18 Jun
2013
18 Jun
'13
11 a.m.
[Using the prefix as the decimal point]
Especially, as I was taught, on a third-generation
photocopy. Those
decimal points like to hide.
Actaully some scans are just as good for adding or removing dots. And my
handwriting is bad enough that I use the convention on my hand-drawn
scheamtics a lot of the time.
Another convention, used on the components themselves, is to give the
value as a 3 digit number -- 2 digits and a power of 10. So that, for
example,. '472' means 47*10^2 = 4k7 (if a resistor). Very common on
surface mount components.
Alas that one has a nasty ambiguity. What is the value of a resistor
marked '220'? Is it 22*10^0 = 22 Ohms, or is it simply 220 ohms? I have
an instrument [1] where one of the resisotr packs for the LED series
resistors was incorrect -- it shouyld be 220 Ohms, it was labelled 220,
but was 22 Ohms. The other pack on the same PCB was also labelled 220 but
was 220 Ohms (the 2 resisotr packs came from different manufacturers).
Yes, I did replace it.
[1] A telephone line simulator. Probably off-topic, even though it does
have IEEE-488 and RS232 interfaces and contains 6 microprocessors.
-tony