metal film or carbon film?

[Roushon]

purchased a bulk amount of resistors from auction. these are mixture of metal film and carbon film resistors. how do i distinguish which one is metal film or which one is carbon film?

thanks

 

[analog_sa]

You listen to them.

 

[SY]

I tried that and they didn't make any noise. Even when I put them into a nice, big pile and cupped my ear near it, they were absolutely silent.

Roushon, you might consider sacrificing a few; break off some of the conformal coating and take a look at what the resistor element looks like.

 

[JensRasmussen]

Carbon types are often 5% with 3 colour rings with one gold (5%)
Metal film types are often 1% and have more rings than the carbon types.

Try posting a picture of them, maybe we can sort it out this way

\Jens

 

[Mr Evil]

Quite often metal films are blue and carbon films are beige.

 

[zanash]

Rarely ....banded ones are any good sound wise. Look for the closer tolerance like .1% and .05%. Again these will varry in sound considerably.....in my opinion the best sounding are welwyn, holco, vishay......then there are the exotic types !

 

[Roushon]

details

the following are some details of the resistors. these are exactly what I read on the resistors.

1. 5 colour bands
2. 6 colour bands
3. JV-8K2, single yellow band
4. 1X-22R, single yellow band
5. 4 colour bands
6. FAC-1K1, single blue band
7. GWC-10K, single blue band
8. GXC-48R7, single blue band
9. GAC-56K2, single blue band
10. GU-150K, no colour band
11. GXC-3K83, single blue band

i do not have a digi-cam. so i am not able to show the pictures.

 

[Roushon]

Carbon types are often 5% with 3 colour rings with one gold (5%)
Metal film types are often 1% and have more rings than the carbon types.

Try posting a picture of them, maybe we can sort it out this way

\Jens

i guess that the resistors 1,2,6,8,9,11 above are metal film.

 

[peranders]

Quite often metal films are blue and carbon films are beige.

The colour of the body is no indication at all. Metal flim can also be beige.

 

[Mr Evil]

The colour of the body is no indication at all. Metal flim can also be beige.

Nothing external is any certain indication - both the body colour and the tolerance can be anything for either type, but usually they follow a pattern.

 

[jacco vermeulen]

All very amusing.

Ever considered that metal is magnetic, carbon is not.
The body of a metalfilm sticks to a magnet, the leads generally do not as most leads are tinned copper.
Even MOX metaloxide bodies stick to a magnet.
None of the Vitrohm, Amroh, or Allan Bradley's carbon composites i have do

 

[JensRasmussen]

Jacco,

You are the smartes man I have the pleasure to know!

\Jens

 

[SY]

I don't want to be the skunk at the picnic, but...

Nichrome is not ferromagnetic.

If it were, the film is too thin to have any significant attraction to a magnet.

What the magnet is attracting is the ferromagnetic end caps which make contact with the resistive film/ceramic substrate.

 

[jacco vermeulen]

SY,

do some or all carbon composites have ferro-magnetic end caps ?

 

[SY]

Composition resistors, no, but carbon film resistors, yes. And to further confuse things, some metal film and some carbon film resistors use nonmagnetic end caps.

 

[peranders]

.... so what exacltly does the magnetism do? Nobody have to answer because this is only a fashion, no?

 

[jacco vermeulen]

True, nickel-chrome is not ferromagnetic.

Neither is a metaloxide layer, nor a carbon resistance track, a ceramic body, tinned copper or alloy leads.
The carbon composition resistors do not have end caps.
All of the carbon film resistors i have do not seem to have nickel-ferro end caps.
I know Beyschlag(Vishay BC / Philips BC) makes/made 2% accurate carbon films that look almost identical to the metal films they produce.

One way of finding out could be to check the TK value.
Regular low power metal films have a TK of 50, carbon films are in the order of TK = 200.
Yageo MF series have a TK of 25.
A reason for not using carbon films.

Any one of you have an idea how to check the power rating of a resistor, 1/4W, 0.4W, 1/2W, 0.6W, without having to destroy it ?

 

[SY]

JV, a resistor costs maybe a nickel. It's cheap to destroy two or three in the interests of understanding construction and testing of limits.

 

[zanash]

power rating of a resistor is a function of it size, the abillity to disapate the heat created when acurrent flows. So the smaller they are the less power they can handle.....this is only good for descretes not smt's

 

[jacco vermeulen]

SY-master,

you are right that it is far easier to just open up a couple.
i was merely wondering if there is a neat way of measuring the temperature of a resistor under load.
(i only buy resistors with a datasheet)

0.4 watt Yageo's are half the size of a 0.4 watt Beyschlag Components metal film resistor.