I know, Hp (and A0). But Hp in your words "youth is best enjoyed when young" so what's to do?

I dunno -- 'seems I'm one of those old-fashion types suffering under the delusion that the 'takeaways' of (even 'modern') youth should be more auspicious than alcohol-induced organ damage, legal issues and STDs -- But then what does a fossil like me know?!

Hp it's for sure Andropov and Chernenko and those guys were way more formidable foes than that spoiled fatboy with his poorly designed "bottle rockets" and wussy fission warheads!

Well spotted! - It really is the difference between a global catastrophe approaching 'ELE proportions' -VS- a local to regional disaster (at worst) -- But then neither potentiality excuses reckless irresponsibility -in any event- but especially to one's own future

the whole graveyard spiral our culture is in! I mean all the factions, all the us and them! Hp plz remember that as children of the 90's and 00's the only credible threats to NA soil A0 and I saw while growing up was from terrorism which is pretty minor league compared to direct strikes from a foreign military!

Agreed and understood!

The Faraday cage is awesome! I also like how it's secured by a single post for easy installation and removal!

Thank you! -- Inasmuch as the shield is not required below 25kV and owing to some people's 'issues' with viewing objects overlayed by mesh/lattice structures I chose to include same as an accessory as opposed to a permanent feature...

I dig your point that a strip taped to a conductive substrate is basically a floating capacitor plate b/c the adhesive insulates it from the substrate but why is that a problem?

Where 'immersed' in an intense electric field, such 'capacitors' will invariably charge via 'ion migration' with corollary corona and/or disruptive discharge attending dielectric breakdown of the adhesive, air, etc. (à la a 'relaxation oscillator') -- Said condition{s} being undesirable on a number of 'fronts' - not the least of which being introduction of spurious 'modes' corollary to induced surface loop dynamics... Bottom line! NOISE is the enemy of DC instrumentation!

Yo @Aleph(0)! Welcome back! Like Hp says "things get mighty dull around here w/o you, gal!"

DITTO!

Very best regards
HP

 

I have a question on the "Faraday cage". What good is it only covering the meter face? Was the anodizing removed between the frame and the 'shielding' mesh? If not the anodized layer makes a much more potent 'capacitor' than the foil tape does. One that will take more voltage before the dielectric(anodized layer) is pierced.

 

I have a question on the "Faraday cage". What good is it only covering the meter face? Was the anodizing removed between the frame and the 'shielding' mesh? If not the anodized layer makes a much more potent 'capacitor' than the foil tape does. One that will take more voltage before the dielectric(anodized layer) is pierced.

Excellent questions/observations!

I have a question on the "Faraday cage". What good is it only covering the meter face?

Please be advised that the entire movement external to the metallic cabinet (and not covered by the shield) is clad in Al tape - the conductive surfaces of which being 'electrically bonded' to said cabinet (and, hence, grounded).

Note also that the tape 'sections' are applied in such fashion as to form a contiguous electrical conductor...

--Post continued below images--

Reverse side of the d'Arsonval movement -- Please note the Al tape (back and sides) and the unfinished Al mesh - the latter's function being 'enhancement' of tape-to-cabinet electrical contact (à la a 'star washer').

Appearance of cabinet as prepared for movement installation.

Was the anodizing removed between the frame and the 'shielding' mesh?

Indeed it was - on all edges!

If not the anodized layer makes a much more potent 'capacitor' than the foil tape does. One that will take more voltage before the dielectric(anodized layer) is pierced.

Yupper Even a single ungrounded 'strand' would put the 'Rice Krispies Trio' to shame - with corollary 'downward pressure' upon my 'sunny disposition' -- Hence the painstaking procedure of verifying each and every strand's ground continuity prior to 'trimming back' the excess mesh (post framing)...

Many sincere thanks for your interest! -- Please don't hesitate should you have further questions/comments!

Very best regards
HP

 

Why not mount the meter inside the box? Drilling through the square plastic face to free the mounting studs, then place the mesh over the face using through bolts and nuts. to mount the whole thing to the box. Then just a hole the size of the actual dial, covered with the mesh would be the face of the box. I thought you said earlier the mesh was anodized?

 

Why not mount the meter inside the box? Drilling through the square plastic face to free the mounting studs, then place the mesh over the face using through bolts and nuts. to mount the whole thing to the box. Then just a hole the size of the actual dial, covered with the mesh would be the face of the box.

An excellent idea! Especially for those possessed of large cabinets and/or d'Arsonval styles 'unamenable' to cladding... Then too your suggestion provides for more 'rugged' construction!

Please know that your suggestion is especially helpful inasmuch as, in anticipation of 'spotty' parts availability, the EHT Indicator 'mini tutorial' will be offered merely as a construction example (as opposed to a 'strict' project) such that the readers are provided a 'starting point' and acquainted with the 'fundamentals'/critical features but granted latitude to adapt their specific designs to available materials -- Your suggestion will be included with credit in the 'alternatives'/'workarounds' appendices! Many thanks!

I thought you said earlier the mesh was anodized?

The shield mesh is anodized -- The 'contact enhancement' mesh (intervening the back of the movement and the cabinet) is fashioned of 'bare' Al...

BTW, If you're interested, uploaded images for this 'project' may be found in my blog under all entries entitled: "Passive EHT Indicator Construction" Beginning HERE

Best regards
HP

 

The following assumes you intended 'beneficiaries' with the above emphasized text...

HP thanks! I don't how that happened but anyhow it's corrected now

they have every motivation to report difficulty and no reason whatever to 'humour' me!

HP I say either you're being totally too modest or you looked at eclipse w/o eye protection so now u can't see mirror! So being serious I know you're not _that kind of teacher_ but twenty-something guys will have their dreams!

I dunno -- 'seems I'm one of those old-fashion types suffering under the delusion that the 'takeaways' of (even 'modern') youth should be more auspicious than alcohol-induced organ damage, legal issues and STDs -- But then what does a fossil like me know?!

HP that's just restatement of claim that all simple pleasures are unhealthy, dangerous or just wrong, so I'm not worried cuz most ppl in every generation survive to old age in spite of all that!

The same as yours, A0! Being drunk! After that the rest is basically predestined

JC I say you need to look at this!

Yet another excellent suggestion from 'The Prodigal Aleph'

HP TNX! I try!

Why not mount the meter inside the box? Drilling through the square plastic face to free the mounting studs, then place the mesh over the face using through bolts and nuts. to mount the whole thing to the box. Then just a hole the size of the actual dial, covered with the mesh would be the face of the box.

An excellent idea! Especially for those possessed of large cabinets and/or d'Arsonval styles 'unamenable' to cladding... Then too your suggestion provides for more 'rugged' construction!

@shortbus The only problem I can think of with that is scale shading of meters that have more than like 5mm of setback from glass but it's perfect for like round meters (like Weston) which are small and have vry shallow setback! So Tnx cuz it can save a lot of work for ppl with small flange-mount meters w/o beetled cabinet!

 

ATTN: @Aleph(0) , @Jazz2C

Evacuation pump update:

Please disregard my recommendation of the RobinAir 15300 in favor of the Robinair 15400

Having purchased and (now) tested several of the latter (i.e. 15400) it is my observation that the (as it turns out, conservatively stipulated) improvements in specification more than justify the scant increase in cost!

Specifically, Re: my test sample (which being again 10 units bearing well separated SNs):

-Worst case minimum pressure = 10μmHg (which being 'two times better' than Spec.)
-Drastically increased oil 'life' owed to the 'gas ballast' feature...
-Significantly improved transfer rates - especially at low pressures.

@Aleph(0) -- Please convey this to all 'concerned parties'!

Gotta run!
HP

 

OK, new idea. Is there a reason for using the flyback type in the beginning of this post? As opposed to other more modern types? While Googling "flyback transformers" I came across other people doing similar things with them, maybe not exactly what is being done here but is this so different from what is being done by the guy on this link? Or am I missing something that hasn't been shown yet?

http://www.angelfire.com/oh3/ebjoew/Flyback.html

 

@shortbus The only problem I can think of with that is scale shading of meters that have more than like 5mm of setback from glass but it's perfect for like round meters (like Weston) which are small and have vry shallow setback! So Tnx cuz it can save a lot of work for ppl with small flange-mount meters w/o beetled cabinet!

Guess I'm again missing what your saying. How is the thickness of the panel any different than the fabricated 'surround' that HP made? By back mounting the meter the panel looks, to my mind anyway, more "professional". While I've never worked with a KV meter, most of the meters of that type the face surround is easily pried off without breaking the surround or the meter body itself. Doing that the mounting bolts are easy to remove.

 

Is there a reason for using the flyback type in the beginning of this post? As opposed to other more modern types?

Absolutely!


Why do I despise integrally rectified/hard-potted LOPTs? - Let me count (but a few) of the 'ways'...

'Modern' LOPTs...

-Contain internal semiconductors (DST arrangements being typical) and are thus 'immutably dedicated' half-wave, unipolar devices...

Note that while it is, of course, possible to circumvent the EMF limitations imposed by the integral rectifiers' PIV restrictions via asymmetrical drive topologies (e.g. current-mode PWM) - such is not generally applicable to net-reactive loads (should the foregoing appear less than obvious, please see the below embedded exposition entitled Reference #1) -- Moreover, non-resonant/'pulse' excitation topologies typically provide very little energy at EHT potentials (often less than 1% of that available) thus limiting their utility to applications requiring only a 'fleeting' EHT pulse to 'open' an 'ion channel' to low EMF/high current flow (e.g. ignition systems, electric shock weapons, electrical demonstration, etc...)

-Are 'intractably' end-point grounded.

-Exhibit inferior power handling capability (a few tens of watts continuously and perhaps 200W momentarily (which representing ≈ one tenth the capability of the recommended 'tyre-wound' units )

-Exhibit relatively poor 'high frequency' performance and generally poor frequency agility (thus increasing the cost and complexity of 'resonation' MMCs and 'multiplier' cascades, etc...)

-Are compromised by irremovable auxiliary and primary windings.

-Are 'hard potted' rendering them, as a practical matter, both unmodifiable and unrepairable.

-Are (ironically) more difficult to reliably source than the vastly superior 'tyre wound' units...


Succinctly; 'modern' (i.e. integrally rectified, 'hard potted') LOPTs' internal rectification and all around dearth of versatility/'modifyabilty', electrical 'robustness' and power handling capability render them less than useless for any purpose beyond certain demonstration devices (i.e. 'toys') and, of course, their designed function...

FWIW - Had I my 'druthers' I'd recommend exclusive use of 'high frequency' radiography transformers -- Unfortunately it seems (based upon several informal discussions with various 'interested parties') that an additional expense of $3k-$5k and the requirement messing about with dielectric oil 'straight out of the gate' as it were, would likely be 'off-putting' to many of our 'target demographic'

The good news being that 'tyre wound' LOPTs are yet widely available -- For instance @Jazz2C only recently found literally hundreds of highly desirable NOS units (in a 'back woods' 'bricks and mortar' shop) following a few local inquiries! (Such being representative of my long-time experience in said regard) -- While I cannot claim understanding of the ongoing (well-neigh) ubiquity of Ca. fifty-plus year old components, I prefer to regard same as a 'gift horse' whose tonsils I've no desire to examine!


Reference #1
Development of asymmetrical output does not necessarily circumvent rectifier PIV limitations where net-reactive loads are at issue - Here it may be seen that the (inverse) stress applied to the rectifier{s} is equal to the peak-to-peak 'excursion' of the winding (i.e. the sum of the p-p excursions of all windings) --regardless of 'offset'-- when 'working into' a capacitive load...

As regards indicator mounting -- I'll leave it to @Aleph(0) to expand upon her concerns (I failed to entirely follow them myself)

@shortbus - as far as I'm concerned, your method represents a generally superior, less labour intensive and, I daresay, markedly more aesthetic alternative to that of my prototype!

But then, in light of their scarcity, I hesitate to advise opening and/or modification of d'Arsonval movements -- While I'm certain such may be successfully accomplished via special techniques and/or a "jeweler's touch" my experience following such 'interventions' has too often been a 'sticky' indicator within a fortnight following breakage of the seal

Thus it is that (with reference to the below imaged movements) I may confidently recommend yours as the 'method of choice' applied to 'form factors' consistent with those on the left (whereon no disassembly/modification is required) -- Howbeit I prefer to eschew 'tempting fate' via advising any modification violative of the hermeticity of units akin to that on the right... Perhaps proper reassembly requires (gentle) heat-treating or 'flooding' with dehydrated air/nitrogen prior to closure?

With very best regards/many thanks to you - and profound apologies to E.B. Browning
HP

 

Thus it is that (with reference to the below imaged movements) I may confidently recommend yours as the 'method of choice' applied to 'form factors' consistent with those on the left (whereon no disassembly/modification is required) -- Howbeit I prefer to eschew 'tempting fate' via advising any modification violative of the hermeticity of units akin to that on the right... Perhaps proper reassembly requires (gentle) heat-treating or 'flooding' with dehydrated air/nitrogen prior to closure?

So you're saying the KV meters are 'hermetically' sealed? Like I said before, never had a chance to use or even see one, but have never seen any of the other typical electrical meter that were made that way. And I have my doubts that any using a plastic housing are even capable of being done that way. The meter on the right in the picture would still be able to be back mounted in the panel, unless I'm missing something that isn't seen in the picture, a side view would tell me more though.

To do that meter would take another easily made part. In the panel itself the square hole would be cut slightly smaller than the outside dimensions of the meter. Then another square of metal bigger on all sides than the meter, with a square hole the size of the meter face would need to be made. This would be to keep the meter centered in the panel opening and to anchor the mesh to the inside of the panel thus grounding it to the panel. If you want I can make a sketch if my description in good enough.

 

Note that while it is, of course, possible to circumvent the EMF limitations imposed by the integral rectifiers' PIV restrictions via asymmetrical drive topologies (e.g. current-mode PWM) - such is not generally applicable to net-reactive loads (should the foregoing appear less than obvious, please see the below embedded exposition entitled Reference #1) -- Moreover, non-resonant/'pulse' excitation topologies typically provide very little energy at EHT potentials (often less than 1% of that available) thus limiting their utility to applications requiring only a 'fleeting' EHT pulse to 'open' an 'ion channel' to low EMF/high current flow (e.g. ignition systems, electric shock weapons, electrical demonstration, etc...)

But and again probably showing more of my inherent ignorance, isn't that what he was doing in the link I provided, removing the output diodes? And making the flyback non polarized? I also don't understand why removing the other winding's are a necessity, when there is no load on them aren't they just "along for the ride"? Your reference link is not accessible to the public or at least not to me. And your explanations following the part I quoted are way above my understanding.

 

So you're saying the KV meters are 'hermetically' sealed?

Actually... The movement is merely a 'Plain Jane' μA 'meter' (FWIW the divider resistors thread in through the top of the cabinet - hence all EMFs within the cabinet are in the 'low' millivolts) -- But yes, in my experience most d'Arsonval movements are hermetically sealed...

And I have my doubts that any using a plastic housing are even capable of being done that way.

Plastic units are typically sealed via adhesive tape and/or resilient glues...

The meter on the right in the picture would still be able to be back mounted in the panel, unless I'm missing something that isn't seen in the picture, a side view would tell me more though.

For your convenience/edification I'll post alternate angle and (yikes!) disassembly views of the mAs indicator by tomorrow morning

To do that meter would take another easily made part. In the panel itself the square hole would be cut slightly smaller than the outside dimensions of the meter. Then another square of metal bigger on all sides than the meter, with a square hole the size of the meter face would need to be made.

If I correctly understand the above quoted text, you are suggesting mounting the movement to a panel which is in turn back-mounted to the front panel of the cabinet (hence obviating modification of the movement)? -- Sounds promising!

If you want I can make a sketch if my description in good enough.

A sketch would be great! With your permission I'll include it (with credit) with the project text?

isn't that what he was doing in the link I provided, removing the output diodes? And making the flyback non polarized?

So it would seem...
Re: the linked page: The LOPT at the top of the page is essentially a miniature 'tyre wound' unit with an external rectifier mounted to the core/frame via an insulating bracket. Whereas the second unit is slightly newer (albeit pre-DST) featuring a potted rectifier and -UGG!- capacitors... So... the first transformer is of the 'desirable' style but too small for our purposes -- The second unit is good for absolutely nothing save certain EHT toys (e.g. plasma spheres, etc) and, of course, supplying a diminutive CRT's acceleration/focus electrodes -- FWIW Neither of them are 'modern'...

I also don't understand why removing the other winding's are a necessity, when there is no load on them aren't they just "along for the ride"?

The principal objections to extraneous windings relate to said features' introduction of 'parasitic' capacitance/loading and cross-arcing/corona where brought out to pins -- And yup!... You guessed it! Removal of said pins does not solve the problem! -- Note that the re-purposed application's greater demands in the ways of EMF, frequency and power tend to exacerbate every 'weakness'...

Your reference link is not accessible to the public or at least not to me.

I apologize for the confusion It is not a link -- "Reference #1" refers to the image (embedded immediately below this text) - Please advise me if it fails to display here and/or on post #1252

And your explanations following the part I quoted are way above my understanding.

I believe you'll find my discussion of LOPT selection 'whys and wherefores' (in the intro to the tutorial) much clearer -- As per the "Alpha Crew's" request, I'm presently working on embedding the images (for automatic display) in said document - Hence you may expect posting of said 'reader friendly-ized' version of same to (the end of) this thread sometime tomorrow

Very best regards
HP

 

I apologize for the confusion It is not a link

It was highlighted like a link, and when to the page when clicked on it. It did show up in both posts just not on the page.

A sketch would be great! With your permission I'll include it (with credit) with the project text?

Will do.

 

It was highlighted like a link, and when to the page when clicked on it. It did show up in both posts just not on the page.

Indeed... Said behaviour owes to a Xenforo feature whereby 'clicking' on an image toggles between 'standard' and 'full size' views...

Will do.

Thanks!

Best regards
HP

 

If you use 'Upload a File' to post pictures, you get an option to display full size or thumbnail. Thumbnails would be better for those with slower or mobile connections especially considering the detailed, hi-res pics. here. Also, when you open one, you get a nice selection screen.

Just a thought.

 

If you use 'Upload a File' to post pictures, you get an option to display full size or thumbnail. Thumbnails would be better for those with slower or mobile connections especially considering the detailed, hi-res pics. here. Also, when you open one, you get a nice selection screen.
View attachment 134548View attachment 134547
Just a thought.

Thanks, @JohnInTX

FWIW Embedding images as 'thumbnails' was my first choice. Unfortunately the on-fora viewer (i.e. 'selector feature') is intermittently 'buggy' - especially with larger images (common symptoms being lock-ups, failure to display thumbnails, failure to load images, displaying wrong images, etc...) then too it is unavailable to 'guests' despite the images' location in my blog with access rights set for 'all visitors'

We experienced so much difficulty with reliable image display/complaints (Ca. two years ago) that I nearly abandoned the project pending location of an acceptable off-site image hosting service... Happily there was a modification to this site's image upload software (well over a year ago) whereby images are automatically 'scaled' -- after which images display reliably all the time, every time when embedded via 'full image'

@JohnInTX (and all others whom it may concern) please do not 'phase out' or otherwise disable the 'embed as full image' option! It may be slow on low bandwidth connections but it's 100% reliable -- which being much more than one can hope for Re: all things 'internet'!

Best regards
HP

 

Guess I'm again missing what your saying. How is the thickness of the panel any different than the fabricated 'surround' that HP made? By back mounting the meter the panel looks, to my mind anyway, more "professional". While I've never worked with a KV meter, most of the meters of that type the face surround is easily pried off without breaking the surround or the meter body itself. Doing that the mounting bolts are easy to remove.

As regards indicator mounting -- I'll leave it to @Aleph(0) to expand upon her concerns (I failed to entirely follow them myself)

@Hypatia's Protege and @shortbus all I'm saying is if meter has like _picture frame_ trim around window (like the one HP's using in demo) the window will have to sit whole depth of trim behind back of panel which can cause visibility problems cuz of being in a recess plus covered by screen. Also since we agreed backlighting meter is nix cuz of hassles with batteries u should know that frontal illumination above room level will make it hard to see through screen cuz of scatter!

So anyhow shortbus I totally like ur idea so if it works it works! But I say it might be too shaded when shape of meter case doesn't let window sit flush with panel.

 

Thanks, @JohnInTX

FWIW Embedding images as 'thumbnails' was my first choice. Unfortunately the on-fora viewer (i.e. 'selector feature') is intermittently 'buggy' - especially with larger images (common symptoms being lock-ups, failure to display thumbnails, failure to load images, displaying wrong images, etc...) then too it is unavailable to 'guests' despite the images' location in my blog with access rights set for 'all visitors'

We experienced so much difficulty with reliable image display/complaints (Ca. two years ago) that I nearly abandoned the project pending location of an acceptable off-site image hosting service... Happily there was a modification to this site's image upload software (well over a year ago) whereby images are automatically 'scaled' -- after which images display reliably all the time, every time when embedded via 'full image'

@JohnInTX (an all others whom it may concern) please do not 'phase out' or otherwise disable the 'embed as full image' option! It may be slow on low bandwidth connections but it's 100% reliable -- which being much more than one can hope for Re: all things 'internet'!

Best regards
HP

HP I totally agree that built in viewer is a train wreck and anyhow like u say it doesn't let guests view pics from blog! But I'm also saying automatically loading 50 full sized pics per post will totally drive ppl with slow connection crazy!

So I have an idea! All u need to do is directly link thumbnails to full size pic so built in viewer is totally bypassed! @JohnInTX do you know of a way to do that?

 

The second unit is good for absolutely nothing save certain EHT toys (e.g. plasma spheres, etc)

HP sry I disagree cuz even w/o the filter caps DC wouldn't produce vry interesting plasma effects! Also even though it's only like 25kV in soft vacuum I say sphere glass is too thin to be sure of healthy shielding! Just sayin'