Solving Differential Equation - getting strange results.

Hi, i am using LabView to model the mathematic pendulum which comes down to solving the quation numericaly:
where w is constant and 0 is an angle between the pendulum's cord and the vertical which i want to plot against time. I built this very simple model to solve this equation (this is what our teacher showed us) [x is the angle]
and this is what i get:
"fi" is the starting angle. The result is a cosine , as it is to be expected, with the right period, but why the amplitude is so low? Am i missing something here? No matter how i change the initial value, the amplitude is always 5 oders of magnitude lower. It wouldnt be a problem, since what we are required is to solve the equation, but when i want to factor that in the equation above 0 should be sin0 , the problem arises - sinx for so low x , is...x. So my questions are:
- am i setting the initial conditions wrong?
- has the value of dt anything to do with it?
- is the method correct?
- am i clueless?
A week ago i had no idea what LabView is. We were all thrown into the deep water, we were shown the method, but were not teached how the LabView works,so please, be kind.
Thank You in advance .
Attachments:
pendulum.vi ‏14 KB

Hello;
Noise is a difficult issue to advise about.
There are some things you can try, but the result will depend on different factors, such as, environment, lenght of cables, equipment on vicinity, etc.
Anyways, you can try to hook up a BIAS resistor in between the ch- and AIGND on your BNC device. That resistor will bleed out the common voltage current and help on noise balancing. Another thing you can try is to hook up a simple RC low pass filter at the analog input. That might help to get rid of that noise.
I'm also attaching an App Note that talks about Noise and some ways to get around it.
Hope this helps.
Filipe A.
Applications Engineer
National Instruments
Attachments:
Field_Wiring_and_Noise_Considerations.zip ‏196 KB

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Hi!!
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explore the following link.
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Solving Differential Equation - getting strange results.

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