A servo accelerometer when powered by batteries has a clean output, but when used with this SMPS supply its output seems like have switching artifacts from the power supply(the datasheet says its switching freq is 100kHz). Now since the desired range is very low I can easily filter out such noise at the sensor output.
But having said that, I want to know what we can say about the noise at the accelerometer output. So by using a digital scope(at AC coupling mode) I made two measurements and logged the time series data for the standing accelerometer output. The first one is for longer period, here is the screenshot:
Then I plotted the time series and FFT of this as follows:
Then I did the same thing for a smaller time scale:
So by having all these information what can we say about the frequency of the switching noise? I'm trying to learn in such a situation how to quantify the switching noise. Should we look at the time series data or the spectrum for that? And for this particular case what steps should one follow?
For a much longer acquisition I observe the following:
MEASURED DIRECTLY AT THE POWER SUPPLY OUTPUT:
Supply Output at 50us scale:
Time series and FFT:
The PSU noise(yellow) directly appears at the sensor output(blue):