Standard Resistor Teardowns

What do you do, when you want an ohm? What is an ohm, for that matter? Take a wander over to the textbook definitions, and you’re soon deep in a world of coulombs and parallel infinite planes one meter apart in a vacuum that you probably only half remember from your high school physics class. It’s hard work, this metrology lark.

Of course, you can just order a resistor. A few cents each when you’re buying small quantities or much less when you’re buying a reel of five thousand, and there you have it. An ohm. Only it’s not really an ohm, more like nearly an ohm. Within 1% of an ohm is pretty good, but Vishay or Bourns or whoever don’t have the margins to get philosophical about those infinite planes when you’re only giving them a few cents.

When you REALLY want an ohm, you buy a standard resistor, and you pay a more significant sum. You’re never going to wire one of these up to bias a transistor or drive an LED, instead it’s about as close as it’s possible to get on your bench to the value it says on the box and you can use it for calibration purposes. PPM figures well in excess of the resolution of even superior DMMs sound pretty good to us!

[Zlymex] was curious about standard resistors, so performed a teardown of a few to see what they contain. And after a pithy explanation of the terms involved he’s managed to look inside quite a few of them.

Inside he finds hermetically sealed wire-wound resistors, some oil-filled wire-wound resistors, and the occasional hefty piece of manganin. He also tears down some of the hermetically sealed resistors themselves, finding both wire-wound and foil resistance elements within.

It is a curious obsession that permeates hacker culture, that of standard measurements, and it’s one we’ve covered quite a few times here. Time enthusiasts with atomic clocks like this rather beautiful discrete logic build, or voltage enthusiasts with their temperature compensated references or programmable standards. Surprisingly though, this appears to be the first time we’ve looked at standard resistors.

Thanks [David Gustafik] for the tip.

21 thoughts on “Standard Resistor Teardowns

    1. For me this seems to be a replica of the legacy carbon composite resistor, probably just less stable than industrially manufactured pieces. They were/are well known for high noise level. Who does want that in his audio project?

  1. If you bust open anything electrical from before the 1980’s and you find what looks like oil, use some caution. It is likely to be PCB (Polychlorinated biphenyl). It was used for lots of stuff. Power pole US transformers had gallons in them. Sealed geophones. Anyplace a good dielectric was needed and you would rather not use mineral oil or 10W30, you found PCB. Toxic. Maybe causes cancer depending on what agency you ask, persistent in the environment or can break down or react and form dioxin or dioxin-like molecules. Mimics hormones. Might not be nearly as bad as it was made out to be in the great rush to environmental control of the 1970’s. (I knew chemists who were absolutely convinced the entire ecosystem was going to be dead in 20 years from dioxin pollution.) Do some searching on cleanup. Don’t call the authorities if you want to keep your house – look how they panic over metallic mercury from a broken thermometer!

    1. Older surplus high voltage (kilovolts) oil-filled capacitors are often filled with PCB oils. I’ve been warned they smell sweet. Unless the capacitor is newer or has markings to indicate it’s PCB Free (many from the late 70’s and 80’s have such markings), assume PCBs.

      Not an expert on the stuff, but I’ve been told that residue transferred from washing contaminated work clothing with other pieces of clothing are enough to cause chronic skin conditions in people otherwise not exposed. Bad stuff.

  2. “Standard” resistor”, initial reaction, what the hell is as standard resistor? Is it a standard composition resistor, and standard wire wound resistor being spoken about after bit of reading the topic is clear. Seeing at least on of the the enclosures had resistance standard printed on it. For tyhe sake of better communications I wonder why that term wasn’t used? Better yet resistance calibration standard. That way the subject of the article is given right off rather than reading several paragraphs to get to the meat and potatoes.

  3. JENNY,

    I see you like to write in phases of strange syntax and odd flow.

    See…as I just did.

    Now, try it my way: “Jenny is an obnoxious writer.” Simple syntax, direct, active voice, NOT cute.

    Spare me the cute and just get the words out. This is meant as 1% annoyed and 99% constructive criticism.

    1. Why thank you, we like our flames-of-the-month here at Hackaday :)

      I’m afraid I must disappoint you though. Famously the brief for the BBC is to “Educate, inform, and entertain”, and they are words to live by for any publication including Hackaday. Our articles have to be accessible and engaging for all our readers even if they are not interested in the subject matter of a particular piece. We’re not writing in the dry language of a scientific paper but the expressive language of the Bard, and if that means a little collateral damage from the BFG of lexical enlightenment then so be it.

        1. When I was a kid they told my parents I was dyslexic. I don’t know about that but I do struggle with reading certain types of text. The sentence structure, font, font colours etc have surprisingly profound effects on my reading speed. Many short sentences with less than perfect structure bring me to a halt. It’s like my eyes don’t know where to look, they end up bouncing line to line, letter to letter.

          For some reason textbooks and formal papers never give me this problem.

          Bridget Jones’ diary was fucking impossible to read. This article was okay, I appreciated the jovial nature but I skipped most of it due to the structure. Elliot’s are the best.

          Horses for courses I guess.

  4. If (troll){
    !(feed);
    }//the rule your broke and so will I….in an effort to make you a better writer

    Direct can be informative and interesting. Let me help you…

    “I’m afraid I must disappoint you though. Famously the brief for the BBC is to “Educate, inform, and entertain”, and they are words to live by for any publication including Hackaday. Our articles have to be accessible and engaging for all our readers even if they are not interested in the subject matter of a particular piece. We’re not writing in the dry language of a scientific paper but the expressive language of the Bard, and if that means little collateral damage from the BFG of lexical enlightenment then so be it.”

    Becomes:

    “You will be disappointed. The BBC briefs “Educate, inform, and entertain,” and Hackaday honors those words. Our articles must be accessible and engaging for all our readers; even if they are not interested in the subject matter of a particular piece. I am not writing a dry scientific paper, but in an expressive way that may compromise the dry rules of writing.”

    One of my favorite quotes is, “a clever writer is an unread writer.” I like your article topics and your projects, but not your writing.

    And in case your need a reminder, I am only one person out of the whole world…and NEVER feed the trolls.

    1. You would have gotten on famously with one of my English teacher (I got an A+ in Higher English back in the day, despite her sanctimonious pedantry). English language ‘aint C++ there are no rules in it that can’t be broken.

      For what it is worth, I didn’t even notice the writing style, because I was more interested in the content.

      When style triumphs over content, we start to head off either in to the land of advertising or Janet and John books.

      Another rule broken. Troll duly fed, “have a nice day” – There I’ve managed to use two English language words that should have the troll fuses blowing out of the troll ears. Gotten… nice… nice.. gotten… those used to wind the pedantic old duffer up no end too. See I even managed to use to, too and two correctly.

    2. For me, public speakers that use inflection when making a comparison is the worst. Usually their eyes move to an upwards angle during the inflection. It’s as though they are asking a question, but not actually asking a question. Knock it off.

    3. So give us your credentials there, professor. Enlighten us with your lengthy education background in English grammar. Else your just yet another abusive shit head with a big mouth who needs to go find a bridge or tall building to jump off of sans parachute and spare us your obnoxious and odious personality. You will not be missed. I promise.

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