Making RMS measurments of noise

[lmc]

My input an amplified voltage noise signal. I want Labview to take 1000 samples (say) of this noise signal and return the average of the 1000 samples as an RMS value - and stop there! How do I get Labview to do this ? Thanks.

[johnsold]

RMS is defined as the square root of the mean of the squares. Take your 1000 samples, square them, calculate the mean (sum divided by number of samples) and take the square root of the result.

The average of the samples is just that - the average; it is not the RMS value.

Lynn

[johnsold]

Also, look at the Analyze Palette for RMS functions.

Lynn

[lmc]

Thanks. As a LabVIEW novice though I was more looking for a lower-level answer regarding the best way to do what you describe above. My guess, would be that reading the 1000 samples into an array would be the way to proceed ?..

[johnsold]

Yes. Put the samples into an array as they are acquired. If you are doing the acquisition in a loop you can enable indexing at the tunnel where the data leaves the loop and it will automatically create an array of the data. For loops have this auto-indexing enabled by default and while loops have it disabled. Either can be changed by popping up on the tunnel.

There are other ways which also work and may be better if arrays get very large or memory allocation and speed become an issue. Autoindexing will get you started.

Lynn

[lmc]

Yep - seems to be working fine, thanks for the help!