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  17030   Mon Jul 25 09:05:50 2022 PacoSummaryGeneralTesting 950nm laser found in trash pile

[Paco, Yehonathan]

==== Late elog from Friday ====

Koji provided us with a QFLD-950-3S (QPHOTONICS) salvaged from Aidan's junk pile (LD is alive according to him). We tested the Jenne laser setup with this just to decide if we should order another one, and it worked.

The laser driver anode and cathode pins (8/9, 4/5 respectively) on the rear DB9 port from the  ILX Lightwave LDX-3412 driver were connected to the corresponding anode and cathode pins in the laser package (5, and 9; note the numbers are reversed between driver and laser). Then, interlock pins 1 and 2 in the driver were shorted to enable operation. This is all illustrated in Attachments #1-2.

After setting a limit of 27.6 mA current in the driver, we slowly increased the actual current to ~ 19 mA until we could see light on a beam card. We can go ahead and get a 1060 nm replacement.

Attachment 1: PXL_20220722_234600124.jpg
Attachment 2: PXL_20220722_234551918.jpg
  17037   Tue Jul 26 20:54:08 2022 PacoUpdateBHDBHD MICH test - LO phase control

[Yuta, Paco]

TL;DR Successfully controlled LO phase, and did BHD-MICH readout with various MICH offsets and LO phases.

Today we implemented a DCPD based LO phase control. First, we remeasured the balancing gain at 311.1 Hz (the MICH oscillator freq) and combined C1:HPC-DCPD_A_OUT with C1:HPC-DCPD_B_OUT to produce the balanced homodyne error signal (A-B). We feed this error signal to C1:HPC-LO_PHASE_IN1 and for the main loop filters we simply recycled the LSC-MICH loop filters FM2 through FM5 (we also copied FM8, but didn't end up using it much). Then, we verified the LO phase can be controlled by actuating either on LO1 or LO2. For LO2, we added an oscillator in the HPC LOCKINS at 318.75 Hz (we kept this on at 1000 counts for the measurements below).

The LO phase control was achieved with a loop gain in the range of 10-30 (we used 20), no offset, and FM4, and FM5 engaged. FM2 can be added to boost, but we usually skipped FM3. Then, we went through a set of measurements similar to the ones described in a previous elog. A key difference with respect to the measurements from before is that we locked MICH using AS55Q (as opposed to REFL55Q). This allowed us to reach higher MICH offsets without losing lock. After turning on the MICH oscillator at 3000 counts, we looked at:

  1. LO misaligned + MICH at dark fringe (offset = -21).
    • Here, we don't expect to see any MICH signal and indeed we don't, except for a small residual peak from perhaps a MICH offset or slightly imbalanced PDs.
  2. LO aligned, but uncontrolled + MICH at dark fringe (offset = -21).
    • Here we would naively expect MICH to show up in A-B, but because of the uncontrolled LO phase, we mostly see the noise baseline (mostly from LO RIN? ...see measurement 3) under which this signal is probably buried. Indeed, the LO fringe increased noise in A, B, and A-B but not in A+B. This is nice. yes
  3. LO aligned, but uncontrolled + MICH with dc readout (offset = +50).
    • Here we expected the MICH signal to show up due to the large offset, and we can indeed see it in A, B, and A+B, but not in A-B. Nevertheless we see almost exactly the same noise level even though we allow some AS light into the BHD readout, so maybe the noise observed in the A-B channel from measurements 2 and 3 is mostly from LO RIN. This needs further investigation...
  4. LO aligned, controlled at no offset + MICH with dc readout (offset = +50).
    • In general here we expected to see a noise reduction in the A-B channel since the LO fringe is stable, and a MICH signal should appear. Furthermore, since LO phase is under control, we expect the LO2 Oscillator to appear which it does for this and the following measurements. Because of the relative freedom, we tried this measurement in two cases:
      1. When feeding back to LO1
        • We actually see MICH in the A-B channel, as expected, after the noise level dropped by ~ 5. We also observed small sidebands +- 1 Hz away from the MICH peak, probably due to local damping in either LO or AS paths.
      2. When feeding back to LO2
        • We also see MICH here, with a slightly better drop in noise (relative to feeding back to LO1). Sidebands persisted here, but around at +- 2 Hz.
  5. LO aligned, controlled (offset = 10) + MICH with dc readout (offset = +50). *
    • Here, we expected the A-B MICH content to increase dramatically, and indeed it does after a little tuning of the LO phase heart. The noise level decreased slightly because LO phase noise is decreased around the optimal point.
  6. LO aligned, controlled (offset = 20) + MICH with dc readout (offset = +30). *
    • Here, we naively expected A+B MICH content to decrease, but A-B remain constant. In order to see this we tried to keep the balance between the offsets, but this was hard. We don't really see much of this effect, so this also needs further investigation. As long as we keep controlling the LO phase using the DCPDs because the offsets tend to reduce the error signal we will have a harder time.

* For these measurements we actuated on LO2 to keep the LO phase under control.

Note that the color code above corresponds to the traces shown in Attachment #1.

What's next?

  • Alignment of LO and AS might be far from optimized, so it should be tried more seriously.
  • What's the actual LO power? How does it compare with AS power at whatever MICH offsets?
  • Try audio dither LO phase control.
    • With MICH offset.
    • Without MICH offset, double demod (after dolphin fix crying)
Attachment 1: 20220726_BICHD.pdf
  17102   Wed Aug 24 12:02:24 2022 PacoUpdateSUSITMX SUS is sus UL glitches?

[Yehonathan, Paco]

This morning, while attempting to align the IFO to continue with noise-budgeting, we noted the XARM lock was not stable and showed glitches in the C1:LSC-TRX_OUT (arm cavity transmission). Inspecting the SUS screens, we found the ULSEN rms ~ 6 times higher than the other coils so we opened an ndscope with the four face OSEM signals and overlay the XARM transmission. We immediately noticed the ULSEN input is noisy, jumping around randomly and where bigger glitches correlated with the arm cavity transmission glitches. This is appreciated in Attachment #1.

Signal chain investigation

We'll do a full signal investigation on ITMX SUS electronics to try and narrow down the issue, but it seems the glitches come and go... Is this from the gold satamp box? ...

Attachment 1: ITMX_UL_badness_08242022.png
  17104   Thu Aug 25 15:24:06 2022 PacoHowToElectronicsRFSoC 2x2 board -- fandango

[Paco, Chris Stoughton, Leo -- remote]

This morning Chris came over to the 40m lab to help us get the RFSoC board going. After checking out our setup, we decided to do a very basic series of checks to see if we can at least get the ADCs to run coherently (independent of the DACs). For this I borrowed the Marconi 2023B from inside the lab and set its output to 1.137 GHz, 0 dBm. Then, I plugged it into the ADC1 and just ran the usual spectrum analyzer notebook on the rfsoc jupyter lab server. Attachment #1 - 2 shows the screen captured PSDs for ADCs 0 and 1 respectively with the 1137 MHz peaks alright.

The fast ADCs are indeed reading our input signals.

Before this simple test, we actually reached out to Leo over at Fermilab for some remote assistance on building up our minimally working firmware. For this, Chris started a new vivado project on his laptop, and realized the rfsoc 2x2 board files are not included in it by default. In order to add them, we had to go into Tools, Settings and add the 2020.1 Vivado Xilinx shop board repository path to the rfsoc2x2 v1.1 files. After a little bit of struggling, uninstalling, reinstalling them, and restarting Vivado, we managed to get into the actual overlay design. In there, with Leo's assistance, we dropped the Zynq MPSoC core (this includes the main interface drivers for the rfsoc 2x2 board). We then dropped an rf converter IP block, which we customized to use the right PLL settings. The settings, from the System Clocking tab were changed to have a 409.6 MHz Reference Clock (default was 122.88 MHz). This was not straightforward, as the default sampling rate of 2.00 GSPS was not integer-related so we had to also update that to 4.096 GSPS. Then, we saw that the max available Clock Out option was 256 MHz (we need to be >= 409.6 MHz), so Leo suggested we dropped a Clocking Wizard block to provide a 512 MHz clock input for the rfdc. The final settings are captured in Attachment # 3. The Clocking Wizard was added, and configured on its Output Clocks tab to provide a Requested Output Freq of 512 MHz. The finall settings of the Clocking wizard are captured in Attachment #4. Finally, we connected the blocks as shown in Attachment #5.

We will continue with this design tomorrow.

Attachment 1: adc0_1137MHz.png
Attachment 2: adc1_1137MHz.png
Attachment 3: rfdc_PLLsettings.png
Attachment 4: clockingwiz_settings.png
Attachment 5: blockIPdiag.png
  17133   Tue Sep 6 17:39:40 2022 PacoUpdateSUSLO1 LO2 AS1 AS4 damping loop step responses

I tuned the local damping gains for LO1, LO2, AS1, and AS4 by looking at step responses in the DOF basis (i.e. POS, PIT, YAW, and SIDE). The procedure was:

  1. Grab an ndscope with the error point signals in the DOF basis, e.g. C1:SUS-LO1_SUSPOS_IN1_DQ
  2. Apply an offset to the relevant DOF using the alignment slider offset (or coil offset for the SIDE DOF) while being careful not to trip the watchdog. The nominal offsets found for this tuning are summarized below:
Alignment/Coil Step sizes
LO1 800 300 300 10000
LO2 800 300 400 -10000
AS1 800 500 500 20000
AS4 800 400 400 -10000
  1. Tune the damping gains until the DOF shows a residual Q with ~ 5 or more oscillations.
  2. The new damping gains are below for all optics and their DOFs, and Attachments #1-4 summarize the tuned step responses as well as the other DOFs (cross-coupled).
Local damping gains
LO1 10.000 5.000 3.000 40.000
LO2 10.000 3.000 3.000 50.000
AS1 14.000 2.500 3.000 85.000
AS4 15.000 3.100 3.000 41.000

Note that during this test, FM5 has been populated for all these optics with a BounceRoll (notches at 16.6, 23.7 Hz) filter, apart from the Cheby (HF rolloff) and the 0.0:30 filters.

Attachment 1: LO1_Step_Response_Test_2022-09-06_17-19.pdf
LO1_Step_Response_Test_2022-09-06_17-19.pdf LO1_Step_Response_Test_2022-09-06_17-19.pdf LO1_Step_Response_Test_2022-09-06_17-19.pdf LO1_Step_Response_Test_2022-09-06_17-19.pdf
Attachment 2: LO2_Step_Response_Test_2022-09-06_17-30.pdf
LO2_Step_Response_Test_2022-09-06_17-30.pdf LO2_Step_Response_Test_2022-09-06_17-30.pdf LO2_Step_Response_Test_2022-09-06_17-30.pdf LO2_Step_Response_Test_2022-09-06_17-30.pdf
Attachment 3: AS1_Step_Response_Test_2022-09-06_17-53.pdf
AS1_Step_Response_Test_2022-09-06_17-53.pdf AS1_Step_Response_Test_2022-09-06_17-53.pdf AS1_Step_Response_Test_2022-09-06_17-53.pdf AS1_Step_Response_Test_2022-09-06_17-53.pdf
Attachment 4: AS4_Step_Response_Test_2022-09-06_18-16.pdf
AS4_Step_Response_Test_2022-09-06_18-16.pdf AS4_Step_Response_Test_2022-09-06_18-16.pdf AS4_Step_Response_Test_2022-09-06_18-16.pdf AS4_Step_Response_Test_2022-09-06_18-16.pdf
  17142   Thu Sep 15 21:12:53 2022 PacoUpdateBHDLO phase "dc" control

Locked the LO phase with a MICH offset=+91. The LO is midfringe (locked using the A-B zero crossing), so it's far from being "useful" for any readout but we can at least look at residual noise spectra.

I spent some time playing with the loop gains, filters, and overall lock acquisition, and established a quick TF template at Git/40m/measurements/BHD/HPC_LO_PHASE_TF.xml

So far, it seems that actuating on the LO phase through LO2 POS requires 1.9 times more strength (with the same "A-B" dc sensing). After closing the loop by FM4, and FM5, actuating on LO2 with a filter gain of 0.4 closes the loop robustly. Then, FM3 and FM6 can be enabled and the gain stepped up to 0.5 without problem. The measured UGF (Attachment #1) here was ~ 20 Hz. It can be increased to 55 Hz but then it quickly becomes unstable. I added FM1 (boost) to the HPC_LO_PHASE bank but didn't get to try it.

The noise spectra (Attachment #2) is still uncalibrated... but has been saved under Git/40m/measurements/BHD/HPC_residual_noise_spectra.xml

Attachment 1: lophase_oltf.pdf
Attachment 2: lophase_noise_spectra.pdf
  17143   Mon Sep 19 17:02:57 2022 PacoSummaryGeneralPower Outage 220916 -- restored all

Restore lab

[Paco, Tega, JC, Yehonathan]

We followed the instructions here. There were no major issues, apart from the fb1 ntp server sync taking long time after rebooting once.

ETMY damping

[Yehonathan, Paco]

We noticed that ETMY had to much RMS motion when the OpLevs were off. We played with it a bit and noticed two things: Cheby4 filter was on for SUS_POS and the limiter on ULCOIL was on at 0 limit. We turned both off.

We did some damping test and observed that the PIT and YAW motion were overdamped. We tune the gain of the filters in the following way:


SUSPOS_GAIN 200->150


These action seem to make things better.

  17145   Tue Sep 20 07:03:04 2022 PacoSummaryGeneralPower Outage 220916 -- restored all

[JC, Tega, Paco ]

I would like to mention that during the Vacuum startup, after the AUX pump was turned on, Tega and I were walking away while the pressure decreases. While we were, valves opened on their own. Nobody was near the VAC Desktop during this. I asked Koji if this may be an automatic startup, but he said the valves shouldn't open unless they are explicitely told to do so. Has anyone encountered this before?


Restore lab

[Paco, Tega, JC, Yehonathan]

We followed the instructions here. There were no major issues, apart from the fb1 ntp server sync taking long time after rebooting once.

ETMY damping

[Yehonathan, Paco]

We noticed that ETMY had to much RMS motion when the OpLevs were off. We played with it a bit and noticed two things: Cheby4 filter was on for SUS_POS and the limiter on ULCOIL was on at 0 limit. We turned both off.

We did some damping test and observed that the PIT and YAW motion were overdamped. We tune the gain of the filters in the following way:


SUSPOS_GAIN 200->150


These action seem to make things better.


  17150   Wed Sep 21 17:01:59 2022 PacoUpdateBHDBH55 RFPD installed - part I

[Radhika, Paco]

Optical path setup

We realized the DCPD - B beam path was already using a 95:5 beamsplitter to steer the beam, so we are repurposing the 5% pickoff for a 55 MHz RFPD. For the RFPD we are using a gold RFPD labeled "POP55 (POY55)" which was on the large optical table near the vertex. We have decided to test this in-situ because the PD test setup is currently offline.

Radhika used a Y1-1025-45S mirror to steer the B-beam path into the RFPD, but a lens should be added next in the path to focus the beam spot into the PD sensitive area. The current path is illustrated by Attachment #1.

We removed some unused OPLEV optics to make room for the RFPD box, and these were moved to the optics cabinet along Y-arm [Attachment #2].


[Anchal, Yehonathan]

PD interfacing and connections

In parallel to setting up the optical path configuration in the ITMY table, we repurposed a DB15 cable from a PD interface board in the LSC rack to the RFPD in question. Then, an SMA cable was routed from the RFPD RF output to an "UNUSED" I&Q demod board on the LSC rack. Lucky us, we also found a terminated REFL55 LO port, so we can draw our demod LO from there. There are a couple (14,15,20,21) ADC free inputs after the WF2 and WF3 whitening filter interfaces.

Next steps

  • Finish alignment of BH55 beam to RFPD
  • Test RF output of RFPD once powered
  • Modify LSC model, rebuild and restart
Attachment 1: IMG_3760.jpeg
Attachment 2: IMG_3764.jpeg
  17159   Mon Sep 26 11:39:37 2022 PacoUpdateBHDBH55 RFPD installed - part II

[Paco, Anchal]

We followed rana's suggestion for stress relief on the SMA joint in the BH55 RFPD that Radhika resoldered. We used a single core, pigtailed wire segment after cleaning up the solder joint on J7 (RF Out) and also soldered the SMA shield to the RF cage (see Attachment #1). This had a really good effect on the rigidity of the connection, so we moved back to the ITMY table.

We measured the TEST in to RF Out transfer function using the Agilent network analyzer, just to see the qualitative features (resonant gain at around 55 MHz and second harmonic suppression at around 110 MHz) shown in Attachment #2. We used 10kOhm series resistance in test input path to calibrate the measured transimpedance in V/A. The RFPD has been installed in the ITMY table and connected to the PD interface box and IQ demod boards in the LSC rack as before.

Measurement files

Attachment 1: PXL_20220926_175010061.MOTION.jpg
Attachment 2: BH55_Transimpedance_Measurement.pdf
  17160   Tue Sep 27 10:50:11 2022 PacoUpdateBHDcalibrated LO phase noise

Locked LO phase to ITMX single bounce beam at the AS port, using the DCPD (A-B) error point and actuating on LO1 POS. For this the gain was tuned from 0.6 to 4.0. A rough Michelson fringe calibration gives a counts to meters conversion of ~0.212 nm/count, and the OLTF looks qualitatively like the one in a previous measurement (~ 20 dB at 1 Hz, UGF = 30 Hz). The displacement was then converted to phase using lambda=1e-6; I'm not sure what the requirement is on the LO phase (G1802014 says 1e-4 rad/rtHz at 1 Hz, but our requirement doc says 1 to 20 nrad/rtHz (rms?)... anyways wit this rough calibration we are still off in either case.

The balancing gain is obvious at DC in the individual DCPD spectra, and the common mode rejection in the (A-B) signal is also appreciable. I'll keep working on refining this, and implementing a different control scheme.

Attachment 1: lo_phase_asd.pdf
  17161   Wed Sep 28 16:37:26 2022 PacoUpdateBHDcalibrated LO phase noise; update

[yuta, paco]

Update; the high frequency ( > 100 Hz) drop is of course not real and comes from a 4th order LP filter in the HPC demod I filter which I haven't accounted for. Furthermore, we have gone through the calibration factors and corrected a factor of 2 in the optical gain. Then, I also added the CLTF to show in loop and out of loop error respectively. The updated plot, though not final, is in Attachment #1.

Attachment 1: lo_phase_asd.pdf
  17163   Wed Sep 28 21:54:08 2022 PacoUpdateBHDcalibrated LO phase noise; update

Repeated the LO phase noise measurement, this time with the LO - ITMY single bounce, and a couple of fixes Koji hinted at including:

  1. The DEMOD angle was the missing piece! The previous error point showed lower noise than the individual DCPDs because the demodulation angle had not been checked. I corrected it so that the error point in LO_PHASE control was exactly equal to the LO-ITMY single bounce fringe. With this, the gain on the servo had to be adjusted from 4.00 to 0.12, still using FM4, FM5, and this time also FM8 (BLP600).
  2. Turned off 60 Hz harmonics comb notches on DCPDs, they are unecessary.
  3. Acquired noise spectra down to 0.1 Hz, with 0.03 Hz bin width to increase resolution and identify resonant SUS noise near 1 Hz.

This time, after alignment the fringe amplitude was 500 counts. Attachment #1 shows the updated plot with the calibrated noise spectra for the individual DCPD signals A and B as well as their rms values. Attachment #2 shows the error point, in loop and the estimated out of loop spectra with their rms as well. The peak at ~ 240 Hz is quite noticeable in the error point time series, and dominates the high frequency rms noise. The estimated rms out of loop noise is ~ 9.2 rad, down to 100 mHz.

Attachment 1: dcpd_phase_asd.pdf
Attachment 2: lo_phase_asd.pdf
  17167   Fri Sep 30 20:18:55 2022 PacoUpdateBHDLO phase noise with different actuation points

[Paco, Koji]

We took lo phase noise spectra actuating on the for different optics-- LO1, LO2, AS1, and AS4. The servo was not changed during this time with a gain of 0.2, and we also took a noise spectrum without any light on the DCPDs. The plot is shown in Attachment #1, calibrated in rad/rtHz, and shown along with the rms values for the different suspension actuation points. The best one appears to be AS1 from this measurement, and all the optics seem to show the same 270 Hz (actually 268 Hz) resonant peak.

268 Hz noise investigation

Koji suspected the observed noise peak belongs to some servo oscillation, perhaps of mechanical origin so we first monitored the amplitude in an exponentially averaging spectrum. The noise didn't really seem to change too much, so we decided to try adding a bandstop filter around 268 Hz. After the filter was added in FM6, we turned it on and monitored the peak height as it began to fall slowly. We measured the half-decay time to be 264 seconds, which implies an oscillation with Q = 4.53 * f0 * tau ~ 3.2e5. This may or may not be mechanical, further investigation might be needed, but if it is mechanical it might explain why the peak persisted in Attachment #1 even when we change the actuation point; anyways we saw the peak drop ~ 20 dB after more than half an hour... After a while, we noticed the 536 Hz peak, its second harmonic, was persisting, even the third harmonic was visible.

So this may be LO1 violin mode & friends -

We should try and repeat this measurement after the oscillation has stopped, maybe looking at the spectra before we close the LO_PHASE control loop, then closing it carefully with our violin output filter on, and move on to other optics to see if they also show this noise.

Attachment 1: BHDC_asd_actuation_point.png
  17171   Mon Oct 3 15:19:05 2022 PacoUpdateBHDLO phase noise and control after violin mode filters

[Anchal, Paco]

We started the day by taking a spectrum of C1:HPC-LO_PHASE_IN1, the BHD error point, and confirming the absence of 268 Hz peaks believed to be violin modes on LO1. We then locked the LO phase by actuating on LO2, and AS1. We couldn't get a stable loop with AS4 this morning. In all of these trials, we looked to see if the noise increased at 268 Hz or its harmonics but luckily it didn't. We then decided to add the necessary output filters to avoid exciting these violin modes. The added filters are in the C1:SUS-LO1_LSC bank, slots FM1-3 and comprise bandstop filters at first, second and third harmonics observed previously (268, 536, and 1072 Hz); bode plots for the foton transfer functions are shown in Attachment #1. We made sure we weren't adding too much phase lag near the UGF (~ 1 degree @ 30 Hz).

We repeated the LO phase noise measurement by actuating on LO1, LO2 and AS1, and observe no noise peaks related to 268 Hz this time. The calibrated spectra are in Attachment #2. Now the spectra look very similar to one another, which is nice. The rms is still better when actuating with AS1.


After the above work ended, I tried enabling FM1-3 on the C1:HPC_LO_PHASE control filters. These filters boost the gain to suppress noise at low frequencies. I carefully enabled them when actuating on LO1, and managed to suppress the noise by another factor of 20 below the UGF of ~ 30 Hz. Attachment #3 shows the screenshot of the uncalibrated noise spectra for (1) unsupressed (black, dashed), (2) suppressed with FM4-5 (blue, solid), and (3) boosted FM1-5 suppression (red).

Next steps:

  • Compare LO-ITMY and LO-ITMX single bounce noise spectra and MICH.
  • Compare DC locking scheme versus BH55 once it's working.
Attachment 1: filters_c1sus_lo1_lsc.png
Attachment 2: BHDC_asd_act.png
Attachment 3: boosted_lo_phase_control.png
  4985   Mon Jul 18 21:06:32 2011 PSL Table GuardianOmnistructurePSLDon't leave the PSL table open, unattended!!!!!!!!!!!!11111

I found the PSL table left open, and unattended again. 

As far as I know, Jamie and Jenne (working on the LSC rack, so no lasers / optics work involved) have been the only ones in the IFO room for several hours now. 

I'm going to start taking laser keys, or finding other suitable punishments.  Like a day of lab cleanup chores or something.  Seriously, don't leave the PSL table open if you're not actively working on it.

  1349   Tue Mar 3 11:39:50 2009 OsamuDAQComputers2 PCs in Martian

 Kiwamu and I brought 2 SUPER MICRO PCs from Willson house into 40m.

Both PCs are hooked up into Martian network. One is named as bscteststand for BSC which has been set up by Cds people and another one is named kami1 for temporary use for CLIO which is a bland new, no operating installed PC. This bland new PC will be returned Cds or 40m once another new PC which we will order within several days arrives.

IP address for each machine is and respectively.

We have installed CentOS5.2 into the new PC.

  1381   Mon Mar 9 23:55:38 2009 OsamuDAQComputersbscteststand and kami1 outside martian

This morning there was a confliction of tpman running on fb40m and kami1. Alex fixed it temporary but Rana suggested it was better to move both PCs outside martian. We moved both PCs physically to the control room and connected to general network with a local router. I believe it won't conflict anymore but if you guess these PC might have trouble please feel free to shutdown.


Today's work summary:

 *connected expansion chassis to bscteststand

 *obtained signals on dataviewer, dtt for both realtime and past data on bscteststand with 64kHz timing signal



Excitation channels are not shown, only "other" is shown.

qts.mdl should run with 16kHz but 16kHz timing causes a slow speed on dataviewer and failing data aquisition on dtt. We are using 64kHz timing but is it really correct?

  1407   Mon Mar 16 15:19:52 2009 OsamuDAQElectronicsSR785

I borrowed SR785 to measure AA, AI noise and TF.

  4032   Thu Dec 9 00:34:53 2010 OsamuUpdateSUSITMX oplev Pitch OLTF

We measured Open loop TF for oplev pitch on ITMX.



 All feed back filter of oplev  was on as same as before. Original notch filters which notches above 10Hz resonance should be modified with some measurements of present resonant frequency. Up to 10Hz, a simple f^2 filter is used, so the notch should not affect this measurement.

Measured upper UGF is about 2Hz with gain slider 1, and lower UGF is 1.3Hz. Phase margin is 40 degree, so it is not a good idea to increase the gain drastically.

I have measured the coherence also but I could not find a way to put it on this picture. Anyway coherence below 0.6Hz was not so good like ~0.95. This can be improved if larger excitation is used next time.

During this measurement around 0.2-0.3Hz, small earthquake happened but seemed OK for the control.

We will measure the other TF, yaw, ETMX or somthing, maybe tomorrow, due to free swinging ITMX and ETMX tonight.


  4033   Thu Dec 9 01:14:42 2010 OsamuUpdateSUS 

After Kiwamu had set the free swinging mode for ITMX and ETMX, I found a big jump of ITMX pitch and yaw. This jump is shown on oplev and OSEM plots.


I talked with Kiwamu on the phone that a shutdown of suspensions does not add a big offset, and so that it should not make a big jump.

We were not sure that this jump was due to the shutdown or drift or something else. Anyway I put ITMY oplev on center again at 0;57am.

  4035   Thu Dec 9 11:13:37 2010 OsamuUpdateSUS 


After Kiwamu had set the free swinging mode for ITMX and ETMX, I found a big jump of ITMX pitch and yaw. This jump is shown on oplev and OSEM plots.


I talked with Kiwamu on the phone that a shutdown of suspensions does not add a big offset, and so that it should not make a big jump.

We were not sure that this jump was due to the shutdown or drift or something else. Anyway I put ITMY oplev on center again at 0;57am.

In this morning, the same thing happened but to opposit direction when Kiwamu activated ITMX and ETMX. Then it turned out that 1000ct offset was existing on pit of ITMX. Erasing the offset fixed ITMX to normal position.

However a big drift exists in 11hours plot on ITMX 0.1->-0.25 at OLPIT, -580->-605 at SUSPIT and 0.08->0.15 at OLYAW, no significan drift at SUSYAW. On the other hand, ETMX has no big drift but has 10-30minites order fluctuations.

After 6am both the drift and the fluctuation became, roughly saying, 10 times larger, probably due to the human activity.



  4041   Fri Dec 10 11:04:03 2010 OsamuUpdateSUSETM oplev mufunctioning



This plot shows ETM oplev and OSEM trend for 10 hours on day before yesterday as almost the same as plot shown this entry. I reported the 10-30minites fluctuations were seen, but I noticed it comes from not suspension but from oplev power fluctuation.

After Kiwamu fixed the ETM OSEM touch yesterday afternoon, still the same trend was seen, so we had thought what we fixed was not enough. This morning I looked at the yesterday's and day before yesterday's trend and noticed the simila trend both the pit and yaw in ETM oplev but not on the OSEM trend. Kiwamu suggested me to put the oplev sum on the same plot. It was!

So, ETMX is not bad, but in fact, still alignment fluctuation exist on the cavity. ITM?


  4042   Fri Dec 10 11:51:20 2010 OsamuUpdateSUSITM seems bad


This graph shows 5 hours data in minute trend for ITMX and ETMX from 5am to 10 am today. ITM pitch drift is 3 times lager than ETM pitch if the OSEM sensitivity is assumed to be the same.



This graph is last 1 hour data of above graph in second trend.

It is clealy seen that ITM yaw is jumping between two stages. I guess ITM is something wrong, touching magnets or earthquake stops?

Needs inspection.


  4087   Wed Dec 22 15:30:47 2010 OsamuUpdateASCETMY oplev fixed

According to c1scy.mdl, OL signals should be connected to adc_0_24 to adc_0_27 but they were connected to adc_0_16 to adc_0_19 which are assigned to QPD signals.

Actually cable connections were messed up. One ribbon cable was connected from QPD driver and ADC ports assigned for OL, and another ribbon cable was connected from the board combining the signals of oplev and QPD to ADC port assigned for QPD.

Now ETMY oplev is working well and aligned to center.

  4124   Fri Jan 7 12:01:39 2011 OsamuUpdateComputersc1lsc running

I got a new adapter board for expansion chassis from CDS and exchanged the existing adapter board which was laid on the floor around ETMX to new one.

Then I connected the chassis to c1lcs,  c1lsc seems to be running now. I will return the old board to CDS since Rolf says he wants to return it to manufacture.

 I found an interface box from ADC to D-SUB37pin and a cable to connect them.

I needed to make cables to connect the interface box to existing LSC whitening filters that has a 37 pin female D-SUB connector on one end and a 40pin female flat connector on the other end. We should use shielded cables for them, but unfortunately CDS did not have right one. Temporarily I made one cable for 1-8ch using a ribbon twist cable like Joe did.

I found a saturation at ch5 of ADC0 on c1lsc. I did not check carefully but it seemed to come from the LSC whitening board. Input of ch5 of the whitening board was not terminated and had a huge output voltage, but also ch6 was not terminated and had no big output. I guess something wrong on the LSC whitening board. Needs to be checked. Anyway I unplugged the small ribbon cable between the whitening board and the next LSC AA filter board.

Finally I realized that fiber connection of RFM did not exist. What I saw was the fiber cable of Dolphin. We need a RFM PCIe interface board, and a long fiber cable between c1lsc and RFM hub.

  4158   Fri Jan 14 17:58:50 2011 OsamuConfigurationGeneralStandalone RT setup

 I'll be gone to Hanford site next week and come back to Caltech on 24th's week.

I setup a standalone RT system at the desk around circuit stock in the 40m.

Please leave this setup until I come back. I'll keep working when I come back.


  4201   Tue Jan 25 20:42:46 2011 OsamuUpdateGreen LockingSlow servo for green laser

I implemented a slow servo for green laser thermal control on c1scx.mdl. Ch6,7 of ADC and ch6 of DAC are assigned for this servo as below;


Ch6 of ADC: PDH error signal

CH7 of ADC: PZT feedback signal

CH6 of DAC: feedback signal to thermal of green laser


Note that old EPICS themal control cable is not hooked anymore.

I made a simple MEDM screen(...medm/c1scx/master/C1SCX_BCX_SLOW.adl) linked from GREEN medm screen (C1GCV.adl) on sitemap.

During this work, I noticed that some of the epics switch is not recovered by autoburt. What I noticed is filter switch of SUSPOS, SUSPIT, SUSYAW, SDSEN, and all coil output for ETMX.

I had no idea to fix them, probably Joe knows. I guess other suspensitons has the same problems.

  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.

  12469   Mon Sep 5 19:57:24 2016 OsamuUpdateSUSOSEM adjustments

Hi 40m people,

As Rana is saying, the bounce mode does not matter, or we cannot do anything. Generally speaking, the bounce mode cannot be damped by the setting of 40m SUS. Some tweak techniques may damp a bounce mode by res-gain or something, but it is not a proper way, I think.

This is also that Rana is already saying that the important thing is to find a good direction of OSEM to hit the LED beam to the magnet. Even if the magnet is not located at the center of OSEM hole, still you can find the optimal orientation of OSEM to hit the LED beam to the center of magnet by rotating the OSEM.

I know only an old document of T040054 that Shihori summarized how to adjust the matrix at the 40m. Too bad input/output matrix may introduce some troubles, but even roughly adjusted matrix should be still fine.

I will be at Caltech on 12-14 of September. If I can help something, I am willing to work with you!

  9106   Wed Sep 4 21:44:54 2013 Not JenneUpdateElectronicsRF distribution box: Reinstalled

Temporary fix for the switch: give a bit of oil to the button

Permanent fix: buy better switches.

  12047   Fri Mar 25 19:17:28 2016 NikhilUpdatePEMGuralp Seismometers

Calibration of Guralp Seismometers


  • Estimate transfer functions of Guralp A ( near ETMX) and Guralp B ( near ETMY)
  • Calibrate the instruments by estimating Velocity Sensitity Parameter
  • Convert previously measured Voltage Spectrum to Velocity Spectrum

Instruments Used

  • Guralp CMG-40 T Seimometers  : Guralp A (Serial Number: T4Q17)
  • Guralp CMG-40 T Seimometers  : Guralp B (Serial Number: T4157)
  • Guralp Handheld Control Unit (HCU)
  • FFT Spectrum Analyzer: Model SR785: 2 Channel Dynamic Signal Analyzer
  • Oscilloscope: TDS 3014B
  • Function Generator: DS 345

Procedure & Results

Sinusoidal current of known frequency and amplitude was injected to the Seismometer calibration coil using signal generator and handheld control unit & corresponding Magnitude and Phase response were recorded.  For  Guralp B, system response was also estimated with a FFT Spectrum Analyzer. 



Frequnecy Range: 0.1 Hz to 45 Hz.

Equivalent Input Velocity was derived from the Input Voltage measurements using the relation: v = V/ (2*pi*f*R*K) , V is the peak to peak Calibration Signal voltage, f is the calibration signal frequency, R is the calibration resistor and K is the feedback coil constant.  [See Appendix for R & K values]                                     

Velocity Sensitity at the required frequency is obtained by dividing the Output Response Voltage by the Equivalent Input Velocity.


The obtained Velocity Sensitivity is used to convert the recorded Volatge PSD to Velocity PSD as shown below. The obtained results are compared to gloabl high noise model [NHNM] and USGS New Low Noise Model [NLNM,Peterson 1993] which gives the lowest observed vertical seismic noise levels across the seismic frequency band. Plot legend NLNM shows both the high & low levels.


                                                                    Guralp A [X Arm] Low Velocity Output                                          


                                                                    Guralp B [Y Arm] Low Velocity Output                                          


                                                                            DTT Power Spectrum                                                             

Both the Seismometers were connected to the 40 M Control and Data Acquisition System (CDS) and Power Spectrum was estimated for the Vertical, North/South & East/West Channels using Diagnostic Test Tool (DTT) software.



  •  The transfer function from Guralp A [ETMX] looks similar to that of Guralp B [ETMY] in both magnitude and phase but with a lower gain.                                                                                                                                                                                                  
  • Velocity Sensitivity of Guralp A is comparable to the value provided in the Calibration Data Sheet [~ 400] for all the channels [Vertical, North/South, East/West] after 1 Hz. For Guralp B, Velocity Sensitivity is a factor of 2.5 higher [all channels] than the specification [~ 400] after 1 HZ.Below 1 Hz Sensitivity drops down for both sensors. I am not ruling out a missing common factor in the calculation, but anyway, test shows that Guralp B has ~2.5 times better Velocity Sensitivity than Guralp A.                                                                                                                                                               
  • The Calibrated Seismic Velocity Spectrum for Guralp B is within the Globally Observed High and Low Noise Seismic Spectrum while Guralp A's Spectrum is more noisier above 1 Hz [Anthropogenic Activity normally contributes the most in 1 Hz to 10 Hz frequency band].                                                                                                                                                                                                                                                                          
  • Concurrently acquired Power Spectrum using DTT [Diagnostic Test Tools] shows that Guralp A Spectrum behaves rather strangely. The system response seems to be completely different from the one we obtained locally using signal generator. While Guralp B functionality seems normal. One reason for this erratic beahvior might be faulty cables used for data acquisition from Guralp A. This needs to be verified.                                                                                                                        


                                                                            CMG-40T Guralp A Calibration Sheet                                                           

  Velocity Output: V/m/s (Differential) Mass Position Output (Acceleration Output) : V/m/s^2  Feedback Coil Constant : Amp/m/s^2
Vertical 2 x 400 19 0.00397
North/South 2 x 398 23 0.00486
East/West 2 x 401 23 0.00479                 

Calibration Resistor: 51000

                                                                            CMG-40T Guralp B Calibration Sheet                                                           

  Velocity Output: V/m/s (Differential) Mass Position Output (Acceleration Output) : V/m/s^2  Feedback Coil Constant : Amp/m/s^2
Vertical 2 x 401 19 0.00408
North/South 2 x 400 20 0.00421
East/West 2 x 404 22


Calibration Resistor: 51000 

Attachment 3: VelSens_XArm_Guralp_A.png
Attachment 4: VelSens_XArm_Guralp_A.png
Attachment 5: VelSens_YArm_Guralp_B.png
Attachment 8: Vel_PSD_XArm_GurB_E.png
Attachment 9: Vel_PSD_XArm_GurB_N.png
Attachment 16: Guralp_PowerSpectrum.pdf
  4956   Fri Jul 8 09:53:49 2011 Nicole SummarySUSSummer Progress Report 1

A copy of my summer progress report 1 has been uploaded to ligodcc 7/711 and I have just added a copy to the TTsuspension wiki


PDF copy of Summer Progress Report

  4839   Mon Jun 20 11:04:03 2011 NicoleUpdateSUSWork Plan for Week 2

Here is my work plan for this week:

Current Week Plan (Week 2) (As of 6/17/11)


Setting Up for Horizontal Displacement Measurements

1) Help Steve clean small table for experiment

2) Remove aluminum base from TT suspension

3) Mount shaker onto table base

4) Mount horizontal slider onto table base

5) Connect TT suspension, shaker, and horizontal slider

Begin Assembly of Sensors

1) Begin building circuit for displacement photosensors

2) Calibrate photosensor using linear regions of power versus distance curves

3) Circuit box for photosensors?

  4844   Mon Jun 20 18:12:20 2011 NicoleUpdateSUSSmall Table Cleaned and Levelled


The small optical bench (next to the MC-2 Chamber and the tool box tower) has been cleared of the misc. object previously on it, cleaned, and leveled (after much calibration X___X).

PLEASE, PLEASE, PLEASE do NOT MOVE OR HIT THE TABLE! It was incredibly painful to level.

This is how leveling the table made me feel...


VERY SAD...so do not move please!

The shaker has already been moved to the table and the amplifier for my shaking experiment is located behind the table (not on the table, as to prevent scratching).



  4853   Wed Jun 22 12:24:44 2011 NicoleSummarySUSMidweek 2 Work Summary

I have made my transfer function model and posted it to the suspension wiki. Here is the link to my model!

Bode Plot Model

Please let me know if there need to be any adjustments, but I have posted the bode plots, a model image, and an explanation of why I think it's right! ^ ___^ V

I am currently working on the photo sensor circuit for the displacement detector. So far, I have gotten the infared LED to light up! ^ ___^ V

I am now trying to get a plot of forward voltage versus current for the LED. HOPEFULLY it will match the curve provided in the LED datasheet.

I'm using the bread board circuit box and when I'm not working at the bench, I have signs posted. PLEASE DO NOT REMOVE THE CONNECTIONS! It is

fine to move the bread board circuit box, but please do not disturb the connections > ____<

Here is a photo of the workspace


  4858   Wed Jun 22 18:41:23 2011 NicoleSummarySUSBROKEN bread board circuit box and L9337 LED Current Versus Voltage Curve

NOTE: The potentiometers on the bread board circuit box (the one I have been using with the signal generator, DC power, LED displays, and pulse switches) is BROKEN!

The potential across terminals 1 and 2 (also 2&3) fluctuates wildly and there dial does not affect the potential for the second potentiometer (the one with terminals 4, 5, and 6).

This has been confirmed by Koji and Jaimie.  PS I didn't break it! >____<


NEVERTHELESS, using individual resistors and the 500 ohm trim resistor, I have managed to get the current versus forward voltage plot for the Hamamatsu L9337 Infared LED


  4875   Fri Jun 24 01:05:32 2011 NicoleSummarySUSTransfer Function Model Analysis Summary and New Posted LED V vs. I Curve

I have updated the TT suspension wiki to include a new page on my transfer function model. In this new page, an introduction and analysis of my transfer function (including a comparison of the transfer functions for a flexibly- and rigidly-supported damper) are included.  This page contains linear and logarithmic bode plots.  Here is a link to the transfer function page.


I have also updated my photosensor page on the TT suspension wiki so that the experimental data points in my current versus voltage plot are plotted against the curve provided by the Hamamtsu data sheet. I have also included an introduction and analysis for my mini-experiment with the forward voltage and forward current of the LED. Here is link to the photsosensor page.

  4879   Fri Jun 24 17:04:25 2011 NicoleUpdateSUSBasic Laser Safety Training; Moved TT Mirror; Horizontal Displacement Mech Plan

Today Ishwita, Sonali, and I completed basic laser safety training with Peter King. I completed the Laser Safety Quiz and have turned in my certificate sheet.

I just need to turn in a signed copy of the Lab Safety Checklist to SFP (which I can now have signed by Koji after completing the course).


Steve and I have removed the TT mirror from the clean box. It is now on the small optical table in the lab that I have been working on.  Thanks to Steve, all of the mechanical components for the horizontal displacement measurement experiment are compiled and on the small optical table. Here is a photo of the small optical table with the gathered components. CompiledParts.JPG

The plan is to attach the slider and the shaker directly to the black mounting plate. On the slider, we we then place the smaller black mounting plate (with the lip). The lip will attach to the shaker. We know exactly where to drill and everything is lined up. The shaker will be placed on the smaller black mounting plate (with the lip).  The assembly will begin on Monday.


Here is a photo of the planned set-up for the shaker and the horizontal slider + mounting base.


  4908   Wed Jun 29 11:25:07 2011 NicoleSummarySUSWeekly Summary of Work

Update of Week 3 Work:

-I've finished reading The Art of Electronics Ch 1, 2, and 4.

-The mechanical stage for the horizontal displacement measurements is set up.

-I've opened up the circuit box for the quad photodiode and am currently working on the circuit diagram for the box and for the quad photodiode sensors.


Later this week, I plan to finish the circuit diagrams and figure out how the circuits work with the four inputs. I also plan to start working on my first

progress report.


  4913   Wed Jun 29 22:35:06 2011 NicoleSummarySUSCompleted Quad photodiode Box Circuit Diagrams

I have finished drawing the circuit diagrams for the quad photodiode boxes. Here are copies of the circuit diagram.

There are three main operation circuits in the quad photdiode box: a summing circuit (summing the contributions from the four inputs),

a Y output circuit (taking the difference between the input sums 3+2 and 1+4), and an X output circuit (taking the difference between the

input sums 3+4 and 1+2). I will complete an mini report on my examination and conclusions of the QPD circuit for the suspension wiki tomorrow.



  4964   Wed Jul 13 12:24:46 2011 NicoleUpdateSUSWeekly Update
This week, I have been working on the photosensor circuit box.  This photosensor box will contain the current-stabilizing power supply and
voltage readout for the two photosensors I plan to build.
Suresh helped to walk me through the design of the photosensor circuit (image below) so I now understand how the circuit works.
Jaimie helped me to reorganize the original circuit layout I had to make it easier to follow. I have now redone half of the circuit (enough for one LED and photodiode pair). I still need to put in the voltage-regulators to provide the + and - 15 V neeCto power the op-amps but I will do that after testing the circuit.

In order to test this preliminary circuit, I need to build the photosensor heads.  Yesterday, Suresh helped me to open one of the professionally-build photosensors in the lab to understand how to arrange my photosensor heads. I now understand that I need to rigidly-mount the PCB to photosensor head box. I plan to use the PCB below. It will be sufficient for the lower-frequency range (below 10Hz) that I am interested in. 


 I would like to use a metal box like the one below to make each photosensor head. I looked in the lab last night for similar boxes but could not find one. Does anyone know where I can find a similar metal box?



I am now working on accelerometer. I am working on attaching these metal wires to the pins of the accelerometer so that I can use clip leads to power and extract voltage measurements from my circuit.


  4969   Thu Jul 14 20:24:32 2011 NicoleSummarySUSPhotosensor Head Lessons

Today I tested the photosensor head combination (2 Hamamatsu S5971 photodiodes and 1 Hamamatsu L9337 LED). I discovered that I had burnt out the LED and the photodiodes when I soldered them to the PCB board.

After looking up soldering information on Hamamatsu photodiodes, I learned that I need to solder at least 2 mm away from the head. I checked the pins of my burnt-out photodiodes and I had soldered 1.5 mm away from the head. To prevent this problem from happening again, Suresh suggested that I clip a lead onto photodiode/LED pin while I solder on connections to help dissipate some of the heat.

Today I was able to get a single photodiode (not attached to the PCB) to measure light emitted from an LED and I observed how voltage fluctuated as I moved the photodiode around the LED.

Suresh and Jamie also helped me to fix my photosensor head design (to make it more electrically-stable). Originally, I had planned to solder the LED and photodiodes onto a PCB and to mount that PCB to the front of a small metal Pomona Electronics box (with a whole cut out for the photodiodes and LED) using spacers, screws, and nuts.  However, the PCB I am using to solder on the LED and photodiodes has metal connections that may cause problems for the LED and photodiodes lying on the surface. Now, the plan is to have the LED and photodiodes mounted to the PCB with an insulatory PCB in between. Below is an explanatory picture.  I will determine the placement of the LED and photodiodes after making screws holes in the two PCBs to attach to the metal face of the box. I want to attach the screw holes first to make sure that the PCBs (and attached photosensor) are centered.



  4974   Fri Jul 15 14:23:30 2011 NicoleSummarySUSPhotosensor Head Lessons


 Ah! I see! Thank you!

I should put the LEDs and photodiodes closer together so that more of the reflected light falls on the photodiodes and the photodiodes have a higher response.

Also the reflectivity of the mirror will be optimized if the incident light is normal to the mirror surface. We will be setting up the photosensor and mirror so that the LEDs

emit light normal to the mirror surfaceDuring displacement, this light may be slightly off-normal but still close to normal incidence. We want the photodiodes to be close to the LED since we want

them to detect light that is close to the path of normal incidence (small angles of reflection). [Thanks to Jenne for helping me figure this one out!]


Thank you for the suggestion ^___^

  4975   Fri Jul 15 14:29:30 2011 NicoleSummarySUSPhotosensor Head Lessons


 You are right Jamie! Thank you for the correction! I will now use the Teflon sheet instead of the PCB piece.

The photodiodes do have three legs, but I imagined the third one lying on a different plane, since it is spaced apart from the two I have drawn.

I should include this third leg in my drawing?

  4986   Mon Jul 18 22:26:43 2011 NicoleUpdateSAFETYPainful Voltage Regulator and Circuit-Testing Lessons

Today I learned some important circuit-building lessons while testing my photosensor circuit box (i.e. how NOT to test a circuit and, conversely, things that should be done instead). 

I blew my first circuit today. The victim is in the photo below (bottom 7805 voltage regulator). The plastic covering fell off after I removed the fried regulator.  After checking various components, I figured out that I blew the circuit because I had forgotten to ground the regulator.  Although this was very unfortunate, I did make an important discovery. While testing the voltage output of the 7805 voltage regulator (I put a new one), I discovered that contrary to the claims of the datasheet, an input voltage of 5V will not produce a steady 5V supply. I found that at 5V, my regulator was only producing 4.117 V. I was using a 5 V supply because I wanted to use only 1 power supply (I was using a two-channel power supply that had a fixed 5V output to produce the +15, -15, ground, and 5 V I need for my photosensor circuit box).  After seeing this, I got a second power supply and am now using 10V to as an input for the regulator to produce 4.961V. I found that from a voltage range of 10V to 15 V, the regulator produced a steady  4.961 V supply. I have decided to use 10V as an input. My newly-grounded voltage regulator did not smoke or get hot at 10V.

After several more debugging trials (my LED was still not lighting up, according to the infared viewer), I learned another painful lesson. I learned DO NOT USE CLIP LEADS TO TEST CIRCUITS!!!! Initally, I was powering my circuit and making all of my connections between the photosensor head (2 photodiodes and 1 LED) with clip leads. This was a BAD IDEA BECAUSE CLIP LEADS ARE UNSTABLE AND IT IS VERY EASY TO SHORT A CIRCUIT IF THEY ACCIDENTALLY TOUCH! I did not realize this important lesson until my photosensor circuit was once again burning. Confused as to why my circuit was once again burning, I foolishly touched the voltage regulator. As you can see on the top voltage regulator in the photo below, my finger left its mark on the smoldering voltage regulator. As you cannot see the wincing on my face as I try to type this long elog, I will painfully type that the voltage regulator left its own mark on my finger (an ugly sore little welt).  Suresh has taught me a valuable lesson: WHEN DEALING WITH SOMETHING OF QUESTIONABLE/UNKNOWN TEMPERATURE, USE YOUR NOSE, NOT YOUR FINGER TO DETERMINE IF THAT COMPONENT IS HOT!!!! 



To make my circuit-testing safer, upon the suggestion of Suresh, I have since removed the clip leads and inserted a 12 pin IDC component (pictured below). There are 12 pins for the 6 inputs I will get from each of the 2 photosensor heads. I have requested orders for a 16 pin IDC connector, 15 pin Dsub male part, 15 pin Dsub feed-thru, 9 pin Dsub male part (2), and 9 pin Dsub feed-thru (2). After receiving these components, I should be able to safely test my circuit.


 In the meanwhile, I can explore SimMechanics and try to figure out how to use the accelerometer

  5000   Wed Jul 20 12:05:08 2011 NicoleSummarySUSWeekly Summary

Since last week Wednesday, I have since found a Pomona Electronics box (thanks to Jenne)

to use for my photosensor head circuit (to house the LED and 2 photodiodes). Suresh has

shown me how to use the 9-pin Dsub connector punch, and I have punched a hole in this box

to attach the Dsub connector. 


Since this past entry regarding my mechanical design for the photosensor head (Photosensor Head Lessons),

I have modified the design to use a Teflon sheet instead of a copper PCB and I have moved the LED

and photodiodes closer together, upon the suggestions of Jamie and Koji.  The distance between

components is now 0.112" instead of the initial 0.28".  Last night, I cut the PCB board for the LED

and photodiodes and I drilled holes onto the PCB board and Teflon sheet so that the two may be

mounted to the metal plate face of the Pomona box.  I still need to cut the viewer hole for and

drill screws into the face plate.


I have also been attempting to debug my photosensor circuit (box and LED/photodiode combination).

Since this last entry (Painful Votlage Regulator and Circuit Lessons), Suresh has helped me to get the parts

that I need from the Downs Electronics lab (15 wire ribbon cable, two 9 pin D-sub connectors M,

one 15 pin D-sub connector M, one 16 pin IDC connector). Upon the suggestion of Jamie, I have

also made additional safety changes to the circuit by fixing some of the soldering connections

so that all connections are done with wires (I had a few immediate lines connected with solder).

I believe the the photosensor circuit box is finally ready for testing. I may just need some help

attaching the IDC connector to the ribbon cable. After this, I would like to resume SAFELY

testing my circuit.


I have also been exploring SimMechanics. Unfortunately, I haven't been able to run the

inverted pendulum model by Sekiguchi Takanori. Everytime I attempt to run it, it says

there is an error and it shuts down Matlab. In the meanwhile, I have been watching

SimMechanics demos and trying to understand how to build a model. I'm thinking that

maybe once I figure out how SimMechanics works, I can use the image of his model

(I can see the model but it will not run) to construct a similar one that will hopefully work.


I have also been attempting to figure out the circuitry for the pre-assembled

accelerometer (made with the LIS3106AL chip).  I have been trying to use a multi-meter

to figure out what the components are (beyond the accelerometer chip, which I have

printed out the datasheet for), but have been unsuccessful at that. I have figured out

that the small 5 pin chip says LAMR and is a voltage regulator. I am hoping that if I can

find the data sheet for this voltage regulator, I can figure out the circuitry. Unfortunately,

I cannot find any datasheets for a LAMR voltage regulator. There is one by LAMAR, but

the ones I have seen are all much larger. Does anyone know what the miniature voltage

regulator below is called and if "LAMR" is short for "LAMAR"?




  5044   Wed Jul 27 12:19:19 2011 NicoleSummarySUSWeekly Summary

Since last week, I've been working on building the photosensor head and have been making adjustments to my photosensor circuit box.

Changes to photosensor circuit (for box):

1) Last week, I was reading in the two signals from the two heads through a single input. Now there are two separate inputs for the two separate photosensors

2)During one of my many voltage regulator replacements, I apparently used a 7915 voltage regulator instead of a 7805 (thanks, Koji, for pointing that out! I never would have caught that mistake X___X)

3)I was powering my 5V voltage regulator with 10V...Now I'm using 15 V (now I only need 1 power supply and 3 voltage input plugs)

I have also began assembling my first photosensor head. Here is what I have so far:



Here is what needs to be done still for the photosensor head

I need to find four Teflon washers and nuts to rigidly attach the isolated PCB (PCB, Teflon sheet combination) to the box. I already have the plastic screws in (I want to use plastic and Teflon for electrical isolation purposes, so as to not short my circuit).

I need to attach the sheath of my signal cable to the box of the photosensor head for noise reduction (plan: drill screw into photosensor head box to wrap sheath wires around)

I need to attach the D-sub to the other end of my signal cable so that it can connect to the circuit box. So far, I only have the D-sub to connect the cable to my photosensor head

Yesterday, Suresh helped to walk me through the photosensor box circuit so that I now understand what voltages to expect for my circuit box trouble-shooting. After this lesson, we figured out that the problem with my photosensor box was that the two op-amps were saturated (so I fixed the feedback!). After replacing the resistor, I got the LED to light up! I still had problems reading the voltage signals from the photodiodes. I was reading 13.5V from the op amp output, but Koji explained to me that this meant that I was too close to saturation (the photodiodes were perhaps producing too much photocurrent, bringing the output close to saturation). I switched the 150 K resistor in the feedback loop to a 3.4K resistor and have thus successfully gotten displacement-dependent voltage outputs (i.e. the voltage output fluctuates as I move my hand closer and farther from the photosensor head). 

Now that I have a successful circuit to power and read outputs from one photosensor, I can begin working on the other half of the circuit to power the other photosensor! 


  5056   Thu Jul 28 17:04:04 2011 NicoleUpdateSUSPhotosensor Head Calibration Curve

Here is the calibration curve (displacement versus voltage output) for the photosensor head that I made with the S5971 photodiodes and L9337 LEDs. This was made using a regular mirror. The linear region appears to be between 0.4 and 0.75cm. I will need to arrange the photosensor head so it measures displacements in the linear region of this plot. This plot was made using a 287 ohm resistor.


  5098   Tue Aug 2 23:02:48 2011 NicoleUpdateSUSFixed Accelerometer


The EM shaker was broken (the input terminals (banana inputs) had snapped off. To fix this, I have mounted two banana input mounting posts to a metal mount that Steve attached to the shaker.


However, because bananas do not provide a secure connection (they easily fall out), I have made special wires to connect the banana inputs of the shaker to the mounted banana inputs of the amplifier I am using (along with the sine generating function of the HP 3563A signal analyzer). Upon Koji's suggestion, I have made C-shaped clips to attach to the banana post mounts. These clips are made from insulated ring terminals.


Today I tested the  shaker and it works! WOOT! I currently have the shaker attached to the horizontal sliding platform (without the TT suspension on it).

Using a 750mHz signal from the HP 3563A with an amplitude of 500 mV amplified to 0.75V, I have gotten the shaker to displace the platform (without the TT suspension on it) 1 mm.

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