‎07-13-2009 06:13 AM
I am trying to do 'online' uncertainty calculations for my measurements whilst my experiment is running. I have a mathscript node which works out all the systematic uncertainties. I also need to get the random uncertainties, and to do this I've got a separate loop running which does a running average, RMS and standard deviation of the mean (SDOM = RMS / sqrt(N)) calc. So far I've been doing this 'manually' using a shift register. However I know that the 'Basic DC/RMS' and 'Average DC/RMS' vi's would probably be an easier way to do this, certainly to get the mean and RMS. However does anyone know how I would extract the SDOM using these vi's? In order to do so I would need to know the number of data points (N) over which the mean and RMS had been calculated by the vi. Help!
‎07-13-2009 06:17 AM
Is 'Array Size(s)' what you're looking for?
Felix
‎07-13-2009 06:21 AM
‎07-13-2009 06:39 AM
Why would you need to hack into the vi? You can get the number of points by the array size function, use the sqrt funtion and dived the RMS output by that value.
Felix
‎07-13-2009 06:46 AM
‎07-13-2009 06:50 AM
But the input of RMS/DC.vi is an array. Or how else the 'N' is defined?
Felix
‎07-13-2009 08:09 AM
‎07-13-2009 01:11 PM
From the help
default is –1.00, corresponding to average time = input block duration.
Felix