Frequency to voltage convertor using a sound card and Labview

[Moxica]

Goog morning,

I need to get (to plot) the dependence between two signals and for that I want to use our beloved Labview. I intend to convert the original signals in frequency modulated signals (using 2 hardware voltage-frequency convertors) and after that I feed them in Labview using the laptop soundcard. I managed to foound that I can aquire the signal from the sound card by using the AcquireSound.VI, but I don't know how I can get an .VI that take the signal from the AcquireSound.VI and gives me an ("analogue") signal proportional with the frequency of the original signal.

I tried to feed the aquired signal (the output of the Acquiresound.VI) intro the Tone Measurements.Vi because I saw that I has a "Frequency" output. I connected a numerical indicator to that output and it work, it show me the frequency of the original signal, but when I use the "Wrire Measurement File.VI" to save the frequency readings, in the acquisition fine I always find only one row of data: the first frequenncy measurement..

Whould you be kind to give me some ideas about how can I get an frequency to voltage conversion that works continuously during the data acquisition ?

Regards,

Ciprian

[Vijay_J]

Not able to understand the issue from the description. Can you please put a pictorial representation of your system and short description of the issue? 

Frequency modulation is different from Voltage to Frequency Converter and vice versa.

[Moxica]

I attached a block drawing that should make you understand better what I try to do.

[Vijay_J]

You will have to implement the inverse logic of “Hardware voltage to frequency conversion”

I assume the “Hardware voltage to frequency conversion” gives the frequency range output with the fixed amplitude from the range of voltage input. Example: 20-3000 Hz for 0-5V range input.

Form the first order linear equation with the above inputs

X1=20, X2=3000

Y1=0, Y2=5

Y=mX+C, m= slope, C=Intercept

m= (Y2-Y1)/(X2-X1) after finding m

C= Y2-(mX2)

In this case you will have to extract the single tone frequency with the highest amplitude (You can use Extract Single Tone Information VI). Feed that the above equation and it will give you proportional voltage output.

In case if the “Hardware voltage to frequency conversion” produces the frequency modulation. You need to know the exact method and demodulate the signal.

Hope this helps.

[Moxica]

Thank you !

I already solved the problem by intersting the right settings in the Write to Measurement File.VI settings window.