uw-labview/week7 — pull request #9 by huongnvo (2014-12-05 21:37:28+00:00)
Title: Files needed to run the experiment and analyze the waveform

Finished homework for week 7! -- Huong Vo and Reina Kato
container.vi is the main file that includes the fourier transfer and the analysis of the frequencies.
week7fft.vi is the file that generates the frequencies.
Questions --
1.	What is the effect of the pulse width on the experiment? Try settings like 0.1, 1.0, and 10 msec. Report your observations in your documentation.
0.1msec = lower fft amplitude (+/- ~12V)
1.0msec = High fft amplitude (+/- ~90V)
10msec = Very high fft amplitude (~ +175V)
As we increased the # of milliseconds, the amplitude of the fast fourier transform graph increased.
2.	What is the effect of the acquisition rate? Try settings like 1000, 10000 and 100000 points per sec. Also note what the minimum buffer size and scan rate is needed to describe the response up to 2000 Hz.
All the regular amplitude vs time graph looks pretty similar. However the fft graph looks totally different.
Measured frequency between 0 and :
1000 =fft amplitude went up to about only 0.6V. Fft is symmetric about 500Hz
10000 = fft amplitude between 3.5V ~ -3V, and it gets smaller. Fft is symmetric about 5000Hz.
100000 = fft amplitude goes up to +/- 30V. Fft graph is symmetric about 50000Hz.
So we see that increasing the acquisition rate increases the frequency given from the fourier transform.
The minimum scan rate needed to describe the response up to 2000Hz is 4000Hz because according to Nyquist theorem we should have about 2 times the frequency that we want to obtain. The minimum buffer size will be 2000 Hz
3.	Try the effect of signal averaging on the appearance of the power spectrum. For this experiment, reduce the gain of the audio amplifier until the signal is barely detectable.
When we averaged, the graph became too noisy to recognize and detect any changes or shape on the graph.

When you run the container for the analysis of the frequencies, there's a path dependency in there that should be changed. The data we analyzed is included in the repository, called dataforanalysis, which is already clipped in order to analyze the range of frequencies we wanted.