Problem with RMS value in DAQExpress

[Zalac]

Hello everyone,

I tried to perform a RMS calcul from a simulated voltage analog imput [-10V;10V] but when I simulate my VI, the RMS value displayed on the panel fluctuates which isn't normal in my opinion : i need a constant value of 10/sqrt(2) = 7,07 V, eventhough the signal fluctuates, no ? 

Is it because of the duration of my simulation (=0,1s) which causes the problem, or because of the while loop ? 

I attached several images of my VI to illustrate my problem.

[BennyBenson]

Hi Zalac,

The reason that you're seeing it fluctuate is because the RMS value is being calculated each iteration of the loop, and it's not capturing an entire sine wave. If you were to change the duration to where it's able to complete the calculation on an entire sine wave or at least half, then you'll see the expected values. It may not be the exact 7.07, but it'll be close.