Author Topic: Probes for checking voltage references  (Read 10740 times)

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Offline rhbTopic starter

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Re: Probes for checking voltage references
« Reply #50 on: March 30, 2018, 10:21:52 pm »
Thanks.  Is it worth getting that book or is there something better?   It looks as if it would fill a gap in my library. I have "Low Noise Electronics Design" by Motchenbacher and Fitchen, but I don't see anything devoted just to grounding and shielding. The usual intro stuff in a lot of books, but nothing in depth.   Even expensive books are cheaper than trial and error.

I found a couple of 2" x 11" x 7" 29 gauge steel chassis'.   How effective would those be for a test chamber?  I have in mind putting piano hinge between the two.  Should they be annealed?  How much mu metal shielding  would be needed to make a chamber using those reasonably quiet?    Would copper foil be justified?  I don't *think* I have any large fields to contend with other than computers and lab equipment.

This is all the classic "tools to make tools" exercise. but I don't mind spending $150-200 for a good test chamber for precision measurements.  From the pricing I've seen I could cover both chassis' with copper foil and 1-2 mm of mu metal for that price if I look hard enough.
 

Offline MisterDiodes

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Re: Probes for checking voltage references
« Reply #51 on: March 30, 2018, 10:48:11 pm »
...I heard that sometimes you can Google the title and you might find a lower cost PDF version, and then you can decide if it's worth the purchase.  I doubt that's what the publishers had in mind, and I wouldn't post those links here.

Otherwise it's a relatively good introduction to various grounding / noise control techniques.  Not at all what I'd call 100% step-by-step comprehensive but at least an overview to start thinking about the concepts involved.
 

Offline rhbTopic starter

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Re: Probes for checking voltage references
« Reply #52 on: March 30, 2018, 11:04:54 pm »
I like books as evidenced by my 5000+ volume technical library.  I'll order a copy.  If you know of other references you'd recommend having please let me know.

"A Mathematical Introduction to Compressive Sensing" by Foucart and Rauhut is quite comprehensive, but even that doesn't cover all the applications of sparse L1 pursuits.  Indeed, it would take 4-5 volumes to do that. And it is hardly "step by step",  My general experience is that I need 2-3 references for a casual interest and 4-5 or more for anything serious.
 

Offline Echo88

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Re: Probes for checking voltage references
« Reply #53 on: March 31, 2018, 12:03:26 am »
If were talking about shielding and low noise stuff, this book is also very noteworthy: Henry W. Ott: Electromagnetic Compatibility Engineering
Especially the shielding comparisons for steel enclosures and wiring comparisons are interesting.
Im still searching for good and thick-walled steel cases (little bit bigger and more massive than the RF-steel-cases fom TEKO), which can house smaller aluminium cases like the Hammond-case-series.
« Last Edit: March 31, 2018, 11:17:54 am by Echo88 »
 
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Offline MisterDiodes

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Re: Probes for checking voltage references
« Reply #54 on: March 31, 2018, 03:15:06 am »
Sometimes deep drawn or weldied steel standard electrical mains general purpose junction / equipment boxes can work very well, and look nice when they come powder coated.  The better ones to use are the type that have a rated dust-tight close-fitting lid and -don't- have pre-punched knockouts - it's usually better to do your own machining.
« Last Edit: March 31, 2018, 03:23:35 am by MisterDiodes »
 

Offline hwj-d

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Re: Probes for checking voltage references
« Reply #55 on: March 31, 2018, 07:15:46 am »
My opinion about it,

don't see any prof. massive steel cases to prevent RF shielding today. Look at sharias yt-channel, what the industrie is doing.

I mean, this is about voltage references, right? So keep it simple and cost effective. That's for the pcb's too. (€: I don't think, we really want to beat a fluke reference in the first steps... ).

It's more important to pay attention to the basic things and how to measure them correctly. Know, from where the noises really comes from. Read the books, then build a reference, calibrator, or what ever. But not a heavy expensive tank, that doesn't really help much, but tries to solve the problem like under a large pile of sand.

Keep it simple,
have fun,
 ;)
« Last Edit: March 31, 2018, 07:44:50 am by hwj-d »
 

Offline rhbTopic starter

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Re: Probes for checking voltage references
« Reply #56 on: March 31, 2018, 01:06:49 pm »
I've got a mid-size U-haul pile of old '40's and '50's electronics.  Quite a few NOS E.F. Johnson, Bud and similar chassis'.  So in part I'm trying to use up some of Dad's treasures.  The general idea is to fabricate a good basic enclosure and make a series of tests before and after adding refinements like copper foil and mu metal.

I plan to order Ott's book along with a 2000+  page tome entitled "Electromagnetic Compatibility Handbook".   

There's another book I'm considering,"Grounding and Shielding: Circuits and Interference" by Ralph Morrison.  It looks to be very basic physics oriented. which is what I would like in addition to the others.  The more detailed the math the better.  Any comments on that book or suggestions of alternative treatments?
 

Offline eurofox

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Re: Probes for checking voltage references
« Reply #57 on: March 31, 2018, 02:56:49 pm »
My opinion about it,

don't see any prof. massive steel cases to prevent RF shielding today. Look at sharias yt-channel, what the industrie is doing.

I mean, this is about voltage references, right? So keep it simple and cost effective. That's for the pcb's too. (€: I don't think, we really want to beat a fluke reference in the first steps... ).

It's more important to pay attention to the basic things and how to measure them correctly. Know, from where the noises really comes from. Read the books, then build a reference, calibrator, or what ever. But not a heavy expensive tank, that doesn't really help much, but tries to solve the problem like under a large pile of sand.

Keep it simple,
have fun,
 ;)

Using massive block of steel is not only for shielding but to get it hermetic to humidity.
It is simple for me, I have a milling machine, lathe, tig and stick welding and many other mechanical tools, it is easy for me  8)


I just want to test something that I think was never done from volt nuts:

1/ heavy shielding

2/ avoid humidity influence, te massive housing with wall thickness should be about 10 mm, build with 2 parts with gasket (base and cover), silicone isolated wires hermetic sealed, area with silicate gell to remove the humidity after closing the "container", 1 taped hole just above the 10V trimmer but closed with a screw and hermetic gasket. Power supply isolated in a different area shielded from the LTZ1000 pcb.

3/ have a "stable" thermal mass and if needed could easy be heated very accurately.

It will take some months before I can really make some test

And this will cost me just time and maybe 10-20 Euros of metal.

eurofox
« Last Edit: March 31, 2018, 09:13:11 pm by eurofox »
eurofox
 

Offline rhbTopic starter

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Re: Probes for checking voltage references
« Reply #58 on: March 31, 2018, 06:37:04 pm »
Touche!  Never underestimate the skill set of an EEVblog forum member.

I'm looking at $200 to $350 for books.  So $100-200 for a chamber seems pretty reasonable and in line with other costs.










 

Offline hwj-d

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Re: Probes for checking voltage references
« Reply #59 on: March 31, 2018, 06:56:02 pm »
Quote
Touche!  Never underestimate the skill set of an EEVblog forum member.

Keep calm, boy!
I'm definitly not interested in some "fight club" here ...
 

Offline Echo88

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Re: Probes for checking voltage references
« Reply #60 on: March 31, 2018, 07:32:04 pm »
Noise-related throw-in: A few weeks ago i tested a mains-based AM-stereo-radio to see if it could detect RF noise and make it audible, which didnt work for any device i brought close to the radio.
Today i tested a portable battery-driven AM-radio and am amazed how nice it indicates all devices which emit rf-noise. You can hear the noise-spikes from switching the lighting, usb-wall warts (you can hear how the dcdc tries to hold the 5V after being disconnected from the 230V) and even tv remotes make sounds like the phasers from star trek.  ;D

Since it such a nice indicator for RF-noise and -peaks im gonna get the radio a bigger battery and will log the rectified speaker-output together with my longterm resistor measurements on which i still see sharp peaks despite my attempts at shielding and use of CAT-5-cable.

Used handheld radio is the Sony ICF-S22. But i guess every handheld radio should do the trick. Would be also interesting to test the radio in a shielded box and look for rf-peaks which get trough the shield.
 

Offline MisterDiodes

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Re: Probes for checking voltage references
« Reply #61 on: March 31, 2018, 08:51:56 pm »
You haven't lived until you played Trek (a basic Star Trek game, mostly text) on an IMSAI 8080.  The sound system was an AM radio placed next to the computer, and it worked better with the lid off the motherboard box. The programmers had intentionally built various loops into the code to toggle a few unused address bus lines at the correct rate, and that created enough noise on the AM band to be clearly picked up by the radio...So when you fired phasors, you could hear that,  photon torpedos has another sound,  the Klingons yammering at you could even be made out.   The "Red Alert" noise worked surprisingly well too.

Pretty darned clever way  to get a multimedia game experience at a time long before computers had any sort of audio output jack.
 
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Offline ArthurDent

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Re: Probes for checking voltage references
« Reply #62 on: April 01, 2018, 01:27:16 am »
Your Star Trek story reminds me of when my brother worked as a programmer on an IBM360 at a local university years ago. I was visiting him once when another program was stringing together a bunch of variable length do loops and listening to the RFI produced by a cheap 6 transistor AM radio. By varying the length of the loops he could generate different ‘notes’ and the final product was ‘Daisy’. Phasor noises were still in the future in the mid 1960s.

There were Teletype 33 terminals scattered around campus and one of the games available for students to play (with the limited sign-on time allotted) was a text only adventure game. You had to wait for an interrupt to get a reply so the game was very slow and you had to use your imagination because there were no images.
 


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