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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: 12940     Entry time: Wed Apr 12 00:36:53 2017     In reply to: 12939     Reply to this: 12944
Author: gautam 
Type: Update 
Category: PSL 
Subject: PMC demod moved off servo board 

Here is a more detailed comparison of the spectra of the signals at the front panel DAQ LEMO output, measured with the Agilent analyzer. I've left the scale linear, it looks like when the demodulation is done on the servo board, the 1x, 3x and 5x harmonics of the 35.5MHz modulation are clearly visible. I also plut in a plot of the spectra when both the PD and LO inputs to the servo board are terminated (and so the PMC is unlocked), but with the HV In and OUT of the servo board still connected. In this case, the higher harmonics vanish, but a 35.5MHz peak of ~-50dBm remains. Since this is present with no input to the servo board, this must be direct pickup from the nearby LO board? 

In any case, it looks like many of the harmonics that are present with the nominal demod setup either vanish or are much more suppressed when the error signal demodulation is done off the servo board yes.


Further down the signal chain, I had noticed sometime last week that the ADC signals for the PMC DAQ channels I set up seemed to saturate around 4000 counts. Rana mentioned that the ADC interface box with LEMO connectors on the front is powered with +/-5V. Valera and co. had simply increased the suppy voltage sometime ago to get around this problem, so I did something similar, and increased the supply voltage to +/- 15V. I then confirmed that the ADC doesn't get saturated by driving the input with a +/-5V signal. So now the amplified AD620 signals from the PMC servo board are better matched to the ADC range. 

Here is an uncalibrated spectrum (taken with IMC locked), compared to the current ADC noise and signal levels before the AD620s were given gain.

I now need to think a little about what exactly the control scheme would be if the PMC is used as a reference for the IMC over some frequency range...

 

Attachment 1: PMC_digitalSpec.pdf  92 kB  Uploaded Wed Apr 12 01:48:10 2017  | Hide | Hide all
PMC_digitalSpec.pdf
Attachment 2: PMC_DAQ_spectra.pdf  64 kB  Uploaded Wed Apr 12 12:07:34 2017  | Hide | Hide all
PMC_DAQ_spectra.pdf
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