exponents with units

[tpaulsen]

I have a problem in Mathcad with declaring expressions like Exp(Var) were Var has a unit like meter. Get the message that "cant have anything with units here". Anybody knows how to avoid this kind of errors, other than removing the units.
Thanks in advance
Tor

 

[IRstuff]

Well, that is as it should be. Exponentiation of a meter has neither mathematical nor physical meaning.

If you have an equation where you have units left over in the exponent, the equation is simply wrong or you've ignored a unit somewhere in other term(s) of the exponent.

A typical exponent using range would look like exp(-alpha*range). In these cases, alpha always has units of length^-1. There are no exceptions.

Another typical form is exp(-V/kT). Needless to say, k's equivalent dimension is always volts/degree or something similar.

TTFN

 

[Bung]

Mathcad's handling of units is one of my major reasons for using it - I've lost count of the number of typos and the bad maths I've managed to avoid when the units didn't stackup. A very valuable part of the sanity checking needed when using automated tools, IMHO.


Bung
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