Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Unit Scaling Prefixes: (was Birthday Wish)



It's even worse when you make such prefix mistakes yourself. While preparing
exams on my computer, I have more than once forgotten to change Times Roman to
Symbol in prefixes and units and thus given my students a problem containing
milliFarads instead of microFarads or, even worse, milliwatts instead of
micro-ohms.

Why doesn't someone invent a scientific keyboard having separate keys for the
more common Greek letters?

poj

brian whatcott wrote:

Although I deny that engineers use M for milli- or micro-, I acknowledge
that electronic components are often mismarked in this way.
So there is virtue in Douglas's warning. In these cases, context can
provide guidance. But these days, capacitors can take values between
picofarads to farads and all points between. So the old rule of thumb about
a mismarked
"mF" or "MF" more likely meaning microfarad (uF) than millifarad (mF) has
lost its strength. But because there is no instance of a megafarad capacitor
ever (yet), one can at least discard that possibility.

But in measuring frequency, I have seen reference to measurements in
millihertz just once, while megahertz tags are legion.
There was a reference in the splendid French-U.S work on resolving
breathing mode frequencies of the Sun, that I have mentioned before.
They used the Fourier transform of an unbroken train of solar observations
of the Doppler shift of some hyperfine Sodium line taken in, I think, the
Antarctic.

So as a sweeping generalization, I'd say measurements in millihertz are
to be found rarely among physicists, and not often from engineers, where
the context is generally informative.

Brian
brian whatcott <inet@intellisys.net>
Altus OK