What is the fastest way to calculate the rms voltage from a large voltage measurement file?

[davewilson]

I have collected voltage measurements for a 60Hz waveform and would like to calculate the RMS voltage in order to determine voltage drift. The data was collected at 100KHz and the TDMS file is 4 hours long (a huge amount of data!). I have run the RMS tool in the basic mathematics block with small sets of data successfully, but the large set seems to take forever to run (48 hours so far and it hasn't finished yet).

1. Is there a faster way to analyze this much data?

2. How does the "one sided interval width" affect my results and analysis time?

3. Can I calculate the RMS voltage with FFT?

4. Is there a way to redce the size of my data file to a manageable size file so the RMS function will run quickly, yet maintain accuracy?

[Otmar]

Dave,

Just a quick thought:

Have you tried using the 64-bit version of DIAdem? It has access to more memory and might run your calculation faster.

You can download the DIAdem 2015 64-bit BETA version at www.ni.com/beta

    Otmar

[davewilson]

The computer I have been trying to run the RMS analysis on has Diadem 2012 on it. I will try upgrading to 2015 this weekend and see what happens.

[Brad_Turpin]

Hi davewilson,

You can use the "Calculate RMS" function in the "Basic Mathematics" group in the ANALYSIS panel, if all you want is the time series RMS value-- that will take much less time and memory than returning FFT amplitudes scaled in RMS.

Brad Turpin

DIAdem Product Support Engineer
National Instruments

[Pesmith8]

Hi Dave,

Just a thought, If you have a 60 Hz signal, then the 100 Khz is way overkill for the sampling rate,   If you would resample the waveform at  say 20 X 60 hz= 1200 Hz you should have the same details  that would be in the 100 Khz sample signal.  That should take substantially less time to do a RMS calculation on the resampled channel. The two commands are listed below. 

ChnResampleChnBased

ChnResampleFreqBased

Paul