I read in sci.electronics.design that Wayne <

[email protected]>

wrote (in said:

Can anyone show by example how to calculate the R and C values if you

have both real and imaginary parts of the impedance Z? I do not have

the R and C values but I have the Z(Real) and Z(Imag).

For R and C in series, R = Z(real) and C = 1/(2[pi]fZ(Imag)). f is the

frequency in Hz; you need to know that. And the results assume sine-wave

signals.

Also is there say

a BASIC program that can say produce the correct R & C values from a

Bode plot?

Not unless you know something else about the impedances. A Bode plot can

only tell you the product RC:

RC = 1/(2[pi]f3),

where f3 is the frequency at which the response is 3 dB down or up. And

this works only if the Bode plot shows a 20 dB/decade ultimate slope,

implying a first-order filter network. You hardly need a program to do

that.

These three equations are just rearrangements of bog-standard elementary

a.c. theory equations. Maybe you need a bit of math brush-up.

To analyse more complex Bode plots, you might need a program, but there

are fairly simple graphical methods that actually give you an *insight*

into how the network is behaving, which is very valuable. I can't give

you any references, but a *good* textbook on Bode plots should deal with

'straight-line approximation', which is the key phrase.