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The percentage on a resistor... #4660638
02/09/18 07:45 AM
02/09/18 07:45 AM
Joined: Apr 2004
Posts: 3,674
los angeles
daves66nova Offline OP
daves66nova  Offline OP
Joined: Apr 2004
Posts: 3,674
los angeles
I need to get 0.1 Ohm, 10%, 1 Watt. Question is, is it better to have a 5% or even 1%? I need to get 2 of these for someone to repair a board.


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Re: The percentage on a resistor... [Re: daves66nova] #4660655
02/09/18 08:03 AM
02/09/18 08:03 AM
Joined: Nov 2006
Posts: 20,577
MA, Mittelfranken.de
Trav Offline
Trav  Offline
Joined: Nov 2006
Posts: 20,577
MA, Mittelfranken.de


ASE L1, Master. Deutsch Meisterbrief.
Re: The percentage on a resistor... [Re: daves66nova] #4660660
02/09/18 08:07 AM
02/09/18 08:07 AM
Joined: May 2013
Posts: 152
Peace valley, Missouri
Fitter30 Offline
Fitter30  Offline
Joined: May 2013
Posts: 152
Peace valley, Missouri
1% is a closer tolerance that 10% so it should be closer to .1 ohm but being such a low resistance you might not tell without out a very good meter

Re: The percentage on a resistor... [Re: daves66nova] #4660670
02/09/18 08:20 AM
02/09/18 08:20 AM
Joined: Jul 2015
Posts: 4,655
Down Under
SR5 Offline
SR5  Offline
Joined: Jul 2015
Posts: 4,655
Down Under
The percentage is the error in the resistance value, or how close it is to it's nominal value. So yes a lower % is better.

Most regular resistors are 10% from memory.

Often there is a variable resistor in the circuit to do the fine tuning, so a higher % deviation from the ideal value may not be a big issue, as it can be tuned out later. Still I have found lower % resistors are almost always better made and of better overall quality.

If I needed a 10% resistor, them I would often spend a bit more and get a 5% one.


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Re: The percentage on a resistor... [Re: daves66nova] #4660672
02/09/18 08:24 AM
02/09/18 08:24 AM
Joined: Mar 2004
Posts: 21,121
Upstate NY
Donald Online content
Donald  Online Content
Joined: Mar 2004
Posts: 21,121
Upstate NY
Originally Posted By: daves66nova
I need to get 0.1 Ohm, 10%, 1 Watt. Question is, is it better to have a 5% or even 1%? I need to get 2 of these for someone to repair a board.


The % is tolerance to the stated resistance. So a 1% is best.


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Re: The percentage on a resistor... [Re: daves66nova] #4660686
02/09/18 08:40 AM
02/09/18 08:40 AM
Joined: Oct 2002
Posts: 36,623
Great Lakes
Quattro Pete Offline
Quattro Pete  Offline
Joined: Oct 2002
Posts: 36,623
Great Lakes
Originally Posted By: daves66nova
I need to get 0.1 Ohm, 10%, 1 Watt. Question is, is it better to have a 5% or even 1%? I need to get 2 of these for someone to repair a board.

It depends on how close to 0.1 Ohm you need to be.

With a 10% tolerance, the actual resistance can be anything from 0.09 Ohm to 0.11 Ohm.
With a 1% tolerance, the actual resistance can be anything from 0.099 Ohm to 0.101 Ohm.


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Re: The percentage on a resistor... [Re: daves66nova] #4660741
02/09/18 09:30 AM
02/09/18 09:30 AM
Joined: Jun 2002
Posts: 12,646
The Motor City
Kestas Offline
Kestas  Offline
Joined: Jun 2002
Posts: 12,646
The Motor City
If the circuit originally called for a 10% tolerance resistor, spending more for tighter tolerance would be a waste of money. It's like buying premium fuel for a vehicle that specifies regular.

Why are the resistors being replaced? Did they burn up? If you want to upgrade resistors, go higher in wattage. 2 watts would be appropriate. I restore old radios and I exclusively buy 2W metal film resistors for replacement (which happen to be 5% tolerance). They don't cost much more than 1W, and the physical size of 2W resistors is about the same size as the carbon resistors they replace.

Re: The percentage on a resistor... [Re: daves66nova] #4660774
02/09/18 09:54 AM
02/09/18 09:54 AM
Joined: Sep 2015
Posts: 1,595
USA
mk378 Offline
mk378  Offline
Joined: Sep 2015
Posts: 1,595
USA
In some circuits a low ohm resistor is used as a fuse. This has several implications:

* Find out why it burnt, or the new one is going to do the same thing.
* Don't increase wattage.
* Use a fusible or "flame proof" resistor.

Re: The percentage on a resistor... [Re: daves66nova] #4660904
02/09/18 11:50 AM
02/09/18 11:50 AM
Joined: Aug 2005
Posts: 7,215
Leamington, ON, Canada ..... r...
Papa Bear Offline
Papa Bear  Offline
Joined: Aug 2005
Posts: 7,215
Leamington, ON, Canada ..... r...
Originally Posted By: daves66nova
I need to get 0.1 Ohm, 10%, 1 Watt. Question is, is it better to have a 5% or even 1%? I need to get 2 of these for someone to repair a board.


Why do you need this resistor? What circuit is it in?
Why isn't the tech who is fixing the board getting the part(s)?
Is this a stereo amplifier you are working on?


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Re: The percentage on a resistor... [Re: daves66nova] #4660930
02/09/18 12:22 PM
02/09/18 12:22 PM
Joined: Nov 2008
Posts: 12,761
NH
supton Offline
supton  Offline
Joined: Nov 2008
Posts: 12,761
NH
Lower % is better. However, get the same type, or one better. Most 1%'s film types aren't rated for surge power; they seem to drift if abused. Carbon composition or other power types will take abuse better. I'd think 5% 1W metal film of some sort, maybe surge rated.

I do most of my shopping at Digikey; I assumed thro-hole and narrowed the search donw. Link

Edit: on the off-chance it's SMT: Link

Last edited by supton; 02/09/18 12:24 PM.

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Re: The percentage on a resistor... [Re: daves66nova] #4660934
02/09/18 12:24 PM
02/09/18 12:24 PM
Joined: Feb 2003
Posts: 4,505
Arkansas
Win Offline
Win  Offline
Joined: Feb 2003
Posts: 4,505
Arkansas
Is it being used for a precise voltage drop at a given current?

I would get a 1% resistor. They're only pennies more, if that.

You need special equipment or some other techniques to accurately measure resistance that low, so get the 1% part and hope for the best.


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Re: The percentage on a resistor... [Re: Win] #4660937
02/09/18 12:26 PM
02/09/18 12:26 PM
Joined: Nov 2008
Posts: 12,761
NH
supton Offline
supton  Offline
Joined: Nov 2008
Posts: 12,761
NH
Originally Posted By: Win
Is it being used for a precise voltage drop at a given current?

I would get a 1% resistor. They're only pennies more, if that.

You need special equipment or some other techniques to accurately measure resistance that low, so get the 1% part and hope for the best.



His 1W requirement kinda points otherwise; yeah, one can do high power dividers but it's kinda rare to see that. At least I haven't come across that need.

If the circuit was properly designed and meant to be ok with 10% resistors, then I don't see a need to measure. Replace and move on.


2011 Toyota Camry, base, 2.5L/6MT, 170k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 144k, ours
1999 Toyota Camry LE, 2.2L/4AT, 195k, his
Re: The percentage on a resistor... [Re: Kestas] #4660942
02/09/18 12:30 PM
02/09/18 12:30 PM
Joined: Feb 2003
Posts: 4,505
Arkansas
Win Offline
Win  Offline
Joined: Feb 2003
Posts: 4,505
Arkansas
Originally Posted By: Kestas
.... I restore old radios and I exclusively buy .... metal film resistors ....


They can be more inductive than carbon comp. Modern ones are pretty good, but it can still be an issue at VHF.


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09 Solstice 2.4 I4 Fram 5/30
08 G8 3.6 V6 ST Syn 5/30
04 Xj8 4.2 V8 Hav 5/40
99 S-10 2.2 I4 RECOVERED
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Re: The percentage on a resistor... [Re: supton] #4660943
02/09/18 12:30 PM
02/09/18 12:30 PM
Joined: Feb 2003
Posts: 4,505
Arkansas
Win Offline
Win  Offline
Joined: Feb 2003
Posts: 4,505
Arkansas
Originally Posted By: supton
Originally Posted By: Win
Is it being used for a precise voltage drop at a given current?

I would get a 1% resistor. They're only pennies more, if that.

You need special equipment or some other techniques to accurately measure resistance that low, so get the 1% part and hope for the best.



His 1W requirement kinda points otherwise; yeah, one can do high power dividers but it's kinda rare to see that. At least I haven't come across that need.

If the circuit was properly designed and meant to be ok with 10% resistors, then I don't see a need to measure. Replace and move on.


I was thinking of a meter shunt.


09 Torrent 3.6 V6 M1 0/30
09 Solstice 2.4 I4 Fram 5/30
08 G8 3.6 V6 ST Syn 5/30
04 Xj8 4.2 V8 Hav 5/40
99 S-10 2.2 I4 RECOVERED
94 Xj12 6.0 V12
Re: The percentage on a resistor... [Re: daves66nova] #4660945
02/09/18 12:32 PM
02/09/18 12:32 PM
Joined: Nov 2008
Posts: 12,761
NH
supton Offline
supton  Offline
Joined: Nov 2008
Posts: 12,761
NH
I could see meter, but why would it have used a 10%? I guess if there was a cal pot someplace.

Curious now what the application is.


2011 Toyota Camry, base, 2.5L/6MT, 170k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 144k, ours
1999 Toyota Camry LE, 2.2L/4AT, 195k, his
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