Resistors with the same color code

[spargo]

I've noticed that some resistor values (120R and 10K for example) share the same color code, but backwards.  When looking at a metal film resistor, is there any way to tell which way is the correct way?  I just pulled a resistor off my breadboard that I thought was 120R, but the multimeter reads it at 10K.  A few resistors I had in a bag that were labeled 120R all read 10K as well.

Anyone else ever run into this issue?

[flintstoned]

Alot of them have a bigger gap before the tolerance band.

[rousejeremy]

HAHAHAHA!
Metal film always screws me up. Glad I'm not the only one. I use  multimeter to test them when I'm stoned/drunk/confused

[spargo]

All of mine seem to be evenly spaced.  Some resistors have a thinner band on one end, but not all. Some of my 10K's do, some don't.

This would explain the effect having problems, with a 10K in place of a 120R...

[darron]

i think there are a couple of combos which have this problem. it's great for a laugh when you debug!

metal films should have said gap, but it can be tiny.

if you are reading someone else's circuit and they are courteous in their construction, then the tolerance band will be at the bottom/right, last as you read it.

[spargo]

I'm just a little irked as I believe my supplier sent me 10K's instead of the 120R's that I ordered.  Either that or they're buried in the rest of my 10K's somewhere.

[deadastronaut]

it would just be easier if they just had the value in letters on them....but hey thats too simple i guess.. ...

same thing with caps...103=  472=  ....etc......just write the @#$%ing value..they went to the trouble of writing 472...so why not just put 4.7n..

[darron]

it would just be easier if they just had the value in letters on them....but hey thats too simple i guess.. ...

same thing with caps...103=  472=  ....etc......just write the @#$%ing value..they went to the trouble of writing 472...so why not just put 4.7n..

people LIKE feeling smart... why the hell else would people learn Latin/Klingon??? haha

[Taylor]

it would just be easier if they just had the value in letters on them....but hey thats too simple i guess.. ...

same thing with caps...103=  472=  ....etc......just write the @#$%ing value..they went to the trouble of writing 472...so why not just put 4.7n..

A couple of reasons for this that I have surmised, perhaps someone who actually knows can confirm/deny.

If the resistor value was written in text, you would have to take care to insert them in a particular way for the value to be readable. Impossible in a machine load situation. I think it's Vishay Dale that makes the little c.ocktail weenie resistors with the value printed instead of the color code. If you don't think about how you're putting them in the board, then you may end up with some that are not readable once in the board. Bad for troubleshooting in a production environment (and we buy parts designed for big companies)

The cap thing: especially on tiny caps, just reading a number can sometimes be hard. Reading a decimal point would be impossible. Since space is at a premium, being able to represent any value with only 3 digits is big.

Now, some caps indeed do write the value as µ1, for 100n, 2µ2 for 2.2uf, etc.

But, it's actually not that hard to read the cap system. the first two numbers are the first two numbers. The last is the number of zeros, and the number is in pf.

[deadastronaut]

^ well explained

i have to use a magnifier anyway on resistors n caps as my eyesight is piss poor,so a tiny dot wouldn't be that much of a problem...but i see your point.(with glasses on  lol)..


by the way, while were on the subject:

why do some people insist on the metric system on layouts/schematics....i e.  0.000001uf.... to get 1pf.....i dont get that  

i'm sick of trying to read 0.00000000000000000000000000000000000000000000000000000000000000000000000000000000000000001uf.....

[darron]

i don't think it's anything to do with the metric system... the metric system is design to relate all kinds of measurements together. IE 1KG (weight) of water = 1L (volume) of water

the unit of measure is still the same.


i assume people are pains in the arse with 0.00000x*10^-x uF measures for the reason of cataloguing. you could read 0.0000022 uF, or 2.2pF, or 2p2 ... some search facilities on websites aren't smart enough to translate them all across and have people still find what they are searching for... the uF is a good starting point to decimalise/multiply if you're going to do that...

i guess?

[deadastronaut]

yep sorry meant decimal.....

[Perrow]

But, it's actually not that hard to read the cap system. the first two numbers are the first two numbers. The last is the number of zeros, and the number is in pf.

And then there's those ceramic caps with four or five different three digit numbers on them in tiny tiny print

[deadastronaut]

i concur.......

[Derringer]

+1 for using a multimeter to read metal film resistors

I'm pretty good with C.comp resistors, but the colors on the metal film are different and too hard for me to distinguish

[phector2004]

I don't get why they can't use a different color for the tolerance... say pink... or maybe skipping the 4th/5th/6th band altogether and setting resistor color to indicate tolerance?

[PRR]

> if they just had the value in letters on them

Fine-print rapid-change printing didn't arrive until the late 1980s (mature inkjet technology).

Back in 1930, resistors and capacitors were marked with paint and a fine brush. Look at pre-1950 mica capacitors. Six-dot domino with hand-painted colors. Resistors got some kind of all-around auto-painting by 1935. Better non-paper film caps also had stripes. (But paper-wrap caps often used printed paper.)

So why change? Stripe-resistors in 20% 10% and 5% work fine. The cost is low; critical because resistors are the most common part and nobody does this for fun (except us!).

And stripe-markings are probably cited in thousands of procurement contracts.

And as Talor says you can read them all the way around.

I agree that the 2%-1% series are VERY difficult to eye-ball. And in the beginning, they were not cheap. Some actually had numbers on them. But as prices fell, they used stripe-code.

Think how a factory works. The assembler does NOT look at every resistor, does not know codes. She pulls it out of a bin. The bins are in order of board-insertion (or have simple labels like "resistor B"). The bins are filled from marked boxes. Only if boxes are spilled, does someone have to squint the code. After once or twice, boxes don't get spilled (it's too much of a pain). So stripes are a rare last resort.

[Perrow]

And you'd have to use pretty low cost labour for it to be cost effective to actually do anything with spilled boxes of resistors than to do anything but scoop them into the bin, unless they're on a roll.

[deadastronaut]

i'm going to get my wife to write the number on all my resistors individually....it'll keep her busy for a while.......

i keep all my 1--- series in the same drawer...same as 2---- 3---- etc....

one question, why are there no 7's... e'g. 700k , 750k, etc.... or is there and i just don't have them... i have 6's- 8's ?   but no 7 series?...hmmm....

[PRR]

75 is a fairly common value in the 5% series.

http://www.hobby-hour.com/electronics/e24-resistors.php

The 10% series jumps 68Ω, 82Ω. 68 plus 10% plus 10% is 82.