LabVIEW

cancel
Showing results for 
Search instead for 
Did you mean: 

Problems in data aquisition, after FFT.

Hi all,
 
I am currently working on a project that requires me to come up with a program that converts a time domain function into a frequency domain function.
 
The project is a simple setup of light tubes, which the intensity is captured by photosensors in voltage/time domain, which I want to make it undergo a FFT into frequency domain.
 
Currently, I am using pure generation of Signal Express formula given to me by seniors. I understand that SE can convert into LV but my objective is to come up something independent of SE, purely LV only.
 
After capturing 30Hz at a sampling rate of 1000/sec up to 2 secs, I will need to collect the data, but the waveform graphs shows me points at per Hz instead of 0.5Hz when I try to get the element out by using array.
 
I would also wish to have some advice on whether I have made any errors in the programming and appreciate all pointers as I just began learning this software.
 
Formula:
v(t) = Vdc*sin(w*t)+ Interharmonics magnitude*a*sin(2*pi* Interharmonics frequency* t )
 
edit : Well, "After FFT2" Wave form shows 0.5 Hz per sample, but FFT3 shows per hertz instead. How do I rectify this problem?

Message Edited by How81 on 07-01-2007 10:09 PM

0 Kudos
Message 1 of 3
(2,439 Views)
The problem is that the FFT2 indicator is displaying the waveform datatype output which includes the timing data. FFT3 is plotting just the 1D array which doesn't include any timing data. To make it display property you need to use the dF output from the FFT to set the graph's XScale.Multiplier property.

Mike...

Certified Professional Instructor
Certified LabVIEW Architect
LabVIEW Champion

"... after all, He's not a tame lion..."

For help with grief and grieving.
Message 2 of 3
(2,430 Views)

Thanks Mike!

It works now. 🙂

0 Kudos
Message 3 of 3
(2,427 Views)