Generating, acquiring signals looping over frequencies

[studengineer]

Hi,

I am a novice to labview and I am trying to design a VI that can: generate a desired signal, measure an external signal (e.g from a signal generator) and also possibly convert an external signal sample into its phasor equivalent (or real and imaginary parts). Having achieved that, i wish to be able to measure these over a range of stepping frequencies. the aim of this is to be able to somehow compute the complex impedance of the load using a simple voltage divider rule.

Vl = Vs * Z/(R+Z)

and then i would like to plot Z vs freq. and look at the results. Any help with any part of this project will be much appreciated.I am working with labview 8 and a BNC 2110.

- Generate signal

- Acquire/Measure external signal

- Convert measured signal into complex form

- measure Vl, Vs and Z over a range of frequencies

- plot Z vs f

Thanks!

Charles

[sparkysquared]

tmobile,

     If I'm correctly understanding what you're trying to do, it should be pretty simple. You can use a DAQ Assist to pull in the signal from your BNC 2110. For the generated signal you can use another DAQ Assist, or use the Simulate Signal VI. To convert the signals to their phasor equivalents use the Spectral Measurements VI, or Dual Channel Spectral Measurement VI depending on your desired interaction of the two signals. Then plug in the values to your voltage divider equation and place the Z and frequency values into an array. Finally, graph the array and you should be good to go.

--Ryan

[studengineer]

Thank you so much for your quick response. I will update you on my progress shortly.

Charles

[studengineer]

I have been able to sucessfully acquire and generate signals using the DAQ Assist. but I am having troubles getting the phasor equivalent. I tried using the spectral measurements VI but it did no twork and then I tried using the Dual Channel Spectral Measurement VI and it gives an error saying that the 'the two time signal waveform contain different dt' (error- 20306). I have not been able to fix this so far. Please help!

Please find attached my humble progress

Charles

[studengineer]

I am also thinking of using a 'script'like function to convert to real and imaginary.

Please view the attached wordfile to see what I am trying to describe.

 Charles

[Beutlich]

Have you tried using the VIs in the Signal Processing»Waveform Measurements Palette? In particular, one of the VIs, NI_MAPro.lvlib:FFT Spectrum (Real-Im).vi, it allows you to send in a waveform data type and returns the real and imaginary components. You may need to use a Convert from DDT Express VI (Express»Signal Manipulation»From DDT), but the FFT Spectrum does cast the dynamic data to waveform at the terminal which may give you the results you are looking for, so play around with it.