1939 microvolt potentiometer measurement article

[Overspeed]

Hello

An article from 1939 on microvolt measurement

Interesting reading on mechanical setup

Regards
OS

[mycroft]

Original article at https://nvlpubs.nist.gov/nistpubs/jres/22/jresv22n4p431_A1b.pdf.

[Overspeed]

Hello

Unfortunately the article pictures don t provide a lot of details on the mechanical parts

Regards
OS

[dietert1]

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

[DavidKo]

Today will be probably cheaper to cut aluminum plates and screw them together. On the other hand why not to use thicker steel like 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.

[Overspeed]

@Dietert1

Hello

Lost 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 low

Other 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 .

Regards
OS

[DavidKo]

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.

[Overspeed]

Hello

Yes circular saw works fine I agree

That 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 mainly

To 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 .

Regards
OS

[iMo]

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/Permalloy

For 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_effect
https://en.wikipedia.org/wiki/Penetration_depth

In 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..

[dietert1]

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

[Overspeed]

Hello

I 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 clarity

That 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 heavy

Regards
OS

[coppercone2]

I have not seen something so interesting in a very long time