On Thursday, new huddle test data for the Wilcoxon 731A was aquired by Eric.
The difference between this new data and the previous data, is:
1) We used three accelerometers instead of six this time around.
2) We used a foam box, and clamped cables on the experimental set up as shown in the previous elog, http://nodus.ligo.caltech.edu:8080/40m/11389
I have analyzed the new data. Here I present my results.
The following plot shows the ASD's for the three accelerometers raw outputs as well as their error signals computed using the three cornered hat method,
As before, I computed the mean for the output signals of the accelerometers above as well as their mean self noise to get the following plot
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Now, below I compare the new results with the results that I got from the old data,
Did the enclosure and cable clamping do much? Not really, according to the computed three hat results. Also, notice how much better, even if its a small improvement, we get from using six accelerometers and calculating their self noise by the six cornered hat method.
Now, I moved on to analyzing the same data with Wiener Filtering.
Here are again, the raw outputs, and the self noises of each individual accelerometer calculated using Wiener filtering,
The accelerometer in the Y direction is show a kind of funky signal at low frequncies. Why? Anyways, I calculated the mean of the above signals as I did for the three cornered hat method above to get the following, I also show the means of the signals computed with the old data using wiener filtering,
Is the enclosure really doing much? The Wiener filter that I applied to the huddle test old data gave me a much better, by an order of magnitude better self noise curve. Keep in mind that this was using SIX accelerometers, not THREE as we did this time. I want to REDO the huddle test for the WIlcoxon accelerometers using SIX accelerometers with the improved experimental setup to see what I get.
Finally, I compare the computed self noises above with what the manufacturer gives,
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As I expected, the self noise using six accelerometers and Wiener filtering is the best I could work out. The three cornered hat method works out pretty well from 1 to 10 Hz, but the noise is just too much anywhere higher than 10 Hz. The enclosed, clamped, 3 accelerometer wiener filter result is an order of magnitude worse than the six accelerometer wiener filtered result, and two orders of magnitude worse than the three cornered hat method in the 1 to 10 Hz frequency band.
As I stated, I think we must performed the huddle test with SIX accelerometers and see what kind of results we get. |