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Emoncms
21

Sorry to be pedantic, but every day is a learning day. Where a unit of measurement is named after a person, the unit is (usually) in capitals so it should be

kWh/d

I used to get it wrong until I learnt this method of easily remembering it. :grin:.

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22

K is degrees Kelvin, and D as a multiplier would be Deka (×10, there’s no unit D) :grinning:

The rules are:

  1. Units named after a person have a Capital letter, and this rule overrides the others.
  2. Units not named after a person have a lower case letter.
  3. Multipliers greater than one have an UPPER CASE letter, unless this rule is overridden.
  4. Multipliers less than one have a lower case letter.

As far as I know, it is always, not usually. But in a sentence, “watts” is correct, “Watts” is wrong unless it starts the sentence.
The only exception that I can think of is the relatively modern practice of using b for bits and B for bytes, as in 1 kB/s = 8 kb/s. (Because Byte was not a person.)

The one that always gets me - the people who use their RFM radios to talk to submarines under water at 0.433 Hz. Those are the people who write 433 mhz, and upset poor Heinrich Hertz in the process.

2 Likes
23

To qualify a little more:

It’s just the symbol that is capitalised so K is the symbol for the unit kelvin.

The most important counter-example to rule 3 is kilo, which is abbreviated k.

There is a space between a quantity (such as 4.2) and a unit (such as J), thus 4.2 J

24

We were discussing the symbols, not the names of the units:

It is overridden by Rule 1, as I stated.

If you’ve noticed, I always write it that way.

25

Indeed and I’m sorry I seem to have given some offence by trying to clarify things for anybody else reading who may not have appreciated some points.

Indeed but just above:

I’m sorry, what does rule 1 have to do with kilo? It’s not a unit. I was simply pointing out the specific and very common error that James had made

I wasn’t making any comment about your habits; I was just pointing out another very common error that people make.

26

After the man’s title (not name in this case): William Thomson, Baron Kelvin of Largs.

No, kilo is the multiplier × 1000 and as such under Rule 3 it ought to be K, except that K is already in use for degrees of absolute temperature named after Lord Kelvin, so Rule 1 overrides Rule 3 as it applies to kilo. Hence k for × 1000 must be lower case, as that’s all that’s left.

I agree, it annoys me too, especially since we’re no longer allowed to correct errors like these, so let’s try to lead by example.

And another not quite so common mistake: TB for terabytes - T is the unit of magnetic flux density, Tesla.

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