Hi Im learning to test resistors.How can I tell wich color is the first digit?Cant tell whats top or bottom

 

The last band (tolerance) is often gold or silver.

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i cheat, and use a multi meter to test the resistance!!!

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After you've worked with electronics for a time, you'll begin to recognize the standard values of parts. There are 24 standard values per decade for resistors and when what you think are the first two digits look "funny", you'll quickly start from the other end to find a more familiar value. The 24 standard values for 5% resistors are 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82 and 91. That is, you'll find as a standard value 0.62, 6.2, 62, 620, 6.2K, 62K, 620K, 6.2M and 62M ohms, although the first and last won't be very common, especially the 62M. 10% standard values use every other of the 5% values, 20% standard values use every other of the 10% values, always beginning with 10.

Dean

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Generally, the only ones that you'll use are 10, 12, 22, 27, 33, 47, 56, and 68.
With these, you can approximate values or use them in series and parallel.

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theres 3 resistors im doing something wrong on or they are bad.all 3 are the same,br-bl-rd-gld...i have 10*100=1000 with a tolerance of 5%(50) these resistors are on 3 totally diff parts of the same board..2 of them are reading 799 wich im confused to wich way to lean..good or bad.. my reading should be from 950 to 1050..the third one really got me.its 01.2..

im using a fluke to test.
when a res goes bad is the reading tottaly off or can it be a lil bit off the tolarence and still not work..or is it open..

what causes a res to go bad

is there visual evidince when it goes bad

when i test the ends is it ok to test the sodered part if my probe cant fit between the bottom of the res and the board

and is it normal for a res to go bad

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Have you disconected the resistors from the rest of the circuit?

All your readings are low....I suspect that you are reading the 1000hm: resistors in paralell with another part of your circuit.

To measure a resistor you should disconect at least one terminal from the rest of the circuit.

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I think that a more accurate thing to say would be that you'll use those the most, although I don't know why you included the 12 with that group since it's only 20% away from 10. However, I certainly don't agree with the approximating values or using them in series and parallel. Nothing like having to have triple the number of resistors necessary for each project you build if you limit yourself to a very narrow range of value like that.

You're much better off stocking a few of all the 5% standard values rather than kludging together values from what you can find laying around. Series and parallel combos can push power and voltage ratings if you're not careful.

Dean

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It all depends on the kinds of projects you do. The stuff that I make can manage having resistor values a little off.

I try to avoid doing that, and if I do, I limit myself to no more than 2 resistors per series/parallel combination. If I can't manage to do that, it means giving up the project or making a trip to the nearest good electronics store; conveniently located 2 cities away.

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Sounds like you need to be stocking up on resistors by doing some board salvage or begin collecting parts via mail order.

I can't sympathize with you on your need to travel to find parts. The nearest electronics store that's worth the trip for me is 3 hours away. There's a Radio Shack in the nearest town 12 miles away, but Radio Shack in the U.S. is as worthless as the mammary glands on a boar as they carry very few piece parts these days. They're only good for cell phones, overpriced computers and other consumer products.

Dean

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R.I.P.

 

Usually too much power dissipated; in other words, too much heat, can cause the value to increase

sometimes there is, but often there isn't - usually if the thing has gotten nearly to flame out it will be darker in overall color

A node is a node; the wire between components is CONSIDERED to have no resistance, and anything connected with wire is on the same node, so you should be ok here.

If the thing was designed well, resistors normally do not fail, and when they do they tend to fail open, or partially open. The cause of the failure may be elsewhere in the circuit, which has cause increased current through, or voltage across a resistor, finally causing the demise of the resistor.

 

Resistor value chart attached, hope it helps

Cheers, Rodalco

Attached Images

colorCode.gif (14.1 KB, 12 views)

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Rodalco,

Re: The chart's 6 band resistor colour code

What is the sixth band used for? The chart does not say.
I think there is an error too. I see the 6 band example as 650K, not 620K as stated.

Bob

 

http://www.google.com/search?client=...utf-8&oe=utf-8

Generally the most popular values are multiples of 10, followed closely by 47 and 22. This is because 10, 22 and 47 form the E3 series which is still very common even though 50% tollerence resitors probably went out of fashion back in the 1890s.

Generally when stocking an inventory I resomend a set of the E24 values, plus more of the E12 values, even more of the E6 values and loads of the E3 values. Generally as the E number goes up, the values become less common and as the E number goes down they become more common.

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