resistors with 5 colors with silver as the 3rd color?

[bitman]

This is probably covered in all Electrical Engineering classes 1:1 - but since I'm color blind I've always just skipped this chapter after yet another try where I totally fail to tell what colors each band is on a resistor.

However, I have a rather large one that my ohm-meter isn't really too precise about. It looks like 0.2ohms but I'm not sure, so I thought well, this is nice and large so I tried to use the color codes. ARGH - sorry, which side is which here? I see what looks like silver in the middle - it's definitely NOT white or gray and no chart I've found shows silver in the middle!  I know these large power resistors aren't exactly common, the little ones I can barely see there are color bands, let alone the color and of course with SMD we just look at the code under a magnifying glass and look that up. So I guess this skill is going a bit out of fashion, but I would still like to know from the old-timers here. I took a picture to clarify my "dilemma".  First how do you tell which side is "first" and second, am I seeing it right that silver is in the middle - which may explain why I cannot see how the color codes would cover <1ohm resistors ... so maybe my chart just doesn't take into account that some resistors are less than 1 ohm.

My quest is to learn so a link to something that explains this would suffice. Thanks!

[IanB]

Here's the first link that comes up, that I expect you have already looked at:

https://www.allaboutcircuits.com/textbook/reference/chpt-2/resistor-color-codes/

If there were four bands, it would look like brown-black-silver with gold tolerance, which would be 0.1 Ω, 5% tolerance.

However, the violet band messes that up. So I have no idea. Someone else, perhaps?

[Richard Crowley]

It looks like you can see the resistance element under the conformal coating.  It is quite large and has very few turns. So I would expect that it is a very low-value resistor with a decent power rating, and a low tolerance.

[Nusa]

It sure looks like a resistor, but consider the possibility it's an inductor or capacitor instead. How old is the equipment it came out of?

You can calculate a pretty accurate resistance value using a different method. Put it in a simple test circuit with a voltage source and current-limiting resistor in series and measure both current in the circuit and voltage drop across your mystery item. R=V/I

[Zero999]

It's not a capacitor, otherwise it would read open circuit, on the meter.

0.1Ω sounds like a reasonable number. You could test it with a constant current source, which can be made with an LM317, a resistor and a >5V power supply. Connect it in series with the resistor, measure both the current (the LM317 has a considerable tolerance) and voltage and work out the resistor's value with Ohm's law. This may not be super accurate, but it'll be better than the low resistance range on a typical meter.


http://www.bristolwatch.com/ccs/LM317.htm

[bitman]

It sure looks like a resistor, but consider the possibility it's an inductor or capacitor instead. How old is the equipment it came out of?

Well, *I* purchased it   Just a few months ago (https://www.digikey.com/product-detail/en/yageo/PNP300JR-73-0R1/0.1AECT-ND/2059169). I know what it is based on what I purchased - that's not the question I have.  Turns out, I had to replace this resistor with another to get better results, so these are just going into a drawer but I want to know how to tell what it is, without looking for my old order.

My Fluke doesn't give me 0.1 ohm - I realize that ohm-meters/multimeters aren't as precise as I once thought. Partly because I'm cheap and don't get quality equipment partly because it isn't meant to measure fine steps like 0.1ohms precisely.  Because I cannot see colors like others do, I measure EVERY component to validate them when building stuff, and when putting things back to organize. And I simply want to understand how to make sense of the color bands here. Because I'm not used to use the color bands, I'm obviously missing something "easy" and I'm just trying to learn to tell a resistor based on the color band. Given that I cannot find any band schema that has silver as the 3rd band out of 5 - I thought of asking in this forum.

You can calculate a pretty accurate resistance value using a different method. Put it in a simple test circuit with a voltage source and current-limiting resistor in series and measure both current in the circuit and voltage drop across your mystery item. R=V/I

That assumes the other components are precise   With 5-10% tolerance values, I'm no better off than with the current meter - it won't be precise at these numbers. 

THAT said - had I not purchased this myself, I appreciate the ideas you present here to "find out".

[george4657]

According to datasheet provided by Digikey   "5th color code: violet"  so color code is violet so code is Brown,black,silver,gold

[bitman]

I've tried from three different systems (around the cloud web) to download the data-sheet and it comes up "page cannot be displayed" every time.  I just got DigiKey to tell me the same thing - the datasheet is still inaccessible to me - I'm very curious to how you managed to download it   But yeah, I was about to post exactly what george4657 wrote.

[IanB]

Well, here's your answer: it's a non-standard manufacturer code:

The resistor element is a resistive wire which is wound in a single layer on a ceramic rod, with tinned connecting wires of electrolytic copper welded to the end-caps. The ends of the resistive wire are connected to the caps by welding. The resistors are coated with layers of green color flame-proof lacquer. High power in small package. The 5th color band is violet to represent PNP V series.

The well-organized person (not me!) will keep a note of the product details (manufacturer part no. and data sheet) with the part when storing it, so as to avoid problems with identification later on.

[LektroiD]

Looks like a coil inside, my first thought was an inductor, have you measured it for uH?

[IanB]

Looks like a coil inside, my first thought was an inductor, have you measured it for uH?

It's a power resistor, manufactured by Yageo.

[StillTrying]

  Are you sure it's not a diode?

I almost never count the bands, I just start at one end and see if it starts to make sense, even with perfect colour vision it's often difficult to decide if a band is brown, red or orange, even before it's been cooked.

[Yansi]

Deleted.

Sry, there is the gold bar there. Huh.

//EDIT: IanB seems to have the correct answer.  I thought it to be the same as one of the resistors I have here, but unfortunately I have no violet bar. But it is the same type of probably Yageo 100mR resistor.