by Guest » Thu Jul 14, 2005 3:25 pm
[quote="Anonymous"]Representing "normal meter cubed" as Nm³ or nm³ is a bad practice, contrary to SI conventions because "n" is reserved as a prefix for nano-, and "N" is reserved for newton. This is guarenteed to cause confusion for some people who read it. Since "normal" is not usually used in the US, I don't know what the preferred notation is.
Not too sure that it is bad practice to use N for 'normal'. There are precendents for multiple use of the same letters, e.g. m for milli and metre. The key thing is to ensure that units are separated with spaces or full stops (e.g. N m or N.m for Newton metres) whereas prefixes are adjacent (e.g. Nm3 for normal metres cubed).
However, use of 'Normal' has always created confusion regarding what temperature is applied, e.g. 0 C, 15 C, 20 C, 60 F. I used to think it was 20 C but have now been converted to the 0 C definition (although this is anything but 'normal' where I live!). Perhaps the important thing is to ensure that the document/spec/data sheet that refers to Nm3 has a clear definition in terms of temperature. Don't thing there is any confusion on the pressure of 1.013 bar a though?