Python High Pass Filter
<p>I implemented an high pass filter in python using this code:</p>

<pre><code>from scipy.signal import butter, filtfilt
import numpy as np

def butter_highpass(cutoff, fs, order=5):
    nyq = 0.5 * fs
    normal_cutoff = cutoff / nyq
    b, a = butter(order, normal_cutoff, btype='high', analog=False)
    return b, a

def butter_highpass_filter(data, cutoff, fs, order=5):
    b, a = butter_highpass(cutoff, fs, order=order)
    y = filtfilt(b, a, data)
    return y

rawdata = np.loadtxt('sampleSignal.txt', skiprows=0)
signal = rawdata
fs = 100000.0

cutoff = 100
order = 6
conditioned_signal = butter_highpass_filter(signal, cutoff, fs, order)
</code></pre>

<p>I am applying this filter on a 100 kHz voltage signal and it works fine for cutoff frequencies >= 60 Hz. But it doesn't work below. I would like to cut off all the frequencies below 10 Hz. Any hints where my mistake is? What I observed is the lower the order of the filter the lower the cutoff frequency could be. </p>

<p><a href="https://www.dropbox.com/home/Turbulence%20Spectrum" rel="noreferrer">The sample Signal can be found here.</a></p>