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 Mon Dec 2 00:27:20 2019, gautam, Update, ALS, Green ALS resurrection 
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 Mon Dec 2 18:20:29 2019, gautam, Update, ALS, EY uPDH post mixer LPF
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Mon Dec 2 20:18:18 2019, rana, Update, ALS, EY uPDH post mixer LPF
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Tue Dec 3 18:15:42 2019, gautam, Update, ALS, EY uPDH post mixer LPF
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Tue Dec 3 21:28:24 2019, gautam, Update, ALS, EY uPDH post mixer LPF
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Tue Dec 3 00:10:15 2019, Koji, Update, ALS, EY uPDH post mixer LPF
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Tue Dec 3 00:51:25 2019, gautam, Update, ALS, EY uPDH post mixer LPF
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Message ID: 15059
Entry time: Mon Dec 2 18:20:29 2019
In reply to: 15058
Reply to this: 15060
15063
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| Author: |
gautam |
| Type: |
Update |
| Category: |
ALS |
| Subject: |
EY uPDH post mixer LPF |
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As part of characterization, I wanted to calibrate the EY uPDH error point monitor into units of Hz. So I thought I'd measure the PDH horn-to-horn voltage with the cable to the laser PZT disconnected. However, I saw no clean PDH fringe while monitoring the signal after the LPF that is immediately downstream of the mixer IF output. I then decided to measure the low pass filter OLTF, and found that it seems to have some complex poles (f0~57kHz, Q~5), that amplify the signal by ~x6 relative to the DC level before beginning to roll-off (see Attachment #1). Is this the desired filter shape? Can't find anything in the elog/wiki about such a filter shape being implemented...
The actual OLTF looks alright to me though, see Attachment #2. |
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