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Confusion about resistors with 'R' value

Posted: 09 Jul 2013, 18:28
by Spefinzephyr
I'm sure this is a stupid question.. In a few of the layouts I'm planning to tackle, I'll see a resistor value of say, 100R, or on the Metal Simplex 10kr

On that layouts I also see everything labeled normally like 10k, 100k, etc. usual suspects..

Is R another label for OHM as in 820ohm resistor

So when ordering these resistors I've been having trouble.. Often the search will lead me to 100 ohm resistors.. The guys at Altex down the street from me give me this look like what the fuck are you talking about when I ask them if they have any 100r resistors in stock :lol:

Could someone crack an egg of knowledge over this noob?

Re: Confusion about resistors with 'R' value

Posted: 09 Jul 2013, 18:31
by induction
Spefinzephyr wrote:Is R another label for OHM as in 820ohm resistor
yes

Re: Confusion about resistors with 'R' value

Posted: 09 Jul 2013, 18:40
by Dirk_Hendrik
Yep indeed. Another one is "E"

Re: Confusion about resistors with 'R' value

Posted: 09 Jul 2013, 18:50
by Dirk_Hendrik
Spefinzephyr wrote:The guys at Altex down the street from me give me this look like what the fuck are you talking about when I ask them if they have any 100r resistors in stock :lol:
And you wonder wether you ask a perhaps stupid question? The fact alone you dare to ask the question places you one step on the ladder higher than these guys already. They should know to serve their customer.. and apparently are to stupid even for that.... :slap:

Remember the time when I walked into a store for some BC137's. Guy looks up what it is.. transistor (no shit!) inventory... not there but a BC547 will do. Huh. Without knowing anything of the application you suggest a completely different and definitely not equivalent trannie!? Salesguys in electronics shops... what's the reason these kinds of shops become extinct in the first place?... Avoid em whenever you can. :secret:

Re: Confusion about resistors with 'R' value

Posted: 09 Jul 2013, 23:40
by Lucifer
You can also get the R used as a decimal point on low value resistors, eg, 4R7 is 4.7 Ohms, and R47 is 0.47 Ohms, etc. Equally, 4k7 is 4.7 kOhms, and 4M7 is 4.7 MegOhms, etc.

This system - which has a British Standard number (BS1852 and it's later replacement BS EN 60062) and there may be other international equivalents - is also often used on schematics, where a decimal point may not be so clear. This is especially true on printed schematics, where printers often leave tiny blobs of ink in the wrong places (or a plague of flies have crapped on your schematic). So, if you saw a resistor on the circuit that looked like 4.7R, provided the schematic was done to the BS or equivalent, you would know that the 'decimal point' was really just a blob and not meant to be there, and the actual value of the resistor was 47R (ie, 47 Ohms).

Check out BS1852 on the web for a full explanation and examples.

Re: Confusion about resistors with 'R' value

Posted: 10 Jul 2013, 11:34
by DrNomis
Lucifer is correct, we use the same standard over here in Australia too..... :thumbsup

Re: Confusion about resistors with 'R' value

Posted: 10 Jul 2013, 21:20
by Spefinzephyr
Great, that clears it up.. But just out of curiosity why would the author of this layout label one(R2) of the 10k ohms 10kr if they're all 10k ohms? :scratch:

Image

Re: Confusion about resistors with 'R' value

Posted: 11 Jul 2013, 06:16
by DrNomis
Spefinzephyr wrote:Great, that clears it up.. But just out of curiosity why would the author of this layout label one(R2) of the 10k ohms 10kr if they're all 10k ohms? :scratch:

[ Image ]

Not sure, possibly a typo.... :hmmm:

Re: Confusion about resistors with 'R' value

Posted: 11 Jul 2013, 09:20
by Lucifer
Yeah, I agree with DrNomis - it's probably just a typo.