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ID Date Author Type Category Subjectup
  14594   Fri May 3 15:40:33 2019 gautamUpdateGeneralCVI 2" beamsplitters delivered

Four new 2" CVI 50/50 beamsplitters (2 for p-pol and 2 for s-pol) were delivered. They have been stored in the optics cabinet, along with the "Test Data" sheets from CVI.

  9006   Tue Aug 13 13:30:41 2013 Alex ColeConfigurationElectronicsCable Routing

 I routed cables (RG405 SMA-SMA) from several demodulator boards in rack 1Y2 to the RF Switch in rack 1Y1 using the overhead track. Our switch chassis contains two 8x1 switches. The COM of the "right" switch goes to channel 7 of the "left" switch to effectively form a 16x1 switch. The following is a table of correspondences between PD and RF Switch input.


PD Left/Right Switch Channel Number


POX11 L 0
AS55 R 1
REFL55 R 7
POP22 R 6
REFL165 R 5
REFL33 L 7


ThePOP110 demod board has not yet had a cable routed from it to the switch because I ran out of RG405.

We should also consider how important it is to include MCREFL in our setup. Doing so would require fabrication of a ~70 ft RG405 cable. 

Attachment 1: photo_(6).JPG
  3520   Fri Sep 3 11:03:41 2010 AlbertoFrogsElectronicsCable cutting tools

I found this very interesting German maker of cool cable cutting tools. It's called Jokari.

We should keep it as a reference for the future if we want to buy something like that, ie RF coax cable cutting knives.


  3522   Fri Sep 3 13:04:30 2010 KojiFrogsElectronicsCable cutting tools

Yeah, this looks nice.

And I also like to have something I have attached. This is "HOZAN P-90", but we should investigate American ones
so that we can cut the wires classified by AWG.


I found this very interesting German maker of cool cable cutting tools. It's called Jokari.

We should keep it as a reference for the future if we want to buy something like that, ie RF coax cable cutting knives.



Attachment 1: P90.jpg
  4346   Wed Feb 23 16:56:17 2011 Larisa ThorneUpdateVIDEOCable laying...continued

Having finished labeling the existing cables to match their new names, we (Steve, Kiwamu and Larisa) moved on to start laying new cables and labeling them according to the list.


Newly laid cables include: ETMXT (235'), ETMX (235'), POP (110') and MC2 (105').  All were checked by connecting a camera to a monitor and checking the clarity of the resulting image. Note that these cables were only laid, so they are not plugged in.


The MC2 cable needs to be ~10' longer; it won't reach to where it's supposed to. It is currently still in its place. 

The three other cables were all a lot longer than necessary.

  4462   Wed Mar 30 17:01:08 2011 Larisa ThorneUpdateVIDEOCable laying...continued

[Steve, Suresh, Kiwamu, Larisa]


Only the PRM/BS cable was laid today.

In one of the previous updates on cable laying, it was noted that the MC2 cable needed an additional 10' and the MC2T needed an additional 15' to reach their destinations.  We cut and put BNC ends on 10' and 15' cables and connected them to the original cables in order to make them long enough.


This concludes the laying of new cables. Suresh is currently working on the QUADs...

  4474   Thu Mar 31 08:31:44 2011 SureshUpdateVIDEOCable laying...continued

The video work has crossed a milestone.    

Kiwamu and Steve have shifted the three quads from the control room to the Video MUX rack (1Y1) and have wired them to the MUX.

The monitors in the control room have been repositioned and renumbered.  They are now connected directly to the MUX. 

Please see the new cable list for the input and output channels on the MUX.

As of today, all cables according the new plan are in place.  Their status   indicated on the wiki page above is not verified .  Please ignore that column for now, we will be updating that soon.

I shifted the MC1F/MC3F camera and the MC2F cameras onto the new cables.  Also connected the monitors at the BS chamber and end of the X arm to their respective cables.  I have removed the RG58B BNC (black) cables running from MC2 to BS and from ETMXF to the top of the Flow Bench. 

Some of the old video cables are still in place but are not used.   We might consider removing them to clear up the clutter. 

Some of the video cables in use are orange and if the lab's  cable color code is to be enforced these will have to be replaced with blue ones..

Some of the cables in use running from the MUX to the monitor in the control room are the white 50 Ohm variety.  There are also black RG59 Cables running the same way ( we have surplus cables in that path)  and we have to use those instead of the white ones. 

There are a number of tasks remaining:

a)  The inputs from the various existing cameras have to be verified. 

b) There are quite a few cameras which are yet to be installed.

c) The Outputs may not not be connected to their monitors.  That the monitors may still be connected to an old cable which is not connected to the MUX.  The new cable should be lying around close by.  So if you see a blank monitor please connect it to its new cable. 

d) The status column on the wiki page has to be updated.

e) Some of the currently in place may need to be replaced and some need to be removed.  We need to discuss our priorities and come up with a plan for that.

After checking everything we can certify that the video cabling system is complete.

I would like Joon Ho to take care of this verification+documenting process and declaring that the job is complete. 


Steve attached these two pictures.

Attachment 1: P1070489.JPG
Attachment 2: P1070494.JPG
  4492   Wed Apr 6 16:02:07 2011 Larisa ThorneUpdateElectronicsCable laying...continued

[Steve, Kiwamu, Larisa]


Having finished laying new cable last week, we moved on to connecting those on PSL table and AP table.

Cables connected:

--RCR, RCT, PMCR (all three are blue)

--OMCR (blue cable, ***now has a camera***), PMCT, IMCR, REFL, AS (white cable), OMCT (***now has camera***)


Unless otherwise noted, the cables are black on the AP table. Also on the AP table: cables were connected directly to the power source.

The wiki has been updated accordingly.


Steve noted that MC2T and POP cameras are not there.



  16805   Fri Apr 22 12:15:08 2022 AnchalUpdateBHDCable post installation

If someone gets time, let's put in all the cable posts and clean up our cable routing on the tables.


  16810   Mon Apr 25 16:57:57 2022 AnchalUpdateBHDCable post installation

[Anchal, Tega, JC]

We installed cable posts in ITMY, BS, and ITMX chambers for all the new suspensions. Now, there is no point where the OSEM connections are hanging freely.

In BS chamber, we installed one post for LO2 near the north edge of the table and another post for PR3 on the Western edge with the blue cable running around the table on the floor.

In ITMY chamber, we installed the cable post in between AS1 and AS4 with the blue cables running around the table on the floor. This is to ensure the useful part of the table remains empty for future and none of the OSEM cables are taught in air.


  8676   Wed Jun 5 10:46:43 2013 GautamUpdateGeneralCable re-routing at 1Y4

 There were 4 cables running over the front side of rack 1Y4 such that the front door could not be closed. I re-routed them (one at a time) through the opening on the top of the rack. The concerned channels were

  • Green refl mon
  • Err mon
  • Pzt out (temp) (has been marked "Door Damaged BNC")
  • Laser temp ctrl

Before and after pics attached.








  3369   Thu Aug 5 17:59:23 2010 KojiUpdatePSLCable removal from the control room

[Alberto, Kiwamu, and Koji]

We removed the BNC cables from the control room.
The work was as hard as the one I had when I swept a 300m tunnel with a vacuum...

If we could remove the video cables, that would be a real epoch.

We found that the cabling behind the AP table is still quite ugly....grurrrh

Attachment 1: IMG_2684.jpg
  16812   Mon Apr 25 18:00:03 2022 Ian MacMillanUpdateUpgradeCable supports update

I have designed new cable supports for the new ribbon cables running up the side of the tables in the vacuum chambers. 

The clamps that I have designed (shown in basic sketch attachment 1) will secure the cable at each of the currently used cable supports. 

The support consists of a backplate and a frontplate. The backplate is secured to the leg of the table using a threaded screw. The frontplate clamps the cable to the backplate using two screws: one on either side. Between two fascinating points, the cable should have some slack. This should keep the cable from being stiff and help reduce the transfer of seismic noise to the table. 

It is possible to stack multiple cables in one of these fasteners. Either you can put two cables together and clamp them down with one faceplate or you can stack multiple faceplates with one cable between each faceplate. in this case the stack would go backplate then cable then faceplate then cable then the second faceplate. this configuration would require longer screws.

The exact specifics about which size screws and which size plates to use still have not been measured by me. But it will happen

Attachment 1: Chamber_Leg_Ribbon_Cable_Attachments.pdf
  4739   Wed May 18 16:52:23 2011 SureshUpdateRF SystemCables for AS11 PD are in place

[Larisa, Suresh]

All the cables needed for the AS11 PD are in place... the heliax cable runs from the AS table to the PSL rack.  The LO and RF cables to demod board as well as the I and Q cables into the LSC Whitening board are connected.

The cables get rather densely packed when the LSC Whitening filter sits between the PD Interface Board and the LSC AA filter board.  This makes it difficult to access the SMA connectors on the LSC whitening filter.  So we shifted the LSC Whitening and AA Filter boards one slot to the right.  The LSC rack looks like this just now.  We have also shifted the binary cables at the back of the Eurocart by one slot so the same cables are associated with the cards.




  3342   Sat Jul 31 17:37:36 2010 josephbUpdateCDSCables needed for CDS test

Last Thursday, Kiwamu and I went through the cabling necessary for a full damping test of the vertex optics controled by the sus subsytem, i.e. BS, ITMX, ITMY, PRM, SRM.  The sus IO chassis is sitting in the middle of the 1X4 rack.  The c1sus computer is the top 1U computer in that rack.


The hardest part is placing the 2x D-sub connectors to scsi on the lemo break out boxes connected to the 110Bs.  The breakout boxes can be seen at the very top of the picture Kiwamu took here.  These will require a minor modification to the back panel to allow the scsi cable to get out.  There are two of these boxes in the new 1X5 rack.  These would be connected by scsi to the ADC adapters in the back of the sus IO chassis in 1X4.  The connectors are currently behind the new 1X5 rack (along with some spare ADCs/DACs/BOs.

There are 3 cables going from 40 IDC to 37 D-sub (the last 3 wires are not used and do not need to be connected, i.e. 38-40).  These plug into the blue and gold ADC adapter box, the top one shown here.  There is one spare connection which will remain unused for the moment.  The 40 IPC ends plug into the Optical Lever PD boxes in the upper right of the new 1X4 rack (as seen in the top picture here - the boards on the right). At the back of the blue and gold adapter box is a scsi adapter which goes to the back of the IO chassis and plugs into an ADC.

In the back of the IO chassis is a 4th ADC which can be left unconnected at this point.  It will eventually be plugged into the BNC breakout box for PEM signals over in the new 1X7 rack, but is unneeded for a sus test.


There are 5 cables going from 3 SOS dewhite/anti-image boards and 2 LSC anti-image boards into 3 blue and gold DAC adapter boxes.  Currently they plug into the Pentek DACs at the bottom of the new 1X4 rack.  Ideally we should be able to simply unplug these from the Pentek DACs and plug them directly into the blue and gold adapter boxes.  However at the time we checked, it was unclear if they would reach.  So its possible new cables may need to be made (or 40 pin IDC extenders made). These boxes are then connected to the back of the IO chassis by SCSI cables.  One of the DAC outputs will be left unconnected for now.

Binary Output:

The Binary output adapter boxes are plugged into the IO chassis BO cards via D-sub 37 cables.  Note one has to go past the ADC/DAC adapter board in the back of IO chassis and plug directly into the Binary Output cards in the middle of the chassis.  The 50 pin IDC cables should be unplugged from XY220s and plugged into the BO adapter boxes.  It is unclear if these will reach.


We have a short fiber cable (sitting on the top shelf of the new 1X3 rack) which we can plug into the master timing distribution (blue box located in the new 1X6 rack) and into the front of the SUS IO chassis.  It doesn't quite make it going through all the holes at the top of the racks and through the cabling trays, so I generally only plug it in for actual tests.

The IO chassis is already plugged into the c1sus chassis with an Infiniband cable.


So in Summary to plug everything in for a SUS test requires:

  • 6x SCSI cables (3 ADC, 3 DAC) (several near bottom of new 1X3 rack)
  • 4x 37 D-sub to 37 D-sub connector (end connectors can be found behind new 1X5/1X6 area with the IO chassis stuff - Need to be made) (4 BO)
  • 3x 40 IDC to 37 D-sub connectors (end connectors can be found behind new 1X5/1X6 area - Need to be made)(ADC)
  • 5x 64 pin ribbon to 40 IDC cable (already exist, unclear if they will reach) (DAC)
  • 8x 50 pin IDC ribbon (already exist, unclear if they will reach) (BO)
  • 1x Double fiber from timing master to timing card
  • 1x Infiniband cable (already plugged in)

Tomorrow, I will finish up a channel numbering plan I started with Kiwamu on Thursday and place it in the wiki and elog.  This is for knowing which ADC/DAC/BO channel numbers correspond to which signals.  Which ADCs/DACs/BOs the cables plug into matter for the actual control model, otherwise you'll be sending signals to the wrong destinations.

WARNING: The channel numbers on the front Binary Output blue and gold adapter boxes are labeled incorrectly.  Channels 1-16 are really in the middle, and 17-32 are on the left when looking at the front of the box.  The "To Binary IO Module" is correct.

  3848   Tue Nov 2 16:49:02 2010 JenneConfigurationCamerasCabling on the PSL table

Dear whomever setup the camera on the SW corner of the PSL table,

It would be handy if, even for temporary setups, all cables went underneath the white frame around the PSL table.  As it is now, the cables are in the way of the door.  The door is pretty much closed all the way, but if someone were to open other doors, the far door can easily be pushed all the way to the end of the track, thus squishing the cables.  Squished cables are bad cables.


  5583   Fri Sep 30 06:25:20 2011 kiwamuUpdateLSCCalbiration of BS, ITMs and PRM actuators
The AC responses of the BS, ITMs and PRM actuators have been calibrated.
 To perform some interferometric works such as #5582, the actuator responses must be measured.
     BS = 2.190e-08 / f2     [m/counts]
     ITMX  = 4.913e-09 / f2   [m/counts]
     ITMY  = 4.832e-09 / f2   [m/counts]
     PRM   = 2.022e-08 / f2  [m/counts]
The same technique as I reported some times ago (#4721) were used for measuring the BS and ITMs actuators.
In order to measure the PRM actuator, power-recycled ITMY (PR-ITMY) was locked and the same measurement was applied.
The sensor response of PR-ITMY was calibrated by exciting the ITMY actuator since the response of the ITMY had been already measured.
  4347   Thu Feb 24 00:54:33 2011 KevinUpdateElectronicsCalculated Dark Noise for POX and POY

[Kevin, Rana, Koji]

I calculated the dark noise of POX and POY due to Johnson noise and voltage and current noise from the MAX4107 op-amp using nominal values for the circuit components found in their data sheets. I found that the dark noise should be approximately 15.5 nV/rtHz. The measured dark noise values are 18.35 nV/rtHz and 98.5 nV/rtHz for POX and POY respectively. The shot noise plots on the wiki have been updated to show these calculated dark noise sources.

The measured dark noise for POY is too high. I will look into the cause of this large noise. It is possible that the shot noise measurement for POY was bad so I will start by redoing the measurement.

  10374   Wed Aug 13 10:50:04 2014 AndresUpdateIMCCalculation for the input mode cleaner

  Calculation for the input mode cleaner

I have been working on the calculation for the input mode cleaner. I have come out with a new optical setup that will allow us increase the Gouy phase different between the WFS to 90 degrees. I use a la mode to calculate it. The a la mode solution :

   label            z (m)      type             parameters         
    -----            -----      ----             ----------         
    MC1                    0    flat mirror      none:            
    MC3               0.1753    flat mirror      none:            
    MC2              13.4587    curved mirror    ROC: 17.8700       
    Lens1            29.6300    lens             focalLength: 1.7183
    BS2              29.9475    flat mirror      none:            
    First Mirror     30.0237    flat mirror      none:            
    WFS1             30.2269    flat mirror      none:            
    Second Mirror    30.2650    flat mirror      none:            
    Third Mirror     30.5698    flat mirror      none:            
    Lens2            30.9885    lens             focalLength: 1     
    Fourth Mirror    31.0778    flat mirror      none:            
    Lens3            31.4604    lens             focalLength: 0.1000
    Fifth Mirror     31.5350    flat mirror      none:            
    Sixth Mirror     31.9414    flat mirror      none:            
    WFS2             31.9922    flat mirror      none:    

I attached a pictures how the new setup is supposed to look like. 

Attachment 1: ModeCleanerSetup0.PNG
Attachment 2: alaModeModeCleanersolution.png
  10375   Wed Aug 13 13:08:24 2014 ranaUpdateIMCCalculation for the input mode cleaner

Can you please give us some more details on how this design was decided upon? What were the design considerations?

It would be nice to have a shorter path length for WFS2. What is the desired spot size on the WFS? How sensitive are they going to be to IMC input alignment? Are we still going to be recentering the WFS all the time?

  10379   Wed Aug 13 22:01:57 2014 ranaUpdateIMCCalculation for the input mode cleaner

Nic, Andres, and I discussed some more about the MC WFS project today. We want to shorten the proposed WFS2 path. Andres is going to explore moving the 2" diameter lens in coming up with layouts. We also want the WFS to face west so that we can see the diode face with an IR viewer easily and dump the reflected beams in the razor dumps.

We wondered about fixing the power levels and optical gain:

  1. What is the MC modulations depth? What would happen if we increase it a little? Does anyone know how to set it? Will this help the MC frequency noise?
  2. What is the max power on the WFS? I guess it should be set so that the power dissipation of the detector is less than 1 W with the MC unlocked. So P_diss = (100 V)*(I_tot), means that we should have less than 10 mA or ~50 mW when the MC is unlocked.
  3. Another consideration is saturation. The RF signals are tiny, but maybe the DC will saturate if we use any more power. The quadrants are saturated when unlocked and ~200 mV locked. According to D990249, the DC gain in the head is 1000 V/A. The measured power levels going into the heads (w/ MC unlocked) are: P_WFS1 = 4.9 mW and P_WFS2 = 7.7 mW. We don't have control of the DC gain, but there is a 10x and 100x switch available inside the demod board (D980233). From these numbers, I figure that we're in the 100x position and so the effective DC gain between photocurrent and the DC readback voltages is 100 kOhm. Therefore, we are in no danger of optical or electronics saturation. And the unlocked photocurrent of ~40/100000=0.4 mA => 0.04 W heat generated in the diode, so we're OK to increase the power level by another factor of 2-4 if we want.
  4.  We noticed that the ADC inputs are moving by ~50 counts out of 65000, so we're doing a really bad job of signal conditioning. This was previously noticed 6 years ago but we failed to follow up on it. Feh.

While checking this out, I converted the McWFS DC offsets script from csh to bash and committed it to the SVN. We need to remove the prefix 'feature' that Jamie has introduced to cdsutils so that we can use C1 again.


  10384   Thu Aug 14 15:10:47 2014 AndresUpdateIMCCalculation for the input mode cleaner


Can you please give us some more details on how this design was decided upon? What were the design considerations?

It would be nice to have a shorter path length for WFS2. What is the desired spot size on the WFS? How sensitive are they going to be to IMC input alignment? Are we still going to be recentering the WFS all the time?

 I did the calculation, and I reduced the beam Path. In my calculation, I restricted the waist size at the WFSs to be between 1mm-2mm also the other parameter is that the Gouy Phase different between the WFSs have to be 90 degrees. I also try to minimize the amount of mirrors used. I found the Gouy phase to be 89.0622 degrees between the WFSs and the following table shows the solution that I got from a la mode:


  label                         z (m)                   type               parameters         
    -----                         -----                    ----                  ----------         
    MC1                    0                        flat mirror           none:            
    MC3                    0.1753               flat mirror           none:            
    MC2                   13.4587              curved mirror    ROC: 17.8700 (m)       
    Lens1                 28.8172              lens                   focalLength: 1.7183(m)
    BS2                    29.9475              flat mirror           none:            
    First Mirror         30.0237              flat mirror           none:            
    Lens3                 30.1253              lens                  focalLength: -0.100 (m)
    Lens2                 30.1635              lens                 focalLength: 0.1250(m)
    WFS1                 30.2269              flat mirror         none:            
    Second Mirror    30.2650              flat mirror         none:            
    Third Mirror       30.5698              flat mirror         none:            
    Lens4                30.8113              lens                  focalLength: -0.075 (m)
    WFS2                31.0778              flat mirror         none:     

In the first image attached below is the a la mode solution that show the waist size in the first WFS, and I used that solution to calculate the solution of the waist size for the second WFS, which is shown in figure 2. I photoshop a picture to illustrate how the new setup it supposed to look like. 

Attachment 1: SolutionForTheModeCleanerSetup00.png
Attachment 2: SolutionForTheModeCleanerSetup11.png
Attachment 3: PossibleSetupForModeCleaner.PNG
Attachment 4: alaModeSolution.zip
  4471   Wed Mar 30 21:43:31 2011 Aidan, KiwamuSummaryGreen LockingCalculation of the green contrast on the RF PD

Skip to final thought ...

Kiwamu and I have set about measuring the contrast of the signal on the RF PD. We can only do this when the end green laser is locked to the cavity. This is because the green transmission through the cavity, when unlocked, is too low. Unfortunately, once we lock the green beam to the cavity, we can't keep the beatnote on the RF PD stable to within a few hundred Hz of DC (remember that the cavity is swinging around by a couple of FSRs). So we also lock the PSL to cavity.

At this point we're stuck because we can't get both of these beams resonant within the cavity AND have the frequency difference between them be less 1kHz - when the lasers are locked to the cavity, their frequencies are separated by an integer number of FSRs + a fixed frequency offset, f_offset, that is set by the phase difference on reflection from the coating between the two wavelengths (532nm and 1064nm). We can never get the frequency difference between the lasers to be less than this offset frequency AND still have them both locked to the cavity.


So our contrast measuring method will have to use the RF signal.


So this is our method. We know the incident power from each beam on the RF PD (see Kiwamu's elog entry here), but to recap,

P_green_PSL = 72 uW (as measured today)

P_green_XARM = 560 uW (as measured by Kiwamu last week).

The trans-impedance of the RF PD is 240 Ohms. We'll assume a responsitivity of 0.25 A/W. So, if the XARM transmission and PSL green beams are perfectly matched then the maximum value of the RF beat note should be:

RF_amplitude_max = 2* SQRT(P_green_PSL*P_green_XARM) * responsivity * transimpedance = 240*0.25*2*(72E-6*560E-6)^(1/2) (volts)

= 24 mV = -19.5 dBm (or 27.5dBm after the +47 dB from the two  ZFL-1000LN+ amplifiers - with +15V in - that protrude from the top of the PD)

The maximum RF strength of the beat-note that we measure is around -75 dBm (at the RF output of the PD). This means the contrast is down nearly 600x from optimal. Or it means something is broken.

Final thought: at the end of this procedure we found that the RF beat note amplitude would jump to a different and much higher amplitude state. This renders a lot of the above useless until we discover the cause.

  7695   Fri Nov 9 18:28:23 2012 CharlesUpdateSummary PagesCalendar

The calendar tab now displays calendars with weeks that run from Sunday to Saturday (as opposed to Monday to Sunday). However, the frame on the left hand side of the main page still has 'incorrect' calendars.


  1100   Wed Oct 29 12:54:28 2008 JenneUpdatePEMCalibrated Guralp Noise compared to average ground motion
Here is a calibrated noise plot of the Guralp seismometer box. This is the same noise measured on Friday, measured at TP3 (just after the first gain stage), with the inputs shorted.

The Guralp calibration is:
                TP3 noise
noise in m/s = -------------------
                 10 * 802(V/(m/s))
The 10 is from the gain of 10 between the output of the seismometer and the input of the breakout box, and the 802 V/(m/s) is from the calibration data that came with the seismometer.

From elog 881 by Rana, in the ~1-50Hz band, the calibration of the Ranger seismometer is 488*10^6 counts/(m/s). Using DataViewer, I estimated that the nighttime ground motion measured by the Ranger is ~3500 counts, and the max daytime ground motion is ~8000 counts. This is what was used for the nighttime/daytime lines in this plot.

It seems like the noise of the Guralp box is fine just as it is, and we don't need to worry about replacing the first gain stage (differential instrumentation amp) with a lower-noise op-amp, since at even the lowest freqs, we have almost a factor of 100 at night, and better than that at higher freqs.

NOTE about the plot: the legend isn't showing the correct colors for the night and day motion - obviously the nighttime motion is the lower RED line, and the day is the higher GREEN line.

Yet another note: When I was measuring the counts on the Ranger, I forgot to subtract the mean, so these numbers are overestimating the ambient ground motion. The blue curve is correct however.
Attachment 1: GuralpVert1Noise_mPERs_Ranger.png
  694   Fri Jul 18 16:57:37 2008 JenneUpdateIOOCalibrated MC_F
I have calibrated MC_F. The conversion factor is 137.49 MHz/count.

The calibration data taken is attached, along with a calibrated power spectrum.

On the data plot, the x axis is volts from the C1:IOO-MC_FAST_MON channel, with the calibration between FAST_MON and MC_F = -788.18 volts/count.
The linear term of the fit line = -0.085MHz/volt. Error bars are +/- 1 in the last digit of what the spectrum analyzer gave me for frequency (+/- 0.01MHz).

The net conversion factor is then (-788.18)*(-0.085)*(2) = 137.49 MHz/count. The factor of 2 is because the light passes through the AOM twice.

On the power spectrum,
REF0 and REF1 = MC unlocked, HEPAs on, MC Refl gain = 22
REF2 and REF3 = MC locked, HEPAs on, MC Refl gain = 22
REF4 and REF5 = MC locked, HEPAs on, MC Refl gain = 19
REF6 and REF7 = MC locked, HEPAs off, MC Refl gain = 19
Attachment 1: MC_Fcalib.png
Attachment 2: 20080717MC_F-MC_I.pdf
  13969   Fri Jun 15 00:53:21 2018 gautamUpdateLSCCalibrated MICH spectrum

Using the numbers from the sensing measurement, I calibrated the measured in-loop MICH spectrum from Tuesday night into free-running displacement noise. For convenience, I used the noise-budgeting utilities to make this plot, but I omitted all the technical noise curves as the coupling has probably changed and I did not measure these. The overall noise seems ~x3  higher everywhere from the best I had last year, but this is hardly surprising as I haven't optimized anything for low noise recently. To summarize:

  • DRMI was locked using 1f error signals.
  • MICH was controlled using AS55_Q.
  • Main difference is that we have a little less (supposedly 10%) light on the AS55 PD now because of the AUX laser injection setup. But the AUX laser was shuttered.
  • 1f LSC PDs (REFL11, REFL55 and AS55) had ADC whitening filters engaged in while this data was taken.
  • ITM and BS coils were not de-whitened.

I will do a more thorough careful characterization and add in the technical noises in the coming days. The dominant uncertainty in the sensing matrix measurement, and hence this free-running noise spectrum, is that I haven't calibrated the actuators in a while.


I finally analyzed the sensing measurement I ran on Tuesday evening. Sensing responses for the DRMI DOFs seems consistent with what I measured in October 2017, although the relative phasing of the DoFs in the sensing PDs has changed significantly. For what it's worth, my Finesse simulation is here

Attachment 1: C1NB_disp_40m_MICH_NB_2018-06-14.pdf
  6858   Fri Jun 22 20:58:15 2012 JenneUpdateGreen LockingCalibrated POX spectra - Xarm stabilized by ALS

[Yuta, Jenne, Koji]

We stabilized the Xarm using the ALS and took a spectrum of POX as our out of loop sensor.  We used the calibration from elog 6841 to go from counts to meters.

We find (see attached pdf) that the RMS is around 60pm, dominated by 1Hz motion.


In other, related, news, I took out the beam pipe connecting the AP and PSL tables and covered the holes with foil.  This makes it much easier and faster to get to the X beat setup for alignment.  Eventually we'll have to put it back, but while the AUX laser on the AP table is not being used for beating against the PSL it'll be nice to have it out of the way.

Attachment 1: POX11_I_ERR_calib_residualCavityMotion_better.pdf
  9630   Wed Feb 12 19:47:40 2014 JenneUpdateLSCCalibrated REFL signals

I calibrated the REFL signals to meters from counts.  The I-phase signals all line up very nicely, but the Q-phase signals do not at all.  I'm not sure what the deal is.

 I locked  the PRMI on sidebands, and drove the PRM.  I looked at the peak values at the drive frequency in the REFL signals, and used that as my "COUNTS" value for each PD. 

I know the PRM actuator calibration is 19.6e-9 (Hz/f)^2 m/ct , so if I plug in my drive frequency (564 Hz, with the notch in the PRC loop enabled), and multiply by my drive amplitude in counts, I know how many meters I am pushing the PRM.  Then, to get a meters per count calibration, I divide this calibration number (common for every PD) by the peak value in each PD, to get each signal's calibration.

As a side note, I also drove MICH, and tried to use this technique for the Q-phase calibrations, but neither calibration (using the PRCL drive nor the MICH drive) made the Q-phase signals line up at all.

At least for the I-phase signals, it's clear that REFL33 has more noise than REFL11 or REFL165, and that REFL55 has even more noise than REFL33. 

Here are the calibration values that I used:


PD m/ct calibration
REFL11 I 1.71e-13
REFL11 Q 2.05e-11
REFL33 I 1.22e-12
REFL33 Q 3.80e-11
REFL55 I 9.54e-13
REFL55 Q 6.29e-12
REFL165 I 6.98e-14
REFL165 Q 8.63e-13


Attachment 1: CalibratedUsingPRMdrive.pdf
  9631   Wed Feb 12 20:30:41 2014 KojiUpdateLSCCalibrated REFL signals

We usually want to remove PRCL from the Q quadrature for each PD.
Therefore, you are not supposed to see any PRCL in Q assuming the tuning of the demod phases are perfect.
Of curse we are not perfect but close to this regime. Namely, the PRCL in Qs are JUNK.

In the condition where MICH is supressed by the servo, it is difficult to make all of the Qs line up because of the above PRCL junk.
But you shook MICH at a certain freq and the signal in each Q signal was calibrated such that the peak has the same height.
So the calibration should give you a correct sensing matrix.

If you tune the demod phases precisely and use less integrations for MICH, you might be able to see the residual MICH lines up on the Q plot.

  10298   Wed Jul 30 15:33:48 2014 AkhilSummaryGeneralCalibrated Thermal Actuator TFs

 The goal of the measurements we made ( my previous 3 elogs) was to characterize the laser frequency thermal actuator that is a part of the FOL- PID loop.

For this we made indirect TF measurements for the thermal actuator by looking at the PZT response by 1)arm cavity( ETM ,ITM) displacement  and 2) temperature offset excitation. The goal was to do something like getting G1=TF3/TF1 and G2=TF3/TF2 and ultimately dividing G2/G1 to get TF2/TF1 with correct calibration. The final TFs obtained are the X and Y arm TFs for Laser frequency response vs temperature offset in(HZ/count). The calculations  in detail are:


Obtained    G1 = PZT response/ Temperature Offset (count/count): (in detail here )

Obtained    G2 = PZT response/  X and Y arm displacement( count/ count) : (in detail here)

Calibrated G2 to count/m ( in detail here)

Divided G2/G1 to get X and Y arm displacement/ Temperature Offset( m/ count) to get G3

Did these calculations:

dL/ L = dF /F

F = c/lambda ;Lambda = 532 nm  ; L = 

X arm length = 37.79 +/- 0.05 m

Y arm length = 37.81 +/- 0.01 m

TF: Laser Freq/ Temperature Offset = G3 *F/L       (HZ/Count)

The calibration coefficients for the ends  are :

X End:  [23.04 +/-  0.23 ]* 10^3  (HZ/Count)

Y End:    [18.71 +/-  0.2 ]* 10^3 (HZ/Count)

For the TFs of the temperature actuator on laser frequency I used ITMs for both the arms. The bode plots for the calibrated( HZ/Temp Count) are attached.

 For the X-Arm Thermal Actuator, I calculated the TFs at two different frequency ranges and combined the results where the coherence is high(>0.7). At 1 Hz the coherence was not as good as the other frequencies(due to the suspension resonance at 0.977 Hz).

The poles and zeroes are estimated after fitting this data using Matlab vectfit tool.The  graphs showing fit and measured values are attached.

Y arm Thermal Actuator:

5th order TF fitted: 

Gain: 9000


z1 = -0.9799;

z2 = 2.1655; 

z3 = -2.9746- i * 3.7697

z4 = -2.9746+ i * 3.7697

z5 =  95.7703 + 0.0000i 


p1 = -0.0985- i* -0.0845

p2 = -0.0985+ i* -0.0845

p3 = -0.6673- i* -0.7084

p4 = -0.6673+ i* -0.7084

p5 = -8.7979.


X-arm Thermal Actuator:

5th order TF fitted: 

Gain = 20


z1= -305.7766

z2 =   -18.2774

 z3 =  -16.6167

 z4 =   -1.2486

 z5 =   28.1080



p1  = -0.1311 - 0.1287i

p2 =  -0.1311 + 0.1287i

 p3  =  -8.3797 + 0.0000i

 p4 =  -4.0588 - 7.5613i

  p5 = -4.0588 + 7.5613i

I will use get the poles and zeroes from these fitted  bode plots and use it to build the PID loop.


Attachment 1: Y_Arm_TA_TF.pdf
Attachment 2: X_Arm_TA_TF.pdf
Attachment 3: Y_Arm_TA_with_fit.pdf
Attachment 4: X_Arm_TA_with_fit.pdf
  1390   Wed Mar 11 22:57:48 2009 YoichiUpdateLockingCalibrated XARM error signal spectrum
I did a rough calibration of the XARM error spectrum.
See the attached calibrated spectrum.

I started from this Rana's elog entry.

I first injected a 20Hz sin signal into C1:SUS-ETMX_LSC_EXC and measured the response to the ETMX SUSPOS.
Using the calibration of the SUSPOS given in the above entry, I calibrated the ETMX coil actuation efficiency.
It was 3.4e-12 m/cnt @20Hz for C1:SUS-ETMX_LSC_EXC.

Then I locked the X-arm and injected a calibration peak at 20Hz.
From the ratio of the peaks in C1:SUS-ETMX_LSC_IN2 and C1:LSC-XARM_IN1, I calibrated the X-arm error signal to be 4.2e-13 m/cnt.
We have to also take into account the cavity pole of the arm, 1525Hz (the design value, may not be actual).
So I used the following calibration in the DTT:

G: 4.2e-13
P: 1525

Note that the attached spectrum shows the actual motion of the X-arm (or equivalent frequency noise) after suppressed by the feedback servo,
unlike conventional noise spectra showing "virtual" displacement which would have been induced in the absence of servos.
Attachment 1: XarmErrorSpeCalibrated.pdf
  1402   Fri Mar 13 22:07:14 2009 YoichiUpdateLockingCalibrated XARM error signal spectrum
Of course I made a mistake.
I put a pole at 1525Hz whereas it should have been a zero.

The correct calibration factor is:
G: 4.2e-13
Z: 1525

I attached a revised spectrum.

I did a rough calibration of the XARM error spectrum.
See the attached calibrated spectrum.

I started from this Rana's elog entry.

I first injected a 20Hz sin signal into C1:SUS-ETMX_LSC_EXC and measured the response to the ETMX SUSPOS.
Using the calibration of the SUSPOS given in the above entry, I calibrated the ETMX coil actuation efficiency.
It was 3.4e-12 m/cnt @20Hz for C1:SUS-ETMX_LSC_EXC.

Then I locked the X-arm and injected a calibration peak at 20Hz.
From the ratio of the peaks in C1:SUS-ETMX_LSC_IN2 and C1:LSC-XARM_IN1, I calibrated the X-arm error signal to be 4.2e-13 m/cnt.
We have to also take into account the cavity pole of the arm, 1525Hz (the design value, may not be actual).
So I used the following calibration in the DTT:

G: 4.2e-13
P: 1525

Note that the attached spectrum shows the actual motion of the X-arm (or equivalent frequency noise) after suppressed by the feedback servo,
unlike conventional noise spectra showing "virtual" displacement which would have been induced in the absence of servos.
Attachment 1: XarmErrorSpeCalibrated.pdf
  9105   Wed Sep 4 20:47:15 2013 manasaUpdateLSCCalibrated in-loop MICH noise

To estimate in-loop MICH noise:

(a) Calibrate MICH_ERR:

1. Lock the arms for IR using POX11 and POY11.
2. Misalign the ETMs.
3. Obtain the average peak-to peak (bright to dark fringe) counts from the time series of AS55_Q_ERR. I measured this to be d = 6.358 counts.
4. This gives the calibration factor for AS55_Q_ERR [Calibration factor = 2*pi*d/1064/10^-9 = 3.7546x10^7 counts/m]

(b) In-loop MICH noise:

1. Lock MICH using AS55_Q.
2. Since LSC input matrix sets MICH_IN1 = 1* AS55_Q_ERR, the power spectrum measured using dtt and calibrated using the calibration factor from step 4 in (a) gives us the calibrated in-loop MICH noise.

The plot below shows the in-loop MICH noise and the dark noise (measured by closing the PSL shutter):

Compared with old measurements done by Keiko elog 6385 the noise levels are much better in the low frequency region below 100 Hz.
(No, no, no... this is not an apple-to-apple comparison: KA)

Attachment 1: MICH_noise.pdf
  4214   Thu Jan 27 21:10:47 2011 OsamuUpdate40m UpgradingCalibrated noise of green

I calibrated noise spectrum of green lock.

1. Measurement of conversion factor of ADC input from V to ct:

As a preparation, first I measured a conversion factor at ADC input of C1;GCX1SLOW_SERVO1.

It was measured while the output of AI ch6 as the output of C1;GCX1SLOW_SERVO2 with 1Hz, 1000ct(2000ct_pp) was directly connected into AA ch7 as the input of C1;GCX1SLOW_SERVO1. Amplitude at the output at AI ch6 was 616mVpp measured by oscilloscope, and C1;GCX1SLOW_SERVO1_IN1 read as 971.9ct_pp. So the conversion factor is calculated as 6.338e-4[V/ct].

2. Injection of a calibration signal:

When Green laser was locked to cavity with fast PZT and slow thermal, I injected 100Hz, 1000ct EXC at ETMX ASL. The signal was measured at C1:GCX1SLOW_SERVO1_IN1 as 5.314ct_rms. It can be converted into 3.368e-3Vrms using above result, and then converted into 3368Hz_rms using PZT efficiency as 1MHz/V. This efficiency was obtained from Koji's knowledge, but he says that it might have 30% or higher error. If somebody get more accurate value, put it into the conversion process from V to Hz here.

3. Conversion;

Frequency of green f=c/532nm=5.635e14[Hz] is fluctuating with above 3368Hz_rms,so the fluctuation ratio is 3368/5.635=5.977e-12, and it corresponds to length fluctuation of 37.5m. So, cavity fluctuation will be 5.977e-12*37.5=2.241e-10m_rms by 100Hz, 1000ct EXC at ETMX ASL.

4. Results;

Finally, we knew 5.314ct corresponds to 3368Hz and 2.241e-10m, so conversion factor from ct to Hz and ct to m are ;

633.8[Hz/ct] @ C1:GCX1SLOW_SERVO1

4.217e-11[m/ct] @ C1:GCX1SLOW_SERVO1


5. Calibration:

You can measure green noise spectrum at C1;GCX1SLOW_SERVO1_IN1 during lock,  and mutiply above result to convert Hz or m.

This calibration is effective above corner frequency of slow and fast servo around 0.5Hz and UGF of fast servo around 4kHz.

I show an example of calibrated green noise.



Each color show different band-width. Of course this results of calibration cactor does not depend on band-width. Noise around 1.2Hz is 6e-8Hz/rHz. It sounds a bit too good by factor ~2. The VCO efficiency might be too small.


Note that there are several assumptions in this calibration;

1. TF from actual PZT voltage to PZT mon is assumed to be 1 in all frequency. Probably this is not a bad assumption because circuit diagram shows monitor point is extracted PZT voltage directly.

2. However above assumption is not correct if the input impedance of AI is low.

3. As I said, PZT efficiency of 1MHz/V might be wrong.


I also measured a TF from C1:SUS-ETMX_ALS_EXC to C1:GCX1SLOW_SERVO1_IN1. It is similar as calibration injection above but for wide frequency. This shows a clear line of f^-2 of suspension.



Files are located in /users/osamu/:20110127_Green_calibration.

  850   Tue Aug 19 10:36:34 2008 SharonUpdate Calibrating accelerometers
I took apart the accelerometers near MC1 and MC2.
The 2 sets of 3 accelerometers are now covered by a box on the floor. Please try not to move them... I will place it all back once I am done calibrating.
  1139   Mon Nov 17 11:01:15 2008 AlbertoHowToElectronicsCalibrating the Frequency Standard of the Marconi
I locked the SRS Rubidium Frequency Standard FS275 to the the 1pps from the GPS. The specs from the manual provide a frequency accuracy of 5x10^-11, that is 5x10-4 @ 10 MHz, since this is the reference signal frequency we're are going to use.
The Marconi internal frequency standard is provided by a TCXO oscillator. The instrument can be set in either one of these ways: 1) Indirect Synchronization, by which the internal TCXO is phase-locked to the external frequency standard (i.e. the SRS FS275 in our case) 2) Direct Sync, in which the internal TCXO is bypassed and the frequency standard is the external one.

I checked the specs of both frequency standards and found:

SRS FS275: 5x10^-11 -> 5x10^-10 Hz @ 10 MHz

Marconi: here what the data sheet says is that "the temperature coefficient is 7 in 10^7 in the temperature range between 0 and 55 C" and so should be also the frequency accuracy.

The SRS FS275 seems more accurate than the TCXO therefore I'm going to set the Marconi on the direct external mode.
Attachment 1: 2023ASeriesOperatingManual.pdf
2023ASeriesOperatingManual.pdf 2023ASeriesOperatingManual.pdf 2023ASeriesOperatingManual.pdf 2023ASeriesOperatingManual.pdf
Attachment 2: SRS_FS275_Rubidium_Frequency_Standard.pdf
SRS_FS275_Rubidium_Frequency_Standard.pdf SRS_FS275_Rubidium_Frequency_Standard.pdf
  10286   Tue Jul 29 18:00:20 2014 AkhilUpdateLSCCalibration of ETMX and ETMY actuators

The ultimate goal of characterizing the temperature actuator turned to be fruitful in obtaining the calibration values for ETMX and ETMY (Calibration of ITMs were done previously  here but not for ETM). In this process, I measured the PZT response by  displacing one of the test masses in the frequency range of 20 Hz and 900 Hz  and measured the transfer functions in counts/counts. 

ETMX = [12.27  x 10 -9/ f2 m/count

ETMY = [14.17  x 10 -9/ f2] m/count


I calculated these calibration values from the measurements that we have taken( in detail : elog)  and did the following calculations: 

The measurements I made were :PZT count/ Actuator Count separately for all the test masses.

PZT count/ Actuator count = [PZT count/ arm cavity displacement(m) ]*[ displacement of a test mass(m) / Actuator Count]

For a same laser and assuming flat response of the PZT, the term [PZT count/ arm cavity displacement(m) ] remains for all the test masses.

The fitting was done on the gain plots of the PZT Response vs Test mass displacement and a function G * f ^-2 was fitted. The resulting G values were:

ETMX: 8.007* f ^-2 

ITMX: 3.067* f ^-2

ETMY :11.389* f ^-2

ITMY : 3.745* f ^-2

To calculate the calibration of ETMX:

 [PZT count/ Actuator count : ETMX ] / [ displacement of a test mass(m) / Actuator Count :ETMX] =  [PZT count/ Actuator count : ITMX ] / [ displacement of a test mass(m) / Actuator Count :ITMX]

putting the values from the above fitting and Kiwamu's elog,

the calibrated value was calculated to be [12.27 * 10^-9 /f^-2 ]m/count.

A similar calculation was done for ETMY.

The attached are the fitting plots for the measurements taken.

 Now using these and the previously measured calibrations, I will get the complete calibrated TF of the thermal actuator.






Attachment 1: PZT_ETMX_TF.png
Attachment 2: PZT_ETMY_TF.png
Attachment 3: PZT_ITMX_TF.png
Attachment 4: PZT_ITMY_TF.png
  8242   Wed Mar 6 18:14:33 2013 ManasaSummaryLSCCalibration of BS, ITMX and ITMY actuators

[Yuta, Manasa]

Measured actuator response between 50Hz and 200 Hz in (m/counts).

BS     = (20.7 +/- 0.1)    x 10 -9 / f2

ITMX = (4.70 +/- 0.02) 
x 10 -9/ f2

ITMY = (4.66 +/- 0.02)
x 10 -9/ f2

Actuator response differs by 30% for all the 3 mirrors from the previous measurements made by Kiwamu in 2011.

Calibration of BS, ITMX and ITMY actuators

We calibrated the actuators using the same technique as in Kiwamu's elog.

A) Measure MICH error

1. Locked Y-arm and X-arm looking at TRY and TRX.
2. Misaligned ETMs
3. Measured  MICH error using ASDC and AS55_Q err (MICH_OFFSET = 20 - to compensate for offset in AS_Qerr which exists even after resetting LSC offsets)


B) Open loop transfer function for MICH control

1. Measured the transfer function between C1:LSC-MICH_IN1 and C1:LSC-MICH_IN2 by exciting on  C1:LSC-MICH_EXC.
MICH filter modules used for measurements(0:1 , 2000:1, ELP50). ELP50 used so that actuation signals above 50 Hz are not suppressed.


C) Calibration of BS/ ITMX/ ITMY actuators

1. Measured transfer function between actuation channels on BS/ ITMX/ ITMY and C1:LSC-AS55_Q_ERR.


  11841   Thu Dec 3 03:01:07 2015 gautamUpdateLSCCalibration of C1CAL

[ericq, gautam]

While trying to resolve the strange SRCL loop shape seen yesterday (which has been resolved, eric will elog about it later), we got a chance to put in the correct filters to the "CINV" branch in the C1CAL model for MICH, PRCL, and SRCL - so we have some calibrated spectra now (Attachment #1). The procedure followed was as follows:

  1. Turn on the LO gain for the relevant channel (we used 50 for MICH and SRCL, 5 for PRCL)
  2. Look at the power spectra of the outputs of the "A" and "CINV" filter banks - the former has some calibrated filters in place already (though I believe they have not accounted for everything).
  3. Find the peak height at the LO excitation frequency for the two spectra, and calculate their ratio. Use this to install a gain filter in the CINV filter module for that channel. 
  4. Look at the spectrum of the output of the "W" filter bank for that channel - the plot attached shows this information.

The final set of gains used were:

MICH: -247 dB

PRCL: -256 dB

SRCL: -212 dB

and the gain-only filters in the CINV filter banks are all called "DRMI1f".

Once we are able to lock the DRFPMI again, we can do the same for CARM and DARM as well...

Attachment 1: 2015-12-C1CAL_Calibration.pdf
  6402   Mon Mar 12 22:14:56 2012 SureshUpdateRF SystemCalibration of Demod Board Efficiency.

I have completed the calibration of the demod board efficiencies.  Here is the schematic of the set-up.


The data is given below and the data-file is attached in several different formats.



Attachment 3: Demod_calib.txt
	Measurements			 After corrections			Efficiency= out/in	
Demod Board	mV_ampl	mV_pk-pk	mV_pk-pk	mV_ampl	mV_ampl	mV_ampl	Vout/Vin	Vout/Vin
	PD in	Q out	I out	PD in	Q out	I out	Q out	I out
REFL33	10.6	10.0	10.0	9.4	5.0	5.0	0.53	0.53
AS11	24.0	10.0	11.0	21.3	5.0	5.5	0.23	0.26
REFL11	22.5	240.0	255.0	20.0	120.0	127.5	6.00	6.38
POX11	24.0	9.2	8.5	21.3	4.6	4.3	0.22	0.20
POY11	22.4	10.5	9.0	19.9	5.3	4.5	0.26	0.23
AS55	17.6	268.0	268.0	15.6	134.0	134.0	8.57	8.57
REFL55	19.7	15.8	15.5	17.5	7.9	7.8	0.45	0.44
POP55	18.8	278.0	274.0	16.7	139.0	137.0	8.32	8.20
REFL165	21.2	16.0	16.4	18.8	8.0	8.2	0.42	0.44
POY110	23.4	14.7	14.4	20.8	7.4	7.2	0.35	0.35
POY22	17.5	11.9	9.3	15.6	6.0	4.6	0.38	0.30
Attachment 4: Demod_calib.xlsx
  5172   Wed Aug 10 14:27:39 2011 Ishwita , ManuelUpdatePEMCalibration of Guralp and STS2

ADC: 216counts = 4V Hence, calibration of ADC is 214counts/V.

Gain of the AA board, g1 = 0.1


Sensitivity = 800 V/ms-1

214 counts/V x 800  V/ms-1 = 13107200 counts/ms-1 -----> 7.6294e-08 ms-1/count

Gain, g2 = 10

Calibration = 7.6294e-08 ms-1/count x g1 x g2 = 7.6294e-08 ms-1/count


Sensitivity = 1500 V/ms-1

214 counts/V x 1500  V/ms-1 = 24576000 counts/ms-1 -----> 4.069e-08 ms-1/count

Gain of the STS electronic breakout box, g3 = 10

Calibration = 4.069e-08 ms-1/count x g1 x g3 = 4.069e-08 ms-1/count

  5174   Wed Aug 10 14:35:39 2011 ranaUpdatePEMCalibration of Guralp and STS2

I'm pretty sure that don't have any ADC's with this gain. It should be +/- 10V for 16 bits. 

  5175   Wed Aug 10 15:17:39 2011 Ishwita, ManuelUpdatePEMCalibration of Guralp and STS2


I'm pretty sure that don't have any ADC's with this gain. It should be +/- 10V for 16 bits. 

Jenne told us that the ADC was +/- 2V for 16 bits so our calibration is wrong. Since, the ADC is +/- 10V for 16 bits we need to change our calibration and now we can also use the purple STS breakout box.

  5185   Thu Aug 11 09:39:25 2011 Ishwita, ManuelUpdatePEMCalibration of Guralp and STS2



I'm pretty sure that don't have any ADC's with this gain. It should be +/- 10V for 16 bits. 

Jenne told us that the ADC was +/- 2V for 16 bits so our calibration is wrong. Since, the ADC is +/- 10V for 16 bits we need to change our calibration and now we can also use the purple STS breakout box.

 New calibration for Guralp:

ADC: 216counts = 20V Hence, calibration of ADC is (215x0.1) counts/V.


Sensitivity = 800 V/ms-1

(215 x 0.1) counts/V x 800  V/ms-1 = 2621440 counts/ms-1 ----->  3.8147e-07 ms-1/count

Calibration = 3.8147e-07 ms-1/count

Using the above calibration we obtain the following plot:


When we compare this plot with the old plot (see here) we see that in our calibration, we have got a factor of 10 less than the old plot. We do not know the gain of the Guralp. If we assume this missing 10 factor to be the gain of Guralp then we can get the same calibration as the old plot. But is it correct to do so?

  5187   Thu Aug 11 11:50:56 2011 Manuel , IshwitaUpdatePEMCalibration of Guralp and STS2


 We just checked with a function generator the calibration of the ADC. We set a square wave with amplitude 1V. We measured the voltage with the oscilloscope and we found on the data viewer that one volt is 3208 counts. That's what we expected (+/- 10V for 16bits) but now we are more sure.


  5196   Thu Aug 11 16:15:59 2011 Ishwita, ManuelUpdatePEMCalibration of Guralp and STS2


Finally, we have found the correct calibration of Guralp and STS2 seismometers.

ADC: 216counts = 20V Hence, calibration of ADC is 3.2768e+03 counts/V.



Sensitivity of seismometer = 800 V/ms-1

Gain of the guralp breakout box (reference elog entry) = 20

Calibration = 3.2768e+03 counts/V x 800  V/ms-1 x 20 = 52428800 counts/ms-1 -----> 1.9073e-08 ms-1/count


Sensitivity = 1500 V/ms-1

Gain of the STS electronic breakout box = 10

Calibration = 3.2768e+03 counts/V x 1500  V/ms-1 x 10 = 49152000 counts/ms-1 -----> 2.0345e-08 ms-1/count


  7017   Tue Jul 24 03:14:13 2012 JenneUpdateASSCalibration of MC ASS lockins

I wanted to check that the calibration of the MC ASS lockins was sensible, before trusting them forevermore.

To measure the calibration, I took a 30sec average of C1:IOO-MC_ASS_LOCKIN(1-6)_I_OUT with no misalignment. 

Then step MC1 pitch by 10% (add 0.1 to the coil output gains).  Remeasure the lockin outputs.

2.63 / (Lockin1noStep - Lockin1withStep) = calibration.

Repeat, with Lockin2 = MC2 pit, lockin3 = MC3 pit, and lockins 4-6 are MC1-3 yaw.


The number 2.63 comes from: half the side of the square between all 4 magnets.  Since our offsets are in pitch and yaw, we want the distance between the line connecting the lower magnets and the center line of the optic, and similar for yaw.  Presumably if all of the magnets are in the correct place, this number is the same for all magnets.  The optics are 3 inches in diameter.  I assume that the center of each magnet is 0.9mm from the edge of the optic, since the magnets and dumbbells are 1.9mm in diameter. Actually, I should probably assume that they're farther than that from the edge of the optic, since the edge of the dumbbell ~touches the edge of the flat surface, but there's the bevel which is ~1mm wide, looking normal to the surface of the optic.  Anyhow, what I haven't done yet (planned for tomorrow...) is to figure out how well we need to know all of these numbers.

We shouldn't care more than ~100um, since the spots on the optics move by about that much anyway.

For now, I get the following #'s for the calibration:

Lockin1 = 7.83

Lockin2 = 9.29

Lockin3 = 8.06

Lockin4 = 8.21

Lockin5 = 10.15

Lockin6 = 6.39

The old values were:


The new values measured tonight are pretty far from the old values, so perhaps it is in fact useful to re-calibrate the lockins every time we try to measure the spot positions?

  4721   Sun May 15 19:10:12 2011 kiwamuUpdateLSCCalibration of actuators : BS, ITMX and ITMY

The AC response of the actuators on BS, ITMX and ITMY were re-measured by another technique.

Last time I estimated them by measuring the open-loop transfer functions, but this time the responses were measured in a more direct way.

The measured AC responses (60 Hz - 200 Hz) are :

      BS   = 1.643e-98 / f2  [m/counts] (corrected based on the plot below - Manasa)

     ITMX = 3.568e-9 / f2 [m/counts]

     ITMY = 3.542e-9 / f2 [m/counts]

Next : measurement of the PRM actuator response

(The technique) 

 This time a technique that Rana told me a week ago was used.

This technique allows us to directly measure the response of an actuator at high frequency without any loop corrections.

First of all, MICH has to be locked to keep MICH within the linear range of the error signal. So now MICH is a linear sensor to the mirror motions.

In the MICH control a steep low pass filter should be inserted in order to avoid unwanted effects from the control loop at the high frequencies.

For example I put a low pass filter composed of an elliptical filter whose cut-off frequency is at 50 Hz such that the control loop doesn't push the mirrors above the cut-off frequency.

Hence the error signal of MICH above 50 Hz directly corresponds to the motion of the mirrors including BS, ITMX and ITMY.

Taking a transfer function from an actuator to the MICH error signal directly gives the actuator response.

In my measurements MICH was locked by feeding the signal back to BS. The plot below is the expected open-loop transfer function for the MICH control.


You can see that the open loop TF suddenly drops above 50 Hz. The UGF was at about 20 Hz, confirmed by looking at the loop oscillation on DTT.



 In the technique the error signal has to be calibrated to [m]. This time AS55_Q was used and calibrated based on a peak-to-peak measurement.

The peak to peak value in the MICH error signal was 8 counts, which corresponds to the sensor efficiency of 4.72e+07 [counts/m].

Then I took transfer functions from each suspension (i.e. C1:SUS-XXX_LSC_EXC) to the error signal at AS55_Q over a frequency range from 60 Hz to 200Hz.

For the transfer function measurements I ran the swept sine on DTT to get the data. Note that the PD whitening filters were on.

The plot below is the results of the measurements together with the fitting lines.


In the fitting I excluded the data pints at 60 Hz, because their coherence was low due to the power line noise.

  10281   Mon Jul 28 16:34:02 2014 AkhilUpdateGeneralCalibration of measured Thermal Actuator TFs

 To calibrate the measured TFs and characterize the thermal actuator for the FOL loop, we [ Me, Eric Q, Koji ] made the TF measurements of PZT response by giving a  disturbance to the position of  each of X and Y arm ETM  and ITM.

In order to make reasonable conclusions, the measurements were done at frequencies greater than 20 Hz (assuming the PZT response to be flat till a few KHz), which is out of the  bandwidth of the control loops operating for other noises at low frequencies, so that we can get the response only( mainly) due to the disturbance of the masses. 

 For this measurement , a Sine sweep excitation was given as an input to one of the test mass and PZT actuation signal was monitored. The channels used for the measurement are: 

Input( Mirror displacement):





Output ( PZT Response):


The units of the TF of these measurements are not calibrated  and are in count/count. For this I will use the ITMX and ITMY calibration values from Izumi's Elog. I will also make some calculations and post in the calibrations of ETMX and ETMY in a separate elog.

I am now estimating the calibrated Thermal Actuator TF and will estimate the location of poles and zeroes to build the PID loop. I will elog the final calibrated TFs in my next elog.

The attached are the Bode Plots  for ETM and ITM for X and Y arms.

Attachment 1: mirrorTF2.pdf
ELOG V3.1.3-