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Entry  Fri Oct 4 13:41:44 2019, anchal, Notes, FSS, FSS Plant Model FSS_Plant_Zero_Sim.pdfPlantModel.pdfPlantModel.zip
    Reply  Fri Oct 4 14:56:42 2019, Ian MacMillan, Notes, FSS, FSS Plant Model PlantModelCircuit.pdf
       Reply  Tue Oct 8 10:41:43 2019, anchal, Notes, FSS, FSS Plant Model 
          Reply  Mon Oct 14 12:54:41 2019, anchal, Notes, FSS, FSS Plant Model v2 FSS_Plant_Zero_Sim.pdfPlantModelv2.pdfPlantModelv2.zip
             Reply  Tue Oct 22 13:07:45 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 PlantDig.pdfEOM_Transfer_Function.pdfPZT_Transfer_Function.pdf
                Reply  Thu Oct 24 11:42:06 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 
                   Reply  Tue Dec 3 17:27:54 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 IMG_8065.jpegIMG_8069.jpeg
                      Reply  Mon Dec 9 18:08:13 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 OutputGraphsTransferFunction.pdf_Circuit_Design_V1.zip
                         Reply  Tue Dec 10 11:57:58 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 IMG_8124.jpeg
                            Reply  Thu Dec 12 11:54:11 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 PZT_LowFq_V1.pdfPZT_HighFq_V1.pdfEOM_LowFq_V1.pdfEOM_HighFq_V1.pdf
                               Reply  Thu Dec 12 19:05:33 2019, rana, Notes, FSS, FSS Plant Model v2 
                                  Reply  Mon Dec 16 09:43:56 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 PZT_TF.pdfEOM_TF.pdfNon-Moku_Data_PlantCir_V1.zip
                                     Reply  Tue Jan 14 13:30:39 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 EOM_TF_V1.pdfPZT_TF_V1.pdfPlant_CIR_TF.zip
                                        Reply  Tue Jan 14 13:32:16 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 FSSPlantModelV2SCH.pdfFSSPlantModelV2.pdfPlant_Circuit_Board_Eagle.zip
                                           Reply  Tue Jan 28 13:27:25 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 LIGO-D2000020-v1.pdfBOARD_LIGO-D2000020-v1.pdfEagle_LIGO-D2000020-v1.zip
                                              Reply  Mon Feb 10 12:46:17 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 
                                              Reply  Fri Feb 14 16:46:47 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 TFAG4395A_14-02-2020_155048.pdfTFAG4395A_14-02-2020_165608.pdf
                                                 Reply  Tue Feb 18 15:42:46 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 PZT_TF_V1.pdfEOM_TF_V1.pdfTransfer_Functions_FSS.zip
                                                    Reply  Tue Mar 3 17:13:04 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 image.pngPLT_Spectrum.pdf20200303_IanSimPlant.zipPLT_Spectrum.pdfPLT_TF.pdf
                                                       Reply  Wed Mar 11 15:40:50 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 TFSR785_06-03-2020_135844_PZT.pdfTF_V1.zip
                                                          Reply  Thu Mar 12 16:21:49 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 TFSR785_10-03-2020_175129.pdfTFSR785_10-03-2020_175129.txt
                                                          Reply  Thu Mar 12 17:18:51 2020, rana, Notes, FSS, FSS Plant Model v2 
Message ID: 2550     Entry time: Tue Mar 3 17:13:04 2020     In reply to: 2541     Reply to this: 2554
Author: Ian MacMillan 
Type: Notes 
Category: FSS 
Subject: FSS Plant Model v2 

Anchal and I connected the circuit to the EOM and PZT in a closed loop (LIGO-D040105). We looked at the output as seen in the Oscilloscope data and it does not look like the sinusoid that I was expecting. It looks like the sum of a square wave and a misshapen sinusoid. I think that there is some sort of reflection of the signal that is causing this but I don't know where. When we took the spectrum of that data and we saw a large peak at around 2kHz and then harmonics of the signal. (Note there are two spectrums both with the same data just one is on a log-log scale)

We also measured the open-loop transfer function of the circuit and the results are given below. The unity gain frequency is 1240 Hz. This is different from the 2688 Hz that is the location of the first peak in the spectrum. We had thought that maybe these harmonics were a result of the UGF but they don't occur at the same frequency.

We will try to figure out why we have harmonics and what we can do to prevent them. We really have no idea what they are.

Attachment 1: image.png  29 kB  | Hide | Hide all
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Attachment 2: PLT_Spectrum.pdf  20 kB  | Hide | Hide all
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Attachment 3: 20200303_IanSimPlant.zip  310 kB
Attachment 4: PLT_Spectrum.pdf  15 kB  Uploaded Wed Mar 4 13:25:08 2020  | Hide | Hide all
PLT_Spectrum.pdf
Attachment 5: PLT_TF.pdf  18 kB  Uploaded Wed Mar 4 15:13:31 2020  | Hide | Hide all
PLT_TF.pdf
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