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Entry  Mon Mar 27 20:41:21 2017, rana, gautam, Update, PSL, PMC DAQ assay for feed-forward integration TEK00000.PNG20170327_194931.jpg20170327_204554.jpg
    Reply  Wed Mar 29 11:41:19 2017, gautam, Update, PSL, PMC DAQ assay for feed-forward integration C1ALS_PSLnamespace.pngPMCcheckout.pdfD980352-A-40m_151119.pdf
       Reply  Thu Mar 30 00:16:09 2017, gautam, Update, PSL, PSL NPRO PZT calibration 
          Reply  Mon Apr 3 17:25:13 2017, gautam, Update, PSL, PSL NPRO PZT calibration PDHerr.pdfNPROcalib.pdf
             Reply  Tue Apr 4 17:27:58 2017, rana, Update, PSL, PSL NPRO PZT calibration 
       Reply  Thu Mar 30 18:11:01 2017, rana, Update, PSL, PMC DAQ assay for feed-forward integration 
          Reply  Mon Apr 3 23:07:09 2017, gautam, Update, PSL, PMC DAQ assay for feed-forward integration 
             Reply  Tue Apr 11 00:38:37 2017, gautam, Update, PSL, PMC demod moved off servo board PMC_Ctrl_spec.pdf
                Reply  Wed Apr 12 00:36:53 2017, gautam, Update, PSL, PMC demod moved off servo board PMC_digitalSpec.pdfPMC_DAQ_spectra.pdf
                   Reply  Tue Apr 18 01:01:03 2017, gautam, Update, PSL, PMC OLTF measured, DAQ channels calibrated PMCspectra_calibrated.pdfPMC_MEDMs.png
                      Reply  Tue Apr 18 16:10:00 2017, gautam, Update, PSL, PMC OLTF measured, DAQ channels calibrated PMC_OLTF_170418.pdf
                         Reply  Tue Apr 18 23:37:15 2017, rana, Update, PSL, PMC OLTF measured, DAQ channels calibrated 
                         Reply  Wed Apr 19 15:13:30 2017, gautam, Update, PSL, PMC/MCL multicoherence PMC_MCL_multicoherence.pdf
Message ID: 12916     Entry time: Wed Mar 29 11:41:19 2017     In reply to: 12911     Reply to this: 12918   12920
Author: gautam 
Type: Update 
Category: PSL 
Subject: PMC DAQ assay for feed-forward integration 

The C1IOO frontend machine that resides in 1X1/1X2 has 2 ADCs, ADC0 and ADC1. The latter has 28 out of 32 channels unused at the moment, so I decided to use this for setting up fast channels for the PMC DAQ. On the RTCDS side of things, the PSL namespace block lives in the C1ALS model. I made the following modifications to it:

  1. Added channels for the PMC DAQ
  2. Added CDS filters for both the newly added PMC DAQ channels and the existing FSS DAQ channels, so that we can calibrate these into physical units
  3. Changed the names of the existing FSS channels from FSS_MIXER and FSS_NPRO to FSS_ERR and FSS_CTRL. The latter is still a bit ambiguous, but I felt that FSS_CM_BOARD_CTRL was too long. 
  4. Added DQ channels for the new PMC channels. These are recording at 16K at the moment, but since we have the fast testpoints courtesy of the CDS filter modules for diagnostics, perhaps the DQ channels need only be recorded at 2K?

The PSL namespace block in C1ALS looks like this now:

I then tried hooking up the DAQ signals from the PMC servo board to the ADC via the 1U generic ADC interface chassis in 1X2 - this has 4pin LEMO inputs corresponding to 2 differential input channels. I used J6 (corresponding to ADC channels 10 and 11) for the PMC_ERR and PMC_CTRL respectively. I was a little confused about the status of the 4 pin LEMO output on the front panel of the PMC servo board. According to the DCC page for the modified 40m servo board, the DAQ outputs are wired to the backplane connector instead of the 4 pin LEMO. But looking at photographs on the same DCC page, there are wires soldered on the rear-side of the PCB from the 4-pin LEMO to the backplane connector. Also, I believe the measurements made by Rana in the preceeding elog were made via the front panel LEMO. In any case, I decided to use the single pin LEMO monitor points on the front panel as a preliminary test. The uncalibrated spectra with ADC terminated, IMC unlocked and IMC locked look like:

So it looks like at the very least, we want to add some gain to the AD620 instrumentation amplifiers to better match the input range of the ADC. We also want to make the PZT voltage monitor path AC coupled. My plan then is the following:

  1. Figure out what is going on with the 4-pin LEMO connector on the front panel - is it connected to the DAQ monitor points or not?
  2. Ground pin 5 of U15 (this has already been done by Koji for U14 according to the DCC page)
  3. Add a resistor between pins 1 and 8 of U14 and U15 to get some gain. According to the datasheet, a 1k resistor will give a gain of 50, which for U15 will mean that we undo the existing 1/50 attenuation. Of course we need to AC couple this path first by adding a capacitor in series with R14. 
  4. Figure out where the RF harmonics are coming from and what is the best way to attenuate them.

I will update with a circuit diagram with proposed changes shortly.

Proposed changes:

  1. Cut PCB trace between R14 and R13, install capacitor - what is is correct type of capacitor to use here? I figured installing a series capacitor after the resistive divider, to the input of the instrumentation amplifier avoids the need for a HV capacitor, so we can use a 1uF WIMA capacitor.
  2. Add gains to U14 and U15 (error and control signal monitors respectively). Based on the uncalibrated spectra attached, I think we should go for a gain of ~50 for U15 (1kohm between pins 1 and 8), and a gain of ~200 for U14 (250ohms between pins 1 and 8).

The PCB layout is such that I think using components with leads is easier rather than SMD components.

If this sounds like a reasonable plan, I will pull out the servo card from the eurocrate and implement these changes today evening...

Attachment 2: PMCcheckout.pdf  97 kB  Uploaded Wed Mar 29 12:48:43 2017  | Show | Show all
Attachment 3: D980352-A-40m_151119.pdf  190 kB  Uploaded Wed Mar 29 17:36:09 2017  | Show | Show all
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