40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Entry  Tue Jun 25 19:18:07 2013, gautam, Configuration, endtable upgrade, plan of action for PZT installation 
    Reply  Wed Jul 3 21:19:04 2013, gautam, Configuration, endtable upgrade, plan of action for PZT installation DAC_bank.pngASC_schematic.pdf
       Reply  Mon Jul 8 13:45:19 2013, gautam, Configuration, endtable upgrade, Driver board verification 
          Reply  Wed Jul 10 22:41:06 2013, gautam, Configuration, endtable upgrade, PZT Driver Board HV_Amplifier.pdf
             Reply  Thu Jul 11 23:50:57 2013, gautam, Configuration, , PZT Driver Board-changes made ASC_schematic.pdfDAC_Max_output.JPG
                Reply  Mon Jul 15 11:51:18 2013, gautam, Configuration, endtable upgrade, DAC at 1Y4-Max Output and Power Spectrum max_amp.JPGmax_amp_all_channels.JPGDACOffPowerSpec.pdfDACOnPowerSpec.pdfDAC2kPowerSpectrum.pdf
                   Reply  Mon Jul 15 13:51:17 2013, Koji, Configuration, endtable upgrade, DAC at 1Y4-Max Output and Power Spectrum 
                      Reply  Mon Jul 15 15:54:20 2013, gautam, Configuration, endtable upgrade, DAC at 1Y4- Power Spectrum -with the right units DACOffPSD.pdfDAC500PSD.pdfDAC2000PSD.pdf
                         Reply  Mon Jul 15 17:20:43 2013, Jenne, Configuration, endtable upgrade, DAC at 1Y4- Power Spectrum -with the right units 
                            Reply  Mon Jul 15 17:59:31 2013, gautam, Configuration, endtable upgrade, DAC at 1Y4- Power Spectrum -6.4kHz bandwidth DAC-6.4_kHz_BW_PSD.pdf
                               Reply  Tue Jul 16 14:51:09 2013, gautam, Configuration, endtable upgrade, AI Board-D000186-Modified notches D000186_Frequency_Response.pdf
                                  Reply  Thu Jul 18 19:09:08 2013, gautam, Configuration, endtable upgrade, QPD Calibration for PZT Calibration QPD-XCalib.pdfQPD-YCalib.pdfError_Function_Fitting.zip
                                     Reply  Thu Jul 18 20:20:52 2013, gautam, Configuration, endtable upgrade, First mirror glued to PZT and mounted in modified mounts Piezo-mirror.jpg
                                        Reply  Thu Jul 18 23:34:40 2013, gautam, Configuration, endtable upgrade, Coarse adjustment of PZT axes orientation in mount PZT_out_waveform.jpg
                                           Reply  Fri Jul 19 23:35:31 2013, gautam, Configuration, endtable upgrade, Preliminary Calibration of PZT QPD-XCalib.pdfQPD-YCalib.pdfPiezo_Yaw_Calib-in_QPD_linear_range-Pitch_tilt.pdfPiezo_Yaw_Calib-in_QPD_linear_range-Yaw_tilt.pdf
                                              Reply  Tue Jul 23 20:41:40 2013, gautam, Configuration, endtable upgrade, Full range calibration and installation of PZT-mounted mirrors M1_Pitch_calib.pdfM1_Yaw_calib.pdfM2_Pitch_calib.pdfM2_Yaw_calib.pdfPI_S330.20L.pdf
                                                 Reply  Mon Aug 5 18:48:44 2013, gautam, Configuration, endtable upgrade, Full range calibration of PZT mounted mirrors for Y-endtable 2-inch-CVI-Yawcalib.pdf2-inch-CVI-Pitchcalib.pdf1-inch-Laseroptik-Yawcalib.pdf1-inch-Laseroptik-Pitchcalib.pdf
                                        Reply  Fri Jul 19 22:51:40 2013, gautam, Configuration, endtable upgrade, Second mirror glued to PZT and mounted  Piezo-mirror_2.JPG
                                           Reply  Tue Jul 30 19:44:05 2013, gautam, Configuration, endtable upgrade, Second mirror glued to PZT and mounted  
                                  Reply  Thu Jul 18 21:12:58 2013, gautam, Configuration, endtable upgrade, AI Board-D000186-All channels modified AI_Board_Output.jpg
                Reply  Mon Jul 29 13:39:25 2013, gautam, Configuration, endtable upgrade, PZT Driver Board-further changes D980323-C-modified.pdfD980323-C-modified-pg2.pdf
          Reply  Mon Jul 29 21:57:45 2013, gautam, Configuration, endtable upgrade, Hardware installed at 1X9 
             Reply  Tue Jul 30 19:40:47 2013, gautam, Configuration, endtable upgrade, DAC-PZT Driver Board Output Signal Chain Tested 
Message ID: 8884     Entry time: Fri Jul 19 23:35:31 2013     In reply to: 8877     Reply to this: 8912
Author: gautam 
Type: Configuration 
Category: endtable upgrade 
Subject: Preliminary Calibration of PZT 

 I recalibrated the QPD today as I had shifted its position a little. I then identified the linear range of the QPD and performed a preliminary calibration of the Piezo tip-tilt within this range.

 


Details:

-I recalibrated the QPD as I had shifted it around a little in order to see if I could move it to a position such that I could get the full dynamic range of the piezo tilt within the linear regime of the QPD. This proved difficult because there are two reflections from the mirror (seeing as it is AR coated for 532nm and I am using a red laser). At a larger separation, these diverge and the stray spot does not bother me. But it does become a problem when I move the QPD closer to the mirror (in an effort to cut down the range in which the spot on the QPD moves). In any case, I had moved the QPD till it was practically touching the mirror, and even then, could not get the spot motion over the full range of the PZTs motion to stay within the QPD's linear regime (as verified by applying a 20Vpp 1Hz sine wave to the PZT driver board and looking at the X and Y outputs from the QPD amplifier. 

-So I reverted to a configuration in which the QPD was ~40cm away from the mirror (measured using a measuring tape).

-The new calibration constants are as follows (see attached plots):

X-Coordinate: -3.43 V/mm
Y-Coordinate: -3.41 V/mm


-I then determined the linear range of the QPD to be when the output was in the range [-0.5V 0.5V]. 

-Next, at Jenne's suggestion, I decided to do a preliminary calibration of the PZT within this linear range. I used an SR function generator to supply an input voltage to the PZT driver board's input (connected to Channel 1 of the piezo). In order to supply a DC voltage, I set a DC offset, and set the signal amplitude to 0V. I then noted the X and Y-coordinate outputs, being sure to run through the input voltages in a cyclic fashion as one would expect some hysteresis. 

-I did this for both the pitch and yaw inputs, but have only superficially analysed the latter case (I will put up results for the former later). 

 


Comments:

-There is indeed some hysteresis, though the tilt seems to vary linearly with the input voltage. I have not yet included a calibration constant as I wish to perform this calibration over the entire dynamic range of the PZT. 

 

-There is some residual coupling between the pitch and yaw motion of the tip tilt, possibly due to its imperfect orientation in the holder (I have yet to account for the QPD's tilt).

 

-I have not included a graphical representation here, but there is significantly more pitch to yaw coupling when my input signal is applied to the tip-tilts pitch input (Channel 2), as compared to when it is input to channel 1. It is not clear to me why this is so.

 

-I have to think of some smart way of calibrating the PZT over its entire range of motion, keeping the spot in the QPD's linear regime throughout. One idea is to start at one extreme (say with input voltage -10V), and then perform the calibration, re-centering the spot to 0 on the QPD each time the QPD amp output reaches the end of its linear regime. I am not sure if this will work, but it is worth a shot. The other option is to replace the red laser with a green laser (from one of the laser pointers) in the hope that multiple reflections will be avoided from the mirror. Then I will have to recalibrate the set up, and see if I can get the QPD close enough to the mirror such that the spot stays within the linear regime of the QPD. More investigation needs to be done.


Plots:

QPD Calibration Plots:
QPD-XCalib.pdf            QPD-YCalib.pdf

 

 

Piezo tilt vs input voltage plots:

 

                                                          Yaw Tilt                                                                                                                                         Pitch Tilt

Piezo_Yaw_Calib-in_QPD_linear_range-Yaw_tilt.pdf               Piezo_Yaw_Calib-in_QPD_linear_range-Pitch_tilt.pdf 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ELOG V3.1.3-