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Message ID: 220     Entry time: Tue Jun 21 13:32:02 2011
Author: Larisa Thorne 
Type: DailyProgress 
Category: Crackle 
Subject: Q and dampening measurements 

 We went down to the SUS lab and ran some tests to get measurements we could use to calculate the Q and b (dampening factor/constant?) of the blade springs.

 

The setup was fairly simple (see attachment below): a laser beam was set up such that its path to a photo diode would be interrupted by the movement of a mass (which was attached to the spring blade). The resulting wave function as seen through an oscilloscope hooked up to the PD would give us the necessary data to calculate Q and b.

Given these sets of data, we can reference (this) to find that Q=4.53 f0 T1/2. Here T1/2 is the "decay by half life of amplitude", or the time it takes for the amplitude to be half of when it begins, and can be checked by plugging into the equation and seeing if the resulting expression is true: Amplitude( T1/2)/ Amplitude(t@0) = 1/2 .

 

 

 

 

TO DO list:

 

 

-- Take the oscilloscope data and figure out how to calculate  T1/2, so that Q can be calculated

-- Think about how to calculate b

 

 

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