I don't see why mF should be any stranger than mH, mm, mOhm or anything.
Although, when I wrote the value of Boltzmann's constant as 13.8 yW/HzK somewhere, the editor found it necessary to change that into
1.38 * 10^-23 J/K.Not everyone is comfortable with the full range of prefixes, I guess.
Jeroen Belleman
That's the way to go, she probably has good communication skills.
And I am not saying that consultants are always the cat's meouw just because I am one. Once as a manager I did have to fire a consultant, for lack of communications skills. He began fingerpointing and all that, made my engineers unhappy and that just wasn't going to continue. Strange thing is, years before that he used to be an excellent communicator.
We have a document that tells how to assign stock numbers to parts. Resistors and caps wind up being in value order.
In part number 104-1600, the 104 specifies an 0805 ceramic cap; 160 specifies 100 pF, per an algorithm. The last digit allows us to have up to 10 different 0805 100pF parts. We currently have two, 1% and
10%.So you get stuff like...
131-6851 RES 0603 76.8K 1% 131-6891 RES 0603 84.5K 1% 131-6921 RES 0603 90.9K 1% 131-6931 RES 0603 93.1K 1% 131-7000 RES 0603 100K 5% 131-7001 RES 0603 100K 1% 131-7002 RES 0603 100K 0.05% 131-7051 RES 0603 113K 1% 131-7170 RES 0603 150K 5% 131-7181 RES 0603 154K 1% 131-7201 RES 0603 162K 1%which aligns part number with stockroom ordering with value.
John
Ah, interesting. ...although I might be tempted to have an algorithm spit out something more like XYYY where the component value is then 0.YYY * 10^X or something (so 113k->6113, 1.12k->4112, etc. -- this still sorts correctly), but I expect you guys kicked around such an idea and decided your way was preferable. Neat...
A big deal is often made about second-sourcing but in reality it's not possible for most things, outside of passives, discretes, and a few unit-logic glue things. So much of a BOM ends up being single-sourced that it's silly to pretend that a multiple-source policy accomplishes much. Yeah, we give it lip service, too.
Certainly, companies tend to rely on a few people too much and documentation too little. Then under-pay them. OTOH, it's also possible that they'll get run over by a bus...
A lot of that is just another set of eyes. That's why good design reviews are so important. I did that several times, even during interviews.
We needed that last digit as a sequence number for parts with the same value but different tolerances or tc's or whatever. And we liked the idea of a 7-digit "telephone number" as being easy to use.
John
Things turned for the worse and he showed his true colors? When things are going well it's easy to be happy.
Since .1uF is the most common cap, I like to just have '.1' in the value field, rather than '100nF'. Other than that, I'd probably agree. Exceptions are dirty, so we stick to 'F' (we do use a supercap), '', and 'pF'.
I agree. Too Europeon. ;-)
If you need them, be careful. Some aren't very reliable. I'm trying to get rid of the one we're using.
Took me a minute to figure out what you were getting at... Yes, we've run into that too, though it's the first thing to go away at the next board spin. Another thing we've had to resort to a few times is stacked components. A cap on top of a feedback resistor becomes R99T, in the BOM. I don't think any of those have escaped into the wild, though.
Ours aren't, unfortunately (they were, until some inventory droid decided that that didn't make any sense). It only takes a look-up through a table to do the conversion, though.
You don't remember mF and mmF, I suppose.
I don't like mF, either, because it isn't normally used.
ROI
No kidding. One job I got almost had a sad reason. The analog dude at that company owned one of those Japanese death machines that could go from zero to 60mph in 4sec and to 120mph in another 10sec. At around
100mph the frame weldment decided it had enough of this and the bike broke in two. Due to at least three lucky circumstances he survived it.be
Much of my work is just that, design reviews. Plus later the re-design of the more nasty chunks of the circuitry. I can safely say that some of the products would have otherwise become a financial disaster.
Yes, I'm old enough to know that the 'm' once stood for 10^-6.
The point of it all, of course, is to apply these prefixes to
*all* units, using the same rules for all. It's simply not consistent to write 1000?F, but 1mH.But old habits die hard, sure enough.
Jeroen Belleman
Yet 'M' was used for 1000 on early potentiometers. Old volume controls were marked 500M or 1000M.
strive to
'My purchasing people' is _me_ until I hand over to clients, so I double source where possible!
It also makes things easier/cheaper for CEMs to build.
Nial.
That's rather annoying. I have a 100M pot (and it's *actually* 100M).
Tim
Other industries used M for 1000 at that time, so it was an accepted practice. Since everyone knew what it meant, it was no big deal. They also used nF for capacitors at that time.
No, the point is to have the fewest possible misunderstandings. To me, nF is too close to mF. Dump both. There is no reason capacitor and inductor nomenclatures have to be consistent with each other. We use "10" for 10uF or
10 ohms but spell out "10uH" or "10mH".
It's not so much about habits as making readable, concise, documents.
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