BHS -> Staff -> Mr. Stanbrough ->Pasco Interface Notes-> this page
What can you do? First, you should make sure that the motion detector is not getting reflections from some unwanted object. Try clearing the area, re-aiming the detector, and adjusting the beam (near/far). This probably won't remove all of the "jitters" in the data, but it can help a lot. Beyond that, you can either work around it, or try to fix it.
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To create acceleration vs. time graph shown above:
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The Experiment Calculator window shown above displays a smoothing function applied to motion sensor position data. The "smooth" function is found in the "Special" submenu of the "f(x)" menu, and the "@1.x" is found in the "INPUT" menu. |
Well, doesn't that change the data? Yes, it does. Isn't that somehow underhanded and unsavory, if not downright illegal? Well, no, it isn't. If the "jumps and jiggles" are truly random noise (just about the same number of high and low jumps, etc.), then there is nothing wrong with trying to remove it. Just be sure to:
Science WorkshopTM makes it easy to smooth a data set. In the "Special" submenu of the "f(x)" menu in the Experiment Calculator window you will find the "smooth(n, x)" function. Here, "x" is the data set to smooth, and "n" is the number of points to use in the smoothing operation. How many points should you use? You need to play around with it. Too few, and the data isn't really affected by the smoothing operation, and too many can remove a great deal of the information content. It's a judgment call.
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This graph uses the same data as the graph above, but the original round-trip time data (only) was moderately smoothed (n = 5). |