import numpy
from matplotlib.pyplot import *

[t,u0,u1] = numpy.loadtxt("signal-fe100kHz.txt")

figure()
plot(t,u0)
plot(t,u1)
grid()
xlabel("t (s)")
ylabel("U (V)")
axis([0,1e-2,0,5])
            

import numpy.fft

ne=u0.size
te=t[1]-t[0]
fe=1.0/te
A=numpy.absolute(numpy.fft.fft(u0))/ne
f=numpy.arange(ne)*1.0/(ne*te)

figure()
plot(f,A)
xlabel("f (Hz)")
ylabel("A")
grid()
            

axis([0,2000,0,2])
            

delta_f=fe/ne
k1 = int(100.0/delta_f)
k2 = int(1000.0/delta_f)
k = numpy.argmax(A[k1:k2])+k1
f0 = k*delta_f
            

[t,u0,u1] = numpy.loadtxt("signal-fe10kHz.txt")

figure()
plot(t,u0)
plot(t,u1)
grid()
xlabel("t (s)")
ylabel("U (V)")
axis([0,1e-2,0,5])
            

ne=u0.size
te=t[1]-t[0]
fe=1.0/te
A=numpy.absolute(numpy.fft.fft(u0))/ne
f=numpy.arange(ne)*1.0/(ne*te)

figure()
plot(f,A)
xlabel("f (Hz)")
ylabel("A")
grid()
            

axis([0,2000,0,2])
            

delta_f=fe/ne
k1 = int(100.0/delta_f)
k2 = int(1000.0/delta_f)
k = numpy.argmax(A[k1:k2])+k1
f0 = k*delta_f
            

R1=R2=8.2e3
C1=1.44/((R1+2*R2)*f0)
            
f0=605.8

capa = numpy.loadtxt("capa-3.3nF.txt")   
figure()
plot(capa,'.')
xlabel("n")
ylabel("C (nF)")
axis([0,100,0,5])
grid()