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Entry  Fri Sep 4 00:58:29 2015, rana, Update, CDS, soldering the Generic Pentek interface board 
    Reply  Fri Sep 4 08:00:49 2015, Ignacio, Update, CDS, RC low pass circuit (1s stage) of Pentek board circuit.pdfcircuit.png
       Reply  Fri Sep 4 09:23:32 2015, Ignacio, Update, CDS, Modified Pentek schematic schematic.pdf
Message ID: 11570     Entry time: Fri Sep 4 00:58:29 2015     Reply to this: 11573
Author: rana 
Type: Update 
Category: CDS 
Subject: soldering the Generic Pentek interface board 

Q and Ignacio were taking a second look at the Pentek interface board which we're using to acquire the POP QPD, ALS trans, and MCF/MCL channels. It has a differential intput, two jumper able whitening stages inside and some low pass filtering.

I noticed that each channel has a 1.5 kHz pole associate with each 150:15 whitening stage. It also has 2 2nd order Butterworth low pass at 800 Hz. Also there's a RF filter on the front end. We don't need all that low passing, so I started modifying the filters. Tonight I moved the 800 Hz poles to 8000 Hz. Tomorrow we'll move the others if Steve can find us enough (> 16) 1 nF SMD caps (1206 NPO).

After this those signals ought to have less phase lag and more signal above 1 kHz. Since the ADC is running at 64 kHz, we don't need any analog filtering below 8 kHz.

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