Changing Model Units, viz. eps0 & mu0

S. H. Chastain
S. H. Chastain New Altair Community Member
edited February 2021 in Community Q&A

When changing the model unit to millimeters, do we need to adjust eps0 = 8.854e-12/1e3 & mu0 = pi*4e-7/1e3 to depict their units in terms of F/mm & H/mm, respectively?

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  • Adriano Koga_20259
    Adriano Koga_20259 New Altair Community Member
    edited February 2021
    Hi, Can you elaborate better what are you doing? Please, mention what software you are using, what kind of simulation, what are these values about. With only this, it is very hard for anyone to help you. ;)
  • S. H. Chastain
    S. H. Chastain New Altair Community Member
    edited February 2021

    The software being used is FEKO, for electromagnetic simulations, in this case I'm investigating using a modified transmission line as an antenna.

    FEKO uses meters as its default model units, and a number of physical constants defined ahead of time, which can be changed. The values of permittivity of free space (eps0) is 8.854...e-12 F/m & permeability of free space (mu0) is pi*4e-7 H/m in SI units.

    I'm thinking that in switching the model units to millimeters, I should change the values of eps0 & mu0 by dividing by 1e3 to account for the scaling. I'm double-checking, as I've seen a simulation from elsewhere where the model units were mm, but the physical constants, eps0 & mu0, had their original values (i.e., not scaled).

  • S. H. Chastain
    S. H. Chastain New Altair Community Member
    edited February 2021
    Adriano Koga_20259 said:

    Hi, Can you elaborate better what are you doing? Please, mention what software you are using, what kind of simulation, what are these values about. With only this, it is very hard for anyone to help you. ;)

    I can't see how this is considered a "correct answer", as it's merely a clarification; the original question still stands. ;)

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