I am finding it impossible to get a bandstop filter to work. I have 120Hz unfiltered output from a DC motor drive, that I very much would like to eliminate to clarify the current/torque driving the motor. Windows 7, 2204A, Picoscope 6.13.6 . I used the wizard multiple times. The setting is basically "bandstop(A,100, 140)" voltage setting -.05V +.05V. I started off using a much narrower band and widened it to the above setting to hopefully get some results. I can't see the difference between the raw data and the filtered. I have repeatedly checked the 120 Hz using Picoscope.
The Math Channel filters have a 20dB per decade roll-off so you are not going to be able to differentiate between a signal and unwanted distortion/noise if they are too close. For example, if you have a signal at 100Hz and you're attempting to reduce induced interference modulating your signal at 10Hz and noise beyond 1kHz corrupting the signal then you will be able to reduce them by 20dB.
In your case it appears that you have signal components extending up to 2.5Hz or almost 8Hz (depending upon whether the almost 8Hz component is a desired part of the signal), while the 120-ish Hz signal that you want to eliminate is more than a decade above the almost 8Hz component signal. So I'm not quite sure why you would want a bandstop filter (unless you want to also keep what looks like noise at frequencies above 1kHz).
So if you want to remove the 120Hz signal then you would get a reduction of about 20dB using a lowpass(A,12) for only a slight reduction in the signal. You could also use the lowpass filter in the input channel options (if it is available for your PicoScope) which would give you the same result (as shown in the attached psdata file).
If you also want to remove the almost 8Hz component as well then you would need to drop the cut-off further as in the first reply, but then you would loose the component at 2.5Hz (or most of it).