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Message ID: 207     Entry time: Tue Nov 22 08:21:35 2016
Author: Gabriele 
Type: Electronics 
Category: Characterization 
Subject: ADC saturation 

Last night measurements didn't work well: even without exciting the modes, the ADC was saturating because of the low frequency signal, particularly a 58 Hz peak:

When the modes were rang up, thing got clearly even worse:

Modification of whitening filter

So I modified the whitening filter, changing C6 from 2.2u to 220nF. The old and new whitening filters are shown below. We have the same amount of whitening at high frequency, but less amplification of the junk at ~50-100 Hz

With this modification, there's no more saturation, even when the modes are excited.

Attachment 1: saturation_1.png  48 kB  | Hide | Hide all
saturation_1.png
Attachment 2: saturation_2.png  78 kB  | Hide | Hide all
saturation_2.png
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