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ID Date Author Type Category Subjectup
  15865   Thu Mar 4 23:57:35 2021 KojiSummaryElectronicsInspection of the new custom dsub cables

I made the inspection of the new custom DSub cables (came from Texas).

The shelled version gives us some chance to inspect/modify the internal connections. (good)
The wires are well insulated. The conductors are wrapped with the foils and then everything is in the braid tube shield. The braid is soldered on one of the connectors. (Attachment  3/4 shows the soldering of the conductor by intentionally removing one of the insulations).

It wasn't clear that if the conductors are twisted or not (probably not).

  14175   Wed Aug 22 00:22:05 2018 KojiSummaryElectronicsInspection of the possible dual backplane interfaces for Acromag DAQ

[Johannes, Koji]

We went around the LSC, PSL, IOO, and SUS racks to check how many dual backplane interfaces will be required.

Euro card modules are connected to the backplane with two DIN 41612 connectors (as you know). The backplane connectors provide DC supplies and GND connections.
In addition, they are also used for the input and output connections with the fast and slow machines.

According to the past inspection by Johannes, most of the modules just use the upper DIN41612 connector (called P1). But there are some modules exhibited the possibility of the additional use of the other connector (P2).

Tuesday afternoon Johannes and I made the list of the modules with the possible dual use. And I took a time to check the modules with DCC, Jay's schematics, and the visual inspection of the actual modules.

LSC Rack

  • Common mode servo (D040180 Rev B)
    • Schematic source D040180 Rev B D1500308
    • Assesment: Both P1 and P2 are to be connected to Acromag, but there are only a few channels on P2
    • P1: 1A-32A Digital In
    • P2: 1A-3A Analog Out (D32/33/34, SLOW MON and spare?)
            9A Digital Out for D35 (Limitter)
            10A-15A Spare
            16A Digital In (Latch Enable/Disable)
            25A, 25C  Differential Analog in (Differential offset input, indicated as "BIAS") 
  • PD Interface (D990543 Rev B)
    • Schematic source D990543 RevB
    • Assesment: No connection necessary. We don't monitor/control anything of any LSC PDs from Acromag.

PSL Rack

  • Generic DAQ Interface (D990155) - This is a DAC interface.
    • Schematic source: Jay's page D990155 Rev.B All the lines between P2 and P3 are connected.
    • Assesment: Only P2 is to be connected to Acromag.
    • P1 DAC mon -> not necessary
    • P2 A1-A16, Connected to DAC in P2-P3
  • PMC Servo
    • Schematic source: LIGO DCC D980352
    • Assesment: Only P1 (1A-9A) is to be connected to Acromag. (Just one DSub is sufficient)
    • P1 1A-9A
  • Crystal Ref (D980353)
    • Schematic source: LIGO DCC D980353
    • Assesment: Only P1 (1A-4A) is to be connected to Acromag. (Just one DSub is sufficient)
    • P1 1A-4A
    • Schematic source: PNot found
    • Assesment: Probably Only P1 is sufficient. We need to analyze the board to figure out the channel assignment.

IOO Rack

  • PD Interface (D990543 Rev B)
    • Schematic source D990543 RevB
    • Assesment: Only P1 connection is sufficient.
  • Generic DAQ Interface (D990155)
    • Assesment: Remove the module. We already have the same module in PSL Rack. This is redundant.
  • Common mode servo (D040180 Rev B)
    • See above
  • Pentek Generic Input Board D020432
    • Schematic source Jay's page D020432-A
    • Assesment: No connection. There is no signal on the backplane.

SUS Rack

  • SUS Dewhitening
    • Schematic source: Jay's page D000316-A
    • Assesment: No connection.
    • We can omit Mon CHs.
    • Bypass/Inputs are already connected to the fast channels.


  14177   Wed Aug 22 12:22:27 2018 ranaSummaryElectronicsInspection of the possible dual backplane interfaces for Acromag DAQ

I think we don't need to keep Crystal Ref: we can change this into a regular Wenzel box with no outside control or monitoring.



  • Crystal Ref (D980353)
    • Schematic source: LIGO DCC D980353
    • Assesment: Only P1 (1A-4A) is to be connected to Acromag. (Just one DSub is sufficient)
    • P1 1A-4A


  5672   Sat Oct 15 17:06:20 2011 KojiUpdateLSCInstallation REFL165

REFL165 was installed on the AP table last night.

Meanwhile I found the DC power level at the REFL PDs were 0.8~1.2V if the PRM is aligned and the IFO is not locked.
This corresponds to 16~24mA (20~30mW). This is too big.

The HWP of the REFL path were adjusted so that we have 6~10mA (8~12mW) on each PDs.

  4002   Wed Dec 1 02:39:00 2010 SureshUpdateSUSInstallation of ETMU07 as ETMX

[Kiwamu, Jenne, Koji, Suresh]

The following steps in this process were completed.

1)  Secured the current ETMX (Old ETMY) with the earth quake stops.

2) Removed the OSEMs and noted the Sl no. of each and its position

3) Placed four clamps to mark the location of the current ETMX tower (Old ETMY's position on the table)

4) Moved the ETMX (Old ETMY) tower to the clean table flow bench.  In the process the tower had to be tilted during removal because it was too tall to pass upright through the vacuum chamber port.  It was scary but nothing went wrong.

5) Koji calculated the location of the new ETMX and told us that it should be placed on the north end of the table.

6) Moved the OSEM cables, counter balancing weights and  the 'chopper' out of the way.  Had to move some of the clamps securing the cables.

7) Moved the ETMU07 tower from the clean room to the ETMX table

8) Positioned the OSEMs as they were placed in the earlier tower and adjusted their position to the middle of the range of their shadow sensors.  The four OSEMs on the face did not give us any trouble and were positioned as required.  But the side OSEM could not be put in place.  The magnet on the left side, which we are constrained to use since the tower is not designed to hold an OSEM on the right side, seems a little too low (by about a mm) and does not interrupt the light beam in the shadow sensor.  The possible causes are

   a) the optic is rotated.  To check this we need to take the tower back to the clean room and check the location of the optic with the traveling microscope.  If indeed it is rotated, this is easy to correct.

   b) the magnet is not located at the correct place on the optic.  This can also be checked on the clean room optical bench but the solution available immediately is to hold the OSEM askew to accommodate the magnet location.  If time permits the magnet position can be corrected.

We have postponed the testing of the ETMU07 tower to 1st of Nov Dec.


  10261   Wed Jul 23 11:15:54 2014 AkhilUpdateElectronicsInstallation of FCs in the 40m

 As a part of installation of two(X-ARM and Y-ARM) frequency counters in the 40m, I have tested their performance when using them both on a single Raspberry Pi. The timing plots are attached. There are almost no timing issues in this configuration and it can be said that there is no harm using both of the FCs on the same platform.

We will be installing the FC box inside the lab and carry out few tests with RF mon beat note inputs.

  6090   Thu Dec 8 16:54:05 2011 JenneUpdateRF SystemInstallation of new demod box

So far:

* New demod box has been placed in the LSC rack.

* An extra set of +\- 24V has been prepared at the terminal block where all the Crates get their power on the LSC rack.  The grounds were all connected up, but the hot wires weren't.  So there were extra spots available, but none that were pre-wired with my voltages.

     * To do this I turned off all the power supplies in the short rack, since I decided to be a live chicken rather than a dead duck.  After hooking up the new terminal block slots, I turned on the power supplies.

 * Make a power cable to go from the terminal block to the box

Still to do:

 * Connect the spare 55MHz LO and the POP (or POX or POY) unused 11MHz LO to the back of the box

 * Move the PD inputs to the new demod box rather than the borrowed AS11 and POP55 boards

 * Plug the I & Q outs for each freq into some spare ADC channels - must first make sure we have 4 open channels.

 * See if it works.

  15500   Fri Jul 24 15:40:59 2020 JordanUpdateVACInstallation of two new UPS units

I installed the Tripp Lite SMX1000RT2U and Tripp Lite Smart1000LCD at the bottom of the 1x8 electronics rack. These are plugged in to power, and are ready for testing. All other cables (serial, usb, etc.) have been left on the table next to the 1x8 rack.

  16826   Tue May 3 14:02:09 2022 AnchalSummaryBHDInstalled POP path in ITMX Chamber

[Anchal, JC]

I installed POP_SM4 and POP_SM5 in the ITMX chamber in the nominal positions. This must have affected the ITMX Oplev because I could see that one of the ITMX oplev beam was going through POP_SM5. It needs to be changed in order to follow the original plan. However, since POP_SM5 is a 1064 line mirror, it is transparent to the opleve beam, so maybe we can just use the ITMX oplev in the current fashion.

Next steps:

  • Get flashing back on the XARM.
  • Try to get the correct phase angle in POX11 so that we can lock XARM with IR too.
  • Inspect ITMX Oplev. The quadrant sum is low so maybe it needs adjustment in the in-ar table.
  • Check if ITMX oplev path needs to be adjusted inside the chamber.
  15916   Fri Mar 12 18:10:01 2021 AnchalSummaryComputer Scripts / ProgramsInstalled cds-workstation on allegra

allegra had fresh Debian 10 installed on it already. I installed cds-workstation packages (with the help of Erik von Reis). I checked that command line caget, caput etc were working. I'll see if medm and other things are working next time we visit the lab.

  10905   Thu Jan 15 18:06:34 2015 JenneUpdateComputer Scripts / ProgramsInstalled kerberos on Rossa

I have installed kerberos on Rossa, so that I don't have to type my name and password every time I do an svn checkin, since I'm making some modifications and want to be sure that everything is checked in before and afterwards. 

I ran sudo apt-get install krb5-user.  I didn't put in a default_realm when it prompted me to during install, so I went into the /etc/krb5.conf file and changed the default_realm line to read default_realm = LIGO.ORG

Now we can use kinit, but we must (as usual) remember to kdestroy our credentials when we're done.

As a reminder, to use:

> kinit albert.einstein

Password for albert.einstein@LIGO.ORG: (type your pw here)

When you're finished, run

> kdestroy

The end.

  10906   Thu Jan 15 18:10:19 2015 jamieUpdateComputer Scripts / ProgramsInstalled kerberos on Rossa

I have installed kerberos on Rossa, so that I don't have to type my name and password every time I do an svn checkin, since I'm making some modifications and want to be sure that everything is checked in before and afterwards. 

I ran sudo apt-get install krb5-user.  I didn't put in a default_realm when it prompted me to during install, so I went into the /etc/krb5.conf file and changed the default_realm line to read default_realm = LIGO.ORG

Now we can use kinit, but we must (as usual) remember to kdestroy our credentials when we're done.

As a reminder, to use:

> kinit albert.einstein

Password for albert.einstein@LIGO.ORG: (type your pw here)

When you're finished, run

> kdestroy

The end.

WARNING: since the workstations are all shared user, if you forget to kdestroy the next user can commit under your user ID.  It might be good to set the timeout to be something much shorter than 24 hours, like maybe 1, or 2.

  10907   Thu Jan 15 18:30:18 2015 JenneUpdateComputer Scripts / ProgramsInstalled kerberos on Rossa



WARNING: since the workstations are all shared user, if you forget to kdestroy the next user can commit under your user ID.  It might be good to set the timeout to be something much shorter than 24 hours, like maybe 1, or 2.

Good call.  I added a line ticket_lifetime = 3600, which should make it destroy the credentials after an hour.

  4511   Mon Apr 11 19:09:59 2011 SureshUpdateRF SystemInstalled low pass filters in the demod boards


As part of the RF system upgrade some of the demod boards in the lab were modfied.  The filter U5 (see the circuit schematic) was replaced. These changes are tabulated below.


Filters installed in the demod boards
Serial number Old name of the card New name of the card Filter installed Remarks
107 POY33 REFL33 SCLF-33+ R14=50Ohm
118 AP133, ASDD133 REFL55 SCLF-65  
114 PO199 REFL165 SCLF-190 R14=50Ohm
120 PO133 POP110 SCLF-135  
123 SP133 POP55 SCLF-65+ AT1 removed, R14=50Ohm
122 SP199, REFLDD199 AS165 SCLF-190  
121 SP166, REFL16 POP11 SCLF-10.7  
116 AP199 199 MHz POP165 SCLF-190  
126 AS166 33.3 MHz POX11 SCLF-10.7  
119 POX 33.3 MHz POY11 SCLF-10.7  
021 24.5 MHz (LLO) REFL11 SCLF-10.7  
020 24.5 MHz SCLF-45 POP22 SCLF-21.4  
022 24.5 MHz SCLF-45 AS11 with amp SCLF-10.7  
029 24.5          SCLF-f5 AS55 with amp SCLF-65  


Next, I and Q phase has to be checked for orthogonality. And noise levels of the cards have to measured.




  4514   Mon Apr 11 23:35:02 2011 ranaUpdateRF SystemInstalled low pass filters in the demod boards

I am a little concerned about using these low pass filters so close to the band edge. Recall that there is no on-board preamp for the RF input to the mixer.

So, if the input impedance of the filters is not 50 Ohms, we will get some unwanted reflections and sensitivity to cable length.

I think its worth while to check the impedance or S-parameters of these things with the LO activated to find out if we need to remove them or not.

  10890   Tue Jan 13 03:47:46 2015 ericqUpdateCDSInstalled new ethernet driver on Chiara

Chiara threw another network hissy fit. Dmesg was spammed with a bunch of messages like eth0: link up appearing rapidly. 

Some googling indicated that this error message in conjuction with the very ethernet board and driver that Chiara had in use could be solved by updating with an appropriate driver from the manufacturer.

In essence, I followed steps 1-7 from here: http://ubuntuforums.org/showthread.php?t=1661489

So far, so good. We'll keep an eye out to see how it works...

  4238   Wed Feb 2 09:56:55 2011 KojiSummaryGreen LockingInstalled the freq divider and Rana's PFD

- The freq divider and Rana's PFD were hooked up to the ADCs. (Attachment 1)
(I leave the analog PFD not explained in this entry.)
For this purpose, the VCO feedback signal has been disconnected and the beat signal was moved from the VCO loop to the analog PFD.

The output level of the splitter was +12dBm and was too high for the freq divider.
So, I had to stupidly add an attenuator of 10dB before the box.

- Gain of the digital PFD LPF

The LPF of the digital PFD had the gain of -4096 to let the output signal indicate the direct frequency reading.

The gain has been changed to -67.108864
such that the output shows the direct reading of the beat freq in the unit of MHz

-4096*2^14/10^6 = -67.108864


- Attachment 2 shows the acquired beat note through the freq divider.
The blue is the beat note between "green locked" and "IR locked only to MC" (i.e. MC vs XARM)
The red is the beat note with the both beam locked to the arm

The freq divider is a bit flaky in some freq region as the divided output sometimes shows freq jumps or the captured at a freq.
I still don't know why it happens. We have to check why this happens.

  3650   Tue Oct 5 13:59:17 2010 Leo SingerConfigurationComputersInstalled x264-devel on Allegra

 I installed the package x264-devel on allegra.martian.  This package provides headers and libraries for the popular h264 video codec.  I am going to use this in the GStreamer streaming media server on Allegra.

  4806   Fri Jun 10 18:49:40 2011 kiwamuUpdateIOOIntensity Noise after the MC

Last night the relative intensity noise (RIN) of the beam after MC was measured.

It looks like the RIN is dominated by the motion of the MC mirrors, possibly the angular motions because we don't have any angular stabilization servos.

Suresh will estimate the contribution from the MC mirrors' angular motion to the RIN in order to see if this plot makes sense.



 The spectrum below 30 Hz seems to be dominated by the motion of the MC suspensions because it very resembles the spectra of those.

Above 30 Hz the spectrum becomes somehow flat, which I don't know why at the moment.

A rough estimation of the shot noise gave me a level of 10^{-9} RIN/sqrtHz, which is way below the measured spectrum.




 All of the suspended mirrors were intentionally misaligned except for the MC mirrors and PRM to avoid interference from the other optics.

In this setup it allows us to measure the intensity noise of the laser which is transmitted from MC.

The beam transmitted from MC is reflected by PRM and finally enters into the REFL11 RFPD.

The DC signal from the RFPD was acquired at C1:LSC-REFL_DC_DQ as the laser intensity.

As well as the RIN measurement I took a spectrum when the beam is blocked by a mechanical shutter on the PSL table.

This data contains the dark noise from REFL11 and circuit noise from the whitening, AA board and ADC. It is drawn in black in the plot.

The cut off at 15 Hz is possibly due to the digital unwhitening (two poles at 15 Hz and two zeros at 150 Hz) filter to correct the analog whitening filter.

  8224   Mon Mar 4 19:38:21 2013 CharlesUpdateGeneralIntensity Stabilization and Control Systems

 I have been studying Jamies master's thesis concerning intensity stabilization of a solid-state laser (the 1064 nm specifically) to the ~10^-9 level, as well as relevant supporting material. I have also been reading about general control systems, photodiodes and acousto-optic modulators to help facilitate work on the ISS. 

Now that Altium has been properly installed, I have also begun familiarizing myself with the program and general libraries of boards and devices that have already been modeled with the program.

  4392   Wed Mar 9 18:17:11 2011 kiwamuUpdateGreen LockingIntensity noise coupling

Here is a new plot for the differential noise measurement. I plot a noise contribution from the intensity noise (brown curve).

If we believe this data, the differential noise is NOT dominated by the intensity noise of the PSL.



(intensity noise coupling measurement)

 Here is a plot for the transfer functions (TFs) from the intensity noise DCPD to the beat signal.


   In principle these TFs tell us how much intensity noise are contributed into the differential noise.

When I measured the spectra shown above, the frequency offset of the beatnote was at about 8 MHz from the zero cross point.

Keeping the same lock, I measured the transfer function (red curve) by using the swept sine technique on DTT. The setup for this measurement is depicted on the last entry (#4389).

Then I made the spectra above by multiplying the intensity spectrum by this TF.

  Later I measured another transfer function when the beatnote was at about 2 MHz from the zero cross point.

According to this measurement, our MFD gets insensitive to the intensity noise as the beat offset goes close to the zero cross point. This is consistent with what we expected.

  4397   Thu Mar 10 14:06:54 2011 kiwamuUpdateGreen LockingIntensity noise limits the beatnote sensitivity

We are limited by the intensity noise of the X arm transmitted green light.

Since the intensity noise from the PSL wasn't big enough to explain the differential noise (#4392), so this time I measured the noise contribution from the X arm transmitted light.


(coupling measurement)


  I performed the same intensity noise coupling measurement, but this time between the DC signal of the beatnote RFPD and the beatnote signal.

 While measuring it, I excited the intensity of the PSL laser by using the same AOM like I did yesterday. This AM cause the observable intensity noise on the beatnote RFPD.

With the excited AM, we can pretend to have an excited AM on the green transmitted light from the X arm, of course assuming the intensity noise coupling from the PSL is less.

  4398   Thu Mar 10 14:22:58 2011 kiwamuUpdateGreen LockingIntensity noise limits the beatnote sensitivity

The next steps we should do are :

    - to investigate a cause of the intensity fluctuation
          * end green laser
          * suspensions' angular motions
          * doublecheck the RIN contribution if it's from the PSL or the X arm in the beatnote RFPD to make sure the RIN is dominated by the X arm transmitted light
    - to think about how to make the system insensitive to the intensity noise
          - bring the beat frequency to the zero cross point of the MFDs ?
          - PLL ?


We are limited by the intensity noise of the X arm transmitted green light.

  4399   Thu Mar 10 14:29:05 2011 KojiUpdateGreen LockingIntensity noise limits the beatnote sensitivity

We can modify the freq divider circuit to make it a comparator.


The next steps we should do are :

    - to investigate a cause of the intensity fluctuation
          * end green laser
          * suspensions' angular motions
          * doublecheck the RIN contribution if it's from the PSL or the X arm in the beatnote RFPD to make sure the RIN is dominated by the X arm transmitted light
    - to think about how to make the system insensitive to the intensity noise
          - bring the beat frequency to the zero cross point of the MFDs ?
          - PLL ?


We are limited by the intensity noise of the X arm transmitted green light.


  4400   Thu Mar 10 14:30:53 2011 ranaUpdateGreen LockingIntensity noise limits the beatnote sensitivity

There are 3 standard techniques to reduce this effect:

1) Stabilize the end laser by sensing the green light coming into the PSL before recombination and feeding back with SR560 (this is the only one that you should try at first).

2) Moving to the center of the MFD fringe via ETM steps.

3) Auto-alignment of the beam to the arm.

  4383   Tue Mar 8 06:29:06 2011 kiwamuUpdateGreen LockingIntensity noise setup

[Jenne, Chris, Kiwamu]

 A photo diode and an AOM driver have been newly setup on the PSL table to measure the intensity noise coupling to the beat note signal.

We tried taking a transfer function from the PD to the beat, but the SNR wasn't sufficient on the PD. So we didn't get reasonable data.


(what we did)

  - put a DCPD after the doubling crystal on the PSL table. The PD is sitting after the Y1 mirror, which has been used for picking off the undesired IR beam.

  - installed the AOM driver (the AOM itself had been already in place)

  - injected some signals onto the AOM to see if we can see an intensity fluctuation on the PD as well as the beat signal


(intensity noise)

  In order to have better SNR for the intensity measurement, we put an AC coupled SR560 with the gain of 100 just before the ADCs.

When a single frequency signal was applied from a Stanford Research's function generator to the AOM, we could clearly see a peak at the doubled frequency of the injected signal.

Also a peak at the same frequency was found on the beat note signal as well.

But when random noise was injected from the same function generator, the random noise looked below the ADC noise.

Jenne adjusted the output voltage from the PD to about 1 V to avoid a saturation in the analog path, but later we realized that the ADC counts was marely ~ 20 counts.

So we will check the ADC tomorrow. Hopefully we will get a good SNR.

  4401   Thu Mar 10 16:00:53 2011 Aidan, JoeUpdateGreen LockingIntensity stabilization loop using beatnote DC.

Aidan: Joe and I have added a channel that takes the DC output from the vertex beatnote PD and sends it, via RFM, to a DAC at the ETMX end. Immediately before the output is a filter C1GCX_AMP_CTRL. The output of the DAC is connected to the CURRENT LASER DIODE modulation input on the back of the Innolight driver. This will modulate the current by 0.1A/V input.

We should be able to modulate the green laser on the end now and stabilize the intensity of the amplitude on the beatnote PD at the vertex. (In this configuration, the ampltiude noise of the PSL laser will be injected onto the end laser - we may want to revisit that).

Joe's comments on model change:

I added a RFM connection at the output of the C1:GCV-XARM_BEAT_DC filter in the c1gcv model.  The RFM connection is called: C1:GCV-SCX_ETMX_AMP_CTRL.

This RFM connection goes to the c1scx model and into Kiwamu's GCX box, which uses top_names.  There's a filter inside called AMP_CTRL, so the full filter name is C1:GCX-AMP_CTRL.  The output then goes to the 7th DAC output.


  1. NPRO CURRENT CTRL plugged into DAC channel 7
  2. You can actually see it's channel 7 in this image
  3. The other end plugged into the back of the Innolight driver
  4. Schematic of the setup
  5. Updated C1ALS_OVERVIEW MEDM screen (I don't know why the field in the background turned orange - maybe it's coming into a long dry summer?)



There are 3 standard techniques to reduce this effect:

1) Stabilize the end laser by sensing the green light coming into the PSL before recombination and feeding back with SR560 (this is the only one that you should try at first).


The reason that I chose this PD is that, apparently, the green light coming from the cavity is clipped when it is picked off for its DC PD.

  4403   Thu Mar 10 21:45:34 2011 ranaUpdateGreen LockingIntensity stabilization loop using beatnote DC.

Ridiculous and hacky. Digital stabilization removed as well as the old "leave a pile of equipment on a stool" strategy.

We used a a BNC cable to send a pickoff of the beam before the recombination to the end via an SR560.

  10020   Tue Jun 10 12:49:46 2014 AkhilUpdateComputer Scripts / ProgramsInterfacing UFC-6000 with Raspberry Pi completed


 To interface the Mini Circuits RF Frequency Counter(FC) Model UFC-6000 with Raspberry Pi on Linux platform. Also to create a User friendly interface, to control the FC with command lines.


Highlights of the Code(script attached):

The  code enables the user to communicate and control different parameters of the UFC like:

1)Frequency Range Selection( for the device to read different frequencies, AutoRange is set by default).

2)Sampling Time (The time intervals for which the data will be retrieved)

3)Read Device Status(Whether the device is reading data or not).


Description of the Code:

HID USB Interfacing by sending byte Values.


 1)Read The Freq or Range 

Reading the Freq is done by reading the 1st and 2nd LCD of the Frequency counter.

1st line containing Range information, 2nd line is the Frequency result

the code should be send is 2

1st byte: 2

The returned 64 byte array is as follows:

1st byte: 2

2nd byte to Byte17 the ascii value of 16 characters of the 1st LCD line

Byte18 to Byte33  the ascii value of 16 characters of the 2nd LCD line


2) Set the Range  

By default Freq Counter is in "AutoRange" mode.

To set the range manually send the code 4

1st byte: 4

2nd byte: the range value. can be any legal range value. for auto range  need to be 255.

the 64 byte array is:

1st byte: 4


3)Set the Sample Time   

By default Freq Counter Sample Time is 1 sec.

you can set the sample time from 0.1 sec and up in step of 0.1 sec.To set the Sample Time send the code 3

1st byte: 3

2nd byte: the sample value in sec double 10.

for example: to set the sample time  to 0.4 sec 2nd byte need to be: 4

the 64 byte array is:

1st byte: 3


These bytes can be changed by changing the values of buffer[0] and buffer[1]  in function /*Send Report to the device*/ in the main program.

The data is written into a .txt file(example attached) and the user can  control the recording of data. The frequency data can now be made to talk to EPICS through slow channels.

The data from the .txt file can be used for error analysis at different sampling periods.



The interface of the FC with the Pi is now complete.



 Make this FC talk to EPICS through slow channels.







  2504   Mon Jan 11 16:59:14 2010 AlbertoUpdateABSLInterferometer Busy

I'm currently running a measurement on the PRC.

Please don't interfere with the IFO until it is done. Talk with Alberto if you've been intending to work inside the lab.

Thank you.

  6595   Thu May 3 13:07:05 2012 KojiBureaucracyGeneralInterferometer check-up session

From 2PM, Jenne/Den/Koji. Finished at 10:30PM

  • General
    • More LCD screens! Wider screens!
      • Allegra - only can handle single head right now, but should prepare for the eventual upgrade of that videocard/whole computer and get 2 monitors.
      • Every workstation should have 2 24" monitors.  We currently have 2 good ones (one on Rossa, one on Pianosa), so we need 6.
    • Remove Control room shelf currently holding OSA 'scopes
    • Adjust both TV shelves so that they're at the same height, ~6" higher than the current left shelf.
      This gives space for stacking the 24" monitors for each computer.
    • Audio system for the signals!!!! Even a crappy one!
           (really /cvs/cds, not /opt)

  • IOO
    • PZT or Picomotor mounts for PSL/ALS beams
    • ALS on the both arm simultaneously / common/diff ALS scripts
  • SUS
    • PRM OPLEV servos are sometimes not stable. (fixed, JCD/DM/KA, 5/2/2012)
    • ETMX oplev - replace 1064nm lens with 632nm lens (KBC037, -100)
  • IFO
    • It seems that there is an occasional common-mode power transient in the arm transmissions.
      -> Track down the cause and fix.
    • Fix arm ASS even on CentOS
    • Drift of the green incident axis -> Assess the amount of the drift / replace the mount
    • Calibration of POP22 / AS110
    • PMC/IMC/ARM characterization (loss, finesse, reflectivity, etc)
  • CDS
    • Capture OSA signals in CDS (the 'scope TDS1001B has a USB port in the back for connecting to the computer)
    • Transmon (arms) for high and low power
    • POX11 whitening is not toggling the analog whitening???
    • CentOS machines cannot open simulink models properly (get "Bad Link"s everywhere, so you can't do anything useful).
    • Dataviewer and DTT can't connect to framebuilder from CentIOS machines
  • Electronics
    • Actuator noise level characterization (coil driver response in V/m & coil driver noise level V/rtHz)
    • Beat box
    • I/Q DFD
    • Improvement of POP22/110/AS110 RF circuits.
  • MEDM
    • OL alert in the watch dog screen (this is awesome!) should have small text saying "OL" (done, JCD, 5May2012)
    • Complete 40m overview screen - everything should be clickable with pseudo 3D icons
    • Script to generate a MEDM tree
    • Resurrect MEDM snapshots
    • The LSC screen has some "white" boxes -> investigate and fix them (done, KA, 5/2/2012)
    • Make the LSC control screen (compact) in the vertical arrangement (done, KA, 5/2/2012)
    • The signals of the watch dog screen should go red if any of the WDs are not enabled.
      =>Copy the logic of the signals in LSC screen.
      (done, KA, 5/2/2012)
    • Remove c1gfd from the cds status screen (done, KA, 5/2/2012)
    • Add "BURT" status indicators on the cds status screen (done, KA, 5/2/2012)
    • Locking scripts with integrator triggers / disabling when unlocked
    • Daily diagnosis of the MC spot positions (there must be something already...)
    • Daily/occasional adjustment of the incident axis on the MC
    • Suspension "misalign/restore" script is too wild => make a new script (Done, JCD, 7May2012)
    • IFO_CONFIGURE scripts still do a burt restore, so step the optics.  Need to remove optic alignment from config .snap files, use reg restore script instead.
    • OPLEV/OSEM trending script before the IFO work for diagnosis.
    • Auto-locker for PMC/Arm/etc
  • Video
    • If each video screen has a caption, that would be great
    • GUI interface of "videoswitch" Mike!
    • Mouse Jiggler for Zita (called Swinput?)
  • Ubuntu
    • burttoday is not aliased in ubuntu. burttoday:      aliased to cd /opt/rtcds/caltech/c1/burt/autoburt/today/
    • ASS doesn't run on Ubuntu!
      ezcawrite: error while loading shared libraries: libca.so: cannot open shared object file: No such file or directory
      ezcaswitch: error while loading shared libraries: libca.so: cannot open shared object file: No such file or directory
  2271   Sun Nov 15 18:42:10 2009 AlbertoUpdateLockingInterferometer fully locked for 3331 seconds

This afternoon, I tried to lock the interferometer again after a few days.

After a couple of failed attempts, and relocks of the MZ, the interferometer stayed locked continuously for about 50 minutes, with arm power of about 92.

I just wanted to check the status of the interferometer so I didn't do any particular measurement in the meantime.

  10613   Wed Oct 15 20:10:29 2014 ericqUpdateLSCInterim DARM Signal

I've done some preliminary modeling to see if there is a good candidate for an IR DARM control signal that is available before the AS55 sign flip. From a DC sweep point of view, ASDC/(TRX+TRY) may be a candidate for further exploration. 

As a reminder, both Finesse and MIST predict a sign flip in the AS55 Q control signal for DARM in the PRFPMI configuration, at a CARM offset of around 118pm.


The CARM offset where this sign flip occurs isn't too far off of where we're currently losing lock, so we have not had the opportunity to switch DARM control off of ALS and over to the quieter IR RF signal of AS55. 

Here are simulated DC DARM sweep plots of our current PRFPMI configuration, with a whole bunch of potential signals that struck me. 

Although the units of most traces are arbitrary in each plot (to fit on the same scale), each plot uses the same arbitrary units (if that makes any sense) so slopes and ratios of values can be read off. 


In the 300 and 120pm plot, you can see that the zero crossing of AS55 is at some considerable DARM offset, and normalizing by TRX doesn't change much about that. "Hold on a second," I hear you say. "Your first plots said that the sign flip happens at around 120pm, so why does the AS55 profile still look bad at 50pm?!" My guess is that, probably due to a combination of Schnupp and arm length asymmetry, CARM offsets move where the peak power is in the DARM coordinate. This picture makes what I mean more clear, perhaps:


Thus, once we're on the other side of the sign flip, I'm confident that we can use AS55 Q without much problem. 

Now, back to thoughts about an interim signal:

ASDC by itself does not really have the kind of behavior we want; but the power out of AS as a fraction of the ARM power (i.e. ASDC/TRX in the plot) seems to have a rational shape, that is not too unlike what the REFLDC CARM profile looks like.

Why not use POPDC or REFLDC? Well, at the CARM offsets we're currently at, POPDC is dominated by the PRC resonating sidebands, and REFLDC has barely begun to decline, and at lower CARM offsets, they each flatten out before the peak of the little ASDC hill, and so don't do much to improve the shape. Meanwhile, ASDC/TRX has a smooth response to points within some fraction of the DARM line width in all of the plots. 

Thus, as was discussed at today's meeting, I feel it may be possible to lock DARM on ASDC/(TRX+TRY) with some offset, until AS55 becomes feasible.

(In practice, I figure we would divide by the sum of the powers, to reduce the influence of the DARM component of just TRX; we don't want to have DARM/DARM in the error signal for DARM)

Two caveats are:

  • The slope of this signal actually looks more quadratic than linear. Is this ok/manageable?
  • I have not yet made any investigation into the frequency dependent behavior of this thing. Transmission in the denominator will have the CARM pole in it, might get complicated. 

[Code and plots live in /svn/trunk/modeling/PRFPMI_radpressure]


  10618   Thu Oct 16 16:21:42 2014 ericqUpdateLSCInterim DARM Signal

I've added (TRX-TRY)/(TRX+TRY) to the DC DARM sweep plots, and it looks like an even better candidate. The slope is closer to linear, and it has a zero crossing within ~10pm of the true DARM zero across the different CARM offsets, so we might not even need to use an intentional DARM offset. 



  14980   Mon Oct 21 11:44:19 2019 gautamUpdatesafetyInterlock reconnected to Innolight controller

We also took this opportunity to re-connect the interlock to the Innolight controller (after it was disconnected for diagnosing the mysterious NPRO self-shutdowns). The diode pump current was dialled down to 0, the interlock wires reconnected, and then the diode current was ramped back up to the nominal 2.1 A. The fan to cool the unit remains mounted in a flaky way as we couldn't locate the frame Chub had made for a more secure mounting solution. 

It seems like the pointing of the beam out of the laser head varies somewhat after the startup - I had to adjust the pointing into the PMC a couple of times by ~1 full turn of the Polaris mount screws, but the IMC has been locked (mostly) for the last ~16 hours.


I've checked the state of the laser interlock switch and everything looked normal.

  17307   Wed Nov 23 17:21:44 2022 JCUpdateVACInterlocks may have been tripped due to N2 pressure loss

[Paco, JC]

While changing out one of the N2 tanks today, one of the fitting stripped. This caused a major loss of pressure. I replaced one fitting then realized there was a second leak around the area of the gauge. Paco and I changed this and everything should be back up and running. Thhe interlocks may have been tripped  within the last 2 hours.


  4625   Wed May 4 13:51:51 2011 valeraConfiguration Intermittent MC3 UL PD signal

The attached plot shows the 30 day trend of the MC3 UL PD signal. The signal dropped to zero at some point but now it is close to the level it was a few weeks ago. There still could be a problem with the cable.

The rest of the MC1,2,3 PD signals looked ok.

  2598   Fri Feb 12 14:19:28 2010 rana, steveHowToloreInternational Fax

Steve showed me how to send an international fax today:

  1. Load paper.
  2. Dial:   011 - (country code) - number
  3. Press START (either the black or color option)
  4. wait for the screaming fax noise
  5. Done


  6560   Tue Apr 24 14:30:08 2012 JamieUpdateCDSIntroducing: rtcds, a utility for interacting with the CDS RTS/RCG

The new rtcds utility

I have written a new utility for interacting with the CDS RTS/RCG system: "rtcds".  It should be available on all workstations and front-end machines, but certain commands are restricted to run on certain front end machines (build, start, stop, etc.).  Here's the help:

controls@c1lsc ~ 0$ rtcds help
Usage: rtcds <command> [arg]

Available commands:

  build|make SYS      build model
  install SYS         install model
  start SYS|all       start model
  restart SYS|all     restart running model
  stop|kill SYS|all   stop running model
  list                list all models for current host

controls@c1lsc ~ 0$ 

Please use this new utility from now on when interacting with RTS.

I'll be improving and expanding it as we go.   Please let me know if you encounter any problems.


  3193   Mon Jul 12 11:20:56 2010 Gopal HowToCOMSOL TipsIntrusions (Negative Extrusions)

For the sake of future users, I have decided to periodically add tips and tricks in using COMSOL that I have figured out, most probably after hours of circuitous efforts. They will always be listed under the new COMSOL Tips category.

Today's topic: Intrusions

COMSOL has a very user-friendly interface for taking objects from 2D to 3D using the "extrusion" feature. But suppose one wants to design an object which contains screw holes or some other indentation. I've found that creating "punctures" in COMSOL is either impossible or very complicated.

Instead, COMSOL encourages users to always "add" to the object. In other words, one must form the lowest level first, then build layers sequentially on top using new work plane and boolean difference operators. This will probably be a bit clearer with an example:

1) First, create the planar projection in a work plane:


2) Extrude the first layer only in the regular fashion:


 3) Add a new work plane which is offset in the z-direction to the deepest point of the intrusion.


 4) Now, create the shape of the intrusion in this new work plane.


5) Use the Boolean "Difference" to let COMSOL know that, on this plane, the object has a hole.


 6) Extrude once more from the second work plane to complete the intrusion.


  3194   Mon Jul 12 12:16:50 2010 DmassHowToCOMSOL TipsIntrusions (Negative Extrusions)

 An entry on the 40m wiki page might serve you better, and be easier to sift through once all is said and done

  2615   Fri Feb 19 02:38:32 2010 KojiConfigurationoplevsIntsant green oplevs for ITMs shooting from the ends

I set up instant green oplevs for ITMs.

A green laser pointer has been set on each end table. It illuminates the ITM center. The beam goea through the ETM substrate.
The reflected green beam returns to the ETM if the ITMs are aligned. Even though the reflected beam to the end is too big, this can
be a rough reference for each ITM.

Note: The green laser pointer at the ETMX were borrowed from Frank. We must return it to him when we finish the work.

  2083   Mon Oct 12 18:37:55 2009 ZachUpdatePSLInventory

--Apologies for the late post--

I was at the PSL table taking an inventory of the components for a while after Koji, Steve, and Kiwamu were there. I set the HEPAs back to 20% when I left (assuming that they were turned up when the compartment was opened).

  12029   Thu Mar 10 16:29:32 2016 gautamUpdateendtable upgradeInventory check

I did a quick sweep of the lab to find out what hardware has already been acquired for the X-end table upgrade. The attached PDF is an inventory check in the spirit of this elog.

Some things we have to decide:

  • Are we okay with using the old green coloured faraday mount for the IR faraday? I have in hand a piece identical to the one used at the Y-end for the green faraday, that is red in colour, so I guess we can switch this out.
  • The way in which the doubling oven is currently mounted at the X-end is using some posts cobbled together. The Y-end looks to have a custom mount machined for it (see Attachment #2). Do we want to go ahead and get something like this done?
  • I suppose it is okay to reuse all the old optics (mirrors, lenses, harmonic separators) and PDs? It may be that we need to order som extra mirrors/lenses/posts (this will become clear once I do the layout)

I have not gotten around to planning the layout or doing drawings. I will try and first work through a mode-matching solution to make sure we have all the required lenses. It may be that we need some 1" or 2" mirrors as well. The beam from the lightwave NPRO is quite elliptical, but we have a number of cylindrical lenses in hand already if we decide we want to use these, so I guess we don't have to worry about this...

This is quite a preliminary list, and I will add/update over the coming days as I do more detailed planning, but have I missed out anything obvious?

  12030   Thu Mar 10 16:32:45 2016 ranaUpdateendtable upgradeInventory check

Its not a good idea to use green mounts with green lasers. Steve should be able to get another copy of the EY doubler mount made up if we really don't have another one sitting in the Manasa end table box which Koji mentioned.

  12033   Mon Mar 14 22:42:23 2016 gautamUpdateendtable upgradeInventory check

Steve should be able to get another copy of the EY doubler mount made up if we really don't have another one sitting in the Manasa end table box which Koji mentioned.

I located the second doubler mount, it was sitting inside a cabinet along the Y-arm. So this will not have to be machined. The doubling oven mount is black in colour.

So as things stand now, the only thing that needs to be machined is a non-green mount for the IR faraday (IO-5-1064-HP) - is it possible to just coat the existing mount with a different color? I've got a drawing for this part ready, but it seems unnecessary to machine the whole thing from scratch when only the color is an issue. Steve was talking about dipping this in some sort of solution and taking the green off. But if this isn't possible, I'll send Steve the drawings tomorrow so that he can place the order with the machine shop...

I will work on the mode-matching calculations over the next couple of days to make sure we have all the mirrors and lenses we need.


  11587   Wed Sep 9 15:45:11 2015 ericqUpdatePEMInverted STS filters in C1OAF

Our online subtraction filters for PRC angle and MC length were trained on the raw ADC signals, so I've inverted the filters that Rana installed in the PEM filter banks in the OAF signal conditioning filter banks (C1:OAF-WIT_STS1X, etc.)

It's not perfect, since the inversion would be unstable, and thus needs a low pass. I used an ELP at 800Hz. The error in the inversion is then something like half a degree at 5Hz, which is the highest frequency we really ever subtract at. It should be ok.

  15877   Mon Mar 8 12:01:02 2021 Paco, AnchalSummarytrainingInvestigate how-to XARM locking

[Paco, Anchal]

- Started zoom stream; thanks to whoever installed it!
- Spent some time trying to understand how anything we did last thursday lead to the sensing matrix change, but still cannot figure it out. 
- Tracking back on our actions, at ~10:30 we ran burt Restore with the 08:19/.*snap and in lack of a better suspect, we blame it on that action for now.

# ARM locking??
- Reading (not running) the scripts/XARM/lockXarm.py script and try to understand the workflow. It is pretty confusing that the result was to lock Yarm last time.
- It looks like this script was a copy of lockYarm.py, and was never updated (there's a chance we ran it for the first time last thursday)
- *Is there a script to lock the Arms?* Or should we write one? To write one, we first attempt a manual procedure;
    1. No need to change RFPD InMTRX
    2. All filters inputs / outputs are enabled 
    3. Outputs from XARM and YARM in the Output matrix are already going to ETMX and ETMY
      - Maybe we can have the ARM lock engage by changing the MC directly?
    4. Change C1:SUS-MC2_POS_OFFSET from -38 to -0, and enable C1:SUS-MC2_POS_OFFSET_ON
    5. Manually scan MC2_POS_OFFSET to 250 (nothing happens), then -250, then back to -38 (WFS1 PIT and YAW changed a little, but then returned to their nominal values)
      - Or maybe we need to provide the right gain...
    6. Disabled C1:SUS-MC2_POS_OFFSET_ON (back to nominal state)
    7. Look into manually changing C1:LSC-XARM_GAIN;
      From the command line using python:
      >> import epics
      >> ch_name = 'C1:LSC-XARM_GAIN'
      >> epics.caput(ch_name, 0.155) # nominal = 0.150
      - Could be unrelated, but we noted a slow spike on C1:PSL-FSS_PCDRIVE (definitely from before we changed anything)
      - Still nothing is happening
    8. Changed the gain to 0.175, then back to 0.150, no effect... then 0.2, 0.3 ...
      - Stop and check SUS_Watchdogs (should not have changed?) and everything remains nominal
      - Revert all changes symmetrically.
      - Could we have missed enabling FM1?
      - Briefly lost MC lock, but it came back on its own (probably unrelated)

- Wrap it up for the day. In summary; no harm done to our knowledge.

  15878   Mon Mar 8 12:40:35 2021 gautamSummarytrainingInvestigate how-to XARM locking

For the arm locking, the "Restore Xarm (XARM POX)" script from the "IFO_CONFIGURE" MEDM screen should get you there (I just checked it and it works fine). It is worth getting a hang of the PDH signal chain (read what the script is doing and map it to the signal chain) so you get a feel for where there may be offsets, saturations, what the trigger logic is etc. The LSC overview screen is supposed to be pretty intuitive (if you think it can be improved, I'd love to hear it but please don't change it without documenting) and there are also the webviews of the simulink models (these are RO so feel free to click around, for the LSC the c1lsc model is the relevant one).

  10723   Mon Nov 17 20:40:29 2014 rana, diegoUpdateIOOInvestigating the IMC WFS situation

We've known for years that the IMC WFS sensing chain is pointlessly bad, but until recently, we haven't thought it was worth it to fix.

There are problems in all parts of the chain:

  1. The WFS Photodetectors oscillate ~200 MHz when turned up to full gain. Diego and I confirmed this today by measuring the RF spectrum of the signals going into the WFS demod boards and seeing the oscillation change (not much) with RF gain. I recommend we switch the heads into the full gain mode (turn all of the attenuators OFF). At the moment we are operating with the 2dB and 8dB attenuators ON.
  2. The demod board has some bad gain allocation and noisy opamps.
  3. The whitening board has too much up/down of gain with noise injection along the way. And the range cannot fill up the ADC.
ELOG V3.1.3-