If I want to estimate the rms noise of a DC signal, like a DC offset reading of an analog transducer sampled at a certain frequency.
So imagine I used the anti-aliasing filter correctly and and fed the DC output to a a 16-bit ADC and sampled it for 30 seconds and recorded samples of this DC analog signal.
Now since we can plot the data or make analysis of this logged DC by using the samples, my question is about estimating the rms noise of this sampled data of the DC input.
I call the sampled DC signal as s[n] or simply s. The mean of the signal as I call mean(s). And rms of the signal is rms(s) and standard deviation of the signal as stdv(s).
Now if I want to estimate the rms noise which one below is more convenient to use and why?:
1) rms noise = rms(s-mean(s)) ? (Should I subtract the mean value even if I short the ADC inouts+)
2) rms noise = stdv(s) ?
Are the above equivalent? If so, which type of standard deviation is this?