I am using the lock in amplifier kit and sort of sending some of the parameters manually. I choose manually the low pass filter.
Now I find strange behavior depending on the filter I choose.
The lock in results oscillates in time, the higher the dB roll off the longer it seems to take to stabilize. Also the frequency of the oscillations becomes lower. This I don't find too weird, the problem is that it just won't stop.
If I use a small time constant and there is no real change in my signal I can easily follow the shape of the the oscillations.
If I use a larte time constant it seems there is an average over the oscillation and then it looks as if it was noise.
All the time my signal has not changed one bit.
This is very anoying since it produces about 20-300microV of noise. (peak to peak amplitude of the oscillations)
So far I've gotten the best results with the IIR (5dig) with 40dB roll off and order 1
Does anyone have an idea of what to do?
