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  16992   Tue Jul 12 14:56:17 2022 TomislavSummaryElectronicsElectronics noise measurements

[Paco, Tomislav]

We measured the electronics noise of the demodulation board, whitening board, and ADC for WFSs, and OPLEV board and ADC for DC QPD in MC2 transmission. We were using SR785.

Regarding the demodulation board, we did 2 series of measurements. For the first series of measurements, we were blocking WFS (attachment 1) and measuring noise at the output of the demod board (attachment 2a). This measurement includes dark noise of the WFS, electronics noise of demod board, and phase noise from LO. For the second series of the measurements, we were unplugging input to the demod board (attachment 2b & 2c is how they looked like before unplugging) (the mistake we made here is not putting 50-ohm terminator) and again measuring at the output of the demod board. This measurement doesn't include the dark noise of the WFS. We were measuring it for all 8 segments (I1, I2, I3, I4, Q1, Q2, Q3, Q4). The dark noise contribution is negligible with respect to demod board noise. In attachments 3 & 4 please find plots that include detection and demodulation contributions for both WFSs.

For whitening board electronics noise measurement, we were terminating the inputs (attachment 5) and measuring the outputs (attachment 6). Electronics noise of the whitening board is in the attachments 7 & 8.

For ADC electronics noise we terminated ADC input and measured noise using diaggui (attachments 9 & 10). Please find these spectra for WFS1, WFS2, and MC TRANS in attachments 11, 12 & 13.

For MC2 TRANS we measured OPLEV board noise. We did two sets of measurements, as for demod board of WFSs (with and without QPD dark noise) (attachments 14, 15 & 16). In the case of OPLEV board noise without dark noise, we were terminating the OPLEV input. Please find the electronics noise of OPLEV's segment 1 (including dark noise which is again much smaller with respect to the OPLEV's electronics noise) in attachment 17.

For the transfer functions, demod board has flat tf, whitening board tf please find in attachment 18, ADC tf is flat and it is (2**16 - 1)/20 [cts/V], and dewhitening tf please find in attachment 19. Also please find the ASD of the spectral analyzer noise (attachment_20).

Measurements for WFS1 demod and whitening were done on 5th of July between 15h and 18h local time. Measurements for WFS2 demod and whitening were done on 6th of July between 15h and 17h local time. All the rest were done on July 7th between 14h and 19h. In attachment 21 also find the comparison between electronics noise for WFSs and cds error signal (taken on the 28th of June between 17h and 18h). Sorry for bad quality of some pictures.

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  16763   Thu Apr 7 20:33:42 2022 TommyUpdateElectronicsRFSoC 2x2 board -- setup for remote work

To access the board remotely through the 40m lab ethernet port, use

ssh -N -L localhost:1137:localhost:9090 xilinx@<ip_address>

Then in the browser go to

localhost:1137/lab

Other SSH commands using different ports or without the -N -L seemed to fail to open Jupyter. This way has been successful thereafter.

Quote:

[Tommy, Paco]

Since last week I've worked with tommy on getting the RFSoC 2x2 board to get some TFs from simple minicircuits type filters. The first thing I did was set up the board (which is in the office area) for remote access. I hooked up the TCP/IP port to a wall ethernet socket (LIGO-04) and the caltech network assiggned some IP address to our box. I guess eventually we can put this behind the lab network for internal use only.

After fiddling around with the tone-generators and spectrum analyzer tools in loopback configuration (DAC --> ADC direct connection), we noticed that lower frequency (~ 1 MHz) signals were hardly making it out/back into the board... so we looked at some of the schematics found here and saw that both RF data converters (ADC & DAC) interfaces are AC coupled through a BALUN network in the 10 - 8000 MHz band (see Attachment #1). This is in principle not great news if we want to get this board ready for audio-band DSP.

We decided that while Tommy works on measuring TFs for SHP-200 all the way up to ~ 2 GHz (which is possible with the board as is) I will design and put together an analog modulation/demodulation frontend so we can upconvert all our "slow" signals < 1MHz for fast, wideband DSP. and demodulate them back into the audio band. The BALUN network is pictured in Attachment #2 on the board, I'm afraid it's not very simple to bypass without damaging the PCB or causing some other unwanted effect on the high-speed DSP.

 

  16764   Thu Apr 7 20:37:06 2022 TommyUpdateElectronicsRFSoC 2x2 Board -- Simple Tone Generator

In the "Tommy" sub folder, I created a new notebook called "SimpleToneGenerator". This tunes the DAC and ADC mixers to a single frequency and reads off the Time Series and Fourier components. We can alos easily check the demodulation scheme and implement butterworth filters to check their function.

  16765   Thu Apr 7 20:41:15 2022 TommyUpdateElectronicsRFSoC 2x2 Board -- Gain Plotter

In this file (under Tommy), we have a notebook which runs through a spectrum of frequencies and determines the gain response of the attached filter. Below we have the output of a high pass filter. We use IQ demodulation to change IQ componets to DC. Then using a butterworth filter, we read out the DC components and determine the gain's magnitude and phase. However, the phase seems very noisy. This is because the oscillators in the different tiles are independent and a random phase is introduced by changing the mixer frequency in individual tiles. To resolve this we need Multi Tile Synchronization or "MTS". 

Original Pynq Support Forum Query: https://discuss.pynq.io/t/rfsoc-2x2-phase-measurement/3892

We also have the code to fit a resposne function using IIRregular, but this is not as useful without proper phase data.

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  16790   Wed Apr 20 14:56:06 2022 TommyUpdateElectronicsRFSoC 2x2 board -- setup for remote work & BALUN saga

Here are a few options for replacement BALUNs from Mini Circuits and specs:

Current. TCM1-83X+, 10-8000 MHz, 50 Ohms, Impedance Ratio 1, Configuration K

1. Z7550-..., DC-2500 MHz (some DC-2300), 50/75 Ohms, Impedance Ratio 1.5, Configuration Q. There are various types of the Z7550 which have different connectors (SMA and BNCs). These have much larger dimensions than the TCM1-83X. Can handle up to 5A DC current with matching loss 0.6 dB.

2. SFMP-5075+, DC-2500 MHz, 50/75 Ohms, Impedance Ratio 1.5, Configuration D. This is an SMA connected BALUN. It can handle 350mA, has a matching loss 0.4 dB, and has 1W power handling.

Quote:

Seems like it should be possible to just remove the transformer (aka as a BALUN ... BALanced, UNbalanced), or replace it with a lower frequency part. Its just a usual mini-circuits part. Maybe you can ask Chris Stoughton about this and ask Tommy to checkout some of the RFSoC user forums for how to go to DC.

Quote:
 

After fiddling around with the tone-generators and spectrum analyzer tools in loopback configuration (DAC --> ADC direct connection), we noticed that lower frequency (~ 1 MHz) signals were hardly making it out/back into the board... so we looked at some of the schematics found here and saw that both RF data converters (ADC & DAC) interfaces are AC coupled through a BALUN network in the 10 - 8000 MHz band (see Attachment #1). This is in principle not great news if we want to get this board ready for audio-band DSP.

We decided that while Tommy works on measuring TFs for SHP-200 all the way up to ~ 2 GHz (which is possible with the board as is) I will design and put together an analog modulation/demodulation frontend so we can upconvert all our "slow" signals < 1MHz for fast, wideband DSP. and demodulate them back into the audio band. The BALUN network is pictured in Attachment #2 on the board, I'm afraid it's not very simple to bypass without damaging the PCB or causing some other unwanted effect on the high-speed DSP.

 

model_no case_style single2single single2bal bal2bal center_tap dc_iso freq_low freq_high impedance imped_ratio interface tech config
SFMP-5075+ FF1891 Y N N N N DC 2500 50/75 1.5 CON CORE & WIRE D
TCM1-83X+ DB1627 N Y Y N N 10 8000 50 1 SMT CORE & WIRE K
Z7550-BFNF+ H795-14 Y N N N N DC 2500 50/75 1.5 CON CORE & WIRE Q
Z7550-BMBF+ QP1876-1 Y N N N N DC 2300 50/75 1.5 CON CORE & WIRE D1
Z7550-BMNF+ QP1876 Y N N N N DC 2500 50/75 1.5 CON CORE & WIRE Q
Z7550-FFNM+ H795-1 Y N N N N DC 2300 50/75 1.5 CON CORE & WIRE Q
Z7550-FFSF+ H557-1 Y N N N N DC 2500 50/75 1.5 CON CORE & WIRE Q
Z7550-FMSF+ H795-3 Y N N N N DC 2300 50/75 1.5 CON CORE & WIRE Q
Z7550-FMSFDC+ H795-3 Y N N N Y 1 2500 50/75 1.5 CON CORE & WIRE Q
Z7550-NFNF+ H795-10 Y N N N N DC 2500 50/75 1.5 CON CORE & WIRE D1
Z7550-NMNF+ H795-4 Y N N N N DC 2300 50/75 1.5 CON CORE & WIRE Q
  16807   Sun Apr 24 13:17:08 2022 TommyUpdateElectronicsNew RFSoC2x2 Overlay

We recieved an overlay from Chris Stoughton which he used for a ZCU11 board. The overlay is supposed to be compatible with the RFSoC 2x2 and help enable the Multi-Tile Synchronization (MTS) we need. He also provides a .py with the necessary low level connection to the board and its memory along with a few sample notebooks.

Progress So Far:

  • The overlay loads properly and in reasonable time. 
  • We can set the mixer and dac frequencies. However, it is unclear what event_src Chris wanted for the adc mixers. It seems that he was using event_src_immediate (possibly unintenionally) which is not an available adc mixer setting in our board. Instead, we set the event source to "Tile" and will later determine if this is an issue.
  • We then go to get data from the buffer. There are two functions called: capture and transfer. These are called on the pynq DMA. Capture runs fine but we get stuck during the transfer at dma.revchannel.wait(). This issue has not been resolved.
  16813   Tue Apr 26 16:23:22 2022 TommyUpdateElectronicsRFSoC2x2 MTS

We connected a 8 MHz signal generator to the device in order to sync up the ADCs and DACs and hopefully get phase data. 

Some things to note:

  • RF Manual (143)- Need to use XRFDC SYSREF for update event
  • RF Manual (171)- Synchronization steps require us to first enable all clocks and sysref generators (via xrfdc package)
  • RF Manual (173)- Sysref requirments, not clear if PL is syncing as needed.
  • RF Manual (181)- XRFDC example code, see also https://github.com/Xilinx/embeddedsw/blob/master/XilinxProcessorIPLib/drivers/rfdc/examples/xrfdc_mts_example.c

Xilinx RF Manual: https://docs.xilinx.com/v/u/2.4-English/pg269-rf-data-converter

  16857   Mon May 16 14:46:35 2022 TommyUpdateElectronicsRFSoC MTS Work

We followed the manual's guide for setting up MTS to sync on external signal. In the xrfdc package, we update the RFdc class to have RunMTS, SysRefEnable, and SysRefDisable functions as prescribed on page 180 of the manual. Then, we attempted to run the new functions in the notebook and read the DAC signal outputs on an oscilloscope. The DACs were not synced. We were also unable to get FIFOlatency readings. 

  16876   Thu May 26 15:55:10 2022 TommyUpdateElectronicsRFSoC Power Spectrum

Finished building power spectrum analyzer for the RFSoC. There are two things that I would like to address down the road. First is that there is an oscillation between positive and negative voltages at the ADC sampling frequency. This creates an undesirable frequency component at the sampling rate. I have not yet figured out the cause of this positive to negative oscillation and have simply removed half of the samples in order to recover the frequency. Therefore, I would like to figure out the root of this oscillation and remove it. Also, we have a decimation factor of 2 as default by the board which we would like to remove but have been unable to do so.

Example: 8 MHz Square Wave from SRL signal generator.

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  16879   Fri May 27 15:53:17 2022 TommyUpdateElectronicsRFSoC MTS Work

With some help from the forums, we printed the status of the DAC MTS sync and were able to determined that our board's vivado design does not have MTS enabled on each tile. To fix this, we will need to construct a new Vivado desgin for the board. We were also warned to "make sure to generate correctly a PL_clock and a PL_sysref with your on board clock synthesizers and to capture them in the logic according to the requirements in PG269" of the RF Manual. From this we should be able to sync the DAC and ADC tiles as desired.

Quote:

We followed the manual's guide for setting up MTS to sync on external signal. In the xrfdc package, we update the RFdc class to have RunMTS, SysRefEnable, and SysRefDisable functions as prescribed on page 180 of the manual. Then, we attempted to run the new functions in the notebook and read the DAC signal outputs on an oscilloscope. The DACs were not synced. We were also unable to get FIFOlatency readings. 

 

  14014   Mon Jun 25 19:14:02 2018 UditSummaryGeneralRe: A summary of the Tip-TIlt Mirror Holder design changes

2. Weighted screw rod at the bottom for tilting the mirror-holder:

The screw length selected here (2") is not interfering with any part of the assembly.

The 'weights' I have here are just thumb nuts from Mcmaster, so their weight is fixed (1.65g each, btw).

Problem I'd like to solve: Find an assortment of weighted, symmetric nuts with caps on one end to fix position on shaft. 

3. Set-screws on both side of wire clamp to adjust its horizontal position:

Thanks for pointing out the mismatch in travel distance of protrusion and clamp screws. To match them, the clamp screw slot now sticks out of the profile (by 1.5mm). The range of the clamp motion is +/- 3 mm.

Also, here's a screenshot of the slot in the mirror holder:

--

- Excluding the weighted screw rod assembly, the height gap between assembly COM and wire release point is 3.1 mm.

Quote:

> 2. Weighted screw rod at the bottom for tilting the mirror-holder:

Too long. The design of the holder should be check with the entire assembly.
We should be able to make it compact if we heavier weights.
How are these weights fixed on the shaft?
Also can we have options for smaller weights for the case we don't need such a range?
Note the mass of the weights.

> 3. Set-screws on both side of wire clamp to adjust its horizontal position:

How much is the range of the clamp motion limited by the slot for the side screws and the slot for the protrusion? Are they matched?
Can you show us the design of the slot made on the mirror holder?

>>

Where is the center of mass (CoM) for the entire mirror holder assy and how much is the height gap between the CoM and the wire release points. Can you do this with 3/8" and 1/2" fused silica mirrors?

 

  13429   Thu Nov 16 00:14:47 2017 Udit KhandelwalUpdateSUSSOS Sapphire Prism design

Summary:

  • SOS solidworks model is nearly complete
    • Having trouble with the design of the sensor/actuator head assembly and the lower clamps
  • After Gautam's suggestion, installed Abaqus on computer. Teaching it to myself to eventually do FEM analysis and find resonant frequency of the system
    • Goal is to replicate frequency listed in the SOS documents to confirm accuracy of computer model, then replace guide rods with sapphire prisms and change geometry to get same results

 

Questions:

  • How accurate do the details (like fillet, chamfer, placement of little vent holes), and material of the different SOS parts need to be in the model?
  • If I could get pictures of the lower mirror clamp (document D960008), it would be helpful in making solidworks model. Document is unclear. Same for sensor/actuator head assembly. 
  13460   Fri Dec 1 17:09:29 2017 Udit KhandelwalSummaryGeneral 

Current objectives and statuses:

  • CAD Model of 40m lab (facility, chambers, invacuum components etc)
    • Status: On hold since I'm unable to acquire general dimensions of 
  13472   Wed Dec 13 17:46:08 2017 Udit KhandelwalSummaryGeneralSummary of Current Tasks

40m Lab CAD

1. 40m_bldg.dwg has 2D drawing of the 40m building

  • After importing file as a 2D sketch into solidworks, make sure to retrace all the lines before performing any 3D extrusion stuff.
  • Made walls 3m high

2. 40m_VE.dwg has the Vaccuum Envelope.

  • Divided the file into individual sketches for the tubes, test mass, and beam splitter chambers (so they can be individually modified later if required).

3. 40melev.dwg has the relative positioning between (1) and (2).

  • Using this file to position objects inside building cad.

4. All files can be found in Dropbox folder [40m SOS Modeling], which should be renamed to [40m CAD].

5. Next step would be to add the optical table, mirrors.

Tip-Tilt Suspension

1. Current objective: (refer to D070172) - Increase the length of the side arms (so it matches the dimensions of D960001), while keeping the test mass subassembly at the same height.
2. Future objective: Resonant frequency FEM of the frame (sans the test mass), and then change height to get the desired frequency.

Past Work

  • Completed solidworks model of SOS (D960001). I understand this is not the focus right now so this is for reference that the model is ready to be used.

Comments

  • I will be in India from 16th December until 6th January so this is my final visit for this year. I have enough material to work from home, and will correspond with Koji over email regarding Lab CAD and tip-tilt suspension.
  13544   Fri Jan 12 20:35:34 2018 Udit KhandelwalSummaryGeneral2018/01/12 Summary
  1. 40m Lab CAD
    1. Worked further on positioning vacuum tubes and chambers in the building.
    2. Next step would be to find some drawings for optical table positions and vibration isolation stack. Need help with this! 
  2. Tip Tilt Suspension (D070172)
    1. Increased the length of side arms. The overall height of D070172 assembly matches that of D960001.
    2. The files are present in dropbox in [40mShare] > [40m_cad_models] > [TT - Tip Tilt Suspension]
  13560   Fri Jan 19 15:22:19 2018 Udit KhandelwalSummaryGeneral40m CAD update 2018/01/19

40m CAD Project

  1. All parts will be now named according to the numbering system in this excel sheet: LIGO 40m Parts List in dropbox folder [40mShare] > [40m_cad_models] > [40m Lab CAD]
  2. I've placed optical tables in the chambers at 34.82" from the bottom for now. This was chosen by aligning the centre of test mass of SOS assembly (D960001) with that of vacuum tube (Steve however pointed out last week they might not necessarily be concentric).

  13561   Fri Jan 19 20:59:07 2018 Udit KhandelwalUpdateGeneralSolidworks Rendering

Rendered the SOS assembly (D960001) with correct materials and all and it looks very nice. Will extend this to the building cad later.

  13601   Fri Feb 2 21:12:46 2018 Udit KhandelwalSummaryGeneralSummary - 2018/02/02

Tip-Tilt Suspension CAD:
Discussed with Koji about motivation to simplify the design of this assembly, which has many unnecessary over-constraints. I have started to cad alternate parts with the aim of removing these over-constraints.

40m Lab CAD:
Acquired a stack of original engineering drawings of the vacuum chambers from Steve which I will take home, get scanned, and then use as reference for the cad i'm working on.

Other:
Started paperwork at west bridge office to get paid as an "occasional employee". Hopefully I receive old money.

  13638   Fri Feb 16 21:03:17 2018 Udit KhandelwalSummaryGeneralSummary 2018/02/16

40m Lab Cad:
Updated the dimensions of and fleshed out the chambers in greater detail, by referring to the engineering drawings that Steve gave to me. I have scanned and uploaded most of these drawings to Dropbox in [40mShare]>[40m_cad_models]>[Vacuum Chamber Drawing Scans]. The excel file "LIGO 40m Parts List" in the [40m Lab CAD] folder also lists the Steve drawings I referenced for dimensions of each part.


Next steps:
1. Finish details of all chambers.
2. Start placing representative blocks on the optical table.

  13654   Fri Feb 23 20:46:04 2018 Udit KhandelwalSummaryGeneralCAD Summary 2018/02/23

I have more or less finished cadding the test mass chamber by referring to the drawings Steve gave me. Finer details like lugs and bolts and window flaps can be left for later. Here's a quick render:

  13677   Fri Mar 9 20:35:41 2018 Udit KhandelwalSummaryGeneralSummary 2018/03/09

1. Optical Table Layout 

I had discussed with Koji a way to record coordinates of optical table equipments in a text file, and load to solidworks. The goal is to make it easier to move things around on the table in the CAD. While I have succeeded in importing coordinates through txt files, there is still a lot of tediousness in converting these points into sketches. Furthermore, the task has to be redone everytime a coordinate is added to or changed in the txt file. Koji and I think that this can all be automated through solidworks macros, so I will explore that option for the next two weeks.

2. Vacuum Chamber CADs 

Steve will help find manufacturing drawings of the BS chamber. I have completed the ETM chambers, while the ITM ones are identical to them so I will reuse parts for the CAD. 

  13865   Fri May 18 18:14:18 2018 Udit KhandelwalSummaryGeneralSummary 05/18/2018

Tip-Tilt Suspension Design:

Designed a new ECD plate and changed dimensions of the side arms after discussing with Koji. After getting feedback on the changes, I will finish the assembly and send it to him to get approved for manufacturing.

 

  13884   Wed May 23 19:24:37 2018 Udit KhandelwalSummaryGeneralSummary 05/23/2018

Tip-Tilt Redesign Project with Koji:

Did further itirations to the ECD backplate. Going to determine minimum thickness between magnet hole and plus sign for eddy current damping.

Chamber optical table layouts

Finished the positioning of optics and instruments in SolidWorks for the Vertex chambers. The reference for positioning is "40m_upgrade_layout_Dec2012.dwg", and solidworks files I created are in the main 40m CAD folder.

  13996   Thu Jun 21 14:23:22 2018 Udit KhandelwalSummaryGeneralA summary of the Tip-TIlt Mirror Holder design changes

Here’s a quick summary of the Tip-Tilt Design updates (all files are in the dropbox in [TipTiltSus>TT_New]) that I have been working on with Koji and Steve's help.

1. Plate on top to hold mirror in place:

The plate is 0.5 mm thick. I did a rough FEA with 10 N force on the point of pressure on it, and it bent easily.

2. Weighted screw rod at the bottom for tilting the mirror-holder:

I did a very simplified free body analysis to calculate the required length of the rod to achieve a +/- 15 mRad tilt, and got around 1.5 inches.

3. Set-screws on both side of wire clamp to adjust its horizontal position:

  • Front view (showing set screws on either side of the clamp to push it into the desired position, and the clamp in the middle with screws on top and bottom to fix its position):

  • Exploded view showing protrusion in clamp that sits in the mirror holder inset:

 

  • Exploded view showing inset in the mirror holder to slide protrusion in:

 

 

Comments:

1. Used the same screw size in most places to reduce complexity.

2. The mirror holder I have worked on is a little different from the actual piece I have on my table. Which one do you prefer (Koji)?

  14042   Fri Jul 6 19:39:37 2018 Udit KhandelwalSummaryGeneralCAD drawings of cantilever suspension required

Request to Koji to acquire the drawings or 3D CAD of the cantilever suspensions of the Tip-Tilt Assembly!

  14047   Mon Jul 9 17:29:28 2018 Udit KhandelwalSummaryTip-TIltTipTilt mirror holder final changes

Final Summary of changes to mirror holder in Tip-Tilt holder.

Determining minimum range for Side Clamp:

1. The initial distance b/w wire-release point and mirror assembly COM = 0.265 mm


2. But this distance is assuming that wire-release point is at mid-point of clamp. So I'm settling on a range of +/- 1mm. The screenshots below confirm range of ~1mm between (1) side screw & protrusion and (2) clamp screw and clamp.

Determining length of tilt-weight assembly rod at the bottom to get \pm 20mRad range

The tilt-weight assembly is made from following Mcmaster parts:
Rod   - 95412A864 18-8 SS  #2-56 Threaded Rod
Nuts  - 91855A103 18-8 SS #2-56 Acorn Cap Nut

Since the weights are fixed, only rod length can be changed to get the angle range.

tan \theta =\frac{d}{h}

d= h \times tan\theta = 34.25\text{mm} \times tan(20 \text{mRad}) = 0.69 \text{mm}
So a range of 1 mm between nut's inner face and mirror-holder face should be enough. Since holder is 12 mm thick, rod length = 12mm + 2 x 1mm + 2 x (nut length) = 12 + 2 + 9.6 = 23.6 mm = 0.93 inch. So a 1" rod from Mcmaster will be fine.

Attachment 4: 2-1.png
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  6161   Tue Jan 3 17:46:38 2012 Updated Stewart platform design requirementsUpdateGeneralUpdated design requirements for a Stewart platform

I updated the design requirements for the Stewart platform.  I weighed the unloaded "dirty" SOS that was sitting on the workbench in the control room; its mass is 11 kg.  Steve suggested that the OSEMs (not installed on this model) would add another 0.5 kg.  From the specs in the final SOS design document, LIGO-T970135, I added 0.25 kg for the optic itself; I am therefore taking the total payload mass to be 11.75 kg.  (Now, the upper stage of the Stewart platform itself will likely add a nontrivial amount, but I am not worrying about this yet.)

I have e-mailed Janeen Romie to obtain the actual center of mass and principal moments of inertia of the platform.  I also cooked up a simple scheme to measure both quantities, should this information not be available.  It would involve rigidly mounting the dirty SOS to a rigid bar hung from a pivot.  By translating the mount point in two dimensions and measuring the period of the pendulum, I ought to be able to find the center of mass and moments of inertia by multilinear regression.  However, this elaborate scheme is not necessary to just compute some ballpark figures; it could wait until a later stage in the design.  For the time being, I just rescaled the moment of inertia proportional to the increase in mass, such that the torque-to-force ratio is unchanged.

As such, the design requirements are now 

  • linear travel: 40 microns peak to peak (based on SOS design requirements in LIGO-T950011)
  • angular travel: 3 mrad peak to peak (based on SOS design requirements in LIGO-T950011)
  • payload mass: 11.75 kg (measured unloaded mass, plus educated guesses about combined mass of OSEMs and optic)
  • payload moment of inertia: 0.0232 kg m^2 (wild guess)
  • bandwidth: 500 Hz (suggestion of Rana and Koji: ~kHz)

From these assumptions, the revised actuator requirements and dimensions are:

  • peak actuator force: 2.04 kN
  • minimum radius of top platform: 15 cm
  • minimum radius of bottom platform: 30 cm
  • minimum height: 26 cm

See the attached PDF document.

It appears that the actuator that I had originally nominated, PI's model P-225.80, would very nearly meet the actuator force requirement.  Steve also pointed out the following single-axis shakers that are already in use in the 40m:

  • Brüel & Kjær type 4809
  • Brüel & Kjær type 4810

I want to find out if either of these would meet the present need, but I'm waiting on a response from the manufacturer to get access to the data sheets.

 

Attachment 1: stewart.pdf
stewart.pdf stewart.pdf stewart.pdf stewart.pdf stewart.pdf stewart.pdf stewart.pdf stewart.pdf
  397   Sun Mar 23 10:42:54 2008 ValeraSummaryElectronicsRFAM of the RF stabilization box is measured
I reconstructed Tobin's setup to measure the RFAM after the RF stabilization box in the 166 MHz modulation path.
The setup consisted of the splitter and the mixer followed by the RF low pass filter and the SR560 (gain x100).
The RF level into splitter was 20 dBm. The Mini-Circuits ZLW-3H (17 dBm LO) mixer was used. The LO was taken
straight out of the splitter and the RF path was attenuated by 11 dBm, The DC out of the mixer was 700 mV.
The noise floor was measured with the RF input of the mixer terminated on 50 Ohm. The 45 MHz measurement
in broad band setting looks better than the noise floor at high frequencies. I am not sure what was wrong with
one or both of those measurements. The 9 MHz measurements are above the noise floor.

The RFAM meets the AdvLIGO requirements in the detection band (f > 10 Hz).

The attached zipped files are:
SRS003 9 MHz DC-200 Hz
SRS004 9 MHz DC-26 kHz
SRS006 45 MHz DC-200 Hz
SRS005 45 MHz DC-26 kHz
SRS007 Noise floor DC-200 Hz
SRS008 Noise floor DC-26 kHz
Attachment 1: RFAM.zip
Attachment 2: amplitudenoise.pdf
amplitudenoise.pdf
  12121   Wed May 18 17:42:52 2016 VarunUpdateGeneralSURF 2016

Finished writing the code on whitening. I have to still test it. uploaded on github noise cancellation repo. @eric could you give me some data of noise power spectral density for testing the code?

-Varun

Quote:

Hello, I am Varun Kelkar. I will be working at the 40m lab as a SURF student this summer with Eric Quintero on Audio processing for real time control system signals. This week I will mostly be working on implementing basic DSP C-code offline. Currently I am trying to write a code for noise whitening.

-Varun

 

  12123   Fri May 20 00:06:19 2016 VarunUpdateGeneralSURF 2016

I have written a basic version of AGC, and have done some tests with a data file. will do tests on whitening and agc today. Also, today I have to go to the SSN office. Hence will be late.

 

-Varun

Quote:

Finished writing the code on whitening. I have to still test it. uploaded on github noise cancellation repo. @eric could you give me some data of noise power spectral density for testing the code?

-Varun

Quote:

Hello, I am Varun Kelkar. I will be working at the 40m lab as a SURF student this summer with Eric Quintero on Audio processing for real time control system signals. This week I will mostly be working on implementing basic DSP C-code offline. Currently I am trying to write a code for noise whitening.

-Varun

 

 

  12127   Mon May 23 17:47:51 2016 VarunUpdateGeneralSURF 2016

Tested the AGC today with LSC cavity transmission signal and error signal. Not in real time still.

Key to attachments:

cav_tr-eps-converted-to.pdf: LSC cavity transmission signal input

cav_tr_out-eps-converted-to.pdf: LSC cavity transmission signal, output of the AGC.

Attachment 1: cav_tr-eps-converted-to.pdf
cav_tr-eps-converted-to.pdf
Attachment 2: cav_tr_out-eps-converted-to.pdf
cav_tr_out-eps-converted-to.pdf
Attachment 3: err-eps-converted-to.pdf
err-eps-converted-to.pdf
Attachment 4: err_out-eps-converted-to.pdf
err_out-eps-converted-to.pdf
  12129   Tue May 24 17:55:17 2016 VarunUpdateElectronicsUsing Altium

Contacted Charles regarding use of Altium. Got to know that Altium is installed on cit40m iMac in Win7 on VirtualBox. Had to update Virtualbox to get it working. Altium now works for sometime, but then fails, saying that it is unlicensed.

  12136   Wed May 25 14:29:31 2016 VarunUpdateGeneralSURF 2016

Edited the AGC to include overlapping frames yesterday. forgot to put an elog on it!

Quote:

Tested the AGC today with LSC cavity transmission signal and error signal. Not in real time still.

Key to attachments:

cav_tr-eps-converted-to.pdf: LSC cavity transmission signal input

cav_tr_out-eps-converted-to.pdf: LSC cavity transmission signal, output of the AGC.

 

  12137   Thu May 26 18:10:48 2016 VarunUpdateGeneralSURF 2016

Wrote and tested a function for downconversion. It contains a mixer with a sinusoidal input for modulation with the desired frequency and a 2nd order butterworth low pass filter to remove the higher frequency-shifted part of the modulated signal. I have tested this with input of 2kHz giving a good output of 200 Hz on the speaker. Codes are uploaded on github, will update the real time document tomorrow.

 

-Varun

Quote:

Edited the AGC to include overlapping frames yesterday. forgot to put an elog on it!

Quote:

Tested the AGC today with LSC cavity transmission signal and error signal. Not in real time still.

Key to attachments:

cav_tr-eps-converted-to.pdf: LSC cavity transmission signal input

cav_tr_out-eps-converted-to.pdf: LSC cavity transmission signal, output of the AGC.

 

 

Attachment 1: input.png
input.png
Attachment 2: output.png
output.png
  12139   Fri May 27 11:54:22 2016 VarunUpdateGeneralPackage delivery

A package labelled 'UPS Ground' has arrived.

-Varun

  12143   Wed Jun 1 11:19:14 2016 VarunUpdateGeneralUpdate of work till now

Completed:

Wrote and tested a code for AGC using cavity transmission signal and length error signal.

Wrote and tested a code for frequency shifting (downconversion) using mixing and LPF

Wrote a code for whitening using FFT.

Altium working on cit40m iMac

Plans:

Writing codes for Frequency warping and whitening in time domain.

Implement AGC and frequency shifting on the real time control system.

Calculate requirements for Anti-aliasing filter.

  12150   Fri Jun 3 17:56:14 2016 VarunUpdateGeneralDAFI update

Wrote and tested a phase vocoder, with two of its applications:

1) Time scaling: This enables change of time duration without affecting the pitch.

2) Frequency warping: This changes the pitch of the sound without affecting the time duration.

1 & 2 tested offline with cavity transmission signal. 1) gives speedup of 2, and 2 gives frequency warping (pitch lowering by a factor of 2)

codes uploaded on github repo

  12154   Tue Jun 7 18:20:18 2016 VarunUpdateGeneralDAFI update

Tried to implement AGC on FE. Had some trouble bringing the code into the correct form. It looks okay now. However, this agc code as well as idenntity code (input = output) doesnt seem to build on the c1lsc FE. Have not tried too many debugging steps yet, will come and check the problem tomorrow. 

-Varun

Quote:

Wrote and tested a phase vocoder, with two of its applications:

1) Time scaling: This enables change of time duration without affecting the pitch.

2) Frequency warping: This changes the pitch of the sound without affecting the time duration.

1 & 2 tested offline with cavity transmission signal. 1) gives speedup of 2, and 2 gives frequency warping (pitch lowering by a factor of 2)

codes uploaded on github repo

 

  12159   Wed Jun 8 16:12:38 2016 VarunUpdateGeneralDAFI update

Summary: I am implementing digital audio filtering on various interferometer signals in order to listen to the processed audio which will help in characterizing and noise reduction in the interferometer. Following is an implementation of an Automatic Gain control (AGC) block on an LSC input signal.

Details of AGC: Currently, the AGC code implemented on FE takes input to fill a frame, then calculates the power in each frame and gives an appropriate gain to it, so that the new power content is to the required level. It is then written to the output, frame by frame. The frame is currently a rectangular window. The frame length and hop size can be adjusted. Current values are as follows:

frame length is 512 samples

hop length is 128 samples.

The input and output are delayed by 1 frame.

Details of testing: Attachment 1 shows a simulink diagram of the DAF system. Eric made this and I modified it later on. Testing was done using signal from the "LSC1" channel. Attachments 2 and 3 show aquired input and output of the AGC respectively. Gain of the preamp of the LSC input signal was varied over a total time span of 200 s. Each gain value was kept for a duration of about 20 seconds. The varying power levels can be seen in the input plot.

The output shows a uniform power level throughout.

 

Quote:

Tried to implement AGC on FE. Had some trouble bringing the code into the correct form. It looks okay now. However, this agc code as well as idenntity code (input = output) doesnt seem to build on the c1lsc FE. Have not tried too many debugging steps yet, will come and check the problem tomorrow. 

-Varun

Quote:

Wrote and tested a phase vocoder, with two of its applications:

1) Time scaling: This enables change of time duration without affecting the pitch.

2) Frequency warping: This changes the pitch of the sound without affecting the time duration.

1 & 2 tested offline with cavity transmission signal. 1) gives speedup of 2, and 2 gives frequency warping (pitch lowering by a factor of 2)

codes uploaded on github repo

 

 

Attachment 1: dafi.png
dafi.png
Attachment 2: agcin.pdf
agcin.pdf
Attachment 3: agcout.pdf
agcout.pdf
  12164   Thu Jun 9 19:08:58 2016 VarunUpdateElectronicsAnti-Aliasing Filter update

Eric gave me a psd plot of a signal which would be the input of a channel of the AA filter. the Nyquist freq. is about 32.8kHz.

Following are plots depicting the ratio of the aliased downconverted signal and the signal below 32.8 kHz. The first plot is for (to-be) aliased signal frequencies from 32.8 to 65.5k, and the second plot is for (to-be) aliased signals from 65.5k to 98.3k. In case of the first plot, the 36kHz peak will alias to 29kHz, and is about 30 times (29.5dB) greater than the signal there. Hence, the filter should give about 70dB attenuation there. Since this attenuation is not required by most other frequencies up to 65.5k, an option could be to use a notch filter to remove the frequency peak at 36k, and put a requirement of 45-50 dB attenuation on other frequencies.

In case of the second plot, the frequencies between 90 to 100k again need to be attenuated by more than 70 dB. However, if there is a -20dB/decade slope in stop band, we already have about 10 dB attenuation here as compared to around 32k.

The X axis of both plots is in Hz.

Attachment 1: 32to65.jpg
32to65.jpg
Attachment 2: 65to98.png
65to98.png
  12203   Mon Jun 20 16:33:09 2016 VarunUpdateElectronicsAnti-Aliasing Filter circuit schematic

Summary: The aim is to design an analog anti-aliasing (AA) filter placed before the ADC, whose function is to filter out components of the input spectrum that have frequencies higher than the Nyquist frequency. This needs to be done so that there is no contamination of aliased downconverted high-frequency signals into the ADC output. I have put down and simulated a circuit to do this, based on the spectra of a few interferometer signals that eric Provided. Attachment 1 shows such an input PSD, treated with whitening filter, before the AA. The sampling rate is 65536 Hz and hence the Nyquist freq. is 32768 Hz.

Motivation: Attachments 2 and 3 show the plot of required attenuation for various frequencies above the Nyquist. We can see a peak at 36 kHz, which will alias to about 29kHz. It will require about 70 dB attenuation here. This indicates that use of a notch filter combined with a low pass filter can be used.

Details of Schematic: Attachment 4 shows the schematic of a Boctor low pass notch filter, cascaded by a 2nd order LPF. The stopband frequency of the boctor filter can be tuned to around 36 kHz. Its main advantage for the boctor is better insensitivity to component value tolerances, use of a single op amp, and relatively independent tuning of parameters.  The various component values are calculated from here. The transfer functions for the circuit shown in attachment 4 were simulated using TINA - a spice based simulation software. The transfer function is shown in attachment 5.

A few more calculations: Attachment 6 shows the output psd after the signal has been treated with AA. Attachments 7 and 8 show the ratio of aliased downconverted signal and the unaliased signal of the output. Here, we can see that above about 13 kHz, the ratios go above -40dB, which is apparently undesirable. However, we also see from the transfer function of the filter that the gain falls to less than -20dB after about this frequency, and the aliased signals are atleast 20 dB lower than this, atleast upto about 29 kHz in attachment 7 and about 25 kHz in attachment 8. This means that the aliased signals are negligible as compared to the low frequencies even if they are not negligible as compared to the higher frequencies (above 13 kHz) into which they would get downconverted due to sampling. But these higher frequencies (above 13 kHz) themselves are small.

The filter overall, is 4th order. Considering this and the above discussion, I need to decide what changes to make in the existing schematic. For now, I could discuss with eric to finalize the opamp and start building the pcb board design.

Attachment 1: in.pdf
in.pdf
Attachment 2: 32to65att.pdf
32to65att.pdf
Attachment 3: 65to98att.pdf
65to98att.pdf
Attachment 4: lpf_notch.JPG
lpf_notch.JPG
Attachment 5: lpf_notch.pdf
lpf_notch.pdf
Attachment 6: out.pdf
out.pdf
Attachment 7: out_ratio1.pdf
out_ratio1.pdf
Attachment 8: out_ratio2.pdf
out_ratio2.pdf
  12212   Wed Jun 22 14:03:42 2016 VarunUpdateElectronicsAnti-Aliasing Filter circuit schematic

I found an anti-aliasing circuit on the 40m wiki. It consists of A differential LPF made using THS4131 low noise differential op-amp (one of the main applications of which is preprocessing before the ADC), and a notch. I modified it to arrange for the desired bandwidth (about 8 kHz) and notch after the Nyquist frequency at 36 kHz. I simulated it to get the attached results:

Attachment 1: It shows the input PSD (same as the one posted in the previous elog), the filter transfer function, and The resulting output.

Attachment 2: The circuit schematic. The initial part using THS4131 is a differential LPF and the subsequent RC network is the notch.

Attachment 3: This shows the ratio of the aliased downconverted signal to the the in-band signal, representative of the contamination in each bin. Here too, the aliased signals are negligible as compared to the low frequencies but they are not negligible as compared to the higher frequencies (above 10 kHz) into which they would get downconverted due to sampling. However, here, the attenuation at 8kHz is less than 6 dB while in the previous circuit, it was about 12 dB. One problem with this circuit is at about 6kHz, there is aliased signal from the 65k to 98kHz band, but this can be taken care of by adding an LPF later.

Quote:

Summary: The aim is to design an analog anti-aliasing (AA) filter placed before the ADC, whose function is to filter out components of the input spectrum that have frequencies higher than the Nyquist frequency. This needs to be done so that there is no contamination of aliased downconverted high-frequency signals into the ADC output. I have put down and simulated a circuit to do this, based on the spectra of a few interferometer signals that eric Provided. Attachment 1 shows such an input PSD, treated with whitening filter, before the AA. The sampling rate is 65536 Hz and hence the Nyquist freq. is 32768 Hz.

Motivation: Attachments 2 and 3 show the plot of required attenuation for various frequencies above the Nyquist. We can see a peak at 36 kHz, which will alias to about 29kHz. It will require about 70 dB attenuation here. This indicates that use of a notch filter combined with a low pass filter can be used.

Details of Schematic: Attachment 4 shows the schematic of a Boctor low pass notch filter, cascaded by a 2nd order LPF. The stopband frequency of the boctor filter can be tuned to around 36 kHz. Its main advantage for the boctor is better insensitivity to component value tolerances, use of a single op amp, and relatively independent tuning of parameters.  The various component values are calculated from here. The transfer functions for the circuit shown in attachment 4 were simulated using TINA - a spice based simulation software. The transfer function is shown in attachment 5.

A few more calculations: Attachment 6 shows the output psd after the signal has been treated with AA. Attachments 7 and 8 show the ratio of aliased downconverted signal and the unaliased signal of the output. Here, we can see that above about 13 kHz, the ratios go above -40dB, which is apparently undesirable. However, we also see from the transfer function of the filter that the gain falls to less than -20dB after about this frequency, and the aliased signals are atleast 20 dB lower than this, atleast upto about 29 kHz in attachment 7 and about 25 kHz in attachment 8. This means that the aliased signals are negligible as compared to the low frequencies even if they are not negligible as compared to the higher frequencies (above 13 kHz) into which they would get downconverted due to sampling. But these higher frequencies (above 13 kHz) themselves are small.

The filter overall, is 4th order. Considering this and the above discussion, I need to decide what changes to make in the existing schematic. For now, I could discuss with eric to finalize the opamp and start building the pcb board design.

 

Attachment 1: io.pdf
io.pdf
Attachment 2: AA.JPG
AA.JPG
Attachment 3: ratios_v2.pdf
ratios_v2.pdf
  12251   Wed Jul 6 10:58:29 2016 VarunUpdateCDSDAFI review

The DAFI block was reviewed by Rana yesterday. The following changes/improvements were suggested: (Updated on 20th July 2016 with tasks taat remain in red)

1) include all the various channels like PEM, LSC, ASC, SUS, SEI, etc. as the inputs. Currently the inputs are only the LSC.
2) include all the control signals.
3) create a very detailed diagram of the entire signal flow and plan tasks accordingly.
4) Enable cascading of various DSP processes.
5) Adjusting the gain of the AGC such that the amplitude of the output signal comes to about half the peak amplitude offered by the ADC. This will help taking advantage of the entire dynamic range of the ADC.
6) change the enable button styles from a text input based controller to a button controller.
7) Currently, disabling a particular signal terminates the signal. Instead, it should turn into a unity gain block on disabling.
8) Check if the Fibox does AC coupling or not. If not, add an AC coupling arrangement in the DAFI.
9) Check the nature of the ADC1 and ADC2 inputs to the DAFI. I checked them yesterday, and they are channels 25 and 26 of ADC0, which are empty.

  12118   Tue May 17 05:50:43 2016 Varun KelkarUpdateGeneralSURF 2016

Hello, I am Varun Kelkar. I will be working at the 40m lab as a SURF student this summer with Eric Quintero on Audio processing for real time control system signals. This week I will mostly be working on implementing basic DSP C-code offline. Currently I am trying to write a code for noise whitening.

-Varun

  7558   Tue Oct 16 16:46:20 2012 Vent Czar and CzarinaSummaryGeneralvent stuff

We're discussing the plan for the next vent.  Now that we have all the tip-tilt stuff in hand, we should get ready for the big TT installation vent ASAP.  The question is what remains to be done, and when can we be ready

Stuff that needs doing:

* characterize TTs, check electrical connection of quadrupus cables, bake cables and base plates - a week or so (not including baking)

* phase map of LaserOptik mirrors (decide on needed resolution) - a week or so?

* get ready to swap G&H mirrors with LaserOptik mirrors (PR2, PR3, SR2, SR3)

* assembly of black glass beam dumps - one afternoon

* green periscope moving - day or so to make sure greens are resonant in arms, so we have something to align to

* redraw of REFL path?? (rotate 2nd refl mirror to reflect beam to the east, then add mirror to get beam out of IOO chamber viewport), cut hole in BS oplev table's box, install black beam tube

* FI camera mount - make sure it's here, baked

* active TT pitch damping plan

* passive TT weight addition and pitch alignment plan

* camera plan for taking in-chamber photos without touching the tables

* look at layout of ITMY table.  POY pick-off too close to main beam.  Can we move POY pick-off to BS table?

* remount black glass baffles on SOS cages.

 

Stuff to bake:

* Quadrupus cables

* TT base plates

* FI mirror mount for FI camera

* stuff to add to active TTs

* stuff to add to passive TTs

 

  6117   Wed Dec 14 12:22:00 2011 VladimirHowToComputersligo_viewer installed on pianosa

I made a test installation of ligo_viewer in /users/volodya/ligo_viewer-0.5.0c . It runs on pianosa (the Ubuntu machine) and needs Tcl/Tk 8.5.

 

To try it out run the following command on pianosa:

cd /users/volodya/ligo_viewer-0.5.0c/

./ligo_viewer.no_install

 

Press "CONNECT" to connect to the NDS server and explore. There are slides describing ligo_viewer at http://volodya-project.sourceforge.net/Ligo_viewer.pdf

 

Installation notes:

Use /users/volodya/ligo_viewer-0.5.0c.tgz or later version - it has been updated to work with 64 bit machines.

Make sure Tcl and Tk development packages are installed. You can find required packages by running

apt-file search tclConfig.sh

apt-file search tkConfig.sh

If apt-file returns empty output run apt-file update

Unpack ligo_viewer-0.5.0c.tgz, change into the created directory.

Run the following command to configure:

export CFLAGS=-I/usr/include/tcl8.5
./configure --with-tcl=/usr/lib/tcl8.5/ --with-tk=/usr/lib/tk8.5/

This works on Ubuntu machines. --with-tcl and --with-tk should point to the directories containing tclConfig.sh and tkConfig.sh correspondingly.

Run "make".

You can test the compilation with ./ligo_viewer.no_install

If everything works install with make install

If Tcl/Tk 8.5 is unavailable it should work with Tcl/Tk 8.3 or 8.4

 

 

Attachment 1: ligo_viewer_40m2.png
ligo_viewer_40m2.png
  6061   Thu Dec 1 18:30:39 2011 Vladimir, DenUpdatedigital noiseFoton error

Foton Matlab Error     

We investigated some more the discrepancy between Matlab and Foton numbers. The comparison of cheby1(k, 1, 2*12/16384) was done between versions implemented in Matlab, R and Octave. Filters created by R and Octave agree with Foton.

Also, we found that Matlab has gross precision errors for cutoff frequencies just smaller than used in our fitler, for example cheby1(6, 2*3/16384) fails miserably.

  6083   Wed Dec 7 20:55:44 2011 Vladimir, DenUpdatedigital noiseMatlab error

Quote:

It would be useful to see some plots so we could figure out exactly what magnitude and phase error correspond to "gross" and "miserable".

To show why Matlab is bad in filtering at small cut-off frequencies we did the same thing in Matab, Octave and R: we've taken the low-pass chebyshev filter of the type 1, order 6, ripple 1 dB, the sampling frequency was 16384 Hz and cut-off frequency varied from 1 to 1000 Hz. Here is the plot for the gain of the zpk model versus to cut-off frequency.

gain_cmp.png

We can see that Matlab's gain shows surprising gains for low cut-off frequencies through for > 100 Hz it is fine. In the next table we compare gain from Foton, Matlab, R and Octave for the same filter. So Foton is also good

freq R_gain matlab_gain octave_gain Foton_gain
1 3.05186270655452e-24 4.8824152e-22 3.05186271e-24 3.05186e-24
10 3.04698335947093e-18 1.8268825e-16 3.04698336e-18 3.04698e-18
100 2.99910841393644e-12 2.9991084e-12 2.99910841e-12 2.99911e-12
1000 2.60247212721439e-06 2.6024721e-06 2.60247213e-06 2.60247e-06
  16942   Thu Jun 23 15:05:01 2022 Water MonitorUpdateUpgradeWater Bottle Refill

22:05:02 UTC Jordan refilled his water bottle at the water dispenser in the control room.

  6869   Mon Jun 25 15:19:07 2012 YaakovUpdatePEMAdded microphone channels, moved accelorometer channels

Jenne and I renamed the mic channels Den created (elog 6664) to MIC_1, MIC_2, etc from the original accelerometer names to keep things clear. We then added 6 new channels (22-27) for the accelerometers, named ACC_MC1_X, Y, Z, ACC_MC2_X, Y, Z, etc. (See the screenshot below). We also added a DAQ channel block and listed out the IN1 channel of all the sensors. We compiled and started the model, and checked that all the channels were there in DataViewer.

channels.png

ELOG V3.1.3-