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.