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1% metal film resistors: close enough?

Started by Bucksears, June 11, 2019, 05:52:58 PM

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Bucksears

Sometimes I feel like I'm going a bit overboard with tolerances; I got several boxes of 1% metal film resistors from SmallBear a couple of years ago, and still feel the need to measure them to get the strictest tolerance in each value.

Is this overkill? Anyone else do this?

EBK

Generally, it is overkill, especially when you consider that resistor values are often specified somewhat arbitrarily or rounded to the nearest standard value in most circuit designs we work with.  Plus, capacitor values often vary much more widely than resistor values do.

But.....
If it makes you feel more satisfied with your builds having gone through the meticulous process of selecting perfect resistors, then that is valuable to you, and I won't tell you you are wrong to do it.  ;)
"There is a pestilence upon this land. Nothing is sacred. Even those who arrange and design shrubberies are under considerable economic stress in this period in history." --Roger the Shrubber

benny_profane

I agree with Eric. I measure my resistors too, though. Not to sort the tightest tolerances, but to ensure I'm using the correct value. It's pretty easy to get a quick verification while populating the board and gives an extra sense of certainty that the correct value is being used.

somnif

Typically, if a component's value is REALLY important, the designers will specify a weird "extra digit" value. Like 4.73k instead of 4.7. That doesn't necessarily mean it needs to be exactly 4,7300 ohms, but that you want that those parts to be closer to one another than a typical batch of resistors.

I know EHX would do this, though they were usually using 5% carbon film resistors so it makes a little more sense. They'd show up in places like voltage dividers where getting the right output would matter a bit more than elsewhere (and you're too lazy/broke to use trimmers )

Personally I check resistors as I'm installing them, just to make sure I'm putting the right part in the right place (and I still screw up occasionally...). If I find a part that's wildly out of spec I'll toss it, but I'm typically not worried about a bit of wobble. Caps have a ~10-20% tolerance range so they're even goofier, so no reason stressing over 1%!

alanp

Quote from: somnif on June 11, 2019, 08:17:05 PM
I know EHX would do this, though they were usually using 5% carbon film resistors so it makes a little more sense. They'd show up in places like voltage dividers where getting the right output would matter a bit more than elsewhere (and you're too lazy/broke to use trimmers )

Another reason not to use trimmers is that then, customers with screwdrivers cannot "fix" their "broken" pedal, and then bug you that hey, this was fucked from the start, I didn't break it!
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EBK

Quote from: benny_profane on June 11, 2019, 06:43:29 PM
I agree with Eric. I measure my resistors too, though. Not to sort the tightest tolerances, but to ensure I'm using the correct value. It's pretty easy to get a quick verification while populating the board and gives an extra sense of certainty that the correct value is being used.

I should add that I measure all my resistors too, but it is mostly because I cannot for the life of me confidently read the color code on blue resistors.  I used to be able to instantly read the value on the beige ones.  Now, with these 1% resistors, I seem to be unable to reliably distinguish between red, orange, and brown.
"There is a pestilence upon this land. Nothing is sacred. Even those who arrange and design shrubberies are under considerable economic stress in this period in history." --Roger the Shrubber

benny_profane

Quote from: EBK on June 11, 2019, 09:33:42 PM
Quote from: benny_profane on June 11, 2019, 06:43:29 PM
I agree with Eric. I measure my resistors too, though. Not to sort the tightest tolerances, but to ensure I'm using the correct value. It's pretty easy to get a quick verification while populating the board and gives an extra sense of certainty that the correct value is being used.

I should add that I measure all my resistors too, but it is mostly because I cannot for the life of me confidently read the color code on blue resistors.  I used to be able to instantly read the value on the beige ones.  Now, with these 1% resistors, I seem to be unable to reliably distinguish between red, orange, and brown.

And doubly so for 1/8 watt resistors.

Aentons

Quote from: Bucksears on June 11, 2019, 05:52:58 PM
Sometimes I feel like I'm going a bit overboard with tolerances; I got several boxes of 1% metal film resistors from SmallBear a couple of years ago, and still feel the need to measure them to get the strictest tolerance in each value.

Is this overkill? Anyone else do this?

Ive never really thought about it but Im curious why not look into ordering resistors with better tolerances

pickdropper

Go ahead and check that it's the correct value, but I wouldn't sweat the tolerance too much.

And if you do really want to check the tolerance, make sure you zero out the probe leads on your DMM or you might be giving yourself the wrong answer.
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