40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Entry  Fri Dec 8 23:31:31 2017, johannes, Frogs, ASS, c1ass slow channel offloading scripts with small  
    Reply  Wed Dec 13 09:49:23 2017, johannes, Update, ASS, wiring diagram 1Y9.pdf
       Reply  Thu Dec 14 00:32:56 2017, johannes, Update, ASS, Acromag new crate; c1auxex2 configured as gateway server for acromag fp_mod_4U.pdfIMG_20171213_171541850_HDR.jpg
          Reply  Thu Dec 14 23:27:46 2017, johannes, Update, DAQ, aux chassis design auxdaq_40m_4U_front.pdfauxdaq_40m_4U_rear.pdfauxdaq_40m_4U_DSub37x2.pdfauxdaq_40m_4U_IDC50.pdf
             Reply  Tue Jan 9 00:07:03 2018, johannes, Update, DAQ, etmx slow daq chassis 
                Reply  Wed Jan 10 22:24:28 2018, johannes, Update, DAQ, etmx slow daq chassis 
                   Reply  Thu Jan 11 09:57:17 2018, Steve, Update, DAQ, acromag at ETMX Acromg_in_action.png
                   Reply  Thu Jan 11 20:59:41 2018, gautam, Update, DAQ, etmx slow daq chassis 
                      Reply  Wed Jan 17 14:32:51 2018, gautam, Update, DAQ, Acromag checks OSEMPDmon_Acro.png
                         Reply  Wed Jan 17 22:44:14 2018, johannes, Update, DAQ, Acromag checks 
                            Reply  Sun Jan 21 13:11:25 2018, johannes, Update, DAQ, Acromag checks 
                   Reply  Fri Jan 12 10:02:05 2018, johannes, Update, DAQ, etmx slow daq chassis 
                      Reply  Fri Jan 12 19:15:34 2018, johannes, Update, DAQ, etmx slow daq chassis 
                         Reply  Wed Jan 24 18:12:31 2018, johannes, Update, DAQ, ETMX auxiliary DAQ work IMG_20180124_120202019.jpgIMG_20180124_120123064.jpgIMG_20180124_120219278.jpgIMG_20180124_120059765.jpg
                            Reply  Wed Jan 24 19:17:06 2018, johannes, Update, DAQ, c1auxex2 startup behavior 
                               Reply  Wed Jan 24 23:13:30 2018, johannes, Update, DAQ, c1auxex2 startup behavior 
    Reply  Thu Dec 14 19:33:20 2017, gautam, Frogs, ASS, c1ass slow channel offloading scripts with small  
Message ID: 13580     Entry time: Wed Jan 24 23:13:30 2018     In reply to: 13578
Author: johannes 
Type: Update 
Category: DAQ 
Subject: c1auxex2 startup behavior 
Quote:

The result is a smooth transition from idling to the controlled state with no sudden or large offset changes. yes

[Gautam, Johannes]

While checking how smooth the transition is we still noticed significant motion of ETMX by looking at the locked green laser and OpLevs. We found that this motion was not caused by interruption of the slow offset adjust, but rather the Watchdog being re-initialized to its OFF state, which cuts the fast channels OFF. On other optics this is observed too, but not as severe. The cause is a rather large offset on the LR coil coming from the fast DAQ, which was reported as 50mV by the slow readback channel (while other readback values are <10mV). It is present even when turning the output of the CDS model OFF, but vanishes when the watchdog is triggered. This helped us trace it to an offset of the DAC output itself: it is present at the output of the AI board but vanishes when the DAC is disconnected. The actual offset is ~40mV, as opposed to other channels on the same board, which ahve offsets in the range 3-7mV.

While we can compensate for this offset in software - it made us  wonder if the DAC channel is somehow busted and if that's what causing the 'wandering' of ETMX that we have been observing recently. There are two free DAC channels on the AI chassis that has the side coil and the green temperature control signals. We could re-route the LR signal through a different DAC channel to fix this.

gautam: 40mV offset at the AI board output gets multiplied by 3 in the dewhitening board, so there is a 120mV DC offset going to the coil (measured at dewhite board output with DMM). The offset itself isn't hurting us, but the fact that it is several times larger than other channels led us to wonder if it could be drifting around as well. From my SOS pitch balancing forays, in my head I have the number 30mrad as being the full range of the OSEM actuation - so if the offset swings by 120mV, that's ~150urad of motion, which is quite large, and is of the order of magnitude I'm used to seeing ETMX move around by.

ELOG V3.1.3-