• ThePyroPython@lemmy.world
      24·
      20 days ago

      Mathematically yes. Practically, right now? No.

      So you need a resistor of this value for your widget.

      For that many places of precision you’re looking at a potentiometer with a 10 nano-ohm precision.

      I am not aware of any commercially available resistor that can do that but you could create one using microelectronic structures used for ICs and derive a 10 nano-ohm resistor by design and then chain enough of these elements into a resistor network or potentiometer to create the super precise resistance value you want.

      Cool, congratulations.

      Now how are you going to use this 10 nano-ohm resistor? What voltage will you be applying across it? What current do you expect it to handle? And therefore what are your power requirements? What are your tolerances, how much can the true value deviate from the designed ideal?

      Because power generates heat through losses, and that will affect the resistance value so how tightly do you need to manage the power dissipation?

      How will you connect to this resistor to other circuit components? Because a super precise resistor on it’s own is nothing but an over-engineered heating element.

      If you tried connecting other surface mount devices (SMDs) from the E24 or even E96 series to this super precise resistor then the several orders of magnitude wider tolerances of these other components alone will swallow any of the precision from your super accurate resistor.

      So now your entire circuit has to be made to the same precision else all of your design work has been wasted.

      Speaking of which, now your heat management solution now needs to be super precise as well and before you know it you’ve built the world’s most accurate widget that probably took billions of dollars/euros/schmeckles and collaboration from the worlds leading engineers and scientists that probably cost more time and money than the Large Hadron Collider.

    • Retro_unlimited@lemmy.world
      1·
      19 days ago

      I had a potentiometer on a circuit board that adjusted a timer, but I found that the timer varied in timing. I ended up replacing with a few resistors and it corrected the variations.

    • takeda@lemm.ee
      1·
      20 days ago

      Sure, except the resistance will constantly change with time, temperature and other environmental variables.

  • deranger@sh.itjust.works
    18·
    19 days ago

    Numbers like that are why I quit majoring in mechanical engineering. Physics took the beauty of math and made it ugly.

    You knew something was wrong in calculus when you got a fucked up coefficient that wasn’t a nice number.

    • empireOfLove2@lemmy.dbzer0.comEnglish
      16·
      19 days ago

      Numbers like that should have been why you kept going in mech E.

      Once you get past the educational stage, every one of those calculations becomes “OK now round to the closest whole number that gives you the larger factor of safety and move on”

      • LostXOR@fedia.io
        7·
        19 days ago

        Using π = 4 is only a 27% safety margin, better go for π = 10 just to be safe.

      • deranger@sh.itjust.works
        21·
        19 days ago

        Eh, it’s just fundamentally ugly to me and that really turned me off. Rounding doesn’t help, that’s like turning the lights off for sex to make it better. I still know the ugliness exists, even if I don’t see it.

        Engineering is still very cool to me, and I have huge respect for those who do it, but I’d never have made it. It’s physics but even further perverted by reality. Math was beautiful to me because of how “pure” it was. Just straight logic, divorced from the messy world we live in. Tidy coefficients and elegant derivations.

        • applebusch@lemmy.blahaj.zoneEnglish
          4·
          19 days ago

          I have to hard disagree with you there. The beauty of the math equations they test you with in school is completely artificially selected. The vast majority of math does not have nice neat solutions. There is a lot of it that doesn’t have any solution at all. The beauty of engineering is figuring out how much of things you actually need. You might calculate that some quantity should be an irrational number for some design optimum, but the amount of precision you actually need will be some range around that. When you do that and see your design in the real world actually functioning, that’s the greatest feeling in the world by far.

  • abcd@feddit.orgEnglish
    13·
    19 days ago

    Without using fancy components: Just simply adding a 6.2 and a 2400 Ohm resistor in parallel already gives you 6.18402 Ohm ⚡️

  • A_A@lemmy.world
    3·
    19 days ago

    Quantum Ampere Standard
    https://www.nist.gov/noac/technology/current-and-voltage/quantum-ampere-standard
    .
    there also been research for defining a quantum volt and quantumly stable resistors

    https://www.nist.gov/noac/technology/current-and-voltage
    Quantum-based measurements for voltage and current are moving toward greater miniaturization

    P.S. :
    https://en.m.wikipedia.org/wiki/Quantum_Hall_effect
    Quantum Hall effect →
    Applications →
    Electrical resistance standards :

    (…) Later, the 2019 revision of the SI fixed exact values of h and e, resulting in an exact
    RK = h/e2 = 25812.80745… Ω.

    (this is precise to at least 10 significant digits)

  • frezik@midwest.social
    1·
    19 days ago

    That level of precision in a resistor would literally be thrown off if you breathed on it. If you actually needed that, then you need to build an extremely controlled environment around it. Even then, the heat from the electricity itself would throw it off. Maybe in a liquid nitrogen bath?