how to determine the dielectric constant of egg tray?

opticfibering

Hi, can i know how to get the dielectric constant of the egg tray (the one with the paper) beside using dielectric probe technique? is it have same dielectric constant of paper? or it is different? i hope someone can help me.
if the egg tray mix with the carbon or graphite, as i know the graphite dielectric constant for epsilon=12, mue=1, how to calculate the dielectric constant of if both are mix?

thanks in advance.

NascentOxygen

I can't imagine a manufacturer would incorporate graphite into his egg trays. Perhaps this is a thought experiment?

opticfibering

i just do the experiment, using egg tray as material. then the egg tray will mix with graphite and fabricate shape. :)

NascentOxygen

I can't think of any way to determine ε_r apart from incorporating the material between the plates of a capacitor. If the dielectric is not a good insulator, insulate it from the plates and take this into account.

opticfibering

Thanks NascentOxygen.
here, i would like to do the EM wave absorber using egg tray as material. i need to fabricate using egg tray which i plan to put the egg tray in the water and make it wet and then mix or coated with carbon/graphite.
anyway, εr of the egg tray same with the paper or not?
thanks.

opticfibering

or what is the permittivity of paper egg tray? same as paper?

NascentOxygen

Well, it would certainly be related to the permittivity of the recycled newsprint that it is made from. But because egg tray material seems to incorporate more air than does the equivalent thickness of paper, I'm hesitant to guess how this pans out.

berkeman

Interesting, you are wanting to make your own Anechoic RF Absorbent Material (RAM)?

http://en.wikipedia.org/wiki/Radar_absorbent_material

The dielectric constant will not have a big effect on the absorption characteristics. It is more dependent on the conductivity/losses and the shapes of the cones. The rounded bottoms of the paper egg containers are not a great shape for this, but I don't know of many good alternatives offhand. You might be able to figure out a way to cast some material in the shapes of the cones of typical RAM materials...

And what RF frequencies are you hoping to absorb? The depth of the cones should be on the order of the wavelength that you are trying to absorb.

opticfibering

thank you NascentOxygen.
this means that i need to quick to find the permittivity of the egg tray before i proceed

opticfibering

my project is using egg tray as material to absorb EM wave. in my simulation software, i design the absorber in pyramidal shape then using the egg tray as material. the problem is in the library of the software dont have egg tray material, so i need to load a new material with value of epsilon,ε (permittivity) and mu,μ in there.

berkeman

I would think that your simulations should show that the attenuation of the RF doesn't depend much on the permittivity and permeability, and would depend a lot on the lossy-ness (resistance) of the material. There is probably a sweet spot in conductivity between high and low that offers the optimum absorption. Be sure to make your cones large enough for whatever frequency you want absorbed.

berkeman

In fact, I wonder if the optimum impedance would match the 377 Ohms of free space. Not sure how to translate that into the volume resistivity target that you should shoot for, but your simulations should show a curve for absorption versus bulk resistivity that has a maximum at some bulk resistivity value.

And I'm referring to cones that have the same resistivity throughout their volume, not just an egg carton that has some bulk resistivity in the surface of the cups.

opticfibering

ok, thanks. ^^
i will check and try to do regarding to your suggestion/guideline.