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40m Log |
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Wed Dec 23 16:34:25 2009, Koji, Update, IOO, MCT QPD/MC REFL QPD disabled
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Thu Dec 24 19:13:29 2009, Koji, Update, IOO, MCT QPD investigation
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Sun Dec 27 23:44:59 2009, rana, Update, Electronics, MCT QPD investigation
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Mon Dec 28 01:17:01 2009, Koji, Update, Electronics, MCT QPD investigation
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Message ID: 2454
Entry time: Sun Dec 27 23:44:59 2009
In reply to: 2451
Reply to this: 2455
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Author: |
rana |
Type: |
Update |
Category: |
Electronics |
Subject: |
MCT QPD investigation |
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Quote: |
I found that MCT QPD has dependence of the total output on the position of the spot. Since the QPD needs the supply and bias voltages from the sum/diff amp, I could not separate the problems of the QPD iteself and the sum/diff amplifier by the investigation on Tuesday. On Wednesday, I investigated a generic quad photodiode interface module D990692.
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This is indeed sad. But, we can perhaps bypass all of this by just using the individual segment outputs. According to the circuit diagram and the c1iool0 .db file, we should be able to just do the math on the segments and ignore the VERT/HOR/SUM signals completely. In that case, we can just use high impedance for the sum/diff buffers as Koji says and not suffer from the calibration errors at all I think. |