Simple eqn to remember
( 2
skin depth = sqrt ( -------------- )
( w * u * sigma
w is radians per sec; or 2 pi f, with f in Hz
u is permeability . or . u rel * u free space
u free space is 4 pi 10-7
sigma is conductivity in S/m
all MKS units so
skin depth in meters
One important point to remember is that this formula
calculates skin depth, like attenuation versus depth, for a
*PLANAR WAVE*
If the impinging wave has curvature, like from a close by
radiator; that wave really "punches" through and there is
not as much attenuation.
How much? Depends on curvature, but for close sources the
effective thickness can be reduced to less than half.
Conclusion:. Use thicker material than you think you need.
- Robert -
Robert A. Macy, PE .. [email protected]
408 286 3985 . . . .. . . fx 408 297 9121
AJM International Electronics Consultants
101 E San Fernando, Suite 402
San Jose, CA 95112
On Fri, 8 Aug 2003 13:33:24 EDT
[email protected] wrote:
> My anal-retentive self is having some trouble
> with an occasional
> example in the text and I need either a confirmation or a
> slap in the forehead.
> I was just fiddling around with the text and
> reviewing some of the
> examples and in section 6.4 he presents a table of skin
> depth for copper, but
> then in question 6.2 he asks for the skin depth of steel
> - and the numbers for
> the skin depth are the same. My calculations say
> otherwise and makes sense to me
> since the permeability is different between the
> materials. copper = 1 and
> steel is 1000, that and the conductivity is different
> between the two.
> If you have the text and little or nothing else to
> do could you give
> me the number you come up with? ( in mm's or mils)
> When I'm trying to learn or relearn stuff and I'm
> at odds with the
> various references it just drives me wild and I don't
> have anyone else to confer
> with up here. One is torn between the I'm right response
> and the author's
> obvious authority on the subject.
> Thanks
> Befuddled (Gary)
>
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