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Entry  Wed May 19 22:40:19 2010, Dmass, Electronics, Doubling, Oddness with my box Plotted17.pdfMZVoltsLowAvg.pdf
    Reply  Wed May 19 23:33:18 2010, Dmass, Electronics, Doubling, Oddness with my box 
       Reply  Thu May 20 00:41:51 2010, Koji, Electronics, Doubling, Oddness with my box 
          Reply  Thu May 20 21:43:01 2010, Dmass, Electronics, Doubling, Oddness with my box 
             Reply  Fri May 21 17:42:29 2010, Dmass, Electronics, Doubling, The Box Itself MZ_Electronics.pdfMZBoxGoodPic.png
                Reply  Fri Jun 4 13:46:26 2010, Dmass, Electronics, Doubling, The Box Itself 
Message ID: 782     Entry time: Thu May 20 00:41:51 2010     In reply to: 781     Reply to this: 783
Author: Koji 
Type: Electronics 
Category: Doubling 
Subject: Oddness with my box 

Does it happen if you disconnect the IR PDs but touch the outside of the BNCs?

Quote:

Update on "The Effect" (The Voltage Noise at the Green PD Difference in my circuit changes depending on whether or not I have light on my IR PDs)

I checked the circuit a little more in detail, and I see the behavior at the output of the transimpedance amplifier for both PDs.

  • I am using LT1792
  • I short + to ground
  • I put a 50 Ohm between - and ground
  • The feedback is a 100k resistor, and a 100 pF capacitor
  • Again, the behavior is a big noise increase when the IR circuitry is going.
  • I unplugged the control signals from their respective destinations (PZT Drive box and AOM driver), but the behavior persists.
  • With the box off, and the MZ Locked, this noise is (slightly above) about the same as the "MZ Phase Noise" above 10 Hz
  • Below 10Hz the phase noise (or not this noise) is higher
  • If I disconnect the IR PDs from my box the effect is gone (I'm using the same power supply for the ISS box and my box - I was worried that I was tugging the ground around somehow)
  • I pulled EVERY op amp from the IR paths (including the feedback) - just 6 left. The effect persists.
    • The above op amps are the transimpedance amplifiers for each PD, the balancing op amps, and the sum and difference op amps.
  • If I connect either one of the IR PDs (with a terminator on the other input) into either of the inputs, the effect is there

 

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