Low Cost Magnetic + Electrical Shielding Enclosure - Page 1
Forum section: electronics / general

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: August 23, 2025, 01:44:57 pm
content: Planning on creating my own custommagnetic + electrical shielding enclosureto perform more metrology-grade measurements. Using theLT Application Note 124as a guide, I've been struggling to locate a low cost source for MuMetal or MetGlass.I'm thinking of building the innermost "Mu Metal box" instead from silicon steel alloy plates, obtained from large microwave oven transformers (MOT), electrically connected together via either high strength fluxed solder, or rivets.Feedback/opinions/suggestions?

author: iMo
author_rank: Super Contributor
timestamp: August 23, 2025, 02:29:22 pm
content: When talking metall glass - I have a roll of a permalloy glass foil (I was told), the tape is aprox 20mm wide, the foil perhaps 1um or less thin, and the roll (dia 7-8cm) is heavy (like 1kg). Foil is somehow flexible, but fragile, when broken the small foil elements are lightweight (flying around in air draft) and extremely sharp,dangerous stuffindeed, absolutely not suitable for creating a shield. I got it from somebody when I was looking for suitable materials ages back.

author: mawyatt
author_rank: Super Contributor
timestamp: August 23, 2025, 04:50:50 pm
content: This seems a tough problem for hobbiest. In the distant past we had access to MuMetal and even created our own specialized MuMetal enclosures (drawn with lid), but nothing like this today.Just thinking out loud maybe a couple Cookie Tins one within the other could provide enough H field shielding to prove useful. For E field things are easier as one can use Cu tape, or PCB blanks soldered together creating a box within the Cookie Tins. Bringing signals in and out of the overall "enclosure" should consider using feedthru caps and maybe even a small box inside with larger values capacitors/inductors for decoupling the ins and outs.Another thought, what about using a gallon paint can and another 1/2 gallon or quart paint can inside thus having two shielded within? These are available cheap and in full metal.Edit: There's even larger ones available which are looking quite interesting for hosting some sensitive electronicshttps://www.thecarycompany.com/3-gallon-black-open-head-steel-pail-unlined?utm_source=google_shopping&gad_source=1&gad_campaignid=392027054&gbraid=0AAAAAD_MjBiJVDfhM6OOz3XwK01-M0GSz&gclid=EAIaIQobChMIzILIjLShjwMVnAgMAh1TUzCvEAQYBCABEgLM2PD_BwEAnyway, keep us posting on what you come up with!!Best

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: August 23, 2025, 04:57:41 pm
content: Quote from: mawyatt on August 23, 2025, 04:50:50 pmThis is a pretty good alternative idea to MuMetal/MetGlass/silicon steel alloy plates, as the paint cans would have more mass and therefore ability to absorb the magnetic fields, providing better magnetic shielding, in comparison to a thin steel cookie tin.

author: Simmed
author_rank: Frequent Contributor
timestamp: August 23, 2025, 05:20:33 pm
content: if you look at amazon, ebay, ali etc etcthere are blank tinplate boxes for sale (unprinted)i bought some samples from taobao long long agothe largest i have seen i think are 16" on 1 sidethere could be larger onesi also spotted some tinplate sheets on amazonbut they are not big, only 12"im sure there is somewhere that sell like big wide sheetsit could be one of those signage printers, but i dont knowsince paint can are mentionedi remember milkpowder tins have progressive sizeseg : 2+kg > 1++kg > 1?kg = 3 layers ?and they have nice fitting lids !

author: TimFox
author_rank: Super Contributor
timestamp: August 23, 2025, 05:27:24 pm
content: When designing ferrous shields against external magnetic fields, note that the permeable material does not absorb or dissipate the flux, but re-directs it around the enclosed volume.Here is a simplified prose account:The external B field (in Tesla) is the flux density (in Weber/m2). The “broad side” of the enclosure captures a flux equal to the field times the area of that side.That flux is then confined to a much smaller area given by the shield thickness times a dimension depending on the geometry (comparable to the overall size), and the B field inside the metal is magnified by a geometry-dependent factor. To work as a shield, this larger B field must be less than the saturation B field (roughly 2 T for iron alloys or 0.5 T for nickel alloys, including mu-metal).Inside the shield, adjacent to the metal, the B field in air is reduced by the relative permeability of the metal (technically a non-linear function). When deciding between nickel and iron alloys, the first question is avoiding saturation and the second question is the much higher permeability of the nickel alloys. Sometimes, in extreme cases, it is good to use an iron alloy on the outside, with a nickel alloy inside (usually spaced away from the outer shields. Shield metal suppliers often sell both types of metal in sheet or foil.

author: iMo
author_rank: Super Contributor
timestamp: August 23, 2025, 05:41:34 pm
content: FYI -https://www.eevblog.com/forum/metrology/a-portable-box-for-1f-and-low-noise-measurements/msg4652194/#msg4652194As a student I made some calculation when creating that ridiculous box (aprox A4 format, the walls aprox 22 or 25mm thick), on how the stuff will suppress the 50Hz. A lot of math but at the end of the day it depends on the material you are using. Mine was from a "softest material they found around", but hey, I never got the exact parameters. Inside was a copper foil as well - so you had to close the inner box with the copper lid and on top of that the steel lid. The chamber was used for many years there for various measurements, the main objection/criticism was always related to the weight of the lid..When the top cover was placed on the box, it made a sound like when a manhole cover being closed.

author: 1audio
author_rank: Frequent Contributor
timestamp: August 24, 2025, 05:57:47 am
content: I posted a suggestion to use cast iron pipe in another thread. An alternative might be to scavenge the mumetal shield from a scope crt. However if you end or cut it you need to hydrogen anneal it again. Perfection Micahttps://www.magnetic-shield.com/sells mumetal.

author: iMo
author_rank: Super Contributor
timestamp: August 24, 2025, 06:11:57 am
content: What I saw in practice (a nearby EMC lab) - the walls of the Faraday's chamber (like the copper foil or dense mesh is the outer shield) are from inside covered by small ferrite tiles, perhaps 5x5cm large (I did not see its thickness). So find the tiles and glue them around the box, for example..https://www.emc-directory.com/community/what-are-ferrite-tiles-construction-working-principle-and-applicationsQuote.. so no help with 50HzPS: with that mumetal above (Perfection Mica, mu_r=75000 at 60Hz and ro=5.7e-7ohm*m) the skin depth for 60Hz is aprox 0.2mm. To attenuate 50/60Hz say 100x you would need ln(100) times more - like 1mm. And the geometry plays a role too, so with a say 2mm thick box with rounded edges you may see pretty good results, imho..The question is whether a box inside a box (each with 1mm thick mumetal) would not be better?

author: iMo
author_rank: Super Contributor
timestamp: August 24, 2025, 07:02:44 am
content: I also asked AI on my above box..

author: guenthert
author_rank: Frequent Contributor
timestamp: August 24, 2025, 09:46:07 am
content: How 'bout active shielding? Iiuc, low frequency (power line frequency) is the issue at hand -- that's slow enough that active shielding with jelly-bean OpAmps ought to be feasible. A box with six excitation coils at the walls, three measurement coils in the middle (or rather near the sensitive parts) and three servo circuits might do the trick.

author: coppercone2
author_rank: Super Contributor
timestamp: August 24, 2025, 10:25:21 am
content: what is wrong with this 1mm sheet of mu metalhttps://www.ebay.com/itm/324451272160

author: iMo
author_rank: Super Contributor
timestamp: August 24, 2025, 11:02:05 am
content: The problem with creating a box from such a sheet is how to not make gaps between the sheets..The only way how to get good results, imho, is to press the box off the sheet (deep drawing) and the sixth side will be the lid which has to be mounted without a gap. You have to thermally anneal the box after the drawing as well. So it has to be a monolithic "can" with a perfectly matching lid.There are companies offering such custom sized deep-drawn boxes, btw., not sure it is a cheap exercise, though..A random pick:https://www.magnetic-shield.com/mumetal-cans-lids-round-and-rectangular/The 1.58mm thick wall they offer would help much (like 60dB+ at 50/60Hz)..PS: with a 1mm thick walls and with "a box in a box" (so 2 boxes) you may get 80dB attenuation at 50/60Hz, my bet..

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: August 24, 2025, 11:30:50 am
content: Quote from: coppercone2 on August 24, 2025, 10:25:21 amPost title: "Low Cost". $75USD would not be considered low cost to many.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: August 24, 2025, 11:49:20 am
content: Quote from: iMo on August 23, 2025, 05:41:34 pmI did take a look at that box that you made. The quality of it is impressive and it would provide substantial magnetic + electrical shielding, but it's not an easy box to custom manufacture and the weight would limit its usability. I know that I'd personally rarely use this enclosure for testing due to the annoyance caused by the weight.Quote from: guenthert on August 24, 2025, 09:46:07 amThat's an interesting idea to destructively eliminate the electrical fields, but I'd imagine it'll create higher frequency harmonics and minimally eliminate the magnetic fields._______________________Thus far, it seems like the dual paint can idea may be the most feasible, easy, low-cost, and effective measure. Possibly using a conductive adhesive/glue to mount thesilicon steel alloy platesto the outermost can would improve the magnetic shielding, adding minimal weight but greatly improving the magnetic shielding.I'm also thinking of usingeitherhard foam or spray foam or hard rockwool,instead of air gaps. These materials would minimally impact the electrical + magnetic shielding + weight, improve the rigidity of the enclosure, and expand the use of applications that the enclosure could be used for, such as for thermal + noise control.

author: bnz
author_rank: Regular Contributor
timestamp: August 24, 2025, 01:13:49 pm
content: How about the idea to fill the outer air gap with metal powderAll these ferrite cores are made by sintering metal powder. Suitable metal powder should thus be sourceable.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: August 24, 2025, 03:51:24 pm
content: Quote from: bnz on August 24, 2025, 01:13:49 pmThe idea of using metal powder is another great, low-cost idea. Magnetite can be easily found and collected around the world using a strong magnet. I tried to find the magnetic permeability of magnetite but couldn't find any information, as it seems to vary based on various factors (primarily grain size). Additionally, not sure about what the frequency response of magnetite will be and how effective it'll stop 50-60hz, but at least I can fill the paint can with the magnetite and measure the change of magnetism entering the enclosure.Somewhat related, I've been continuing to look into alternatives to MuMetal and MetGlass, and discovered there's quite a few different grades of silicon steel. They don't seem to be very easy to work with (soldering, brazing, and welding, all appear to be quite difficult), but I'm wondering if spot welding would work well to seal the gap.This sitelists various types of electrical steels and their strengths. Additionally, many electrical steel alloys are much cheaper than comparable sizes of MuMetal or MetGlass.

author: TimFox
author_rank: Super Contributor
timestamp: August 24, 2025, 04:35:15 pm
content: Normally, magnetic shields use "soft" magnetic material, with narrow hysteresis curves and small "coercive force" (Hvalue for zeroB), while magnetite is a "hard" material suitable for use as a lodestone, with a large permanent magnetization.Powdered iron, often with insulated granules, is used in RF coils and transformers, to increase inductance with minimal eddy-current losses.Silicon steel is a common material for power transformer cores, and readily available in sheets.When forming magnetic shields out of sheet material, an important problem is the work hardening at bends.For critical applications, it is often necessary to anneal such assemblies after folding to restore the "soft" magnetic property.I believe the term "soft" results from the correlation between the magnetic property and mechanical "softness".

author: Slh
author_rank: Regular Contributor
timestamp: August 24, 2025, 04:51:05 pm
content: I had a play with iron oxide and epoxy to make some magnetic cores a few years ago. The best I could manage was a relative permeability of around 5 but it was good to perhaps 50MHz

author: Simmed
author_rank: Frequent Contributor
timestamp: August 24, 2025, 04:56:56 pm
content: Quote from: bnz on August 24, 2025, 01:13:49 pmi had the same thought quite a very long time agojust from a rough approximationhttps://widerangemetals.com/iron-powder-150-%C2%B5m-100-mesh-0-150-mm-fe-min-99/it says the density of the 100mesh is about 3.7kg per liter volumeso if say we could purchase 1kg from amazonthat would be about 270cm3 volumeby running this thru some web calculatorsthis amount of powder could make a hollow sphere about 15cm diameter (about 3+mm wall thickness)but how do we estimate the permeability ?

author: Simmed
author_rank: Frequent Contributor
timestamp: August 24, 2025, 04:59:23 pm
content: Quote from: Slh on August 24, 2025, 04:51:05 pmnicehow much iron did you have in yours ? did you have a chance to measure density or the weight ratio ?

author: TimFox
author_rank: Super Contributor
timestamp: August 24, 2025, 05:08:50 pm
content: You can estimate permeability of a mixture of high-permeability material (e.g., Fe) with non-permeable binder by considering a toroid of iron with a small (compared with the circumference) air gap.If the permeability of the iron were infinite, the path through iron =D, and the gap thickness =d, the permeability of the core (for calculating the inductance) would beD/d.(This is why air-gap inductors have a more constant inductance with respect to current, but lower inductance, compared with non-gapped inductors.)For the mixture, a gross approximation would use an estimate of the mean path through iron and the mean path through binder (from the material volume ratio), and modify it with the finite permeability of the iron.If you consider the "magnetization curve" for a permeable material (the curve going from zero excitation to saturation, before entering into a hysteresis cycle), the usual parameters are the "initial permeability" at zero, the "maximum permeability" somewhere up the curve towards saturation, theBvalue at maximum permeability, and the saturation values ofBandH.The iron powder in Simmed's post is approximately pure iron, not iron oxide. Solid iron has a density of about 7.88 g/cm3, so the powder is about half air by volume at density 3.7.The two oxides of iron are FeO (wüstite) and Fe2O3(hematite). The mixture Fe3O4= FeO.Fe2O3, called magnetite, is a hard magnetic material, more polarizable than the basic oxides, and is the only material found in nature pre-magnetized, leading to the invention of lodestones and magnetic compasses.

author: Slh
author_rank: Regular Contributor
timestamp: August 24, 2025, 05:13:47 pm
content: I'm afraid that I wasn't very scientific. I just gradually mixed in the iron oxide until it felt like I couldn't get any more in. I then pressed it in a 3d printed mould. I was only really interested in the order of magnitude so that was good enough for me

author: coppercone2
author_rank: Super Contributor
timestamp: August 24, 2025, 07:29:58 pm
content: I know for the cutting edge applications, the deep draw or machined box is the best.But I just wanna remind people within the realm of practicality, of DIY, often you just find a single bent band inside of equipment.Like it or not, its a massive... burden... to get stuck with the idea of these very advanced/technical boxesI can see someone being discouraged from trying because they THINK you need the premium quality solution, but perhaps not, and a leaky box could be worth a try (from sheet metal)I believe the 'ultimate' sheet metal box is the 'zero gauss' box for magnetic earth science BTW.These superior boxes are something akin to a 30oz copper PCB or some crazy contraption with bus bars. We all want them but you might wanna set your sights lower... I still don't think buying a sheet of hymu or amorphous foil is a mistake for a electronics lab. Chances are too, if you wanna sell something, they would MAKE you get a solution like that anyway (for everything but the very most sensitive stuff), because its practical.

author: TimFox
author_rank: Super Contributor
timestamp: August 24, 2025, 07:41:31 pm
content: For a "zero gauss" chamber, to eliminate the Earth's DC magnetic field from the interior, only permeable (e.g., ferrous) shielding works: copper and other conductive metals are only good against AC fields.The simple zero gauss chamber supplied with my lab's F W Bell Hall-effect gaussmeter was merely a cylinder surrounded by multiple layers (wrapped foil?) of mu-metal or similar, to allow inserting the Hall probe into the interior.

author: Simmed
author_rank: Frequent Contributor
timestamp: August 25, 2025, 01:42:20 am
content: Quote from: TimFox on August 24, 2025, 07:41:31 pmhow heavy is your chamber ? 10kg ?

author: TimFox
author_rank: Super Contributor
timestamp: August 25, 2025, 03:32:01 am
content: Quote from: Simmed on August 25, 2025, 01:42:20 amNo: it was in my university lab for use with a Hall probe approximately 6 mm wide. The hole was probably 65 mm long and the overall size was only maybe 30 mm diameter by 70 mm long.

author: iMo
author_rank: Super Contributor
timestamp: August 25, 2025, 07:09:03 am
content: The company I linked above is selling such small pocket sized Zero Gauss chambers for calibration purposes (expensive, however).I do not want to spoil your fun and effort in searching for a low cost chamber, but I highly doubt any of the low cost ideas here would give you any positive results.. Also my chamber above was not good, imho, around 35dB attenuation is a joke for the price it would cost the manufacturing of such box today ($XXXX).If you are serious about the measurements the only way is to use the mumetal sheet deep drawn by press (and thermally annealed - as I wrote above) in form of a continuous cap/box with a perfectly fitting lid, absolute minimum wall thickness 1mm (better 2mm, or 2x 1mm with two boxes).If I were you I would draw a picture of the box (size of the box such you may place there say 8pcs of 18650 cells, the DUT and the LNA) and I would send it to the company for a Quote (see my link).The Lids may be outside fitting / ODLID or inside fitting / IDLID, so ask them which fitting is the best and how the fitting actually looks like..PS: and you will definitely need a copper foil box inside the mumetal box as well, so do count with it..

author: EC8010
author_rank: Frequent Contributor
timestamp: August 25, 2025, 07:27:15 am
content: Quote from: iMo on August 25, 2025, 07:09:03 amAnd good luck with the perfectly fitting lid. As was pointed out earlier, a magnetic shield works by diverting flux away from the enclosed part, so it must be a low reluctance path, requiring the lid to have a large overlap onto the can that fits tightly. Measurements with a pair of Helmholtz coils say that with a good mumetal can (40mm long, 40mm diameter) and lid you can get about 35dB attenuation at 50Hz if everything else is perfect. Magnetic shielding is difficult and expensive.Distance and orientation are your friends when it comes to low frequency magnetic fields. Also, make sure you haven't inadvertently created any loops in your wiring - SMD can be useful for minimising loop area of active electronics.

author: iMo
author_rank: Super Contributor
timestamp: August 25, 2025, 07:37:40 am
content: Quote from: EC8010 on August 25, 2025, 07:27:15 amTherefore we talk also a box in a box, you may get 2x XXdB then. Therefore the offerings of the company there have several boxes stacked (ie 3).Btw. you may ask the company what could be achieved with a single box with say 1mm and that max 1.58mm thickness and their Lid fittings. They are experts and they are making the boxes for defense and scientific purposes (they write there)..Why to speculate, ask the experts (Since 1941)..https://www.magnetic-shield.com/mumetal-cans-lids-round-and-rectangular/https://www.magnetic-shield.com/magnetic-shield-simulation/

author: tszaboo
author_rank: Super Contributor
timestamp: August 25, 2025, 11:40:38 am
content: Linear Technology application notes used several times:Danish butter cookie boxes. I like this one, I like the cookies, and it's not very expensive. The box is made from tin.Paint cans. Cans that had paint for walls in them. It's usually a low grade steel enclosure, easy to oepn and reseal the cover.Diecast Aluminium boxes, often times called wrong. They call it "aluminum" and soddering.

author: TimFox
author_rank: Super Contributor
timestamp: August 25, 2025, 02:38:26 pm
content: Quote from: tszaboo on August 25, 2025, 11:40:38 amNobody makes cookies boxes out of tin: they use tin-plated steel.“Aluminum” is the standard US spelling, “aluminum” with a superfluous letter is used elsewhere.However, I am unaware of anyone spelling soldering with a dd.That is a phonetic pronunciation in US, not orthographic.

author: 1audio
author_rank: Frequent Contributor
timestamp: August 25, 2025, 05:00:02 pm
content: If you order Mumetal cans be sure to request any holes since drilling or cutting can degrade the properties. Normally they are hydrogen annealed after forming.Another option you may be able to find would be a shield can for a tape recorder head. The Ampex cans were several layers of Mumetal and copper. And had a sensitive magnetic pickup inside so getting good performance was important.This may be of interest:https://www.emrss.com/products/magnetic-shielding-mcf5?srsltid=AfmBOoqiNdsE6z-003kETGMQHpAYt1ska-uS49NAR7oCgrMjbY9j5bxZrelatively cheap and adaptible. They claim 30 dB per layer I think.

author: TimFox
author_rank: Super Contributor
timestamp: August 25, 2025, 05:10:23 pm
content: Of course, besides the problems of work-hardening at sheet metal bends, there is the fundamental issue when designing a shield of how does one communicate (power, signals, etc.) between the interior and the exterior where the rest of the system is located.The Ampex shield requires a large opening so that the tape head can contact the moving tape.For AC, one can penetrate the shield wall with feed-through capacitors or filters.At RF frequencies, honeycombs comprising many long tubes of small diameter operate as "waveguides beyond cutoff" to attenuate radiation while allowing airflow.At DC, a reasonable alternative is small holes in the permeable material, possibly with multiple layers where the holes do not overlap.I remember attending an RF conference in the late 1980s where one speaker had a problem with a very high power transmitter that had to operate at the frequency of its master oscillator.(Most such applications use an oscillator at a different frequency than the output, so that the huge output power through a not-high-enough attenuation cannot pull the oscillator frequency.)His solution was a fiber optical link out of the oscillator box to the buffer and output amplifiers.As an aside, he estimated the unwanted backwards coupling from reflections off the receiving photodiode back into the transmitting LED that could give an unwanted electronic coupling, but he believed that to be negligible in practice.

author: tszaboo
author_rank: Super Contributor
timestamp: August 25, 2025, 06:02:53 pm
content: Quote from: TimFox on August 25, 2025, 02:38:26 pmSpelling Aluminium correctly, is really one of those things that separates culture from barbarians.You guys are corrected every time, I'm sure another hundred years or so and you can learn it how to pronounce it right.

author: Simmed
author_rank: Frequent Contributor
timestamp: August 25, 2025, 06:12:31 pm
content: hmmm this is going to sound crazybut i saw a cast iron pot on amazon US$246.8kghttps://www.amazon.com/AmazonBasics-Pre-Seasoned-Dutch-Handles-7-Quart/dp/B074DF92HW?th=1from the weight estimation, it looks like 4mm to 5mm thickwhat do you all think ?there is also larger sizes(ok i laughed at myself when i saw itbecause i remember this discussion here)and then under recommendationsthere is a 1 for bread which has a very nice shapelooks like it could fit a eurocard inside !4mm cast ironanybody want to hazard a guess the shielding capability ? 20 ? 30dB ?** output estimate from grok = 22 to 35dB (ur = 200 to 1000) 12cm dia sphere with 5mm thicknessi guess then a smaller pot may have a higher shielding effect*** and a smaller confit pot that fits inside the largergrok estimate = 28dB upwards (ur = 200)US$24 + 20. its crazy. is this a good price for near 50dB result ?the lids are probably wonky as hell

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: August 25, 2025, 07:08:04 pm
content: Quote from: Simmed on August 25, 2025, 06:12:31 pmIt's a good idea, but the problem is that cast iron is inherently high carbon. High carbon steels have very poor magnetic permeability, so they wouldn't be good for this application. Pure iron, or iron alloys with silicon/cobalt/nickel alloys, generally have higher magnetic permeability.

author: TimFox
author_rank: Super Contributor
timestamp: August 25, 2025, 07:23:21 pm
content: Quote from: tszaboo on August 25, 2025, 06:02:53 pmSpelling aluminum efficiently is a thing that separates knowledge from ignorance.Early in the 19th century, Sir Humphrey Davy (eminent English chemist) named the metal "aluminum".Shortly thereafter, in 1813, prissy pedants offered "aluminium" as more "classical" in sound, but Noah Webster resisted this prettification and kept the "aluminum" spelling in 1828, which has remained the standard in US ever since.English dictionaries came later, using the 1813 version.The American pronunciation is more robust, with the forthright stress on the second syllable instead of the weaker stress on the third syllable of aluminium.See B A GardnerGarner's Modern American UsageOxford University Press 2009, p 39.

author: Simmed
author_rank: Frequent Contributor
timestamp: August 25, 2025, 08:08:21 pm
content: Quote from: LooseJunkHater on August 25, 2025, 07:08:04 pmi know lids are probably crapbut for under $50 and highly plausible resultssome student might try it

author: tszaboo
author_rank: Super Contributor
timestamp: August 25, 2025, 08:31:28 pm
content: Quote from: TimFox on August 25, 2025, 07:23:21 pmHans Christian Oersted in 1825 first made Aluminium. He maned it your version first, but after he realized his mistake, correctly named it afterwards.Sir Humpty Dumpty didn't manage to make the metal, made 3 unsuccessful attempts at making it (self claimed), but also unsuccessful attempt at naming it.Also, we can probably find another 100 languages that can write it correctly, with the exception of USA.But if you really want to go according to Sir Humphry Davy, he also started calling it Aluminium when publishing.

author: TimFox
author_rank: Super Contributor
timestamp: August 25, 2025, 08:51:48 pm
content: If you insist on complaining about my spelling, you should be careful to spell normal words like "named" correctly.By 1813 and 1828, the United States had already declared its independence from England.I prefer the sound of "aluminum" to the sound of "aluminium", as do most of my countrymen.Do you say "platinium" or "lanthanium" or "molybdenium" or "tantalium" No one does.Of course, we all say "actinium", "barium", etc.The IUPAC accepts both spellings, but what do they know?One name that did not catch on is "Thonerde-metall", from the German word for alumina.Another pair of choices is "wolfram" vs "tungsten", where different countries choose one or the other: one word is Germanic, the other is Swedish.

author: trobbins
author_rank: Frequent Contributor
timestamp: August 26, 2025, 12:24:18 am
content: If outer dimensions are not a major restriction, then perhaps purchase available sheet sizes that allow a box with bottom and top to be butt fitted together as an inner box, and then perhaps larger sheets to make up an outer box that is similarly butt fitted. Any gaps between sheets would be at the box edges (inner vertices), and likely quite minor. Sheets could be 'fixed' at right angles using a glue or flexible neutral cure silicone, and with neutral buffer material like wood veneer cut to inner and/or outer box dimensions as a 'form'. Sheets would then remain in original condition, so no specialist fabrication costs, and lowest cost by using stock sizes. An outer frame of some kind could be added for robustness and storage. Any cabling could enter via a minor notch or bend of one sheet at a box vertex.

author: coppercone2
author_rank: Super Contributor
timestamp: August 26, 2025, 12:34:51 am
content: keep in mind with a magnetic box you can make big lap joints. It ends up being better for structural reasons (don't weld corners if you can avoid it)I have SO been meaning to try to acetylene weld mu metal.

author: 1audio
author_rank: Frequent Contributor
timestamp: August 26, 2025, 12:38:18 am
content: For $50 new or maybe less at a thrift store its worth a try and if not useful you can still cook with it.You could check it with a power transformer and a pickup coil to see how much attenuation you get. If I get a break tomorrow I may give it a try. I have some cast iron and somewhere the Perfection Mica field pickup. These are essential for looking at LF EM fields:https://www.ebay.com/itm/266770898124?_skw=AC+Magnetic+Field+Evaluator+Probe&itmmeta=01K3HWM3HET14XDGM5R2A6DT2T&hash=item3e1cc8dccc:g:rV4AAOSw5XtmHnmp&itmprp=enc%3AAQAKAAABAFkggFvd1GGDu0w3yXCmi1fFi0JraPPBiU4jc%2BEe0GO7Pl0XexEpi5ZmsB91HhOQqZBesjjpNxSI6qiPOUizbPw%2B7ZN4Le21mJ2eX%2FvI3XbsRyhvHxhwT2hwWvrfX0892jJeUIuHQwsvhlWYBLEaOI5o2kpYuodnYvawG28ZpPWu7hAjvqWyoMG0g988t1eZ2cg2sI5e54rU9Z5kxjTsRaFC8kqXDKFuRn8q35l8dEV4Z4RKvIR3lgTgkYtZ%2FwBYBYQG1a%2BrByoY8M7%2FisO%2Flhh3x3lZ91a7gFzRZ8FVoObrri2C3%2BAZWH4wl%2Bq7uodGlPGDRVhDs5HJOSmdW9JKLug%3D%7Ctkp%3ABk9SR_y40LycZg

author: trobbins
author_rank: Frequent Contributor
timestamp: August 26, 2025, 03:12:18 am
content: I could use an an oscillator and audio amp into a choke load as the emitter (a choke rather than transformer may splay out more external/leakage magnetic field). I luckily have a vintage MAG-03MCMB three axis magnetic field sensor, and associated calibrator, which have worked well with a soundcard and spectrum analyser. With commonly available software like REW, I could plot default magnetic response at say 0.5meter separation, and then with the choke enclosed in a shield box, to look at magnetic response attenuation with frequency.

author: EC8010
author_rank: Frequent Contributor
timestamp: August 27, 2025, 09:41:00 am
content: You could. Unfortunately, you will find that it is quite difficult to get repeatable magnetic field measurements. A year ago, I made a pair of Helmholtz coils for testing magnetic shields. Using a compass, I calibrated them against the Earth's magnetic field. To get reliable results, I had to take the experiment out into the garden as far away from steel as possible. I really struggled to get down to an uncertainty of +/-1%. Your proposed experiment shouldn't be as finicky, but beware that there are surprisingly large lumps of steel in a lab; central heating radiator, steel girders on bench, steel window lintel, steel brackets and uprights for shelving, etc. They all bend the flux. You will also find that orientation of source and sensor is critical. And the lump inside the shield needs a decent gap (2mm, or more) between it and the shield to stop it coupling to the shield. I'm not trying to put you off, but you will find that attention to detail is crucial.

author: TimFox
author_rank: Super Contributor
timestamp: August 27, 2025, 02:23:36 pm
content: During my studies at the University of Chicago, I had occasion to use some antique lab equipment left over from the time of Prof. A Michelson, who founded the Physics Department there in 1892.He was able to get a new laboratory building, funded by and named after Martin A Ryerson, a millionaire steel distributor and philanthropist.Despite Ryerson's wealth from ferrous alloys, the building was constructed to be non-magnetic: huge timber joists, bronze banister screens, copper plumbing, etc.Of course, during the decades after Michelson, the authorities moved in the normal steel filing cabinets, etc. to ruin that non-magnetic paradise.

author: iMo
author_rank: Super Contributor
timestamp: August 27, 2025, 04:20:06 pm
content: Nicola Tesla "envisioned transporting energy via longitudinal waves through the Earth and atmosphere, using resonant frequencies to transmit power globally without wires..".Imagine that - how thick mumetal shielding would you need in such a world..

author: coppercone2
author_rank: Super Contributor
timestamp: August 28, 2025, 12:37:55 am
content: I am guessing that his idea was that with some special coil geometry or something, that the energy would couple by some other mode. Maybe we would call it quantum resonanceIt must have been obvious when he saw that metals heat up near his high power equipment that upping the power would never be practical outside of a empty space. I thought his experiments were to make that kind of RF field easier to study and experiment on by increasing power level (the tower).The thing I noticed about static magnetic fields, is that if you wanna study.. bulk electromagnetism... that if you look at the B-curve, you can get a area of more linear B if you up the power with a stronger magnitude. When you have some object that needs to be stabilized/captured, going a further distance from a stronger field is easier to experiment on then going to a closer distance with a weaker field. You just have more physical distance for the same B-gradient magnitude, so if you need to position something, its easier to adjust it. So a position error results in a smaller field strength change... so small electromagnets are annoying to work on instead of large ones (finicky). Working too close to a electromagnet is just unstable because everything needs to be unbelievably well positioned.... so if you can, get a bigger one, and go further away, and whatever you are doing will be easier.I imagine that having a high ass power transmitter like W-tower would make whatever he is doing easier to study because positioning objects, and rotating them, would be way more forgiving. Instead of a micrometer you could use a tape measure, that sort of thing.That is always what I thought. I noticed if I have to use a micrometer it is annoying and always gets messed up and requires constant care. However if you can get something to work with a caliper, or better yet a ruler, work flow goes better. Things that require tiny physical adjustments are difficult to study and specialized. Also way cheaper.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: September 27, 2025, 05:41:14 pm
content: As a smaller proof of concept (since I still haven't been able to collect old paint cans, as nobody in my area has been throwing them out recently), I think I'm going to build a smaller version of this enclosure, with only 1x MI shield and 1x EI shield.I'm wondering if anyone can provide clarification on the actual construction of the box.The image shown by LinearTechnology states that> DO NOT CONNECT SHIELD OF OUTPUT COAX TO STEEL TINHowever, the document then states> The internal amplifier board uses coaxial cable to go from the board out to the input and output BNC connectors. However, one must watch connections for the shield of the coaxial cables;only the input shield is connected to the ground plane of the board and the outermost steel can.And then it states>Input and output BNC shields connect to the steel can, while coaxial cable shields tie to the board ground on both sides. If the output shield connections were to be connected to the steel can as well, a ground loop is formed that can pick up stray fields. Each layer of the shielding box electrically connects to the one outside it via metal screws and standoffs with the amplifier board isolated by solder mask. These provide connections between each box without connecting to the ground plane of the amplifier board internally and creating possible loops.___________________________________________________________________________________________________When I probe use a multimeter, it seems that both metal "ground" connections of a BNC connector are actually electrically connected together?___________________________________________________________________________________________________Therefore, I'm confused on how to actually wire the enclosure.. Would it be done as pictured in diagram 1, diagram 2, diagram 3, or some other way?

author: coppercone2
author_rank: Super Contributor
timestamp: September 27, 2025, 06:02:08 pm
content: Lol, this could have something to do with the connector type. there is a expensive special non magnetic special BNC connector. NO nickel diffusion barrier, some kind of other plating method, perhaps other measures against diffusion. Might be as simple as superfinishing or something to reduce solid state diffusion, or just left as pure copper or brass on the surface (not silver)However, normal BNC connector is nickel plated, or uses a nickel diffusion layer, or possibly might even be made with clad steel, or nickel silver or some other semimagnetic alloy.ALso, same is true for the coax itself. Alot of coax is clad steel middle, because it gets weak if its all non ferrous.. notice that in a coaxial cable there is nothing to grip?Not sure how it effects the analysis, but literarly anything can happen to the magnetic properties of the can depending on what hardware its put together with, and what it plugs into.I noticed in the lab, GOOD LUCK trying to get someone to find the 'special' cable to plug something in. If it fits it sits. Especially if they have expensive stuff and its geometrically correct.So I can see a editor of the document possibly go into 'quarantine' mode after considering what to do with the magnetic shield of the container. Asked the lab maybe what they think the most reproducible result from using random material BNC and cable?

author: EC8010
author_rank: Frequent Contributor
timestamp: September 27, 2025, 09:42:08 pm
content: All that the LT diagram means is that you should insulate the BNC shell from chassis on the output side to avoid earth loops. You can either buy BNC chassis connectors made like that, or use standard types plus insulating kit. Insulated BNCs are easier to use on biscuit tins as the insulating kits presume a thicker "chassis" than a biscuit tin. That note about sanding the tin to get electrical contact with the lid is nonsense; solder a wire between the two for a reliable low resistance bond.A mumetal box big enough to contain two "D" cells would be very expensive and probably not very effective. For mumetal to shield against magnetic fields it has to divert flux, so the ratio between its thickness and internal dimensions becomes important. A thick wall and small internal dimensions is far more effective than a big box with the same wall thickness. Thus, for effective magnetic shielding, you want small electronics inside a box only just big enough. There is no need to magnetically shield the batteries. I have 12V lead-acid batteries inside Kit Kat tins for electrostatic screening and power goes to the electronics over BNCs, leaving everything electrostatically screened.

author: coppercone2
author_rank: Super Contributor
timestamp: September 27, 2025, 10:25:17 pm
content: its not nonsense.. its a option.They could have specified double RF finger gasket if they felt like it.I had anamoulous errors from (KS) test equipment at work that seemed like were caused by co-workers new phone. That's when I started to start ignoring people that always downplay shielding practicesGranted, if its poorly fitting, the wire might be better then sanding. But as I noticed on the welding table, simple mechanical fitup, even with steel, can sometimes make a fine ground, so long its cleanish and there is some pressure/tightness. For me, a wire is to help it with high current after its damaged (ground safety) much more so then for anything related to shields. This can be a requirement for panels.Tins are often made with very high end dies to tight tolerances, so sanding them can have good results, so especially if you are gentle. They often even nickel plate them before painting too (usually a thinner nickel layer then you would want for engineering purposes)The biggest problem with tins is that they are not designed for connectors, so unless you add a brace, they often deform substantially, especially with cables hanging off them, if you get extreme, if you see that, then you might wanna add a soldered wire, but its better to reinforce and maintain the dimensions of the precise box. Its unlikely you will see a problem from soft test leads, but something like a thick coaxial cable can cause the side of a small tin to warp when it bends, or if it hangs from equipment (like a DIY splitter, amplifier, filter, etc that you attach directly to a test equipment... )You can simply cut a piece of thicker metal so it fits inside of the box, with holes for the connector. then when you bolt on your connectors, the entire wall is stiffened by a plate. I use 3/32 aluminum flatbar to good results here, brass would be better.But I totally prefer pomona shield boxes, they are great quality, fit together tight, look professional, very stiff... if you have the money its worth it over a tin in many cases, particularly for passive stuff that does not need batteries. Oh but they aint steel ~!

author: AnalogTodd
author_rank: Regular Contributor
timestamp: September 28, 2025, 02:08:19 pm
content: Quote from: LooseJunkHater on September 27, 2025, 05:41:14 pmWe found diagram 2 provided the best immunity to ground loops and the issues they can cause in such high gain circuits. We weren't spending huge amounts on specialized connectors or gaskets, but instead trying to figure out what worked. Most RF was beyond the frequency range we were looking at so we didn't find a need to go in depth on RF shielding. The lower frequency signals that were in the lab showed themselves to be a MUCH bigger issue, such as the 20kHz signal from the nearby oscilloscope. That was why we didn't go for aluminum or copper enclosures--they work great for high frequency but are poor when it comes to keeping low frequency signals at bay.

author: Overspeed
author_rank: Frequent Contributor
timestamp: September 28, 2025, 03:26:09 pm
content: Quote from: Simmed on August 25, 2025, 06:12:31 pmHelloAs low carbon ( SS304) quite cheap that pressure cooker , you can even two as russian dolls ( remove the handle on the smaller ) and keep a gap contant by using stainless steel spongeavailable in Aluminium or SS304 , can be purchase cheap on flea marketLid have a hole for pressure valve so easy to pass throughRegardsOS

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: September 28, 2025, 03:28:00 pm
content: Quote from: EC8010 on September 27, 2025, 09:42:08 pmThis is something I had actually been thinking about, so I'm glad you clarified this, thanks!

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: September 28, 2025, 03:29:26 pm
content: Quote from: AnalogTodd on September 28, 2025, 02:08:19 pmPerfect, thanks! I guess I'll be building the enclosure illustrated in image two.

author: EC8010
author_rank: Frequent Contributor
timestamp: September 28, 2025, 04:28:18 pm
content: Quote from: coppercone2 on September 27, 2025, 10:25:17 pmYes, to make a tin that is sufficiently air-tight that the food inside doesn't go stale requires tight tolerances. Unfortunately, the resulting tin isn't terribly rigid (it's only 0.1mm thick), especially if it's a square. That means that although you can get reasonable contact at the corners of a square box, there is likely to be negligible contact along the straight edges. And connectors need penny washers or large plates to spread the load. Nevertheless, even with those issues, I've made a lot of successful electronics in biscuit tins. Particularly, I've made low current measurements down to fA without hum being a problem. Beware that there's often an epoxy coating on the inside of tins, hence the need to abrade the surface to make electrical contact between lid and box, and to abrade the surface (glass fibre brush works well) to allow soldered joint at each end of the wire bonding lid to box.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: September 28, 2025, 05:13:31 pm
content: Quote from: EC8010 on September 28, 2025, 04:28:18 pmFor your various MI + EI enclosures, do you create standoffs (ex. to hold PCB's, holding a smaller metal enclosure within the larger one) by piercing holes through the enclosure for the standoffs, spot-weld standoffs, or simply leave the items "floating"/unsecured within the enclosure? I'm thinking that by piercing the outermost (MI) enclosure, you then create a path for MI to enter the enclosure, but I'm not sure realistically how much of a problem this will create.

author: EC8010
author_rank: Frequent Contributor
timestamp: September 29, 2025, 09:41:42 am
content: Biscuit tins are only 0.1mm steel, so penetration depth means they only start screening against magnetic interference >200kHz, and none of my experiments have been that high in frequency. I'm not expecting to achieve magnetic screening, only electrostatic.But I entirely take your point that drilling holes for screws creates apertures and I rarely use magnetic fasteners, so any holes are not magnetically plugged. One particularly fussy experiment needed self-adhesive copper tape over the gap between tin and lid all the way around to stop electrostatic hum crawling in through the gap.For tests inside biscuit tins, I have breadboards with a piece of FR4 screwed to their back and with neodymium magnets glued to the copper foil. This stops the boards moving around and (slightly) reduces capacitive coupling between strips. If I do dead bug circuits on FR4, I usually earth bond the FR4 foil to the tin using a few bits of copper foil soldered both to foil and tin, thereby anchoring the circuit; some experiments have been very fussy about their bonds to the tin.

author: tszaboo
author_rank: Super Contributor
timestamp: September 29, 2025, 10:11:34 am
content: Quote from: EC8010 on September 29, 2025, 09:41:42 amYou can buy one of those near field probe kits, and place it inside the box. See if the noise floor decreased compared to the outside.Also, fun fact, coax cables have 3 conductors. You have the inner conductor, the outer shield, and the other side of the shield. Because RF, penetration depth, the two sides of the coax cable shield can carry different currents, which can upset antennas, but in this case, measurements.

author: EC8010
author_rank: Frequent Contributor
timestamp: September 29, 2025, 10:26:11 am
content: Quote from: tszaboo on September 29, 2025, 10:11:34 amI imagine you have to be pretty high in frequency for that to become noticeable; do you have any figures?

author: tszaboo
author_rank: Super Contributor
timestamp: September 29, 2025, 11:19:58 am
content: Quote from: EC8010 on September 29, 2025, 10:26:11 amGood question, I've never thought about it, but it should be interesting to calculate.A RG316 cable has 2.4mm diameter outer shielding, and 2.9mm jacket. Let's say this 0.5mm is mostly the shielding.A skin depth calculator for copper gives me the distance of 65um for 1MHz.206um for 0.1MHz.So I guess at pretty low frequencies this can become an issue.Made a quick check with Grok, it gave me 0.5MHz, because it was calculating with 0.27mm thickness shielding.

author: temperance
author_rank: Super Contributor
timestamp: September 29, 2025, 12:16:43 pm
content: QuoteUnder which circumstances will a HF current flow on the outside of the shield and not return on the inside of the shield?

author: coppercone2
author_rank: Super Contributor
timestamp: September 29, 2025, 12:42:04 pm
content: but a coaxial cable is braid that has some litz like effects for skin depth. I think the basic calculation is for a hard line.Interestingly, at lower frequencies... it might be better not to use a hard line for this reason. I think semi rigid (solder soaked) is also like this. Alot of measurements show that braid by itself is a bit more complicated then most rudimentary analysis.And its further complicated by foil shield options

author: tszaboo
author_rank: Super Contributor
timestamp: September 29, 2025, 01:04:05 pm
content: Quote from: temperance on September 29, 2025, 12:16:43 pmRadio operators typically bring it up because they have dipoles, and it comes up with the discussions about baluns.For measurements, I think... common mode noise?

author: iMo
author_rank: Super Contributor
timestamp: September 29, 2025, 02:33:53 pm
content: ..yep, you have to use a balun ([balanced-unbalanced) at that dipole's feedpoint, sure..But the output of your LNA is unbalanced..