A 27R resistor

Yes. If they left of all units, you might think they just accidentally left off a k or something. I'm not sure why R is the default unit for X1 ohm, though.

John Popelish wrote: I'm not sure why R is the default unit for X1 ohm, though.

probably easier than finding the omega key on the keyboard, less confusing than typing a O (might be confused with 0) and takes less time to type than "ohm"

Thanks for the info. Actually, they had two resistors that said 27R. I figured it was 27 Ohms but I just wanted to make sure before I built it.

I think this is an offshoot from low value (less than 1 ohm) resistors where the part numbers often now are (for instance) 0R01 for a 10 milliohm resistor.

Cheers

PeteS

For a brief while there was a European convention to use E. It never caught on though. You may occasionally see it still.

Graham

The character 'R' has been used to represent the decimal point ever since the days of Morse code. Back then, you were supposed to figure out what di-dah-dit meant by context - it's either 'R' or the dot, which is either period or decimal point.

Another side of the story is that in the early days of pencil-and- paper drawings, and diazo prints, it was used because a dot can get lost in the noise.

Or, it could mean just "resistance", like 2K2 is 2.2K, or 2200R, where they adapted the 'R' from the Morse convention, above.

Hope This Helps! Rich

--- Yes.

That' a convention that was started some time ago in order to resolve any ambiguity which might arise as a result of printing problems and the location of the decimal point (if any) in the resistor's value.

For instance, if your schematic was old and beat up, or badly printed, or a copy of a copy of a copy..., the value of one resistor might read 27k when it fact it was 2.7k.

So, in order to keep that from happening, the decimal point was replaced with the decimal multiplier and 2.7k would be printed '2k7' instead, and 27k would remain '27k'. (Or '27kR' in some cases if it wasn't obvious that the component was a resistor.

For values with no decimal point, 'R' was placed at the end of the value, as in 27R, 100R, 1000R, etc.

-- JF

I think this ohm unit indicator is most useful when it is used as a decimal point for decimal fractional ohms, i.e.

It's even easier to type "27"

John

That'd be confusing for programmers, 2E7 is 20000000 in most programming languages and applications, or is that the way they were using it?

Bye. Jasen

on

Yes it was.

The idea AIUI was E^0 meaning 1.

Graham

John Larkin wrote: > On Wed, 29 Nov 2006 18:28:31 +0000, Mark Fortune > wrote: >

Unless its 27.4 1% Those pesky decimal points often get lost in copies. Seems there was a thread a few years back on that subject. Personally, I use 4K7 resistors, not 4.7K as the schematics are easier to read and by the time the 'K' get lost in a copy, nothing else is readable anyway. As for the 'R' in the resistor value, I always think 'radix' when I see 27R4 or such.

GG

Accountants don't write 2,874,658$45, and their decimal points are a lot more important than ours. It's been decades since people used diazo copies of hand-drawn schematics... dp's just don't get lost any more. Actually, schematics don't get copied much anymore; they go from a cad or PDF file directly to a laser or inkjet copier.

The 4K7 thing is a silly affectation, and the bad-copiers thing is a silly excuse.

John

Well, considering it came from Europe, they did have a lot of languages to reconcile - at least be grateful that the units are still "Ohms" ;-)

Cheers! Rich

I'm still mad about the cps/Hertz and mhos/Siemens things.

Imagine naming one engineering unit that's the reciprocal of an already-named unit!

John