1939 microvolt potentiometer measurement article  - Page 1
Forum section: electronics / general

author: Overspeed
author_rank: Frequent Contributor
timestamp: January 31, 2023, 12:13:14 pm
content: HelloAn article from 1939 on microvolt measurementInteresting reading on mechanical setupRegardsOS

author: mycroft
author_rank: Regular Contributor
timestamp: January 31, 2023, 01:26:03 pm
content: Original article athttps://nvlpubs.nist.gov/nistpubs/jres/22/jresv22n4p431_A1b.pdf.

author: Overspeed
author_rank: Frequent Contributor
timestamp: January 31, 2023, 02:05:07 pm
content: HelloUnfortunately the article pictures don t provide a lot of details on the mechanical partsRegardsOS

author: dietert1
author_rank: Super Contributor
timestamp: January 31, 2023, 05:11:33 pm
content: That die-cast aluminium box with 3/8 " wall thickness is difficult to find. I have been using Weidmüller Klippon boxes that come with about 5 mm wall thickness. One could try to use a smaller one inside a bigger one.Regards, Dieter

author: DavidKo
author_rank: Frequent Contributor
timestamp: February 01, 2023, 06:18:32 am
content: Today will be probably cheaper to cut aluminum plates and screw them together. On the other hand why not to use thicker steellike imo on university. Main downside is weight, but material is easier to get and cheaper (on scrapyard, maybe even suitable box can be found) and thinner copper box can be inserted if needed.

author: Overspeed
author_rank: Frequent Contributor
timestamp: February 01, 2023, 06:47:03 am
content: @Dietert1HelloLost foam cast allow to make nice product at home , you can very easily make the pattern at home and locate a aluminium foundry to cast it as that a no alloy specification price is usually lowOther solution is to cut plate from scrap metal refuse and weld them by MIG welding , aluminium alloy in 10 mm ( 3/8 ) can be easily cutting by using a hand grinder .RegardsOS

author: DavidKo
author_rank: Frequent Contributor
timestamp: February 01, 2023, 07:04:42 am
content: Or you can use the circular saw blade for aluminum/plastic and cut it with handheld circular saw without any issues. The cuts can be nice, straight and perpendicular.

author: Overspeed
author_rank: Frequent Contributor
timestamp: February 01, 2023, 08:26:29 am
content: HelloYes circular saw works fine I agreeThat mandatory to stay in 1000 or 5000 or 6000 serie alloy as they are weldable without problems , 2000 and 7000 are not weldable by using TIG or MIG process , 1000 are pure aluminium so that the softer one , I use 5000 serie mainlyTo help welding that possible to drill and tap some holes and use M4 screws , that allow to pre-assembly the box and make the welding process quicker and easier .RegardsOS

author: iMo
author_rank: Super Contributor
timestamp: February 01, 2023, 10:22:45 am
content: When designing the shielding you have to distinguish the fields you want attenuate as the materials and their thicknesses differ. For low frequency mag fields you need a soft iron alloys, best the permalloy.A "scrap steel/metal" or aluminum will not help you much.https://en.wikipedia.org/wiki/PermalloyFor high freqs e-fields a thin copper foil would do the job.You need to make some math as well - for example "skin depth"..https://en.wikipedia.org/wiki/Skin_effecthttps://en.wikipedia.org/wiki/Penetration_depthIn my chamber you mentioned above we used to use thin copper box inside the thick iron/soft_steel one.PS: see below (from wiki) - in the graph skin depth==penetration depth, the distance in the material where the wave is attenuated e-times (2.7x), Fe-Ni is the permalloy..

author: dietert1
author_rank: Super Contributor
timestamp: February 01, 2023, 11:06:37 am
content: The die-cast alu box in the paper served to reduce temperature gradients - in order to avoid thermal EMF. Observe the wide lips to reduce the temperature difference between the two halves of the case. These lips are missing with the Weidmüller Klippon i mentioned. Maybe one could use thick add-on alu sheets on the four sides of the Klippon case to improve.Regards, Dieter

author: Overspeed
author_rank: Frequent Contributor
timestamp: February 01, 2023, 01:05:35 pm
content: HelloI use this design made by plate cutting (5000 serie alloy )G welding and no milling , that allow to built boxes on purpose up to quite big boxes without massive costs .Cover is showed lifted for clarityThat possible to set two boxes as russian dolls and you can also use several type of material as aluminium alloy for temperature and another boxe ( Russian doll ) in steel ( cheap ) or copper if necessary , but in light alloy or steel the drawing I have linked works without problem except a 10 mm thickness wall box in steel will be quite heavyRegardsOS

author: coppercone2
author_rank: Super Contributor
timestamp: February 06, 2023, 06:07:00 am
content: I have not seen something so interesting in a very long time