marking schemes for SMD resistors

Among 0805's I've got on hand in the 1 to 10 ohm range, x.x seems to be a little more common than xRx, but both occur repeatedly. Eg, 1.1, 2R7, 3.3, etc. Besides those, I haven't seen any 5% SMD resistors or data sheets with direct values.

-jiw

Na. It always is the number of significant digits plus the exponent. For some reason, character were avoided.

Rene

That reason would probably be that e.g." 120K" would require one more character than "124". And the printed text is already small enough. More characters mean an even smaller font.

Joop

For resistors under 10 ohms, yes. Nothing above that?

I ask because I've been analyzing my technician's washing- machine VFD motor-control circuit board. This has an 0805 resistor labeled 120, which must be near 120 ohms, because if it was 12 ohms the circuit not only wouldn't work, it'd go up in smoke. Actually, it did go up in smoke, burning out the "120" resistor (and many other components), so I can't measure it. The circuit board has mostly US-made or familiar parts, but also a few foreign-looking parts. The other 0805 resistors have conventional labeling, a 33-ohm part says 330. But this 120 fellow simply can't be 12 ohms!

Further complicating the issue is that this 120 resistor was thrown away when my technician replaced it, but both he and I clearly remember it said 120, I had even written it down. To my memory it looked just like the others. But hey, it really couldn't have been 12 ohms! :-

Which brand? A universal motor, transmissionless drive?

Ive come accros some marked 1R0, 1210 case size, ive never seen 1k0 etc though, maybe its just the low values. the coding system I came acros on some 1% 0603 is rather anoying, you have to look up a 2 digit code to find the 3 digit value and look up the letter to find the multiplier value.

Colin =^.^=

The "R" is used in place of a decimal point to make sure the value can be read. I wrote some javascripts to decode the three digit 5% values and another for the the four digit 1% and .1% values for production and stockroom workers. I'll put them on my website if anyone is interested. I also have one for SMD capacitors with the number/letter ID codes if anyone needs it.

That sounds both useful and interesting, Michael. I like reading javascript code. :-) Put it up for us, with a link from here.

etc

on

find

Ive only just got into using javascript for some elementry calculations, I got fed up calculating reactances etc ever since i lost my walchart from an early issue of everyday electronics, and a single web page is far easier than creating a whole c++ application wich I would otherwise have done, it was just a smallish table of hand entered values, but I will try and make it so moving the cursor over the table gives all the inbetween values.

I also just did a page to list all the frequencies available from a PLL within a range of N and R divisor values. only drwaback is it seems to get suddenly get very slow once a certain number of array entries is reached although this can be minimised.

Incidently the problem I find with the 2 digit + 1 letter 0603 1% codes is they are extremly hard to distinguish (I need to use a microscope to distuinguish the last letter) its so easy to read 10C (12.4kohm) as 100ohms

I dont know if this is common but I always used to surprise people when I could read colour resistor codes instantly, (especialy when I was working as a software engineer)

Colin =^.^=

Gosh, the "typographic" resistor value markings date back to Apollo times about 40 years ago. they haven't changed much either. i was surprising people by reading the much more varied capacitor color codes.