How can I extract the frequency of a (possibly noisy) signal?

[PaulieQ]

You can't have a graphical indicator in Block Diagram! Only in Front Panel!.

You can make a subVI from a VI. You have to assign the inputs and outputs and it's ready to be Inserted in another VI (my LabView is not in English so it's hard for me to tell you exactly what you have to choose from the menus).

[johnsold]

Paul's moving average filter performs very much like a 2-pole Butterworth low pass filter with a cutoff frequency of 0.05*fs, where fs is the sampling frequency.  I have not worked through the theory, but I built a VI with a filter subVI and tested.  His filter is what I was suggesting.

The white trace is the moving average (10 point) and the blue trace is the Butterworth filter.

Lynn

[Baran]

Looks very nice. I don't know why for some reason it changes the amplitude of the signal for me, but that is constant, so I can amplify it. I am just wondering why is it behaving like that at  the end!

Thanks you both! 

[johnsold]

I did not explore it in detail.  I suspect that some phase shift at the higher frequencies is not the same.  The filters are not identical from a theoretical point of view although they are similar.

The key point for this discussion is not what kind of filter you have, but whether something you can implement fairly simply in the Base version of LV will work for you.

Lynn

[Baran]

yeah. I guess I can use this one. looks pretty neat to me. 

Thanks.