# small error in chap 4

Discussion in 'Feedback and Suggestions' started by jackbenson, Oct 26, 2013.

Oct 26, 2013
2
0
2. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
The 4k7 is the new notation, not the other way around. Care to explain further?

When I was learning electronics in the 70's I learned 4700Ω = 4.7KΩ. This is what I have imprinted on.

3. ### WBahn Moderator

Mar 31, 2012
18,089
4,917
The notation of using the multiplier as the radix dates back nearly a centurt, if not more.

Blueprints and schematics were working documents that got handled, often on the job site, on a regular basis for many years. Thus they got smudged, crumpled, dirty, had cigarette ashes fall on them regularly, and all manner of things that could and did result in lots of small, tiny dots all over the place.

So is that a decimal point there and it is 4.7kΩ, or is it a bit tiny burn from some slag off a welder and it's really 47kΩ?

And then there's the question of whether that 01u next to that capacitor with all the little specks around it is .01μF or 0.1μF. Printing it as u1 of 0u1 removes all doubt.

I've seen lots of (and have afew around somewhere) decades-old (70+ years) schematics that use the notation. If there is no prefix, then the letters R, L, C (or whatever is appropriate than can't be confused with an engineering prefix) are used. So a 4.7Ω resistor would be printed as 4R7 while a 47Ω resistor would be printed at 47R. The Ω was almost never printed (for a variety of reasons, mostly practical typesetting issues) and that was true with F and H for capacitors and inductors as well.

My understanding is that European (particularly British) schematics probably used the prefix-as-decimal-point approach first but it was picked up on by parts manufacturers in the 60's and 70's and lots of parts are marked using this system.

4. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
Perhaps, but I have been a professional since the late 70s, and the various military/civilian manufacturers I've worked for have not used that standard. This leads me to suspect it is a lot more common in the EU. You are not the only one who has a deep background in electronics. I am not an educator, but I've played with it since I was a young teen, which is why I got into the profession. None of the magazines (most of which have fallen by the wayside) used it either. I was a voracious reader when I was a teen, and my Aunt was kind enough to let me go through a lot of old Popular Electronics and Radio Electronics left by another Uncle.

I suspect we were in different worlds sometimes.

From my personal experience I think the book is correct.

Edit: Thinking back on it I did see it occasionally, and thought how odd it was. It is a lot like displaying the day before the month on date conventions, it is a local standard. Having said that it was rare, and never on the work prints I read.

Last edited: Oct 26, 2013
5. ### jackbenson Thread Starter New Member

Oct 26, 2013
2
0
Oops --- I misread. I read it as "instead of" rather than "instead as". Sorry! (and I had double and triple checked to make sure I was "right" before posting, oh well)

Love the book by the way. Makes this topic very accessible. I'm on chapter 5 and smooth sailing so far.

One other thing though, in the safety chapter... "I have no idea why women tend to be more susceptible to electric currents than men! "

Would that not be because men are larger than women?

6. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
I don't know for sure, but I suspect women have thinner skin than men, hence the softer feel. My 2¢ for whatever it is worth.