 2019, 07:29:50 am ---It is really simple SHOW ME EVIDENCE of the material or process not being suitable.

--- End quote ---

Engineers are used to it being the other way around.

--- End quote ---

Maybe in modern times, but Engineers were, in the past, very much in the forefront of finding what materials were most suitable for such use.
This was mainly using real world tests, so most of the evidence of "what works" comes from as much empirical testing, as from any knowledge supplied by the manufacturers of the materials.

--- End quote ---

Some of us also went through the Victorian Technical School system before it was Kennetted  :horse: so we learned a large bunch of practical hands on Engineering method as well as Maths and Science before getting to Uni. ;)

--- End quote ---

Yeah, the WA Tech School was good value, too.
In fact, I think that was where I saw the EHT probe machined out of solid Perspex that I referred to earlier.

The main "Perth Tech" that I went to was an old building in St George's Terrace, Perth.

To get to the Electronics section, you walked through that building, down a lane between a bunch of Ex WW2 transportables & some weatherboard buildings, where all sorts of stuff went on, from training cooks, to running a massive steam engine for the guys doing "Heat Engines 1 & 2".(Steam would come out of the gutter)

In another building there was "hands on" use of a fair sized Radio Transmitter.(We did Semiconductors Lab in the same building, & a uAmmeter carefully set up to read base current would go full scale if the guys next door fired up the Tx)

At the other end was a red brick building, in the sub-basement of which Electrical Engineering had a large quantity of rotating plant, & ancillary test equipment, again, "hands on" for students doing the relevant courses.
From there it was  up two flights of stairs to where we had our lectures.

You really felt like you were learning stuff there, none of this "monkey see, monkey do" crap!

joeqsmith:

--- Quote from: beanflying on April 26, 2019, 01:22:23 am ---WARNING Even if you are a Dumbass don't play with Microwave Oven Transformers with any stick or probe. Unregulated MOTS Kill !

--- End quote ---

Of course the cap can get you as well.   Just a quick search, many are attempting repairs, one some guy burning wood and one a kid trying to replicate a YT video.   

https://www.wkyc.com/article/news/local/lorain-county/teen-dies-from-homemade-science-experiment/145431142
https://www.northjersey.com/story/news/passaic/passaic-city/2017/08/24/passaic-man-killed-after-being-electrocuted-while-fixing-microwave/596748001/
https://www.union-bulletin.com/local/local-man-electrocuted-using-dangerous-wood-art-process/article_daf59a2a-3420-11e7-8508-c7eb2f3dc175.html
https://www.brownsvilleherald.com/news/local/man-fatally-electrocuted-while-repairing-microwave-oven/article_d0749396-3b1a-52f3-9201-65bce57008b3.html
http://www.walb.com/story/19823265/update-deadly-microwave-was-not-plugged-in/
https://dailyegyptian.com/21717/archives/student-dies-in-microwave-electrocution/
https://www.cdc.gov/niosh/nioshtic-2/20026141.html

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