100nF vs. 0.1uF

Sure. But the SNR has been pretty low lately, so we're pathetically grateful even for a thread on ref des.

Cheers

Phil Hobbs

Can't argue with that. Let's hope Trump and AGW don't stray into this thread :-)

Instead of confusing things with an extra '+', why didn't you just give them the arrow? You could delete the erroneous '+' to remove further confusion. It shouldn't be hard to include either(both) change(s) in the symbol and footprint libraries, for future use, either.

Why is it so strange? pF and uF work perfectly well. Millifarads aren't often used, either, preferring 1000uF.

I've seen that both ways and I understand your point but it has no relevance WRT capacitors.

Because you should use the most convenient unit in a given application.

It depends, millifarads are good if the number of uF is large. The values used by one of my design were 12600 and 100000uF, which requires unnecessary zero counting -- boring and potentially leading to a mistake. Technically it could be as well expressed in pF, but 12.6 and 100mF is much more readable.

Best regards, Piotr

It's no more convenient. 'M' and 'm' are too often confused.

You're buying pretty expensive capacitors, there (three significant figures). What's wrong with 0.012F or 0.1F, instead.

As would 'M' and 'm'. My BOMs don't have package sizes.

M makes no sense in the case of caps, the mankind has just barely reached 'k' and it is not sure whether these double layer devices are caps at all. So there is nothing to be confused, contrary to the case of resistance.

Yes, but mostly because of their max. allowed temperature (125 C), not because of capacity. A consumer-grade 100mF is not that expensive.

With 0.1F nothing, the former contains way too many unnecessary zeros, just as 10000pF does. One can also buy 0.001 tonnes of sugar, why not... Technically correct, but looks awkward.

Best regards, Piotr

Not sure what you are saying. "M" is often used to mean "micro" while "m" should mean "milli". But if I see MF I don't know if someone simply made a mistake in capitalization or if they mean uF.

Hey, I was comparison shopping rice at Wallyworld and they had the unit prices in $/ounce. Who the heck buys rice in ounces??? I was looking bags that started at 1 lb and went up to 20 lbs.

I've also seen stores unit price spices in $/pound which makes them look

So it should be 100 mF and 12 mF? I don't find that at all confusing since no one should be abbreviating micro with a lower case "m". If they do the blame is on them.

It does seem more sensible :) Or the hollow anode symbol.

NT

Electronics certainly trumps those.

NT

I was hoping nobody would ask why. It was late in the day. The films for making the PCB had just come back from the photographers and was ready to go to the PCB maker early the next morning. That's when someone reminded me of the polarity problem. I should have made changes to the original PCB silk screen tape up (this was before PCB CAD was common) and sent the originals out for new film. But, that would slide the schedule at least one full day. I wanted to edit the drawings showing the outer foil arrow, but someone from production insisted that the drawings and PCB had to be matching. So, I decided that I could most easily take an xacto knife, and gouge out two "+" signs in the negative, without sending the artwork out for more film. I would have had problems making a larger arrow with a "-" sign in the same manner. Editing the negatives was generally discouraged, but done sometimes in the name of expediency, as long as the originals were updated later to reflect the butchery. I survived the inevitable lecture and tongue lashing, and lived to repeat my gross breach of proper procedure at least once that I can recall.

Also, it would have been difficult to add the arrow to the symbol and footprint libraries. This was not a computer based CAD system. It was a sheet of mylar, plastered with tape, pads, and "Stick Type". Something like this (which I recently threw away):

I wonder why (I think it was the Japanese first) someone set the standard of tagging the negative side of electrolytic caps.

They also had the red terminals of their DVMs the negative voltage in ohmmeter mode, but positive in voltmeter mode. I think they got over that one.

Diodes have their own history.

We do lots of things backwards.

LET ME REPEAT WHAT YOU SNIPPED "three significant digits"?

Absurd.

The blame may be on them but the confusion is all yours.

... like current flow

NT

It's not necessarily the negative side. The arrow signifies that it's the outer foil of the capacitor. In theory, the outer foil could be either negative or positive, depending on how the capacitor is made. If the outer foil were positive, I would expect to see a "+" sign on the arrow. However, I've never seen one like that.

My guess(tm) is that the designed figured that since resistors are not polarized, it didn't matter which lead was positive or negative on the ohms scale. In the tube era, that was probably a good assumption. In the low voltage semiconductor era, not so good.

Yep. The arrow points in the direction opposite the electron flow.

.tnenamrep emoceb dna gnol oot rof ecalp ni tfel era yeht sselnu ,detcerroc teg yeht ,yllautnevE .sdrawkcab enod tseb era sgniht emoS

I was told that the current always flows downhill. Has this changed and we are now paddling against the current?

In a meeting someone once said antennas should be at the bottom of a hill because the electrons flowed downhill... and he wasn't joking. Those were the days!

Probably a carryover from pre-digital days when most analog MMs were made that way.