4 ms·

Wikipedia has a nice table of these values that I actually have printed out and hanging above my bench. https://en.wikipedia.org/wiki/E_series_of_preferred_num

Wikipedia has a nice table of these values that I actually have printed out and hanging above my bench. https://en.wikipedia.org/wiki/E_series_of_preferred_numbers#Table https://en.wikipedia.org/wiki/E_series_of_preferred_numbers#... The fact of the matter is that nowadays, E96 series resistors are readily available and dirt cheap. And if you need more precision than that, you either don't know much about electronics or you know a whole lot about electronics, heh.

eternityforest 2y ago
I'd say if you need more than E3, you either know a lot of not much, unless you're into analog. I've done stuff that needs high precision resistors, but usually the specific value isn't that important, just that it's a known repeatable value.
- nick238 2y ago
  If I want a voltage divider, it's a lot easier to just use some 1% resistors and forward-calculate the expected output (rather than doing a calibration) if you're happy with 1-2% error from the resistors and your ADC or the like. Adding software and testing hardware to do a full on calibration is a lot of work. But yeah, for digital signals, oft times 1k or 100k make no difference.
  - willis936 2y ago
    For voltage dividers it's best to use matched networks. Often not much more expensive and orders of magnitude more precise.
  - eternityforest 2y ago
    I definitely agree that 1% or better resistors are easier than calibration, but that doesn't mean you need values outside of E3 most of the time. I might want want an accurate 1/10 divider or something, but a 1/12 divider would probably be fine too, as long as it's consistent. If it doesn't vary between devices, it's just a line of code to change.
klodolph 2y ago
Yes—although E96 is cheap, I’m still very fond of E12. You get to keep less stock. I’ll even use two resistors rather than use something outside E12, most of the time. Maybe it’s habit? Hell, I don’t even think all of E12 is necessary. I’ll stick to E6 most of the time.
- joemi 2y ago
  How do the tolerances combine when you're using two resistors? I'm pretty sure they'd add together if in series (so two 5%'s become 10%), but I'm having trouble easily intuiting what happens if in parallel. Do they combine in the same way that resistances combine when in parallel? edit: Actually, I'm not so sure anymore that the tolerances would add up in series... I should probably just look this stuff up, since I'm not awake enough to intuit correctly, I think.
  - chongli 2y ago
    If you have 2 identical resistors that are 5% over nominal and you put them in parallel, you'll get a value 5% over nominal. Example: Suppose you had a pair of 105 Ohm resistors that are nominally 100 Ohm. In parallel you get: 1/(1/105 + 1/105) = 105/2 = 52.5 Ohm (5% over expected 50 Ohm) If one is over nominal and the other is under, they'll cancel out for the most part: 1/(1/105 + 1/95) = 49.875 Ohm (0.25% under expected 50 Ohm)
  - racingmars 2y ago
    In series they don't add up... doing a quick example, I find that in the worst case (e.g. each resistor out by 5% in the same direction): 22 - 5% = 20.9 47 - 5% = 44.65 Actual resistance in series: 65.55 Nominal resistance in series: 69 69 - 5% = 65.55 So the combination of the components still appears to maintain the 5% tolerance.
  - Brian_K_White 2y ago
    Values (for resistors) add in series and sort of divide-average in parallel. In either case though, the tolerance divides. The combined tolerance becomes more accurate the more resistors there are in total, whether parallel or serial. The highs and lows, and the chances of high or low, cancel each other out and you get a final actual value that is closer to the nominal statistical center of the bell curve the more individual parts there are. (same goes for other components, just resistors are simpler to talk about because their behavior is simple.) In series, a single 10K might really be 9K or 11K, but if you chain 10 10Ks in series, you don't get a "maybe 90K maybe 110K". That is technically possible but statistics means that what what you actually get is if there was N% chance that a given 10K is 9K or 11K, the there is 1/10th of N% chance (or less, I bet the actual equation is more complicated) that the chain of 10 is 90K or 110K. If the individual 10Ks were 10%, then you get 100K with something like 1% tolerance. (except also in reality, there is such a thing as batches, where all the parts in a given batch are all high or low the same way, because the process was drifting a little high or low while it was cranking out thousands of them that hour. So Ideally your 10 individuals need to come from 10 different batches or even 10 different manufacturers if that were practical or in a pure math world.) In parallel, the statistical division is the same though the value centers on the value/N rather than value*N. 10 10% 10Ks in parallel = 1 1% 1k
MeteorMarc 2y ago
E12 is also great for older users who do not have the keen eyesight anymore to read the 1% codes with certainty without using tools.
_benj 2y ago
There’s also part of, good designs don’t depend on high precision components. I think TAoE emphasized that. For high precision one can use trim potentiometers or maybe even digital potentiometer with an ADC at the other side to measure and get as close as possible, but otherwise depending on resistors for high precision is kinda rough (I’m think like an RC circuit that need a very specific resistance to meet some specific timing requirements)
- picture 2y ago
  High precision resistors are often necessary for metrology applications like very precise and low drift voltage sources. Often parts like Vishay's same-substrate thin film resistor networks [0] are used, as the temperature of each resistor leg are kept the closely relative to each other, resulting in the ratio between them being stable against temperature changes. Even if you use some adjustable/tunable circuit, you usually still require some sort of precision resistor network as an original standard. In general, however, it's much better to measure/sense physical phenomenon by first converting it into frequency, because it is much easier to measure frequency precisely. Using something like a TCXO from Seiko Epson with 1 ppm tolerance, and measuring over time, you can easily achieve 0.00001% precision and beyond. I know that strain gauges used in civil engineering often utilize this concept, where a metal string is "plucked" electronically and the frequency is then measured. [0] https://www.vishay.com/docs/61010/ccc.pdf https://www.vishay.com/docs/61010/ccc.pdf and https://foilresistors.com/docs/63120/hzseries.pdf https://foilresistors.com/docs/63120/hzseries.pdf
  - contingencies 2y ago
    Neat. Next time I see resistors in a splayed or star configuration with one leg in shared proximity I will think of this comment.
  - SAI_Peregrinus 2y ago
    On the frequency note, the primary standards for voltage are superconducting quantum Josephson junction arrays; basically fancy frequenvy-to-voltage converters.
- 2y ago
pclmulqdq 2y ago
One fun thing to do when designing high-precision analog stuff (audio) was to choose component values that are about 1.5-2% off of a value in the E12 series. You can then go test a whole bunch of resistors and you will find a lot within 0.1% of each other (even within 0.01%). Everything within 1% of E12 is binned as a 1% resistor so those aren't polluting your stock. Going within 0.1% of an E12 value is a pricey resistor, but resistors that are matched nearly perfectly and are 2-3% off are cheap and easy to find.
- e-khadem 2y ago
  Raw room temperature value isn't the only reason we use precision resistors. Some parts tend to behave more linearly at higher voltages (especially at the Meg range) and others exhibit much lower tempco's. There is also the problem of long-term stability and value change due to exposure to high temperatures during soldering. In any case, the above trick is neat, thanks for sharing it.
  - amelius 2y ago
    There are solutions to keep matched resistors at the same temperature.

eternityforest 2y ago

I'd say if you need more than E3, you either know a lot of not much, unless you're into analog. I've done stuff that needs high precision resistors, but usually the specific value isn't that important, just that it's a known repeatable value.

nick238 2y ago
If I want a voltage divider, it's a lot easier to just use some 1% resistors and forward-calculate the expected output (rather than doing a calibration) if you're happy with 1-2% error from the resistors and your ADC or the like. Adding software and testing hardware to do a full on calibration is a lot of work. But yeah, for digital signals, oft times 1k or 100k make no difference.
- willis936 2y ago
  For voltage dividers it's best to use matched networks. Often not much more expensive and orders of magnitude more precise.
- eternityforest 2y ago
  I definitely agree that 1% or better resistors are easier than calibration, but that doesn't mean you need values outside of E3 most of the time. I might want want an accurate 1/10 divider or something, but a 1/12 divider would probably be fine too, as long as it's consistent. If it doesn't vary between devices, it's just a line of code to change.

klodolph 2y ago

Yes—although E96 is cheap, I’m still very fond of E12. You get to keep less stock. I’ll even use two resistors rather than use something outside E12, most of the time. Maybe it’s habit? Hell, I don’t even think all of E12 is necessary. I’ll stick to E6 most of the time.

joemi 2y ago
How do the tolerances combine when you're using two resistors? I'm pretty sure they'd add together if in series (so two 5%'s become 10%), but I'm having trouble easily intuiting what happens if in parallel. Do they combine in the same way that resistances combine when in parallel? edit: Actually, I'm not so sure anymore that the tolerances would add up in series... I should probably just look this stuff up, since I'm not awake enough to intuit correctly, I think.
- chongli 2y ago
  If you have 2 identical resistors that are 5% over nominal and you put them in parallel, you'll get a value 5% over nominal. Example: Suppose you had a pair of 105 Ohm resistors that are nominally 100 Ohm. In parallel you get: 1/(1/105 + 1/105) = 105/2 = 52.5 Ohm (5% over expected 50 Ohm) If one is over nominal and the other is under, they'll cancel out for the most part: 1/(1/105 + 1/95) = 49.875 Ohm (0.25% under expected 50 Ohm)
- racingmars 2y ago
  In series they don't add up... doing a quick example, I find that in the worst case (e.g. each resistor out by 5% in the same direction): 22 - 5% = 20.9 47 - 5% = 44.65 Actual resistance in series: 65.55 Nominal resistance in series: 69 69 - 5% = 65.55 So the combination of the components still appears to maintain the 5% tolerance.
- Brian_K_White 2y ago
  Values (for resistors) add in series and sort of divide-average in parallel. In either case though, the tolerance divides. The combined tolerance becomes more accurate the more resistors there are in total, whether parallel or serial. The highs and lows, and the chances of high or low, cancel each other out and you get a final actual value that is closer to the nominal statistical center of the bell curve the more individual parts there are. (same goes for other components, just resistors are simpler to talk about because their behavior is simple.) In series, a single 10K might really be 9K or 11K, but if you chain 10 10Ks in series, you don't get a "maybe 90K maybe 110K". That is technically possible but statistics means that what what you actually get is if there was N% chance that a given 10K is 9K or 11K, the there is 1/10th of N% chance (or less, I bet the actual equation is more complicated) that the chain of 10 is 90K or 110K. If the individual 10Ks were 10%, then you get 100K with something like 1% tolerance. (except also in reality, there is such a thing as batches, where all the parts in a given batch are all high or low the same way, because the process was drifting a little high or low while it was cranking out thousands of them that hour. So Ideally your 10 individuals need to come from 10 different batches or even 10 different manufacturers if that were practical or in a pure math world.) In parallel, the statistical division is the same though the value centers on the value/N rather than value*N. 10 10% 10Ks in parallel = 1 1% 1k

MeteorMarc 2y ago

E12 is also great for older users who do not have the keen eyesight anymore to read the 1% codes with certainty without using tools.

_benj 2y ago

There’s also part of, good designs don’t depend on high precision components. I think TAoE emphasized that. For high precision one can use trim potentiometers or maybe even digital potentiometer with an ADC at the other side to measure and get as close as possible, but otherwise depending on resistors for high precision is kinda rough (I’m think like an RC circuit that need a very specific resistance to meet some specific timing requirements)

picture 2y ago
High precision resistors are often necessary for metrology applications like very precise and low drift voltage sources. Often parts like Vishay's same-substrate thin film resistor networks [0] are used, as the temperature of each resistor leg are kept the closely relative to each other, resulting in the ratio between them being stable against temperature changes. Even if you use some adjustable/tunable circuit, you usually still require some sort of precision resistor network as an original standard. In general, however, it's much better to measure/sense physical phenomenon by first converting it into frequency, because it is much easier to measure frequency precisely. Using something like a TCXO from Seiko Epson with 1 ppm tolerance, and measuring over time, you can easily achieve 0.00001% precision and beyond. I know that strain gauges used in civil engineering often utilize this concept, where a metal string is "plucked" electronically and the frequency is then measured. [0] https://www.vishay.com/docs/61010/ccc.pdf https://www.vishay.com/docs/61010/ccc.pdf and https://foilresistors.com/docs/63120/hzseries.pdf https://foilresistors.com/docs/63120/hzseries.pdf
- contingencies 2y ago
  Neat. Next time I see resistors in a splayed or star configuration with one leg in shared proximity I will think of this comment.
- SAI_Peregrinus 2y ago
  On the frequency note, the primary standards for voltage are superconducting quantum Josephson junction arrays; basically fancy frequenvy-to-voltage converters.
2y ago

pclmulqdq 2y ago

One fun thing to do when designing high-precision analog stuff (audio) was to choose component values that are about 1.5-2% off of a value in the E12 series. You can then go test a whole bunch of resistors and you will find a lot within 0.1% of each other (even within 0.01%). Everything within 1% of E12 is binned as a 1% resistor so those aren't polluting your stock. Going within 0.1% of an E12 value is a pricey resistor, but resistors that are matched nearly perfectly and are 2-3% off are cheap and easy to find.

e-khadem 2y ago
Raw room temperature value isn't the only reason we use precision resistors. Some parts tend to behave more linearly at higher voltages (especially at the Meg range) and others exhibit much lower tempco's. There is also the problem of long-term stability and value change due to exposure to high temperatures during soldering. In any case, the above trick is neat, thanks for sharing it.
- amelius 2y ago
  There are solutions to keep matched resistors at the same temperature.