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ID Date Author Typeup Category Subject
  14877   Fri Sep 13 13:03:35 2019 KojiSummaryCDSDIN 96pin to DSUB37 adapter (single) ready for use

The PCB board of the adapter for DIN 96pin to DSUB37 conversion (single DSUB version) was delivered yesterday and I quickly soldered the connectors.

They are ready for use and stored in a JLCPCB cardboard box on a pile of acromag stuff. (Note that the lacel is written on the box with Sharpie)

  14879   Mon Sep 16 09:11:37 2019 gautamSummaryCDSDIN 96pin to DSUB37 adapter (single) ready for use

I installed 6 of these in 1Y2. Three were for PD INTF #1-3, and I used three more for the AS110, REFL11, and REFL33 Demod board FEs, where the strain-reflief of the DC power cables to the Eurocrate was becoming a problem. So now there are only 4 units available as spares.

Once the strain-relieving of the Dsub cabling to 1Y3 is done, we can move ahead with testing. I'd like to put this to bed this week if possible.

  14885   Mon Sep 16 20:22:19 2019 gautamSummaryCDSUpdate on the Acromag status
  1. Jordan (new Engineer) and Chub neatened out the cabling at 1Y2/1Y3 today. After their work, I plugged in all the Dsubs to the rear Eurocrate DB37->DIN96 adaptors. Jordan nicely fixed up the labels on the cable with some extra sellotape for a more durable label.
  2. As part of the war on cross-connects, Chub removed some cables that were piping BIO signals from the fast CDS system to the whitening boards.
    • There is a SCSI to DB37 custom ribbon cable going from the BIO card in the expansion chassis to a 1U chassis box at the very bottom of 1Y2.
    • This 1U box, with DCC number D080478 (but no schematic exists on the DCC or any of the usual secret hidey-holes) breaks out the 32 BIO channels to 16+16.
    • Each set of 16 channels was supposed to get broken out to 8+8 via some cross connects and then goto the whitening boards. This is the part that got distrubed.
    • Koji and I discussed options - if Chub cannot resotre this easily, we will make a D37--> 4*D15 breakout board, and pipe the signals via the backplane P2 connectors. This will mean ~10 more days before the LSC system can be tested.
    • Some cabling to the TT DACs and an ADC were also disturbed, but these are easily restored.
  3. From the hardware standpoint, some cross-struts for strain relief on the back of 1Y2 need to be installed --> Chub.
  14892   Tue Sep 17 23:43:34 2019 KojiSummaryCDSAcromag logic checker

For the investigation of the latch logic issue for the CARM CM board, I have made the LED logic checkers with DB breakout boards. They require the pull up voltage supply of +15V because the acromag digital out is a open corrector (well... open "source") output.

The logic from Pin1 to Pin16 of DB37 can be monitored. The DB15 connector is only for monitoring the latch enable logic.

What Gautam and I found with the logic outputs was that the latch logic works fine but occasionally we found that the top 2 bits and the bottom 4bit were processed independently.

  15082   Fri Dec 6 17:49:46 2019 ranaSummaryPEMJump test of seismometers: EX needs recentering

Yehonathan, please center the EX seismometer.

The attached PDF shows the seismometer signals (I'm assuming that they're already calibrated into microns/s) during the lab tour for the art students on 11/1. The big spike which I've zoomed in on shows the time when we were in the control room and we all jumped up at the same time. There were approximately 15 students each with a mass of ~50-70 kg. I estimate that out landing times were all sync'd to within ~0.1 s.

  15083   Sun Dec 8 20:15:41 2019 ranaSummaryPEMJump test of seismometers: EX needs recentering

I have re-centered the EX (and EY) seismometers. They are Guralp CMG40-T, and have no special centering procedure except cycling the power a few times. I turned off the power on their interface box, then waited 10s before turning it back on.

The fist atm shows the comparison using data from 8-9 PM Saturday night:

  1. there seems to be a factor of 2 calibration diff between the T240 near the BS, and the Guralp seismometers at the end. Which one is right? surpriseWhen was the last time they were cross calibrated?
  2. The low coherence between BS_X and EX_X shows the problem. They should be very coherent (> 0.9) for 0.1-1 Hz.sad


  15086   Mon Dec 9 13:08:24 2019 YehonathanSummaryPEMJump test of seismometers: EX needs recentering

I check the seismometers in the last 14 hours (Attached). Seems like the coherenece is restored in the x direction.



  15093   Wed Dec 11 15:01:57 2019 JonSummaryPSLPMC cavity ringdown measurement

[Jon, Yehonathan]

We carried out a set of cavity ringdown measurements of the PMC. The 1/e decay time scale is found to be 35.2 +/- 2.4 (systematic) μs. The statistical error is negligible compared to the systematic error, which is taken as the maximum absolute deviation of any measurement from the average value.

To make the measurement, we injected the first order deflection beam of an 80 MHz AOM, then extinguished it quickly by cutting the voltage offset to the AOM driver provided by an RF function generator. A 100 MHz oscilloscope configured to trigger on the falling voltage offset was used to sample the cavity in transmission as sensed by a PDA55. We found the detector noise of the DC-coupled output of the 35.5 MHz REFL PD to be too high for a reflection-side measurement.

Further loss analysis is forthcoming.

  15119   Mon Jan 13 23:30:53 2020 YehonathanSummaryPSLChanges made since Gautam left

As per Gautam's request, I list the changes that were made since he left:

1. The AOM driver was connected to a signal generator.

2. The first order beam from the AOM was coupled into the PMC while the zero-order beam is blocked. We might want to keep this configuration if the pointing stability is adequate.

3. c1psl got Burt restored to Dec 1st.

4. Megatron got updated.

Currently, c1susaux seems unresponsive and needs to be rebooted.

  15121   Tue Jan 14 20:17:09 2020 gautamSummaryGeneralIFO recovery


There was no light entering the IFO. I worked on a few things to bring the interferometer to a somewhat usable state. The goal is to get back to PRFPMI locking ASAP.


Problem: All fast models report a "0x4000" DC error. See Attachment #1.

Solution: I think this is a "known" issue that happened last new year too. The fix was to add a hard-coded 1 second offset to the daqd config files. However, incrementing/decreasing this offset by +/- 1 second did not fix the errors for me today. I'll reach out to JH for more troubleshooting tips.

Update 15 Jan 2020 830am: The problem is now fixed. See here.

Problem: c1susaux and c1auxey were unresponsive.

Solution: Keyed c1auxey. Rebooted c1susaux and as usual, manually started the eth0/eth1 subnets. The Acromag crate did not have to be power-cycled. ITMY got stuck in this process - I released it using the usual bias jiggling. Why did c1susaux fail? When did it fail? Was there some un-elogged cable jiggling in that part of the lab?

Problem: IMC autolocker and FSS slow processes aren't running on megatron after the upgrade.

Solution: Since no one bothered to do this, I setup systemd infrastructure for doing this on megatron. To run these, you do:

sudo systemctl start MCautolocker.service
sudo systemctl start FSSSlow.service

and to check their status, use:

sudo systemctl status MCautolocker.service
sudo systemctl status FSSSlow.service

The systemd setup is currently done in a naive way (using the bash executable to run a series of commands rather than using the systemd infrastructure itself to setup variables etc) but it works. I confirmed that the autolocker can re-acquire IMC lock, and that the FSS loop only runs when the IMC is locked. I also removed the obsolete messages printed to megatron's console (by editing /etc/motd) on ssh-login, advising the usage of initctl - the updated message reflects the above instructions.

In order to do the IMC locking, I changed the DC voltage to the AOM to +1V DC (it was +0.8 V DC). In this setting, the IMC refl level is ~3.6 V DC. When using the undiffracted AOM beam, we had more like +5.6 V DC (so now we have ~65% of the nominal level) from the IMC REFL PD when the IMC was unlocked. IIRC, the diffraction efficiency of the AOM should be somewhat better, at ~85%. Needs investigation, or better yet, let's just go back to the old configuration of using the undiffracted beam.

There was also an UN-ELOGGED angry change of the nominal value of the PMC servo gain to 12.8, and no transfer function measurement. There needs to be a proper characterization of this loop done to decide what the new nominal value should be.

I'm going to leave the PSL shutter open and let the IMC stay locked for stability investigations. Tomorrow, I'll check the single-arm locking and the ALS system.

  15123   Wed Jan 15 10:04:19 2020 gautamSummaryGeneralPOX / POY locking restored

Single arm locking using POX and POY has been restored. After running the dither alignment servos, the TRX/TRY levels are ~0.7. This is consistent with the IMC transmission being ~11000 counts with the AOM 1st order diffracted beam (c.f. 15000 counts with the undiffracted beam).


Tomorrow, I'll check the single-arm locking and the ALS system.

  15201   Mon Feb 10 09:40:54 2020 Larry WallaceSummaryGeneralSolidWorks Computer Upgrade and Printer repair

On February 5, 2020, the Dell engineering workstation located in the 40M lab, was replaced with a newer Engineering workstation, per a request from Koji . The new workstation should perform a good deal better over the older unit. It has more cores, more memory and a better video card. Since this unit is being used by the 40M group, the Comsol s/w pkg. was also installed on the unit.

During the computer swap, Koji had a problem with a print job and it was discovered the bottom tray of the HP5550 printer was broken. The broken tray was replaced from another unit that was being disposed of.

  15226   Wed Feb 26 21:43:48 2020 JonSummaryBHDProjected IFO noise budget, post-BHD upgrade

To supplement the material presented during the BHD review, I've put together a projected noise budget for the 40m. Note these are the expected interferometer noises (originating in the IFO itself), not BHD readout noises. The key parameters for each case are listed in the figure title. Also attached is a tarball (attachment 4) containing the ipython notebook, data files, and rolled-back version of pygwinc which were used to generate these figures.

Attachment 1: Phase quadrature readout.

Attachment 2: Comparison to aLIGO design sensitivity (phase quadrature).

Attachment 3: Amplitude quadrature readout.

  15228   Wed Feb 26 22:09:52 2020 gautamSummaryBHDProjected IFO noise budget, post-BHD upgrade

The quantum noise curves here are not correct. c.f. amplitude quadrature noise budget.

  15241   Mon Mar 2 23:49:03 2020 JonSummaryBHDProjected IFO noise budget, post-BHD upgrade

Updated noise budget curves, now computed using the latest version of pygwinc. This resolves the inconsistency between the gwinc quantum noise curves and Gautam's analytic calculations. As before, the key configuration parameters are listed in the figure titles.

Attachment 1: Phase quadrature

Attachment 2: Amplitude quadrature

Attachment 3: Comparison to aLIGO design (phase quadrature)


The quantum noise curves here are not correct. c.f. amplitude quadrature noise budget.

  15244   Tue Mar 3 18:11:05 2020 JonSummaryBHDProjected IFO noise budget, post-BHD upgrade

Revised noise estimates, correcting a couple of factor of 2 and factor of pi errors found in the coil driver noise calculation. Also resolves a strain vs. displacement units confusion using the new pygwinc. Gautam and I have checked these noises against the analytical predictions and believe they are now accurate. Attachments are again:

Attachment 1: Phase quadrature

Attachment 2: Amplitude quadrature

Attachment 3: Comparison to aLIGO design (phase quadrature)

  15256   Thu Mar 5 19:45:23 2020 JonSummaryPSLC1PSL in-situ test results

We've completed almost all of the in-situ testing of the c1psl channels. During this process, we identified several channels which needed to be rewired to different Acromags (BIO sinking v. sourcing). We also elected to change the connector type of a few channels for practical advantages. Those modifications and other issues found during testing are detailed below. Also attached are the updated channel assignments, with a column indicating the in-situ testing status of each channel.

Post-installation modifications

  • All four channels connected to the sourcing BIO module were found to in fact require sinking I/O. They were reassigned to sinking BIO modules. Affected channels:
    • C1:PSL-FSS_SW1
    • C1:PSL-FSS_SW2
    • C1:PSL-PSL_Shutter
  • Added a new AI channel:
  • Removed an unneccessary AI channel:
  • Moved two AI channels from BNC connectors to a new Dsub connector (labelled DB25M-2 in the spreadsheet).

Issues identified during testing

  • Digital calibration. The following channels work, but we need to verify their EPICS calibration parameters (EGUF/EGUL):
  • IMC servo board. The Acromag channels themselves were found to work, but the linearity of the mbbo gain stages are in question (i.e., a potential problem with the board). GV is currently testing the servo board.
  • PSL QPD board apears to be dead. We connected a scope directly to the test points on the board and measured a high level of noise and no signal (for all four of the QPD channels). I understand this QPD has not been used in some time, so it may not have been noticed before.
  • WFS DC channels are saturating when the IMC is unlocked. The acceptance range of the Acromag ADC is only +/-10 V, but we measured sensor voltages as high as ~14 V. It appears that the old ADCs were somehow accepting a range of 0 to +20 V instead of -10 to +10 V. However, the Acromags do not support the input range 0-20 V. Since SNR is not critical for these channels (they're used only for initial alignment), I propose we simply install a voltage divider inside the chassis, just before the Acromag, for each of these signals.
  15266   Wed Mar 11 18:12:53 2020 gautamSummaryPSLWFS Demod board modifications

[koji, gautam]

Attachment #1 shows the relevant parts of the schematic of the WFS demod board (not whitening board). 

  • The basic problem was that the switchable gain channels were not accounted for in the Acromag channel list 😒.
  • What this meant was that the DC gain was set to the default x100 (since the two DG211s that provide the switchable x10 and x1 gain options had their control logic pins pulled up to +5V because these pins weren't connected to any sinking BIO channel).
  • Rather than set up new connections to Acromags inside the chassis (though we have plenty of spares), Koji and I decided to make these fixed to x1 gain.
  • The actual fix was implemented as shown in the annotated schematic. There are some pictures 📷 of the PCB in the DCC entry linked above.
  • Amusingly, this board will now require a sourcing BIO unit if we want to still have the capability of switching gains.

Before removing the boards from the eurocrate: 

  • I dialled down the Kepco HV supplies
  • disconnected all the cabling to these boards after noting down cable numbers etc.

After Koji effected the fix, the boards were re-installed, HV supplies were dialled back up to nominal voltage/currents, and the PMC/IMC were re-locked. The WFS DC channels now no longer saturate even when the IMC is unlocked 👏 👏 . I leave it to Yehonathan / Jon to calibrate these EPICS channels into physical units of mW of power. We should also fix the MEDM screen and remove the un-necessary EPICS channels.

Later in the evening, I took advantage of the non-saturated readbacks to center the beams better on the WFS heads. Then, with the WFS servos disabled, I manually aligned the IMC mirrors till REFLDC was minimized. Then I centered the beam on the MC2 transmission QPD (looking at individual quadrants), and set the WFS1/2 RF offsets and MC2 Trans QPD offsets in this condition.


WFS DC channels are saturating when the IMC is unlocked.

  15300   Tue Apr 7 15:30:40 2020 JonSummaryNoiseBudget40m noise budget migrated to pygwinc

In the past year, pygwinc has expanded to support not just fundamental noise calculations (e.g., quantum, thermal) but also any number of user-defined noises. These custom noise definitions can do anything, from evaluating an empirical model (e.g., electronics, suspension) to loading real noise measurements (e.g., laser AM/PM noise). Here is an example of the framework applied to H1.

Starting with the BHD review-era noises, I have set up the 40m pygwinc fork with a working noise budget which we can easily expand. Specific actions:

  • Updated the 40m fork to the latest pygwinc version (while preserving the commit history).
  • Added a directory ./CIT40m containing the 40m-specific noise budget files (created by GV).
  • Added an ipython notebook CIT40m.ipynb at the root level showing how to generate a noise budget.
  • Integrated our DAC and seismic noise estimators into pygwinc.
  • Marked the old 40m NB repo as obsolete (last commit > 2 yrs ago). Many of these noise estimates are probably stale, but I will work with GV to identify which ones can be migrated.

I set up our fork in this way to keep the 40m separate from the main pygwinc code (i.e., not added to as a built-in IFO type). With the 40m code all contained within one root-level directory (with a 40m-specific name), we should now always be able to upgrade to the latest pygwinc without creating intractable merge conflicts.

  15302   Mon Apr 13 16:51:49 2020 ranaSummaryDAQNODUS: rsyncd daemon / service set up

I just now modified the /etc/rsyncd.conf file as per Dan Kozak's instructions. The old conf file is still there with the file name appended with today's date.

I then enabled the rsync daemon to run on boot using 'enable'. I'll ask Dan to start the file transfers again and see if this works.

controls@nodus|etc> sudo systemctl start rsyncd.service
controls@nodus|etc> sudo systemctl enable rsyncd.service
Created symlink from /etc/systemd/system/multi-user.target.wants/rsyncd.service to /usr/lib/systemd/system/rsyncd.service.
controls@nodus|etc> sudo systemctl status rsyncd.service
● rsyncd.service - fast remote file copy program daemon
   Loaded: loaded (/usr/lib/systemd/system/rsyncd.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2020-04-13 16:49:12 PDT; 1min 28s ago
 Main PID: 4950 (rsync)
   CGroup: /system.slice/rsyncd.service
           └─4950 /usr/bin/rsync --daemon --no-detach

Apr 13 16:49:12 nodus.martian.113.168.192.in-addr.arpa systemd[1]: Started fast remote file copy program daemon.
Apr 13 16:49:12 nodus.martian.113.168.192.in-addr.arpa systemd[1]: Starting fast remote file copy program daemon...

  15313   Fri Apr 24 00:26:59 2020 ranaSummaryPEML.A. EQ from Tuesday night
  15325   Tue May 12 17:51:25 2020 ranaSummaryComputer Scripts / Programsupdated LESS syntax highlight on nodus

apt install source-highlight

then modified bashrc to point to /usr/share instead of /usr/bin

  15331   Thu May 14 00:47:55 2020 gautamSummaryComputer Scripts / Programspcdev1 added to authorized keys on nodus

This is to facilitate the summary page config fines to be pulled from nodus in a scripted way, without being asked for authentication. If someone knows of a better/more secure way for this to be done, please let me know. The site summary pages seem to pull the config files from a git repo, maybe that's better?

  15374   Thu Jun 4 00:21:28 2020 KojiSummaryCOCITM spares and New PR3 mirrors transported to Downs for phasemap measurement

GariLynn worked on the measurement of E1800089 mirrros.

The result of the data analysis, as well as the data and the codes, have been summarized here:

  15456   Mon Jul 6 15:10:40 2020 JonSummaryBHD40m --> A+ BHD design analysis

As suggested last week, Hang and I have reviewed the A+ BHD status (DRD, CDD, and reviewers' comments) and compiled a list of key unanswered questions which could be addressed through Finesse analysis.

In anticipation of others helping with this modeling effort, we've tried to break questions into self-contained projects and estimated their level of difficulty. As you'll see, they range from beginner to Finesse guru.

  15482   Wed Jul 15 17:46:05 2020 anchalSummaryALSNoise budget for ALS

I started my attempt on noise budgeting of ALS by going back to how Kiwamu did it and adding as many sources as I could find up till now. This calculation is present in ALS_Noise_Budget notebook. I intend to collect data for noise sources and all future work on ALS in the ALS repo.

The noise budget runs simulink through matlab.engine inside python and remaining calculations including the pygwinc ones are done in python. Please point out any errors that I might have done here. I still need to add noise due to DFD and the ADC after it. For the residual frequency noise of AUX laser, I have currently used an upper limit of 1kHz/rt Hz at 10 Hz free-running frequency noise of an NPRO laser.

  15496   Mon Jul 20 19:21:16 2020 anchalSummaryALSFew proposals for Voyager ALS

I've added 4 proposed schemes for implementing ALS in voyager. Major thing to figure out is what AUX laser would be and how we would compare the different PSL and AUX lasers to create an error signal for ALS. Everywhere below, 2um would mean wavelengths near 2 um including the proposed 2128nm. Since it is not fixed, I'm using a categorical name. Same is the case for 1um which actually would mean half of whatever 2 um carries.

Higher Harmonic Generation:

  • We can follow the current system of ALS with using 1.5 times PSL frequency as AUX instead of second harmonic as 1 um is strongly absorbed in Si.
  • To generate 1.5 times PSL frequency, three stages would be required.
    • SHG: Second Harmonic Generation mode matched to convert 2um to 1um. If we are instead making 2 um from 1um to start with, this stage will not be required.
    • SFG: Sum Frequency Generation mode matched to sum 2um photon and 1um photon to give 0.65 um photon.
    • DPDC: Degenerate Parametric Down Conversion mode matched to convert 0.65 um to 1.3 um (which would be 1.5 times PSL frequency).
  • To compare, we can either convert pick-off from PSL to AUX frequency by doing the above 3 stages (Scheme II).
  • Or we can just do SHG and SFG at PSL pick-off and do another SHG at AUX end (Scheme I) to compare the AUX and PSL both converted to 0.65 um (which would be 2 times AUX and 3 times PSL frequency).
  • This method would have added noise from SHG, SFG and DPDC processes along with issues to be inefficiency of conversion.

Arbitrary AUX frequency:

  • We can get away with using some standard laser near 1.5 um region directly as AUX. Most probably this would be 1550 nm.
  • What's left is to devise a method of comparing 1.5 um and 2um frequencies. Following are two possible ways I could think of:

Using a frequency comb:

  • Good stable frequency combs covering the wavelength region from 1.5 um to 2 um are available of the shelf.
  • We would beat PSL and transmitted AUX separately with the frequency comb. The two beat note frequencies would be:
    \Delta_\text{PSL} = \nu_\text{PSL} - \nu_{CEO} - m_1 \nu_\text{Rep}
    \Delta_\text{AUX} = \nu_\text{AUX} - \nu_{CEO} - m_2 \nu_\text{Rep}
  • Here, m1 and m2 represent the nearest modes (comb teeth) of frequency comb to PSL and AUX respectively.
  • Carrier Envelope Offset frequency (\nu_{CEO}) can be easily generated by using an SHG crystal in front of the Frequency comb. This step is not really required since most of the modern frequency combs now comb with inbuilt zero \nu_{CEO} stabilization.
  • Mixing above beatnotes with \nu_{CEO} would remove \nu_{CEO} from them along with any noise associated with \nu_{CEO}.
  • Further, a Direct Digital Synthesis IC is required to multiply the AUX side RF signal by m1/m2. This finally makes the two RF signals to be:
    \nu_{A} = \nu_\text{PSL} - m_1 \nu_{Rep}
    \nu_{B} = \frac{m_1}{m_2}\nu_\text{AUX} - m_1 \nu_{Rep}
  • Which on mixing would give desired error signal for DFD as :
    \nu_\text{PSL} - \frac{m_1}{m_2}\nu_\text{AUX}
  • This method is described in Stenger et al. PRL. 88, 073601 and is useful in comparing two different optical frequencies with a frequency comb with effective cancellation of all noise due to the frequency comb itself. Only extra noise is from the DDS IC which is minimal.
  • This method, however, might be an overkill and expensive. But in case (for whatever reason) we want to send in another AUX at another frequency down the 40m cavity, this method allows the same setup to be used for multiple AUX frequencies at once.

Using a Transfer Cavity:

  • We can make another more easily controlled and higher finesse cavity with a PZT actuator on one of the mirrors.
  • In the schematic, I have imagined it has a triangular cavity with a back end mirror driven by PZT.
  • Shining PSL from one side of the transfer cavity and employing the usual PDH, we can lock the cavity to PSL.
  • This lock would require to be strong and wide bandwidth. If PZT can't provide enough bandwidth, we can also put an EOM inside the cavity! (See this poster from Simon group at UChicago)
  • Another laser at AUX frequency, called AUX2 would be sent from the other side of the cavity and usual PDH is employed to lock AUX2 to the transfer cavity.
  • So clearly, this cavity also requires coatings and coarse length such that it is resonant with both PSL and AUX frequencies simultaneously.
  • And, the FSS for AUX2 needs to be good and high bandwidth as well.
  • The transmitted AUX2 from the transfer cavity now would carry stability of PSL at the frequency of AUX and can be directly beaten with transmitted AUX from the 40m cavity to generate an error signal for DFD.
  • I believe this is a more doable and cheaper option. Even if we want to do a frequency comb scheme, this could be a precursor to it.


EditTue Jul 21 17:24:09 2020: (Jamie's suggestion)

Using Mode Cleaner cavity as Transfer Cavity:

  • If we coat the mode cleaner cavity mirrors appropriately, we can use it to lock AUX2 laser (mentioned above).
  • This will get rid of all extra optics. The only requirement is for FSS to be good on AUX2 to transfer PSL (MC) stability to AUX frequency.
  • I've added suggested schematic for this scheme at the bottom.


  15499   Thu Jul 23 15:58:24 2020 JonSummaryVACVacuum controls refurbishment plan

This year we've struggled with vacuum controls unreliability (e.g., spurious interlock triggers) caused by decaying hardware. Here are details of the vacuum refurbishment plan I described on the 40m call this week.

 Refurbish TP2 and TP3 dry pumps. Completed [ELOG 15417].

 Automated notifications of interlock-trigger events. Email to 40m list and a new interlock flag channel. Completed [ELOG 15424].

Replace failing UPS.

  • Two new Tripp Lite units on order, 110V and 230V [ELOG 15465].
  • Jordan will install them in the vacuum rack once received.
  • Once installed, Jon will come test the new units, set up communications, and integrate them into the interlock system following this plan [ELOG 15446].
  • Jon will move the pumps and other equipment to the new UPS units only after completing the above step.

Remove interlock dependencies on TP2/TP3 serial readbacks. Due to persistent glitching [ELOG 15140, ELOG 15392].

Unlike TP2 and TP3, the TP1 readbacks are real analog signals routed to Acromags. As these have caused us no issues at all, the plan is to eliminate dependence on the TP2/3 digital readbacks in favor of the analog controller outputs. All the digital readback channels will continue to exist, but the interlock system will no longer depend on them. This will require adding 2 new sinking BI channels each for TP2 and TP3 (for a total of 4 new channels). We have 8 open Acromag XT1111 channels in the c1vac system [ELOG 14493], so the new channels can be accommodated. The below table summarizes the proposed changes.

Channel Type Status Description Interlock
C1:Vac-TP1_current AI exists Current draw (A) keep
C1:Vac-TP1_fail BI exists Critical fault has occurred keep
C1:Vac-TP1_norm BI exists Rotation speed is within +/-10% of set point new
C1:Vac-TP2_rot soft exists Rotation speed (krpm) remove
C1:Vac-TP2_temp soft exists Temperature (C) remove
C1:Vac-TP2_current soft exists Current draw (A) remove
C1:Vac-TP2_fail BI new Critical fault has occurred new
C1:Vac-TP2_norm BI new Rotation speed is >80% of set point new
C1:Vac-TP3_rot soft exists Rotation speed (krpm) remove
C1:Vac-TP3_temp soft exists Temperature (C) remove
C1:Vac-TP3_current soft exists Current draw (A) remove
C1:Vac-TP3_fail BI new Critical fault has occurred new
C1:Vac-TP3_norm BI new Rotation speed is >80% of set point new
  15501   Mon Jul 27 15:48:36 2020 JonSummaryVACVacuum parts ordered

To carry out the next steps of the vac refurbishment plan [ELOG 15499], I've ordered parts necessary for interfacing the UPS units and the analog TP2/3 controller outputs with c1vac. The purchase list is appended to the main BHD list and is located here. Some parts we already had in the boxes of Acromag materials. Jordan is gathering what we do already have and staging it on the vacuum controls console table - please don't move them or put them away.


Replace failing UPS.

Remove interlock dependencies on TP2/TP3 serial readbacks. Due to persistent glitching [ELOG 15140, ELOG 15392].

  15566   Wed Sep 9 20:52:45 2020 ranaSummaryIOOwandering line in IMC

since the summary pages are working again, I was clicking through and noticed that there's a wandering peak in the whitened IMC spectrogram that goes from 10-30 Hz over the course of a day.


anyone know what this is ?

  15587   Sat Sep 19 23:59:22 2020 anchalSummaryALSALS noise budget update

Setting the record straight

I found out an error I did in copying some control model values from Kiwamu's matlab code. On fixing those, we get a considerably reduced amount of total noise. However, there was still an unstable region around the unity gain frequency because of a very small phase margin. Attachment 3 shows the noise budget, ALS open-loop transfer function, and AUX PDH open-loop transfer function with ALS disengaged. Attachment 4 is the yaml file containing all required zpk values for the control model used. Note that the noise budget shows out-of-loop residual arm length fluctuations with respect to PSL frequency. The RMS curve on this plot is integrated for the shown frequency region.

Trying to fix the unstable region

Adding two more poles at 100 Hz in the ALS digital filter seems to work in making the ALS loop stable everywhere and additionally provides a steeper roll-off after 100 Hz. Attachment 1 shows the noise budget, ALS open-loop transfer function, and AUX PDH open-loop transfer function with ALS disengaged. Attachment 2 is the yaml file containing all required zpk values for the control model used. Note that the noise budget shows out-of-loop residual arm length fluctuations with respect to PSL frequency. The RMS curve on this plot is integrated for the shown frequency region.

But is it really more stable?

  • I tried to think about it from different aspects. One thing is sure that  1+G_{OL} remains greater than 1 in all of the frequency region plotted for. This is also evident in the common-mode to residual noise transfer function which shows no oscillation peaks and is a clean mirror image of the open-loop transfer function (See Attachment 1, page 2).
  • Another way is to look for the phase margin. This is a little controversial way of checking stability. For clarity, the open-loop transfer function I'm plotting does not contain the '-1' feedback in it. So the bad phase value at unity gain frequency is -180 degrees (or 180 degrees) for us. I've taken the difference from the closest side and got 76.2 degrees of phase margin.
  • Another way I checked was by plotting a Nyquist plot for the open-loop transfer function. It is said that if the contour does not encircle the point '-1' in the real axis, then the loop would be stable even if the f_{180} < f_{UGF} where f_{180} is the frequency where phase lag becomes -180 degrees at the lowest frequency. For us, f_{180} is at 1 Hz because of the test mass actuator pole. But I have verified that the Nyquist contour of the open-loop transfer function does not encircle '-1' point. I have not uploaded the Nyquist plot as it is not straight forward to plot. Because of large dc gain, it covers a large region and one needs to zoom in and out to properly follow what the contour is really doing. I didn't get time to make insets for it.

Is this close to reality?

For that, we'll have to take present noise source estimates but Gautum vaguely confirmed that this looked more realistic now 'shape-wise'. If I remember correctly, he mentioned that we currently can achieve 8 pm of residual rms motion in the arm cavity with respect to the PSL frequency. So we might be overestimating our loop's capability or underestimating some noise source. More feedback on this welcome and required.

Additional Info:

The code used to calculate the transfer functions and plot them is in the repo 40m/ALS/noiseBudget

Attachment 5 here shows a block diagram for the control loop model used. Output port 'Res_Disp' is used for referring all the noise sources at the residual arm length fluctuation in the noise budget. The open-loop transfer function for ALS is calculated by -(ALS_DAC->ALS_Out1 / ALS_DAC->ALS_Out2) (removing the -1 negative feedback by putting in the negative sign.) While the AUX PDH open-loop transfer function is calculated by python controls package with simple series cascading of all the loop elements.



  15589   Sun Sep 20 23:12:13 2020 ranaSummaryALSALS noise budget update

I think the digital loop in the ALS budget is too optimistic. You have to include all the digital delays and anti-aliasing filters to get the real response.

aslo, I recommend grabbing some of the actual spectra from the in-lock times with nds and using the calibrated spectra as inputs to this mode. Although we don't have good models of the stack, you can sort of infer it by using the calibrated seismometer data and the calibrated MC_F or MC_L channels (for IMC) or XARM/YARM signals for those.

  15593   Tue Sep 22 00:14:43 2020 anchalSummaryALSALS noise budget update

This is not a reply to comments given to the last post; Still working on incorporating those suggestions.

Trying out a better filter from scratch

Rana suggested looking first at what needs to be suppressed and then create a filter suited for the noise from scratch. So I discarded all earlier poles and zeros and just kept the resonant gains in the digital filter. With that, I found that all we need is three poles at 1 Hz and a gain of 8.1e5 gives the lowest RMS noise value I could get.

Now there can be some practical reasons unknown to me because of which this filter is not possible, but I just wanted to put it here as I'll add the actual noise spectra into this model now.

Few questions:

  • What anti-aliasing filters are used in ALS?
  • Is the digital delay fixed to a constant upper limit or is it left to change as per filters? I have already used a 470 us delay (modeled with Pade 4th order approximation).
  • I could not find a good place where channel names are listed with corresponding meaning. Where can I find them?
  • Is there a channel which keeps a record of lock status? In short, how do I find the in-lock times
  15594   Tue Sep 22 12:14:42 2020 ranaSummaryALSALS noise budget update

This ALS loop is not stable. Its one of those traps that comes from using only the Bode plot to estimate the loop stability. You have to also look at the time domain response - you can look at my feedback lecture for the SURF students for some functions.

  15601   Wed Sep 23 11:13:49 2020 anchalSummaryALSALS noise budget update

Yes, that loop was unstable. I started using the time domain response to check for the stability of loops now. I have been able to improve the filter slightly with more suppression below 20 Hz but still poor phase margin as before. This removes the lower frequency region bump due to seismic noise. The RMS noise improved only slightly with the bump near UGF still the main contributor to the noise.

For inclusion of real spectra, time delays and the anti-aliasing filters, I still need some more information.

Few questions:

  • What anti-aliasing filters are used in ALS?
  • Is the digital delay fixed to a constant upper limit or is it left to change as per filters? I have already used a 470 us delay (modeled with Pade 4th order approximation).
  • I could not find a good place where channel names are listed with corresponding meaning. Where can I find them?
  • Is there a channel which keeps record of lock status? In short, how do I find the in-lock times

Additional Info:

The code used to calculate the transfer functions and plot them is in the repo 40m/ALS/noiseBudget

Related Elog post with more details: 40m/15587

  15617   Wed Oct 7 16:56:23 2020 anchalSummaryALSALS noise budget update - Updated AUX PDH Loop values

AUX PDH Loop update

I used D1400293 to get the latest logged details about the universal PDH box used to lock the green laser at X end. The uPDH_X_boost.fil file present there was used to obtain the control model for this box. See attachment one for the code used. Since there is a variable gain stage in the box, I tuned the gain of the filter model F_AUX in ALS_controls.yml to get the maximum phase margin in the PDH lock of the green laser. Unity gain frequency of 8.3 kHz can be achieved in this loop and as Gautam pointed out earlier, it can't be increased much further without changes in the box.

ALS Noise Budget update

The ALS control model remains stable with a reduction in total estimate noise because of the above update. There are few things to change though:

  • This model is for a single arm locking where the beatnote signal between green laser and frequency doubled main laser is fed back to ETM at X end. Currently, Gautam is using a different scheme to lock where the feedback is sent to PSL-MC loop and the beat is taken between IR signals.
  • In the LSC controls, I couldn't find a place where the digital ALS filter I have been optimizing and Kiwamu used, was placed. From what I gathered, after demodulation of beat note signal, a digital PLL is employed and the error signal is few to the Servo Filters directly. I might be missing some script which specifically switches on a particular set of filter modules in the XARM/YARM path when arms are locked through ALS.
  • Another straight forward job for me is to verify the PSL-MC loop parameters with he TTFSS used. I'll do this next.
  15619   Thu Oct 8 11:59:52 2020 ranaSummaryALSALS noise budget update - Updated AUX PDH Loop values

For all the loops where we drive the NPRO PZT, there is some notch/resonance feature due to the PZT mechanical resonance. In the IMC loop this limits the PZT/EOM crossove to be less than 25 kHz. I don't have a model for this, btu it should be included.

If you hunt through the elogs, people have measured the TF of ALS NPRO PZT to phase/frequency. Probably there's also a measured ALS PDH loop somewhere that you could use to verify your model.

  15622   Fri Oct 9 18:32:14 2020 anchalSummaryALSALS noise budget update - Updated AUX PDH Loop values

The only two PZT Phase modulation transfer function measurements I could find are 40m/15206 and 40m/12077. Both these measurements were made to find a good modulation frequency and do not go below 50 kHz. So I don't think these will help us. We'll have to do a frequency transfer function measurement at lower frequencies.
I'm still looking for ALS PDH loop measurements to verify the model. I found this 40m/15059 but it is only near the UGF. The UGF measured here though looks very similar to the model prediction. A bit older measurement in 2017 was this 40m/13238 where I assume by ALS OLTF gautum meant the green laser PDH OLTF. It had similar UGF but the model I have has more phase lag, probably because of a 31.5 kHz pole which comes at U7 through the input low pass coupling through R28, C20 and R29 (See D1400293)

If the green laser is not being used, can I go and take some of these measurements myself?

  15626   Wed Oct 14 17:03:55 2020 anchalSummaryALSALS noise budget update - Added whitening filter for ADC

Koji recommended that I can add whitening filters to suppress ADC noise easily. I added a filter before ADC in ALS loop with 4 zeros at 1.5 Hz and 4 poles at 100 Hz and added a reversed filter in the digital filter of ALS. This did not change the performance of the loop but significantly reduced the contribution of ADC noise above 1 Hz. One can see ALS_controls.yaml for the filter description. Please let me know if this does not make sense or there is something that I have overlooked.

Now, the dominant noise source is DFD noise below 100 Hz and green laser frequency noise above that. For DFD noise, I used data dating back to Kiwamu's paper. The noise contribution from DFD in the model is lower than the latest measured ALS noise budget post on elog. I'll look further into design details and noise of DFD.

Code, data, and schematics

  15629   Thu Oct 15 13:48:58 2020 anchalSummaryGeneralLab Entry Notification

I entered 40m today at around 1:20 pm and left by 1:45 pm. I entered 104 through the machine shop entry. I did the following:

  • I took photos and videos of the PSL table with lights on.
  • I uncovered the AP table, took photos and video, and covered it back.
  • I went to the X End table and took a video without opening the enclosure.
  • Apart from flipping light switches, nothing else should have changed.
  15630   Thu Oct 15 20:00:23 2020 KojiSummaryGeneralHEPA AC cord replacement

The AC cord from the PSL HEPA variac to the junction box was replaced.
Now the HEPA is running at 70%

Showed up at the 40m at 7pm


  • Closed the PSL shutter.
  • Closed the innolight shutter
  • Turned off the HEPA mains switch
  • Checked the HEPA fan rating: 115V 4.5A.
  • Brought the thickest power cord from the wall stock: the rating is 125V 15A. This should sufficiently hold two HEPAs.

Cable Replacing

  • Rechecked the wire connection. The new cord has green/black/white wires. And the colors agree with the color of the wires in the junction box.
  • Removed the existing cord.
  • Attached the new cord.
  • Checked the variac AC plug. The terminals in the plug look normal and the AC plug looked sufficiently rigid.
  • Checked the connection again. = OK


  • Turned on the HEPA mains switch
  • VairAC turned to 70%
  • Checked the air flow - The HEPA fans are sucking the air = OK

Closing the work

  • Closed the junction box.
  • Cleaned up the roof
  • Opend the innolight shutter
  • Opened the PSL shutter
  • Locked the PMC
  • Locked the IMC  - found the transmission was ~80% of the pre-work due to misalignment of the PMC
  • Aligned the PMC - this recovered the IMC REFL of ~5.2 when the IMC was unlocked

Leaving the 40m at 9:30pm

Memo: 40m wiring/Mask/Camera/Red Pitaya/Particle Counter

  15632   Fri Oct 16 19:44:41 2020 anchalSummaryGeneralLab Entry Notification

I entered 40m today at around 1:10 pm and left by 1:50 pm. I entered 104 through the machine shop entry. I took top view single picture photos of ITMY, BS, AP, ITMX, ETMX and ETMY tables. The latest photos will be put here on the wiki soon.

  15635   Tue Oct 20 20:12:18 2020 KojiSummaryGeneralDJI OSMO Pocket Camera Kit

I set up an action cam (DJI OSMO Pocket) and brought it back to the 40m. The kit is now placed in the control room cabinet together with the Canon DSLR.

I might have left the USBC chaging cable at home this time. Will bring it back next time.-> The cable was returned to the kit on Oct 23rd.

  15642   Fri Oct 23 19:01:57 2020 KojiSummaryPEMPSL Particle Counter kit removed from the table

The particle counter on the 40m PSL was removed. The package was made together with the OMC lab particle counter (see the packing list below).

The kit was picked up by Radhika for a python code to read out the numbers.

=== Packing List ===

  • MET ONE 227A particle counter
    • used at the 40m. It has the particle reading and the temperature reading.
  • Power supply adapter (AC/DC) for 227A
    • Caution: It is not compatible with GT-321.
  • MET ONE GT-321
    • I found another type of particle counter in West Bridge.
  • Power supply adapter (AC/DC) for GT-321. (Labeled "for GT-321")
    • Caution: It is not compatible with 227A.
  • DB9 cable for GT-321
  • Air Filter G3111
    • When you run a particle counter attach this filter instead of the dust collecting cup to keep the air in take of the particle counter clean. This should keep the particle level down to zero.
  15650   Thu Oct 29 09:50:12 2020 anchalSummaryCalibrationPreliminary calibration measurement taken

I went to 40m yesterday at around 2:30 pm and Koji showed me how to acquire lock in different arms and for different lasers. Finally, we took a preliminary measurement of shaking the ETMX at some discrete frequencies and looking at the beatnote frequency spectrum of X-end laser's fiber-coupled IR and Main laser's IR pick-off.

Basic controls and measurement 101 at 40m

  • I learned a few things from Koji about how to align the cavity mirrors for green laser or IR laser.
  • I learned how to use ASS and how to align the green end laser to the cavity. I also found out about the window at ETMX chamber where we can directly see the cavity mode, cool stuff.
  • Koji also showed me around on how to use diaggui and awggui for taking measurements with any of the channels.

Preliminary measurement for calibration scheme

We verified that we can send discrete frequency excitation signals to ETMX actuators directly and see a corresponding peak in the spectrum of beatnote frequency between fiber-coupled X-end IR laser and main laser IR pickoff.

  • I sent excitation signal at 200 Hz, 250 Hz and 270 Hz at C1:SUS-ETMX_LSC_EXC channel using awggui with an amplitude of 100 cts and gain of 2.
  • I measured corresponding peaks in the beatnote spectrum using diaggui.
  • Page 1 shows the ASD data for the 4 measurements taken with Hanning window and averaging of 10.
  • Page 2 shows close up Spectrum data for the 4 measurements taken with flattop window and averaging of 10.
  • I converted this frequency signal into displacement by using conversion factor \nu_{FSR}/\frac{\lambda}{2} or \frac{L \lambda}{c}.

If full interferometer had been locked, we could have used the DARM error signal output to calibrate it against this measurement.


  15687   Mon Nov 23 23:27:43 2020 KojiSummaryASCQ3000 characterization

Last week and this week I've been working on the characterization of the Q3000 QPDs. The QPDs were named 81, 82, 83, and 94.

  • Dark current [OMC LAB ELOG 402]: All the segments looked similar and acceptable except for the seg1 of #82. It has a smaller reverse breakdown voltage (~6V) but even this is an acceptable level.
  • Impedance [OMC LAB ELOG 403]: All the segments showed a ~300pF junction capacitance with no reverse bias. This looks quite normal.
  • Dark noise [OMC LAB ELOG 404]: All the segments showed ~5pA/rtHz dark noise above 1Hz.

My recommendation is to use #81 and #84 as they have similar dark current characteristics between the segments. But basically, all the QPDs look fine.

The actual junction capacitance and the RF dark noise should be characterized by the actual WFS head circuit.

The QPD packages were labeled and returned to Gautam to be implemented in the WFS heads.

gautam: S/N #84 was installed as the AS WFS QPD. The remaining 3 are stored in the clean cabinet at EX (where the rest of the RF photodiodes are).

  15693   Wed Dec 2 12:35:31 2020 PacoSummaryComputer Scripts / ProgramsTC200 python driver

Given the similarities between the MDT694B (single channel piezo controller) and TC200 (temperature controller) serial interfaces, I added the pyserial driver here

*Warning* this first version of the driver remains untested

  15694   Wed Dec 2 15:27:06 2020 gautamSummaryComputer Scripts / ProgramsTC200 python driver

FYI, there is this. Seems pretty well maintained, and so might be more useful in the long run. The available catalog of instruments is quite impressive - TC200 temp controller and SRS345 func gen are included and are things we use in the lab. maybe you can make a pull request to add MDT694B (there is some nice API already built I think). We should also put our netgpibdata stuff and the vacuum gauge control (basically everything that isn't rtcds) on there (unless there is some intellectual property rights issues that the Caltech lawyers have to sort out).


Given the similarities between the MDT694B (single channel piezo controller) and TC200 (temperature controller) serial interfaces, I added the pyserial driver here

*Warning* this first version of the driver remains untested

  15774   Wed Jan 20 18:07:09 2021 AnchalSummaryBHDHAM-A Coil Driver measurements before modifications

I have taken transfer functions and noise measurements of the two HAM-A coil driver boxes D1100687 #S2100027 and #S2100028. All transfer functions look as expected. I'm not sure about the noise measurements. If anyone sees flaw in my measurement method, please let me know. I'm not sure why in some channels I got 10Hz harmoni peaks in the noise. That was very strange. Also let me know if my current noise estimate is wrong.

Transfer Function Measurement details

  • SR785 source out was connected to the differential amplifier input of D1900068.
  • The one pair of two BNC outputs of this differential amplifier goes directly to the SR785 Input 1 A and B.
  • The DB9 output of the differential amplifier goes to the Coil Input DB9 connector J3.
  • Header W2 was shorted to provide ground to the incoming signal.
  • Header P4 was shorted to enable all the channels manually.
  • Normal operation is the Acquisition mode (Acq) while when pins of header P3 are shorted, we go into the Run mode for respective channel.
  • The “To Satellite Box” DB25 port at the read side was conencted to a DB25 breakout circuit and pins 1-9, 3-11, 5-13 and 7-15 were connected to 36 Ohm resistor to simulate Coil load.
  • The “Output Monitor” on the rear side is then connected to the test switch DB9 port on D1900068.
  • The the pair of BNCs from the test switch is connected to SR785 Input 2 A and B.
  • Measurements are taken with file D1100687_TF.yml and D1100687_TF_LF.yml.
  • A measurement of just cables without the DUT is taken as well.
  • Commands.txt list all the commands used.
  • All data is compiled and plotted in Plotting.ipynb
  • D1100117_S2100027_TF.pdf and D1100117_S2100028_TF.pdf shows all the transfer functions measured.

Spectrum Measurements

  • All channels were kept in disabled mode (Not shorting P4) to ensure their inputs are grounded on the board.
  • I ran two BNC cables with their centers connected to output monitors V2+ and V2- and one of their shields connected to board GND.
  • in SR785, A-B differential mode always runs with grounded shields mode, so effectively the board GND got grounded to SR785 GND through internal 50 Ohm resistor. But all ground loops have been evaded.
  • The two BNC cables were twisted together to minimize the area between the two center cores of the cables as that is the remaining pickoff possible in this measurement.
  • Instrument noise with cables was measured first but shorting the clips of the center cores and one of the shields of the two BNC cables together.
  • Measurements were taken with file D1100687_SP.yml and D1100687_SP_LF.yml.
  • D1100117_S2100027_Voltage_Noise_Spectrum.pdf and D1100117_S2100028_Voltage_Noise_Spectrum.pdf shows the measured voltage noise spectrum at the output monitors when loaded with 36 Ohms.
  • D1100117_S2100027_Current_Noise_Spectrum.pdf and D1100117_S2100028_Current_Noise_Spectrum.pdf shows the esitmate current noise through the coil calculated by dividing the measured voltage noise by 2436 Ohms.
  15776   Mon Jan 25 18:18:04 2021 AnchalSummaryBHDSatellite Amplifier Transfer Functions and noise


I took transfer function and noise measurement of satellite amplifier box's photodiode transimpedance circuit. For the measurement, I created a makeshift connector to convert backside DB25 into DB9 with the 4 channels for PDA input. The output was taken in differential form at the front PD Output port. To feed current to the circuit, I put in 12 kOhm resistors in series at the inputs, so the V/V transfer function measured was multiplied by 12 kOhm to get the transimpedance of the circuit.

Transfer Function Measurement details

  • SR785 source out was fed into PDA input pins using a makeshift BNC-DB9-DB25 converter.
  • The output from PDOut DB9 port was fed to test switch in D1900068 to separate differential signal.
  • This differential signal was fed back to SR785 at input 2 in A-B configuration.
  • Measurements are taken with file D1002818_TF.yml and D1002818_TF_LF.yml.
  • A measurement of just cables without the DUT is taken as well.
  • Commands.txt list all the commands used.
  • All data is compiled and plotted in Plotting.ipynb
  • D1100117_S2100029_TFandNoiseSpectrum.pdf shows all the transfer functions measured.

Spectrum Measurements

  • Two pair of BNC cables were twisted together and clips were added at ends.
  • One of the GND was connected to board GND. Rest were left unconnected to avoid ground loops.
  • Each pair of signal was connected to PDOutP/N.
  • The PDA inputs were shorted together to make zero input current to the board.
  • Instrument noise with cables was measured by shorting the clips of the center cores and one of the shields of the two BNC cables together.
  • Measurements were taken with file D1002818_SP.yml and D1002818_SP_LF.yml.
  • Input referred current noise spectrum was calculated by dividing the output voltage noise spectrum by the measured transfer function.
  • D1100117_S2100029_TFandNoiseSpectrum.pdf shows all the output votlage noise spectrum and input referred current noise spectrum measured.

Edit Wed Feb 10 15:14:13 2021 :


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