how to get rms value of acqiured signal

[ifyo]

hi,

  can any one tell me how i can get the rms value of the  the acquired signal from the AI votage rms. find attached my vi

[NIquist]

What is wrong with the RMS value you're already calculating with the Express VI?  Is it not returning a proper value?

[ifyo]

thanks for your reply Niquist, i am not getting the right rms value. what can i do to start getting the right values

[Dennis_Knutson]

You've configured the DAQmx Read to return the RMS value and then you are taking the RMS value of that? Why?

[ifyo]

thankks dennis for your reply, what i  actually want to do is to be able to acquire the rms voltage  values of the signals that the function generator is generating  once i start the lab view program. i am sweeping the signal generator wave form from 100 hz to 1MHZ.

[Dennis_Knutson]

And I asked why you were taking the rms value of the rms value returned by the DAQmx Read. Either eliminate the express measurement function or set the DAQmx Read to return the absolute voltage.

[ifyo]

thanks dennis for your reply, can u show me how to do what you just said by including it to the vi i attached.

[NIquist]

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@ifyo wrote:

thanks dennis for your reply, can u show me how to do what you just said by including it to the vi i attached.

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You really should try and learn to do this yourself, it's very basic stuff:  The DAQmx Create Channel is set to AI Voltage RMS, change it to AI Voltage.

[Dennis_Knutson]

What do you mean? You are the one that configured the DAQmx Create Channel for RMS instead of the default of volts and you are the one who inserted the measurement function onto the block diagram. You don't know how to delete a function or now you don't know how to select a different DAQmx Create Channel?

I'm posting from my phone right now and cannot edit your VI but this should not be something you need help with (assuming you wrote the VI in the first place).

[ifyo]

thanks dennis and niquit, i have changed it, but the rms values i am getting are strange, instead of getting a decreasing rms value, i am getting an incrasing rms value, whhich will not give me the cut off point of the gain bandwidth product of an op amp. find attached my data