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Fri Dec 8 23:31:31 2017, johannes, Frogs, ASS, c1ass slow channel offloading scripts with small
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Wed Dec 13 09:49:23 2017, johannes, Update, ASS, wiring diagram
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Thu Dec 14 00:32:56 2017, johannes, Update, ASS, Acromag new crate; c1auxex2 configured as gateway server for acromag 
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Thu Dec 14 23:27:46 2017, johannes, Update, DAQ, aux chassis design   
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Tue Jan 9 00:07:03 2018, johannes, Update, DAQ, etmx slow daq chassis
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Wed Jan 10 22:24:28 2018, johannes, Update, DAQ, etmx slow daq chassis
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Thu Jan 11 09:57:17 2018, Steve, Update, DAQ, acromag at ETMX
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Thu Jan 11 20:59:41 2018, gautam, Update, DAQ, etmx slow daq chassis
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Wed Jan 17 14:32:51 2018, gautam, Update, DAQ, Acromag checks
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Wed Jan 17 22:44:14 2018, johannes, Update, DAQ, Acromag checks
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Sun Jan 21 13:11:25 2018, johannes, Update, DAQ, Acromag checks
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Fri Jan 12 10:02:05 2018, johannes, Update, DAQ, etmx slow daq chassis
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Fri Jan 12 19:15:34 2018, johannes, Update, DAQ, etmx slow daq chassis
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Wed Jan 24 18:12:31 2018, johannes, Update, DAQ, ETMX auxiliary DAQ work   
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Wed Jan 24 19:17:06 2018, johannes, Update, DAQ, c1auxex2 startup behavior
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Wed Jan 24 23:13:30 2018, johannes, Update, DAQ, c1auxex2 startup behavior
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Thu Dec 14 19:33:20 2017, gautam, Frogs, ASS, c1ass slow channel offloading scripts with small
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Message ID: 13470
Entry time: Fri Dec 8 23:31:31 2017
Reply to this: 13471
13476
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Author: |
johannes |
Type: |
Frogs |
Category: |
ASS |
Subject: |
c1ass slow channel offloading scripts with small |
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While staring at epics records all day I noticed something about the PIT/YAW offset sliders and ASS offset offloading to slow channels scripts that I'm not sure others are aware off, so I'll briefly discuss it in this post.
The PIT and YAW sliders directly control soft channels that are hosted on the slow machine. Secondary epics records disentangle them for the individual coils:
- UL = PIT+YAW
- LL = -PIT+YAW
- UR = PIT-YAW
- LR = -PIT-YAW
These channels are the direct input for the physical output channels that generate the control voltage.
The fast channels for PIT and YAW have a numerical correction factor built in that accounts for differences between the OSEMs, but the slow channels don't. This means that the slow PIT/YAW controls are not entirely orthogonal but have crosstalk on the order of 10 percent. This in itself is not that dramatic, however the offload offsets scripts for the dither alignment use the fast PIT/YAW values as inputs, which represent the necessary adjustments to the OSEMs only after the individual correction factors have been applied. The offloading to slow knows nothing of this calibration difference between the OSEMs. The result is that there is a ~10 percent of the offset correction error on the mirror alignment AFTER offloading. This will of course converge after a few iterations, but in any case it is recommendable to run the dither alignment again after offloading and not offload the new offsets to the fast channels. |