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Entry  Fri Sep 20 12:55:02 2019, gautam, Update, CDS, c1iscaux testing 
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                   Reply  Tue Oct 8 03:32:42 2019, Koji, Update, CDS, CM servo board testing 7x
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                            Reply  Mon Oct 14 16:06:28 2019, Koji, Update, CDS, CM servo board testing pole_zero_filter.pdf
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Message ID: 14965     Entry time: Mon Oct 14 16:06:28 2019     In reply to: 14955     Reply to this: 14966
Author: Koji 
Type: Update 
Category: CDS 
Subject: CM servo board testing 

CM Board Slow out (digital length control) path transfer function / pole-zero filter pair (79Hz/1.6kHz) transfer function

The excitation was given from EXC A. The denominator was TESTA2, and the numerator was OUT1.

Attachment 1 shows the measured transfer function with and without PZ filter off and on. The PZ filter provides ~26dB attenuation at  high frequency. The output stage has a single order 100kHz LPF and it is visible in the transfer function.

The transfer function without the PZ filter was modelled by LISO as the following PZK representation. There looked a small step in the TF which caused the additional PZ pair (66~67Hz) but has very minor effect in the mag and phase.

pole 66.2720207366
zero 67.2660731875
pole 93.3044858160k

factor -995.5583556921m

The transfer function of the PZ filter was separately analyzed. The TF with the switch ON was normalized by the one with the switch OFF. Thus it revealed the pure effect of the switch. The PZK model of the stage was estimated to be

pole 79.7312926438
zero 1.6395485993k

factor 996.2196584165m

Attachment 1: pole_zero_filter.pdf  143 kB  Uploaded Mon Oct 14 17:09:14 2019  | Hide | Hide all
pole_zero_filter.pdf
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