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Low cost nanovolt switch / scanner (Patreon)

Published:
2024-05-16 14:11:48
Imported:
2026-06
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Content

... made from rotary switches? It looks promising, but it's not yet reliable enough

Files

Previews only

Reinventing Rotary Switches for Nanovolt Accuracy Scanner

PCBWay Open Source Design Contest https://www.pcbway.com/activity/kicad-open-source-design-contest.html Benchtop Voltmeters & 3D Printers at https://www.welectron.com/ More from me at https://www.patreon.com/marcoreps or YouTube Channel subscription NBS Technical Note 430 https://dataproof.com/Publications/NBS430.PDF Nanovolt Scanner Project https://github.com/marcoreps/rotoplexer 10V Standard project https://github.com/marcoreps/ADRmu Keithley 7168 nanovolt switch card https://xdevs.com/review/kei7168/ BIPM Rotary Switch paper https://iopscience.iop.org/article/10.1088/0957-0233/24/2/025008 00:00 Intro 02:34 NBS 430 Method 03:34 How I could do it 09:04 How I will do it 11:35 Mechanical 17:37 Motion control 19:42 Assembly 21:46 First test 24:57 Problems

Comments

Christopher Arena

You could include one position -- one isolated contact pair -- to signal the home position. If the controller understood something about the switching taking place, it could reposition one switch in the chain to isolate the power so that a short circuit couldn't occur. The hardware should want to protect itself or understand how to protect itself to avoid short circuits. A simple matter of software!!!

Christopher Arena

If you had a source of some "inert" gas -- maybe N2 -- you could slowly leak that gas into the box to avoid oxidation effects? a cylinder of N2 could last a long time at low flow rates.

Michael Johnson

Very interesting idea! I am currently having fun with a similar problem. The 1N829 diode in my Solartron 7081 turned out to be very sick, exhibiting 4ppm of popcorn noise. As I wanted to keep the meter as original as possible, I'm currently going through the long and painful selection process to find one golden 1N829 out of six new old stock candidates. The arrival of springtime and greater temperature variations has buried what I'm looking for under the tempco of my measurement device and the relay card in my 3488A multiplexer. I'm almost thinking about building a huge thermal chamber like the one TiN made, but I simply don't have the space for it.

Michael Johnson

Maybe a few ruined Muirhead or GR resistance decades would provide switches with similar qualities to the one pure copper switch that you had donated. They would probably be more consistent and durable than the 3D printed versions.

marcoreps
>>138167442

What a crazy plan, I love it! Maybe a hermetically sealed switch with a one-time filling and magnetically coupled motor?

marcoreps
>>138167187

The isolated contact pair is actually already there, but the size and position I chose make them unreliable :(

marcoreps
>>138167913

Oh what an entertaining problem to have! Please consider joining the discord server, we have many 7081 experts there

Kevin W

I have somewhere a stepper for a pick and place machine. It has a hollow shaft so you could add a small solenoid to lift the contact arm, move it and put it down again.

Max Pearce

Who is the supplier of the solid copper 4mm binding posts?

Max Pearce

Did you consider using a custom built matrix switch with solenoid operated contacts. You could use a pcd for the fixed copper contacts and copper moving contacts mounted on the board and actuated by plastic push rods. The 'switching plane' could therefore be shielded from the actuators. Like your rotary switch system, this is not a 5 minute project to implement but it could work. Just a thought!

Nikolaus Juch
>>138167442

Maybe it's easier to include the motors within the enclosure and use gas-tight wire interfaces instead of gas-tight mechanical interfaces?

Michael Hagemann

After seeing the video a second time on YT, I just had a nanovolt scanner epiphany: why not use a linear instead of a rotary drive? Slide a wiper board over an extendable set of aluminium core contact boards, with 4 analog and 6-8 encoder lanes, for absolute and repeatable positioning? One could use 2 "sleds" for matrix switching (or 2 separate drives, of course). And the best part: I have just the defective photo flatbed SCANNER (get it?!!?) with basically all of the necessary electro-mechanical parts... I'm actually excited! : )

Curtis Seizert

I used cheap Omron G6KU-2G-Y-DC5 latching relays for the front end switches in a DIY nanovoltmeter project, and a 10 ms pulse on the coil only causes the offset to jump by <5 nV. This could probably be further improved by using high sensitivity Panasonic TXS2 relays shortening the pulse length, and reducing the coil excitation voltage. Did you compare the performance of this solution to the nanovolt relay card you mentioned in a previous video?

marcoreps
>>138619094

oooh I've seen your awesome nanovoltmeter on github, but never knew you were here! please consider joining the discord server, we have a special #nuts channel that needs some action 😁

Curtis Seizert
>>138619094

Thanks! I will check it out. Your channel actually started my descent down this rabbit hole!

Max Teicheira

Hello, I've been mulling over a similar problem with connecting some higher voltage testing equipment. I'm thinking I can adapt your strategy with a couple modifications for the higher voltage requirements. My tests measure in the picoamps so the power consumed is similar and the sensitivity requires a similar mechanical solution. I'm new to this Pateron thing, do you have a section for the gerber files and 3d models that I can use? Thanks!