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Entry  Thu Feb 13 00:25:36 2020, Duo, DailyProgress, , Noisemon at L1 L1DACNoise.zipplot.pdf
    Reply  Wed Mar 11 12:46:20 2020, rana, Computing, Noise Budget, Noisemon at L1 
       Reply  Sat Apr 18 16:21:32 2020, Duo, Computing, Noise Budget, Noisemon:DAC noise analysis from L1 and H1 noisebudget.pdfdiagram.pdfDACnoise-comparison.pdf
          Reply  Mon Apr 20 22:56:30 2020, rana, DailyProgress, Noise Budget, Noisemon:DAC noise analysis from L1 and H1 DACnoise-comparison.pdfdacNB.zip
Message ID: 1849     Entry time: Sat Apr 18 16:21:32 2020     In reply to: 1848     Reply to this: 1850
Author: Duo 
Type: Computing 
Category: Noise Budget 
Subject: Noisemon:DAC noise analysis from L1 and H1 

There we go. Based on the noisemon data at L1 and H1, I calculated the DAC noises at those sites, using roughly the same approach as described in 1847.

I used the coherence between the master channel and the noisemon channel to calculate the total noise going into the coils.

Then I converted the ADC noise and noisemon noise to DAC volts and subtracted them from the total noise. I compared the result of the subtraction, which should be DAC noise, at least in the passband (20-100Hz), with the G1401399 model and made a noise budget, shown in attachment 1. We can see that, as designed, the DAC noise is sufficiently amplified so that it dominates over the noisemon noise or the ADC noise in the passband.

Next, I projected the DAC noise to strain noise and summed them up for all the four channels in all the four stations.

Finally, I compared this with the interferometer noise spectrum based on data in L1:OAF-CAL_DARM_DQ and H1:CAL-DELTAL_EXTERNAL_DQ. I calibrated these data with calibration files here. The results are shown in attachment 3. All the data and scripts are included in attachment 4, where analysis.py is the script that does the job. Based on the plots, it seems DAC noise could be potentially a limiting factor for the interferomter sensitivity.

The coil driver states for L1 is LP off, ACQ off (state 1). For H1 is LP on, ACQ off. The LISO files calculating the current transfer functions and the voltage transfer functions are attached in attachment 4. 

I used a resolution of 1mHz in the diaggui measurement. The data files are too large so I can not upload them here. I am figuring out what to do.

Note: I fell into a few traps during the calculation. Many of them was about data and transfer functions. I have been more careful about what data is used in these calculations. For example, the noisemon data downloaded from the sites when MASTER was off still has DAC noise in it. I thought it was ADC noise + noisemon noise before and used it for subtraction. Another example, the transfer function measured at the sites has all the noise in it. We do not see the noises in the passband but ADC noise dominates at high frequencies. If you use this transfer function to figure out how much noisemon noise contributes, you result will be tampered by the noises, like ADC noises at high frequency. Last example, if you use the noisemon noise data measured in the digital system in our lab, you should be aware that, although it does not have DAC noise (I disconnected DAC when measuring the noises), it also has ADC noise. Therefore, it would be better to use data from SR785 or LISO simulations (which has been shown to agree with each other). I drew a diagram in attachment 2 to help thinking about what data or transfer functions should be used. 

Quote:

you have to overlay the estimated displacemnt noise with the existing L1 noise bud or else we cant tell what the importance of the result is

 

Attachment 1: noisebudget.pdf  58 kB  Uploaded Sat Apr 18 17:42:07 2020  | Hide | Hide all
noisebudget.pdf
Attachment 2: diagram.pdf  33 kB  Uploaded Sat Apr 18 17:55:09 2020  | Hide | Hide all
diagram.pdf
Attachment 3: DACnoise-comparison.pdf  88 kB  Uploaded Thu Apr 23 02:11:20 2020  | Hide | Hide all
DACnoise-comparison.pdf
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