40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 203 of 335  Not logged in ELOG logo
ID Date Authordown Type Category Subject
  5169   Wed Aug 10 12:32:09 2011 NicoleSummarySUSWeekly Summary Update

Last night, I attached a metal plate to the Vout faceplate of my photosensor circuit box because the BNC connection terminals were loose. This was Jamie's suggestion to establish a more secure connection (I had originally drilled holes for the BNCs that were much too large).

 

I have also fixed the mechancial set-up of my shaking experiment so that the horizontal sliding platform does not interfere with the photodiode mounting stage. Koji pointed out last night that in the full range of motion, the photodiode mounting stage interferes with the movement of the sliding platform when the platform is at its full range.

 

I have began shaking. I am getting a problem, as my voltage outputs are just appearing a high-frequency noise.

  5178   Wed Aug 10 19:18:26 2011 NicoleSummarySUSFixed Reflective Photosensors; Recalibrated Photosensor 2

Thanks to Koji's help, the second photosensor, which was not working, has been fixed. I have re-calibrated the photosensor after fixing a problem with the circuit.  I have determined the new linear region to lie between 7.6 mm and 19.8mm. The slope defining the linear region is -0.26 V/mm (no longer the same as the first photosensor, which is -0.32 V/mm).

 

Here is the calibration plot.

ps2.jpg

  5183   Thu Aug 11 06:45:14 2011 NicoleSummarySUSShaking Testing

Koji and I have finished shaking the table for the first round of measurements (horizontal shaking). We have cleaned up the lab space used.

The FFT Analyzer has been put back to its position at the back side of the rack (near the seismometers).

 

I will calibrate the photosensor for the suspension frame and piece together/analyze/produce graphs of the data today. If everything is fine (the measurements are fine) and if there is a chance, we hope to shake the TT suspension vertically.

  5188   Thu Aug 11 12:31:39 2011 NicoleSummarySUSPhotosensor Head Calibration Curve for TT Frame

I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2").

As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

ps2frame.jpg

  5191   Thu Aug 11 14:22:00 2011 NicoleSummarySUSPhotosensor Head Calibration Curve for TT Frame

Quote:

I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2").

As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

ps2frame.jpg

I have redone the voltage versus displacement measurements for calibrating "Photosensor 2" (the photosensor measuring the motions of the TT frame). This time, I calibrated the photosensor in the exact position it was in during the experimental excitation ( with respect to the frame ). I have determined the linear region to be 15.2mm to 22.9mm (in my earlier post today, when I calibrated the photosensor for another location on the frame, I determined the linear region to be 15.2mm to 25.4mm). This time, the slope was -0.92 V/mm (instead of -0.1 V/mm).

 

This means that the calibration ratio for photosensor 1 (measuring mirror displacements) and photoensor 2 (measuring frame displacements) is 34.86.

 

Since this "unity" value should be 34.86 for my transfer function magnitude plots (instead of the ~3 value I have), do I need to scale my data? It is strange that it differs by an order of magnitude...

  5195   Thu Aug 11 16:09:05 2011 NicoleSummarySUSBode Plot for TT Suspension

All of my plots have already taken into account the calibration of the photosensor (V/mm ratio)

Here is a bode plot generated for the transfer function measurements we obtained last night/this morning. This is a bode plot for the fully-assembled T.T. (with flexibly-supported dampers and bottom bar). I will continue to upload bode plots (editing this post) as I finish them but for now I will go to sleep and come back later on today.

 

flexwithbase.jpg

Here is a bode plot comparing the no eddy-current damper case with and without the bar that we suspected to induce some non-uniform damping. We have limited data on the NO EDC, no bar measurements (sine swept data from 7 Hz to 50 Hz) and FFT data from 0 Hz to 12.5 Hz because we did not want to induce too much movement in the mirror (didn't want to break the mirror).  This plot shows that there is not much difference in the transfer functions of the TT (no EDC) with and without the bar.

stage1.jpg.jpg

From FFT measurements of  the no eddy-current damper case without the bar (800 data points, integrated 10 times) we can define the resonance peak of the TT mirror (although there are still damping effects from the cantilever blades).

The largest resonance peak occurs at about 1.94 Hz. The response (magnitude) is 230.

The second-largest resonance peak occurs at about 1.67 Hz. The response (magnitude) is 153. This second resonance peak may be due to pitch motion coupling (this is caused by the fact that the clamping attaching the mirror to the wires occurs above the mirror's center of mass, leading to inevitable linear and pitch coupling).

 

Here is a bode plot of the EDC without the bar. It seems very similar to the bode plot with the bar

FULL_BODE.jpg

 

 Here is a bode plot of the rigidly-supported EDC, without bar. I need to do a comparison plot of the rigid and flexibly-supported EDCs (without bar)

 

 FULL_BODErigid.jpg

 

Attachment 1: flexwithbase.jpg
flexwithbase.jpg
Attachment 3: stage1.jpg
stage1.jpg
  5205   Fri Aug 12 11:07:50 2011 NicoleSummarySUSMore TT Shaking Completed This Morning

This morning (about 10am to 11am), I have collected additional transfer function measurements for the T.T. suspension. I have finished taking my measurements. The SR785 has been returned to its place next the the seismometer racks.

 The data has been backed up onto the cit40m computer

  5206   Fri Aug 12 14:15:07 2011 NicoleSummarySUSBode Plot for TT Suspension

Here is my bode plot comparing the flexibly-supported and rigidly-supported EDCs (both with no bar)

It seems as if the rigidly-supported EDC has better isolation below 10 Hz (the mathematically-determined Matlab model predicted this...that for the same magnet strength, the rigid system would have a lower Q than the flexible system). Above 10 Hz (the resonance for the flexibly-supported EDCs seem to be at 9.8 Hz) , we can see that the flexibly-supported EDC has slightly better isolation? I may need to take additional measurements of the transfer function of the flexibly-supported EDC (20 Hz to 100 Hz?)  to hopefully get a less-noisy transfer function at higher frequencies. The isolation does not appear to be that much better in the noisy region (above 20Hz). This may be because of the noise (possibly from the electromagnetic field from the shaker interfering with the magnets in the TT?). There is a 3rd resonance peak at about 22 Hz. I'm not sure what causes this peak...I want to confirm it with an FFT measurement of the flexibly-supported EDC (20 Hz to 40 Hz?)

 

 

EXPrigidvsflex.jpg

 

 

  5208   Fri Aug 12 15:34:16 2011 NicoleSummarySUSBode Plot for TT Suspension

Quote:

Here is my bode plot comparing the flexibly-supported and rigidly-supported EDCs (both with no bar)

It seems as if the rigidly-supported EDC has better isolation below 10 Hz (the mathematically-determined Matlab model predicted this...that for the same magnet strength, the rigid system would have a lower Q than the flexible system). Above 10 Hz (the resonance for the flexibly-supported EDCs seem to be at 9.8 Hz) , we can see that the flexibly-supported EDC has slightly better isolation? I may need to take additional measurements of the transfer function of the flexibly-supported EDC (20 Hz to 100 Hz?)  to hopefully get a less-noisy transfer function at higher frequencies. The isolation does not appear to be that much better in the noisy region (above 20Hz). This may be because of the noise (possibly from the electromagnetic field from the shaker interfering with the magnets in the TT?). There is a 3rd resonance peak at about 22 Hz. I'm not sure what causes this peak...I want to confirm it with an FFT measurement of the flexibly-supported EDC (20 Hz to 40 Hz?)

 

 

EXPrigidvsflex.jpg

 

 

 Since the last post, I have found from the Characterization of TT data (from Jenne) that the resonant frequency of the cantilever springs for TT #4 (the model I am using) have a resonant frequency at 22 Hz. They are in fact inducing the 3rd resonance peak.

 

Here is a bode plot (CORRECTLY SCALED) comparing the rigidly-supported EDCs (model and experimental transfer functions)

RIGIDexp_model.jpg

 

Here is a bode plot comparing the flexibly-supported EDCs (model and experimental transfer functions). I have been working on this graph for FOREVER and with the set parameters, this is is close as I can get it (I've been mixing and matching parameters for well over an hour > <). I think that experimentally, the TTs have better isolation than the model because they have additional damping properties (i.e. cantilever blades that cause resonance peak at 22 Hz). Also, there may be a slight deviation because my model assumes that all four EDCs are a single EDC.

flexmodcomp.jpg

  5222   Sat Aug 13 15:40:38 2011 NicoleSummarySUSTT Shaking Today and Hopefully More?

As reported in my  previous entry of TT supsension bode plots, I found that my experimental data had what appears to be very noise peaks above 20 Hz (as mentioned earlier, the peak at 22 Hz is likely due to vertical coupling, as 22 Hz is the resonant frequency of the cantilever blades). This is very unusual and needs to be explored further. I would like to vertically-shake the TTs to obtain more data on possible coupling. However, I am leaving on Monday and will not return until Thursday (day of SURF talks). I am leaving campus Friday afternoon or so. I would may need some help coming up with an assembly plan/assembling set-up for vertical shaking (if it is possible to do so in such a limited time frame).

 

Today I wanted to see if the "noisy peaks" above 30 Hz were due to EM noise coupling. I tested this hypothesis today, seeing if EM fields generated by the coil at higher frequencies were injecting noise into my transfer function measurements. I found that the "noisy peaks" above 30 Hz are NOT DUE TO EM NOISE COUPLING. I am very curious as to what is causing the high peaks (possibly coupling from other degrees of freedom)?

 

 emnoise_and_flex.jpg

  5223   Sat Aug 13 15:47:47 2011 NicoleSummarySUSTT Optimization Curves

Using my Matlab model of the flexibly-supported eddy current damping system, I have changed parameters to see if/how the TTs can be optimized in isolation. As I found earlier, posted in my bode plot entry, there is only a limited region where the flexibly-supported system provides better isolation than the rigidly-supported system.

 

Here is what I have found, where \gamma is the scale factor of the magnetic strength (proportional to magnetic strength), \beta is the scale factor of the current damper mass (estimated by attempting to fit my model to the experimental data), and \alpha is the scale factor of the current resonant frequency of the dampers.

magstrength1.jpgdampermass.jpg resfreq.jpg

 

Here are my commentaries on these plots. If you have any commentaries, it would be very helpful, as I would like to incorporate this information in my powerpoint presentation.

It seems as if the TT suspensions are already optimized?

It may be difficult to lower the resonant frequency of the dampers because that would mean changing the lengths of the EDC suspensions). Also, it appears that a rather drastic reduction (at most 0.6*current EDC resonant frequency --> reduction from about 10 Hz to 6 Hz or less) is required . Using the calculation that the resonant frequency is sqrt(g/length), for my single-suspended EDC model, this means increasing the wire length to nearly 3 x its current value. I'm not sure how this would translate to four EDCs...

The amplification at resonance caused by increasing the magnet strength almost offsets the isolation benefits of increasing magnet strength. From my modeling, it appears that the magnet strength may be very close (if not already at) isolation optimization.

 

Lowering the mass to 0.2 the current mass may be impractical. It seems as if the benefits of lowering the mass only occur when the mass is reduced by a factor of 0.2 (maybe 0.4)

 

  5225   Sat Aug 13 21:15:47 2011 NicoleSummarySUSTT Optimization Curves

Quote:

What are the parameters you are using? As you have the drawings of the components, you can calculate the masses of the objects.

 

Reducing the ECD resonance from 10Hz->6Hz looks nice.

The resonant freq of the ECDs are not (fully) determined by the gravitational energy but have the contribution of the elastic energy of the wire.

Q1: How much is the res freq of the ECDs if the freq is completely determined by the grav energy? (i.e. the case of using much thinner wires)

Q2: How thin should the wires be?

 The drawings do not have the masses of the objects.

 

For the resonant frequency:

Instead of sqrt (g/l) would the numerator in the square root be[ g + (energy stored in wire)/(mass of damper)] ?

 

  5227   Sun Aug 14 00:26:51 2011 NicoleSummarySUSTT Optimization Curves

Quote:

1) Drawing has the dimensions => You can calculate the volume => You can calculate the mass
Complicated structure can be ignored. We need a rough estimation.

2) Your restoring force can have two terms:
- one comes from the spring constant k
- the other from the gravity

 

 Thank you.

 

The wire used to suspend the EDCs is tungsten?

To verify, for my model, the EDC will be the mass of all four dampers or a single damper? The length of the wire used to suspend the EDC will be the combined length of 4 wires or length of  a single wire?

 

Taking into account the densities for each material (specific material of each component was listed, so I looked up the densities), and trying my best to approximate the volumes of each component, I have determined

the mass of the mirror + mirror holder to be ~100 g and the mass of a single EDC to be ~19 g

  5229   Sun Aug 14 13:57:52 2011 NicoleSummarySUSTT Optimization Curves

Quote:

Quote:

1) Drawing has the dimensions => You can calculate the volume => You can calculate the mass
Complicated structure can be ignored. We need a rough estimation.

2) Your restoring force can have two terms:
- one comes from the spring constant k
- the other from the gravity

 

 Thank you.

 

The wire used to suspend the EDCs is tungsten?

To verify, for my model, the EDC will be the mass of all four dampers or a single damper? The length of the wire used to suspend the EDC will be the combined length of 4 wires or length of  a single wire?

 

Taking into account the densities for each material (specific material of each component was listed, so I looked up the densities), and trying my best to approximate the volumes of each component, I have determined

the mass of the mirror + mirror holder to be ~100 g and the mass of a single EDC to be ~19 g

 I am thinking that perhaps my mass estimations were off? The model that I have used fits the data better than the model that I have made (changing the masses to fit my estimations of the values)

FLEX_exp_mod_comp.jpg

  5231   Sun Aug 14 17:47:39 2011 NicoleSummarySUSTT Shaking Today and Hopefully More?

Quote:

As reported in my  previous entry of TT supsension bode plots, I found that my experimental data had what appears to be very noise peaks above 20 Hz (as mentioned earlier, the peak at 22 Hz is likely due to vertical coupling, as 22 Hz is the resonant frequency of the cantilever blades). This is very unusual and needs to be explored further. I would like to vertically-shake the TTs to obtain more data on possible coupling. However, I am leaving on Monday and will not return until Thursday (day of SURF talks). I am leaving campus Friday afternoon or so. I would may need some help coming up with an assembly plan/assembling set-up for vertical shaking (if it is possible to do so in such a limited time frame).

 

Today I wanted to see if the "noisy peaks" above 30 Hz were due to EM noise coupling. I tested this hypothesis today, seeing if EM fields generated by the coil at higher frequencies were injecting noise into my transfer function measurements. I found that the "noisy peaks" above 30 Hz are NOT DUE TO EM NOISE COUPLING. I am very curious as to what is causing the high peaks (possibly coupling from other degrees of freedom)?

 

 emnoise_and_flex.jpg

 I have been redoing the noise test multiple times today. Here is the best plot that I got

noisetest.jpg

  10009   Mon Jun 9 10:55:48 2014 NichinSummaryElectronicsBBPD D1002969-v8 transimpedence measurement

My SURF week-1 work...

Motivation:

To measure the transimpedence of  the Broadband photodiode (D1002969-v8), using a New focus photodiode (1611) as reference. The amplitude modulated Jenne Laser (1.2mW) was used. 

The steps involved in getting the transimpedence are as follows:

Acquiring data

  • Get 2 sets of data from Network Analyzer Agilent 4395: One set of data will be for the transfer function of Ref PD over RF out. The other set for Test PD over Ref PD.
  • The following conditions were set:

1) Frequency sweep range: 1MHz to 200 MHz.

2) Number of Points sampled in  the range: 201

3) Type of sweep: Logarithmic

  • Set the NA to give the corresponding transfer function values in dB and also Phase response in degrees.
  • Save the data into floppy disk for processing on the computer (The wireless way of acquiring data was not working when the experiment was conducted )

Plotting

  • The matlab code attached (TransimpedencePlot.m) will then give plots for the absolute values of transimpedence in V/A.
  • Logic involved in the code:
    • Transimpedence = Voltage response / (Responsivity of the photodiode * Power incident) 
    • Responsivity for BBPD is taken as 0.1 A/W and for NF1611 as 0.68 A/W as given in their datasheets.
    • Voltage response of Test PD w.r.t RF output of NA (in dB) = Voltage response of Test PD w.r.t Ref PD (in dB) + Voltage response of Ref PD w.r.t RF output of NA (in dB) 

 Results

The Plots of transimpedence obtained are attached (results.pdf) . The results obtained for BBPD is consistent with the ones obtained before, but the same method and code gives a different transimpedence for 1611.

The transimpedence of NF 1611 was obtained to be around 4-5 V/A which is very much off-track compared to the one given in the datasheet (elog: 2906).

 

The transimpedence of  Broadband photodiode (D1002969-v8) was around 1200 - 1300 V/A for most of the range, but the value started falling as the frequency approached 100 MHz. This result is consistent with DCC document: T1100467-v2.

 

Attachment 1: PD_transimpedence_measurement.png
PD_transimpedence_measurement.png
Attachment 2: results.pdf
results.pdf results.pdf
Attachment 3: code_and_data.zip
  10034   Thu Jun 12 16:56:31 2014 NichinUpdateElectronicsPD Inspection

I and Eric Gustafson inspected the automated PD frequency response measurement system which Alex Cole built last summer. We just lifted the tops off the tables [AS table, POY table and ITMX table] and looked at the alignment checking to see if the correct optical fibers from the fiber splitter were illuminating the correct photodiodes. We did not change anything at all and put the covers back on the tables.

The PDF attached shows the state of each PD fiber pair.  The fibers labeled REFL11 and REFL55 were reversed and illuminating the wrong photodiodes.

We will do a manual measurement of REFL33 tomorrow using the network analyzer and the modulatable laser but not the RF switch.  Afterward we will check to make sure the RF cables are connected to the correct channels of the RF switch according to the switch list (/users/alex.cole/switchList).

Attachment 1: Inspection_PD_Freq_Resonse_system_12th_June_2014.pdf
Inspection_PD_Freq_Resonse_system_12th_June_2014.pdf Inspection_PD_Freq_Resonse_system_12th_June_2014.pdf
  10037   Fri Jun 13 18:16:00 2014 NichinUpdateElectronicsChanges to the PD frequency response measurement system

 

As we had planned yesterday (ELOG 10034) I and Eric Gustafson wanted to manually measure the transimpedence for REFL33. But on closer inspection I found the RF signal cable coming from the Photodiode REF DET (mounted on the POY table), that we were supposed to plug into the network analyzer, did not have an SMA connector at the end. There was just the Teflon and metal part sticking out of the insulation. So we disconnected the cable labeled REF DET from the PD and pulled it out to fix it. (POY table and from near the 1Y1 rack)

 

 

Being unable to locate any SMA male connectors in the 40m lab [pasternack PE4025], we headed over to Downs where Rich Abbott did a quick and awesome job of soldering the SMA connector and also teaching me in the process. I will write an ELOG on how to do a clean solder of the SMA connectors to the RF cable shortly for future reference.

 

 

Coming back to the 40m we rerouted the REF DET cable from near the 1Y1 rack and into the POY table. This job was done mostly by Eric. We were also unable to locate a torque wrench to tighten the cable at the PD’s end and had to leave it finger tight. Eric is planning to buy a new torque wrench as we will need it often.

 

 

Also, I cross checked the SwithList located at /users/alex.cole/switchList with the RF switch connections at 1Y1 rack and turns out it is consistent, except that at CH2 of the first switch where MC REFL was to be connected, there is a unlabeled cable. It might belong to the correct PD, but must be made sure of. The rest of the channels that are not mentioned in the list were unconnected on the RF switch.

 

Now instead of disconnecting REFL 33 to make measurements with the NA, we had to take out AS55 from the RF switch, as the former was very hard to remove without the torque wrench. Then Eric removed the optical fiber which was illuminating the AS55 (AS table) from its mount to hook it up to the power meter. But then we were not sure of how to operate the Laser diode controller (LDC 3744C) and decided to leave stuff as it is and continue either tomorrow or on Monday. Right now we closed the optical fiber of AS55 with a cap and it remains unmounted. The RF cables of REF DET and AS55 were left hanging near the 1Y1 rack.

  10058   Wed Jun 18 15:25:06 2014 NichinUpdateElectronicsBBPD Transimepedence plot

 Motivation:

To measure the transimpedence of  the Broadband photodiode (D1002969-v8), using a New focus photodiode (1611) as reference. The amplitude modulated Jenne Laser (1.2mW) was used @20mA

The steps involved in getting the transimpedence:

Acquiring data

  • The following conditions were set on Network Analyzer Agilent 4395:

1) Frequency sweep range: 500KHz to 300 MHz.

2) Number of Points sampled in  the range: 301

3) Type of sweep: Logarithmic

  • Set the NA to give the corresponding transfer function value (output of BBPD over output of 1611) and also Phase response in degrees.
  • Save the data into floppy disk for processing on the computer.

Plotting

  • The matlab code attached (Trans_plot.m) will then give plots for the absolute values of transimpedence in V/A.
  • Logic involved in the code will be presented clearly in a separate Elog. 

 Results

The Plots of transimpedence obtained are attached. The data and matlab code used is in the zip file.

The transimpedence of  Broadband photodiode (D1002969-v8) was around 1200 - 1300 V/A for most of the range (2), but the value started falling as the frequency approached 200 MHz. 

Attachment 1: BBPD.png
BBPD.png
Attachment 2: BBPD_readings_06-18-2014.zip
  10062   Wed Jun 18 18:16:26 2014 NichinUpdateElectronicsChanges to the PD frequency response measurement system

[Nichin, Eric G, Koji]

Continuing out work from elog:10037, we wanted to check if the frequency response of AS55. Having figured out exactly how to use the Laser diode controller (LDC 3744C), we hooked up a fiber power meter to the optical fiber illuminating AS55 (that we disconnected from its mount last Friday ) and raised up the current to 150mA to get almost 0.8mW power reading.

When aligning the fiber to illuminate the PD, we found that the beam was pretty wide. So we pulled out the collimator and tweaked it to get a focused beam. The fiber was mounted back and was aligned to get a maximum DC reading. The multimeter readout 30mV finally. Taking the transimpedence as 200ohm approx., the hot current is about 1.5mA.

Network analyzer was now connected to the modulation input of the laser and the RF output from REF DET and AS55 (inputs to RF switch at rack 1Y1) were connected as input to measure the transfer function. We got just noise on the scope of NA. So, then we tried REFL33 as the Input and still got nothing (We were also not sure if this PD was properly illuminated, we did not check). However the REF DET was giving a nice response on the scope. Turns out all the PDs were disconnected form the Demodulator (D990511) on rack 1Y2.

On closer inspection the RF cable between domodulator and RF switch that was labelled AS55 had a loose SMA connector at the switch end. I will have to fix that tomorrow . For the time being Koji connected the cable labelled REFL33 to the AS55 demodulator and we finally got a response form the AS55 PD on the NA. However no readings were recorded. The power supply to REF DET was turned off in the end as Eric G claimed that it has been ON for almost a year now, which is not a good thing. Also, we removed the modulation input from NA to the diode laser and terminated the input with a 50ohm terminator.

We planned to pull out and check each and every RF cable (especially the SMA ends for faulty soldering and loose connections) and fix/ replace them as needed.

  10079   Fri Jun 20 11:41:18 2014 NichinUpdateElectronicsTransimpedence measurement-BBPD

EDIT: Please ignore the following data. The revised data and plot are in Elog 10089 

Yesterday evening, I conducted the same measurements done in Elog-10059 using the same REF PD (NF 1611) and the same model of BBPD, but on different piece that needed to be checked. 

I moved the NA from near rack 1Y1 to the Jenne laser table and back again after the readings were done.

 Acquiring data

  • The following conditions were set on Network Analyzer Agilent 4395:

1) Frequency sweep range: 1MHz to 300 MHz.

2) Number of Points sampled in  the range: 201

3) Type of sweep: Logarithmic

  • Set the NA to give the corresponding transfer function value (output of BBPD over output of 1611) and also Phase response in degrees.
  • Save the data into floppy disk for processing on the computer.

 Results

The Plots of transimpedence obtained are attached. The data and matlab code used is in the zip file.

The transimpedance of  Broadband photodiode (D1002969-v8) was around 50kV/A-70kV/A (Unusually high) for most of the range (2), but the value started falling as the frequency approached 200 MHz.

 

The high impedance might be because the PD is faulty.   

 

 

 

 

Attachment 1: BBPD_readings_06-19-2014.zip
Attachment 2: BBPD_transimpedence_19thJune2014.pdf
BBPD_transimpedence_19thJune2014.pdf
  10082   Fri Jun 20 16:36:44 2014 NichinUpdateElectronicsRF cables removed

 [Nichin, Eric G]

As mentioned in Elog 10062, we found RF cables running between demodulators in rack 1Y2 and RF switch in 1Y1 to have bad SMA connectors (No shield / bad soldering / no caps).

we pulled out all the cables belonging to PD frequency response measurement system , 8 in total, and all of them about 5.5m in length.

Their labels read :

REFL33, REFL11, REFL55, AS55, POX11, REFL165, POP22 and POP110. 

All of them are now sitting inside a plastic box in the contorl room.

On another note, instead of fixing all the cables ourselves, Steve and Eric G decided to order custom made RF cables from Pasternack as professionally soldered cables are worth it. We have placed an order for 2 cables (RG405-550CM) to check out  and test them before we order all of the cables.

  10086   Sat Jun 21 01:25:12 2014 NichinHowToElectronicsPD Trasimpedence measurement theory

 Here is the logic that I have been using to calculate the transimpedence of PDs. Please let me know if you think anything is wrong.

Attachment 1: Transimpedence_Calculation_.pdf
Transimpedence_Calculation_.pdf
  10087   Sat Jun 21 01:46:28 2014 NichinUpdateElectronicsBBPD Transimepedence plot

Sorry for the late update Koji.

There was a bug in my code that was pointed out by koji and here is the revised plot of transimpedence. The correct code attached.

The transimpedence value is unusually high, about 50kV/A-70kV/A for most of the range. The same was observed when the transimpedence was calculated on another BBPD in Elog.

It is highly unlikely that both the BBPDs are faulty and might be because I am doing the calculations wrong. Must dig deeper into this. Maybe it is a good idea to try the shot noise method of calculating the transimpedence and see how the values turn out. Will do that ASAP.

Attachment 1: BBPD_06-18-2014.pdf
BBPD_06-18-2014.pdf
Attachment 2: BBPD_readings_06-18-2014.zip
  10089   Mon Jun 23 21:16:14 2014 NichinUpdateElectronicsTransimpedence measurement-BBPD

  [Nichin, Koji] 

Today evening, me and koji decided to get down to the problem of why the trasimpedence plots were not as they were supposed to be for Broadband photodiode (D1002969-v8) S1200269. There were a few problems that we encountered:

  • Turns out the REF PD was not illuminated properly, for maximum output. The DC output voltage turned out to be much higher than the previous measurement. Since I assumed that the REF PD had not been touched since the first day I took readings, I did not check this.
  • The fork holding the Test PD was a bit out of shape and only one side of it was clamping down the PD. This made the PD vulnerable swivel about that one side. We replaced it with a new one.
  • I was setting the current diving the Jenne laser to about 20mA and this resulted in nocthes at higer frequencies in the network analyzer due to over driving of the diode laser. Once we reduced this to about 12.5-13 mA they disappeared. Also, the current limit setting was set at 40mA which is way too high for the jenne laser and might have resulted in damaging it if someone had accidentally increased the current. We have now set it at 20mA.

After these changes the measurements are as follows:

I moved the NA from near rack 1Y1 to the Jenne laser table. 

 Acquiring data

  • Jenne Laser driving current: 12.8mA 
  • The following conditions were set on Network Analyzer Agilent 4395:

 

1) Frequency sweep range: 1MHz to 300 MHz.

2) Number of Points sampled in  the range: 801

3) Type of sweep: Logarithmic

  • Set the NA to give the corresponding transfer function value (output of BBPD over output of 1611) and also Phase response in degrees.
  • Save the data into floppy disk for processing on the computer.

 Results

DC output voltage of REF PD: 0.568V

DC output voltage of BBPD: 18mV

Power incident on REF PD and BBPD respectively: 0.184mW  and 0.143mW

Hence, Responsivity for REF PD and BBPD respectively:  0.315 A/W and 0.063 A/W 

Responsivity given in the Datasheet for REF PD and BBPD : 0.68 A/W and 0.1 A/W

 

 

The reason for these differences are unknown to me and must be investigated.

The Plots of transimpedence obtained are attached. The data and matlab code used is in the zip file.

The transimpedance of  Broadband photodiode (D1002969-v8) S1200269 was around 1kV/A-2kV/A for most of the range, but the value started falling as the frequency approached 100 MHz. This BBPD is best when used at 10-30 MHz.

Attachment 1: BBPD_transimpedence_06-23-2014.pdf
BBPD_transimpedence_06-23-2014.pdf
Attachment 2: BBPD_readings_06-23-2014.zip
  10093   Tue Jun 24 16:52:43 2014 NichinUpdateElectronicsAn RF cable re-installed

Quote:

 [Nichin, Eric G]

As mentioned in Elog 10062, we found RF cables running between demodulators in rack 1Y2 and RF switch in 1Y1 to have bad SMA connectors (No shield / bad soldering / no caps).

we pulled out all the cables belonging to PD frequency response measurement system , 8 in total, and all of them about 5.5m in length.

Their labels read :

REFL33, REFL11, REFL55, AS55, POX11, REFL165, POP22 and POP110. 

All of them are now sitting inside a plastic box in the contorl room.

On another note, instead of fixing all the cables ourselves, Steve and Eric G decided to order custom made RF cables from Pasternack as professionally soldered cables are worth it. We have placed an order for 2 cables (RG405-550CM) to check out  and test them before we order all of the cables.

 The new RF cables arrived. But unfortunately we did not realize that RG405 was a Semi-rigid coax cable, with a copper shielding. These are meant to be installed in setups that will not be changed / disturbed. We need to order a different set of cables. The new cables have joined the other cables in the plastic box mentioned above.

For now to check if the old setup is still working, I have installed an RF cable (that we earlier pulled out and looks like in good shape, labelled REFL33) between the AS55 Demodulator output PD RF MON in rack 1Y2 and the network analyzer input. Since Manasa and the others were busy working with the interferometer, I did not switch on the laser and did not take any readings. The power supply to REF DET remains off.

I will continue with the measurements tomorrow morning and also try to get the data wirelessly using Alex's code. 

  10097   Wed Jun 25 02:01:21 2014 NichinSummaryGeneralWeekly Report

 Attached is the weekly work plan / equipment requirement / lab expert's presence needed for the upcoming week.

Attachment 1: Nichin_Week4_update.pdf
Nichin_Week4_update.pdf Nichin_Week4_update.pdf
  10102   Wed Jun 25 17:13:10 2014 NichinUpdateElectronicsLaser power check - PDFR system

[Nichin, Manasa]

I wanted to make sure Alex's system of Diode laser + laser controller + optical splitter was working fine and then make a manual measurement for AS55 PD. Manasa was supervising my work and helping me with unhooking the fibers and taking power meter readings. I have tuned on the power to REF DET from under the POY table.

I switched on the laser sitting in the 1Y1 rack and turned up the driving current to 240mA. On checking the laser power readings at AS55 (AS table) and REF DET (POY table) simultaneously, we got readings of 1.6mA and 2.4mA respectively. This much difference in readings was not expected and I did not continue taking the readings for transimpedence measurement.

I will rectify if this unequal splitting of power by the 1x16 optical splitter is going to cause any difficulties for the automated PDFR system measurement technique and resolve it if needed.

 

  10105   Wed Jun 25 20:45:04 2014 NichinUpdateElectronicsAS55 Bodeplot

 [Nichin]

I finally did carry out a measurement on the network analyzer. This proves that the previous system will work properly. Just the optical splitter problem is to be taken care of.

For this, after Elog 10102, I did not touch any of the tables or photodiodes. Only turned on the laser at 1Y1 and took readings from the NA located nearby. I switched off the laser after measurements. The power to REF PD remains on.

I plotted transimpedence plots in the usual way and got ridiculous values of 15 ohms at 55MHz. Obviously there is the problem of varying amount of power illuminating the REF PD and AS55.

So, I just plotted the bode plots of transfer function got from the NA to check if the characteristics of AS55 looks as it was supposed to be and Yes! I got a nice peak at 55MHz.

 

Acquiring data

 RACK 1Y1

  • Diode Laser driving current: 240mA 
  • The following conditions were set on Network Analyzer Agilent 4395:

 

1) Frequency sweep range: 1MHz to 100 MHz.

2) Number of Points sampled in  the range: 801

3) Type of sweep: Linear

  • Set the NA to give the corresponding transfer function value (output of AS55 over output of 1611) and also Phase response in degrees.
  • Save the data into floppy disk for processing on the computer.

 

 

The experimental values obtained were:

DC output voltage of REF PD: 7.48V

DC output voltage of AS55: 53.7mV

Power incident on REF PD and AS55 respectively: 2.4mW  and 1.6mW

Taking the DC transimpedence of AS55 as 66.2 ohms (from schematic given at D1300586-v1) and for REF PD as 1E04 ohms

Hence, Responsivity for REF PD and AS55 respectively are:  0.312 A/W and 0.51 A/W

 

The data and code used are in the zip file.

Attachment 1: AS55_06-25-2014.zip
Attachment 2: AS55_bodeplot.pdf
AS55_bodeplot.pdf
  10108   Fri Jun 27 18:07:38 2014 NichinUpdateComputer Scripts / ProgramsUpdated script for acquiring data from Agilent 4395A network analyzer

The updated script for remotely getting data from Agilent 4395A network analyzer is located at /users/nichin

This network analyzer device is located at crocetta.martian (192.168.113.108)

How to run the script:

> python NWAG4395A_modified.py [filename.yml]

  1. The script accepts sweep parameters and output options via a .yml file that is written following a template that can be found at /users/nichin/NWAG4395template.yml
  2. The data obtained is stored as a .dat file and the corresponding details regarding the acquired data is in a .par parameter file
  3. You can choose to get a plot of the data obtained by specifying it in the .yml file. The plots are automatically stored as PDF.
  4. Plots, data and parameter files are all stored in a new folder that is created with a timestamp in its name.
  5. NOTE: Plotting options are only available in computers running numpy versions of 1.6.0 or above. The plotting sections of the code worked on Chiara, which has a 1.6.1 numpy, but did not work on Rossa which only had 1.3.0 numpy. Anyway, I have added an extra function that checks the version and skips the plotting part if needed.

Test Run:

I connected a simple 2MHz Low pass filter between the modulation output and signal input of the NA and ran a scan from 0Hz to 20MHz. The script was run from Chiara.

The expected plot was obtained and is attached here.

Further work:

I now have to work on setting up the RF switch in rack 1Y1 to select between required PDs and also on the code that chooses which channel is being selected.

There is also a problem of 2 8x1 RF switches being present, instead of one 16x1. Alex's code for RF switching does not take this into account.

RXA: I've deleted your plot because it didn't meet the minimal Bode plot standards. Please look up "Bode Plot" using Google/Wikipedia and try to follow some good example. Bode plot should contain Phase as well as magnitude. Also, the axes must be labeled with some physical units.

  10111   Mon Jun 30 00:18:15 2014 NichinUpdateComputer Scripts / ProgramsUpdated script for acquiring data from Agilent 4395A network analyzer

Quote:

 

RXA: I've deleted your plot because it didn't meet the minimal Bode plot standards. Please look up "Bode Plot" using Google/Wikipedia and try to follow some good example. Bode plot should contain Phase as well as magnitude. Also, the axes must be labeled with some physical units.

Sorry Rana for not giving much attention to the plot. I will definitely change the way they are being plotted.

I was more focused on getting the data acquisition to work. Also, the current script gets only the magnitude and not the phase... I still have to work on that.

  10123   Wed Jul 2 16:16:45 2014 NichinUpdateGeneralLAN wire added

 [Nichin, Eric Q]

We added a new LAN wire from Rack 1Y4 to 1Y1 to connect the RF switch at 1Y1 to the martian network. The wire is labelled "To RF Switch (1Y1)"

The wire was run along the Y arm in the tray right next to the vaccum chamber, not the one on top.

 

  10128   Thu Jul 3 16:28:38 2014 NichinUpdateElectronicsRF cables installed

 [ Nichin, Eric G]

RF cables have been installed between deomodulator output PD RF MON and the RF switch for the following PDs:

 REFL33, AS55, REFL55,REFL165,REFL11,POX11,POP22

The cables are labelled on both ends and have been run on the overhead tray.

The cabling looks neat on 1Y2, but not so much in 1Y1(RF switch). I will better organize them later.

There were quite a few more demodulator units labelled with PD names. Do any of them need to be included in the automated frequency response measurement system? Please let me know so that I can include them to the RF switch and check them for proper illumination, which i will do for all the above PDs next week.

Test run:

I tested the RF switch selection code and then the data acquisition code for the NWAG4395A network analyzer and they both seemed to work fine. I selected the channel to which AS55 is hooked up to and then remotely got its transfer function.

There is quite some noise in the system as the plot shows. Especially the phase. Maybe my driving power was a bit too low. Have to figure out the reason behind this.

Further work:

  • Make sure all the PDs are properly illuminated.
  • Create a DC voltage reading's database for all PDs.
  • Canonical plots for each PD to compare with the current data.
  • Implement a script to fit the transfer function and extract required information about the PD.

 

 

 

Attachment 1: AS55_03-07-2014_162634.pdf
AS55_03-07-2014_162634.pdf
  10143   Mon Jul 7 17:20:09 2014 NichinUpdateElectronicsRF PDs needed

Quote:

Quote:

 REFL33, AS55, REFL55,REFL165,REFL11,POX11,POP22

There were quite a few more demodulator units labelled with PD names. Do any of them need to be included in the automated frequency response measurement system? Please let me know so that I can include them to the RF switch and check them for proper illumination, which i will do for all the above PDs next week.

 In the order that makes more sense to me, it looks like you have:

REFL11, REFL33, REFL55, REFL165,

AS55

POX11

POP22

We don't really need POP22 right now, although we do want the facility to do both POP22 and POP110 for when we (eventually) put in a better PD there.  Also, we want cabling for POP55, so that we can illuminate it after we re-install it.  If we're working on 2f PDs, we might as well consider AS110 also, although I don't know that there was a fiber layed for it.  The big one that you're missing is POY11.

 A new RF cable has been included for POY11. Cabling for POP55 and POP110 might or might not exist. I will check and report it.

  10145   Mon Jul 7 18:38:27 2014 NichinUpdateElectronicsRF cables rerouted

Quote:

The RF cables have been routed incorrectly. The cables run to the module from the front of the rack. We cannot close the doors to the racks if they are to remain this way.

I have asked Nichin to reroute the cables properly.

RF cables have been rerouted from the side of the rack, under the supervising eye of Manasa.

I moved the red ladder from near 1X4 to 1Y1 and back again.

Current list of RF cables:

REFL11, REFL33, REFL55, REFL165,

AS55

POX11

POP22

POY11

I have not connected them to the RF switch yet. ( until I figure out how to get both the switches working properly)

Attachment 1: 1.png
1.png
Attachment 2: 2.png
2.png
  10152   Tue Jul 8 15:07:24 2014 NichinHowToElectronicsRF Multiplexer in rack 1Y1

The RF multiplexer is configured as shown in the figure. It is now effectively a 15x1 RF mux.

RF_Multiplexers.png

To select a required channel:

Run the script as shown below 

/opt/rtcds/caltech/c1/scripts/general/rfMux.py

>python rfMux.py ch11

For channel 10 to 16, you can just enter the required channel number and it is routed to the output.

For channel 1 to 8, you only need to input the required channel number as above. No need to run the code again to select ch9 after selecting ch1-8

 

How the NI-8100 controller works:

Whenever any channel of one switch is selected, the output of the other switch is set to its ch0 (ch1 and ch9 in the figure).

So selecting ch1-8 will automatically select ch9 as output for the other switch. IF you send a command to select ch9 afterwards, the first switch will be automatically set to ch1 and not stay on what you had selected before.

  10154   Tue Jul 8 16:45:15 2014 NichinUpdateGeneralWeekly plan

 My plan for next week is...

1)    1) Taking DC output readings with multimeter for each PD to create a database for all the PDs. Requires taking off the table tops for each PD.  Also, making sure each PD is illuminated properly.

    2 - 3 Hours inside the lab 

    Requires presence of expert

Occupies all the PDs , RF switch and the Network analyzer.

2)    2)  Integrate the switch selection script with the Network analyzer script to complete the automation part of the project.  (If time permits, build a simple GUI for easy operation)

Occupies the control room computer, RF switch and the Network analyzer

3)    3)  Create a database of canonical plots for each PD to compare with the current plot and maybe even plot the difference between the current plot and canonical plot.

Occupies the control room computer, PDs , RF switch and the Network analyzer.

4)    4)  Fit the transfer function or transimpedance using vector fitting. (vectfit4.m)

5)    5) Update 40m-Wiki

6)    6) Progress Report to be submitted to SFP.

  10166   Wed Jul 9 17:34:11 2014 NichinUpdateElectronicsPDFR: Beam pointing adjustments and DC measurements

 [Nichin, Manasa]

AIM: Taking DC output readings with multimeter for each PD to create a database (required for transimpedance calculations), by taking off the table tops. Also, making sure each PD is illuminated properly.

What we did:

  • In rack 1Y1: Diode laser controller was set to 150.0 mA at all times. This gave powers in the neighbourhood of 1mW at the end of fibers illuminating all PDs. The laser outputs light of 1064nm wavelength. The laser was switched off in the end.
  • Checked the collimation of the fiber for each PD. In some cases they were not focused to give a sharp spot, so we had to unmount the fibers and fix it and mount them back. Manasa did it initially and I learnt how it was done properly. Eventually I got better and did it myself (under her supervision)
  • Set the mount alignment for maximum illumination of the PD.
  • Record the power falling on the laser and also the DC voltage output. Any light that did not come from my fiber was blocked when taking the readings and then unblocked. I also took care of offset voltage present when taking the DC readings.

Recorded measurements:

REFL11:   Pinc = 0.91 mW         VDC = 34.9 mV 

REFL33:   Pinc = 0.83 mW         VDC = 33.2 mV 

REFL55:   Pinc = 1.08 mW         VDC = 42.7 mV 

REFL165: Pinc = 0.79 mW         VDC = 115.3 mV

AS55:         Pinc = 0.78 mW         VDC = 31.3 mV

POX11:      Pinc = 0.83 mW         VDC = 34.7 mV

POP22**:   Pinc = 1.08 mW         VDC = 5.82 mV

POY11:      Not illuminated; there was no optical fiber mount. Although, there was a fiber near it with a cap on the end. It also looks like there is no space to put in a new mount near the PD. 

REF PD:    Pinc = 1.19 mW         VDC = 8.2 V     (REF PD = New focus 1611)

**Note: The current POP 22 PD does not have 2 different outputs for DC and RF signals. I unplugged the RF cable from the output, took readings with the multimeter and then plugged back the RF cable.

Further work:

I will calculate the responsivity for each PD and compare it to the expected values. 

  10183   Fri Jul 11 11:51:03 2014 NichinUpdateElectronicsPDFR: List of DC transimpedances

The following values are going to be entered in the param_[PDname].yml file for each PD. I am elogging them for future reference.

I got the values from combing schematics and old Elog entries. Please let me know if you believe the values are different.

  • AS55: 66.2 ohms
  • REFL11 : 66.2 ohms 
  • REFL33 : 50.2 ohms
  • REFL55: 50 ohms (Elog 4605)
  • REFL165: 50.2 ohms
  • POY11: 66.2 ohms
  • POX11: 50.2 ohms
  • REF (NF1611): 700 ohms
  • POP22: ?? (This is currently a Thorlab BBPD )
  10186   Fri Jul 11 17:49:12 2014 NichinUpdateElectronicsNew Prologix GPIB-Ethernet controller

I have configured a NEW Prologix GPIB-Ethernet controller to use with HP8591E Spectrum analyzer that sits right next to the control room computers.

Static IP: 192.168.113.109

Mask: 255.255.255.0

Gateway: 192.168.113.2

I have no clue how to give it a name like "something.martian" and to update the martian host table (Somebody please help!!)

 

  10192   Mon Jul 14 12:49:07 2014 NichinUpdateElectronicsNew Prologix GPIB-Ethernet controller

Quote:

Quote:

I have configured a NEW Prologix GPIB-Ethernet controller to use with HP8591E Spectrum analyzer that sits right next to the control room computers.

Static IP: 192.168.113.109

Mask: 255.255.255.0

Gateway: 192.168.113.2

I have no clue how to give it a name like "something.martian" and to update the martian host table (Somebody please help!!) 

The instructions for adding a name to the martian DNS table are in the wiki page that I pointed you to:

https://wiki-40m.ligo.caltech.edu/Martian_Host_Table

The instructions at https://wiki-40m.ligo.caltech.edu/Martian_Host_Table   are outdated!

The name server configuration is currently at /etc/bind/zones/martian.db [ source: elog:10067 ]

 

Anyway, I need superuser access to edit the files, which I don't have. Even if I did know the password, I don't think it's a good idea for me to be messing around. So any of the 40m folks please update the martian table to include:

santuzza.martian  192.168.113.109

 

  10196   Mon Jul 14 16:51:07 2014 NichinUpdateElectronicsMartian table updated, Named server restarted

 [Nichin, Jenne]

The martian lookup tables are located at /etc/bind/zones/martian.db  and etc/bind/zones/rev.113.168.192.in-addr.arpa

Jenne updated these to include santuzza.martian  192.168.113.109

 

 

The method to restart named server given at  https://wiki-40m.ligo.caltech.edu/Martian_Host_Table  also does not work.

I restarted it using  >sudo /etc/init.d/bind9 restart

The named server is now updated and works fine. :)  I will update the 40m wiki now.

  10197   Mon Jul 14 17:51:34 2014 NichinUpdateComputer Scripts / ProgramsMEDM for PDFR system

14.pngA

 Successfully completed the rudimentary GUI for PDFR system. (users/nichin/PDFR)

Pressing any of the buttons above runs the script that does the following:

1) Change RF mux channel to the required one.

2) Frequency sweep on the network analyzer. The common sweep parameters are in a file named param_NWAG4395A.yml . PD specific parameters are in param_[PD name].yml in their respective folders

3) The transimpedance is calculated and the plot is saved as PDF in the respective folder for the PD. Each set of measurement data and plot is in a timestamped subfolder.

Further work:

To take transimpedance readings for each PD and create a canonical set of data that can be used to compare with data obtained for every measurement run.

  10202   Tue Jul 15 12:36:17 2014 NichinUpdateElectronicsRF cables rerouted

Quote:

 

I have not connected them to the RF switch yet. ( until I figure out how to get both the switches working properly)

 I went into the lab and connected the RF cables to the Mux. Will take measurements for each PD henceforth.

  10210   Wed Jul 16 01:27:01 2014 NichinHowToComputer Scripts / ProgramsHP8591E spectrum analyzer remote scan

The script for running continuous scans on HP 8591E spectrum analyzer is located at scripts/general/netgpibdata/HP8591E_contdScan.py

Give the file HP8591E_param.yml as an argument when running the script. This contains the sweep parameters: Start and stop frequencies along with the place where the plot is stored as a PDF.

The default PDF is located on the Desktop and is named HP8591E_View.pdf     Open this using okular and then run the script.  (Okular pdf viewer automatically reloads the PDF as and when a new one is created)

What the script does:

1) Set the start and stop frequencies as given in the .yml file

2) Take a data trace and plot it in a PDF.

3) Repeat taking traces and update the PDF. Untill Ctrl+C is pressed (PDF refresh rate: approximately every 3 seconds )

4) Exit smoothly after the keyboard interrupt.

Other details:

This spectrum analyzer is connected to a GPIB - Ethernet controller that is configured as santuzza.martian (192.168.113.109)

I have currently stolen the wireless modem from the spectrum analyzer inside the lab (vanna.martian) and using it for this one. *poker face*

To improve:

Get the plot to show where the two biggest peaks are located. Currently it recognizes only the biggest one.

Possibly have makers on the two peaks.

PFA a sample pdf

Attachment 1: HP8591E_View.pdf
HP8591E_View.pdf
  10212   Wed Jul 16 01:46:41 2014 NichinUpdateElectronicsTest run of PDFR system

A test run was conducted on the PDFR system last afternoon and transimpedance plots were generated for 6 of the PDs. The laser was shut down after the test run.

I have not verified (yet) if the transimpedance values indicated by the plots are correct or not. The values mostly look INCORRECT. But the peaks are exactly where they need to be. *phew!*

Reasons: Incorrect calibration, Light other than from the PDFR system fibers on the PDs

Will have to work on debugging all this.

Attachment 1: PDFR_testRun_15-07-2014.pdf
PDFR_testRun_15-07-2014.pdf PDFR_testRun_15-07-2014.pdf PDFR_testRun_15-07-2014.pdf PDFR_testRun_15-07-2014.pdf PDFR_testRun_15-07-2014.pdf PDFR_testRun_15-07-2014.pdf
  10213   Wed Jul 16 01:54:25 2014 NichinUpdateGeneralWork plan for next week

1) Debugging transimpedance calculations in the PDFR

Requires presence of an expert whenever I get inside the lab to take DC measurements or check the illuminating fibers.

2) Creating and incorporating canonical data plots with every measurement of PDFR.

3) Transfer function fitting for transimpedance

4) Improve the Spectrum analyzer scan scripts as mentioned in my elog.

  10217   Wed Jul 16 17:06:41 2014 NichinUpdateComputer Scripts / ProgramsHP8591E spectrum analyzer remote scan

Updated script does the following:

1) Gets the highest 2 peaks

2) Puts a marker on the peaks. Now it looks very similar to the spectrum analyzer display.

3) The refresh rate is still 3 seconds. It might become better if the analyzer was hooked up to a wired martian LAN port rather than the wireless module I am using now.

PFA a sample pdf

Attachment 1: HP8591E_View.pdf
HP8591E_View.pdf
  10229   Thu Jul 17 16:39:34 2014 NichinUpdateElectronicsPDFR debugging attempt : REFL11

In a attempt to debug the values of transimpedance generated by the PDFR system, I did a manual measurement for REFL11 PD.

  • Took the tops off AS and POY tables. (REFL11 and REF PD) Under the supervising eye of Manasa
  • Verify that no extra light is falling on REFL11.
  • Retake DC voltage readings, power readings.
  • Manually set the sweep parameters and record readings from network analyzer.
  • Put the tops back on the tables
  • Calculate transimpedance 

Results:

REF PD(1611):

Pinc = 1.12 mW                 T_dc = 10000 V/A (datasheet)

Vdc = 7.68 V                      T_rf = 700 V/A (datasheet)

Calculated Responsivity = 0.68 A/W (Which matches perfectly with the datasheet value of 0.68 A/W) 

REFL11:

Pinc = 0.87 mV             T_dc = 66.2 V/A (schematic)

Vdc = 32.5 mV      

Calculated Responsivity = 0.56 A/W

 

 

Network analyzer reading at 11 MHz : 0.42

Calculated RF Transimpedance = 460 V/A

40m Wiki : RF Transimpedance = 4 kV/A

I ran the same measurement using PDFR system and got the same results.

Attached: the automatic data and plot obtained.

Conclusion:  The PDFR system and manual measurements agree with each other. However the values do not match with 40m Wiki. I have no clue about which measurement is correct or any mistakes I might be making in the calculations. 

 

Attachment 1: REFL11_17-07-2014_154534.pdf
REFL11_17-07-2014_154534.pdf
Attachment 2: REFL11_17-07-2014_154534.zip
  10238   Fri Jul 18 17:10:57 2014 NichinSummaryElectronicsCharacterization of demodulator boards.

Rack 1Y2, I took transfer function measurements for each of the following demodulator boards: REFL11, REFL33, REFL55, REFL165, AS55, POP22, POX11 and POY11.

What I did:

1) Removed the wire at PD Input to demodulator board.

2) Put the MOD output from network analyzer into PD input of board.

3) Ran a sweep from 100kHz to 100MHz.

4) Measured the transfer function between PD RF MON and PD Input. (The PD RF MON signal came out of the RF multiplexer, so the mux is included as well )

5) Put the original wire back at PD Input.

Results:

The plots clearly show an attenuation of 20dB (factor of 10) for all the demodulator boards. This explains why my transimpedance measurements are off by 10 times.

Note: for REFL 165, there was an extra 100MHz high pass filter installed at PD Input. I did not remove this and made my measurements along with this.

To Do:

a) Modify the PDFR system to calibrate out this attenuation.

b) Measure the transfer function between the input and output of RF mux, so that we can have just the transfer function between PD input an PD RF MON (for documentation's sake)

 

Attachment 1: Demodulators_TF.pdf
Demodulators_TF.pdf Demodulators_TF.pdf Demodulators_TF.pdf Demodulators_TF.pdf Demodulators_TF.pdf Demodulators_TF.pdf Demodulators_TF.pdf Demodulators_TF.pdf
ELOG V3.1.3-