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Entry  Tue Jul 14 16:52:47 2020, gautam, Update, Electronics, Coil drivers for the test masses coilDriverSchem.pdf
    Reply  Wed Jul 15 21:08:43 2020, gautam, Update, Electronics, ETM coil outputs DQed CDS.pngcoilOutDQed.png
    Reply  Mon Jul 20 17:23:46 2020, gautam, Update, Electronics, Coil drivers for the test masses ALSlock_timeDomain.pdfALSlock.pdfRFlock.pdf
Message ID: 15480     Entry time: Tue Jul 14 16:52:47 2020     Reply to this: 15488   15494
Author: gautam 
Type: Update 
Category: Electronics 
Subject: Coil drivers for the test masses 

Summary:

Koji and I had a discussion last Friday about the suspension electronics. I think there are still a few open questions - see Attachment #1. We should probably make a decision on these soon.

Other useful links:

  1. High-voltage coil driver circuit - D1900163
    • This board is ready to be fabricated and tested on the bench.
    • The way the connectors J2 and J3 are designed currently is meant to interface with the existing coil driver electronics.
    • Depending on the eventual coil driver we choose for the fast path, it may be benificial to change the signals on the connectors J2 and J3, to avoid the need for a custom interface board.
  2. HAM-A coil driver noise analysis.
    • The linked attachment evaluates the noise for the design value of the fast path series resistor, which is 1.2 kohms.
    • Iff we still have ambitions of measuring ponderomotive squeezing, we will need the resistance to be much higher, ~10 kohms (in the linked noise budget, only the Johnson noise of the series resistor is considered, but in reality, the OpAmp voltage and current noises also matter). 
    • This corresponds to a maximum current of 10V/10kohms = 100uA
    • Looking at signals to the ETMs from the current lock acquisition sequence, the RMS current to a single coil is approximately _____ (to be filled in later).
    • So we may need a version of the fast coil driver that supports a low noise mode (with large series resistance) and a high-range mode (with lower series resistance for lock acquisition).
  3. You can follow the links to DCC entries for other parts from Attachment #1.
Attachment 1: coilDriverSchem.pdf  548 kB  Uploaded Tue Jul 14 17:54:19 2020  | Hide | Hide all
coilDriverSchem.pdf
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