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| 40m Log |
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 Fri Nov 7 10:52:57 2008, steve, Update, PEM, AC is back on 
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 Fri Nov 7 15:58:10 2008, rana, Update, PEM, AC is back on
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Mon Nov 10 19:39:40 2008, steve, Update, PEM, thump noise from particle counter
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Tue Nov 12 23:05:06 2013, rana, Update, PEM, thump noise from particle counter
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Wed Nov 13 11:30:07 2013, Steve, Update, PEM, particle counter MOVED
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Message ID: 1129
Entry time: Mon Nov 10 19:39:40 2008
In reply to: 1122
Reply to this: 9369
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| Author: |
steve |
| Type: |
Update |
| Category: |
PEM |
| Subject: |
thump noise from particle counter |
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The particle counter is back on the IOOC location on a piece of FOAM
It needs this isolation, so when the pump is running, it's not shaking things.
The counter was counting for 6 sec and it was on holding for 20 mins.
Now I set the counter for 20 sec so it is easy to recognise it's signal and it holds for 2min only.
This will set the alarm handler in action.
Atm1: 40 mins plot
PEM-ACC_MC2_x,y,z up to 13 mins: pcounter at MC2 table, clamped, counting for 20s and holds for 2 mins
PEM-ACC_MC2_x,y,z from 13 to 26 mins: pcounter at MC2 table, not clamped, seated on 2" foam, counting 20s and holds for 2 mins
PEM-ACC_MC1_x,y,z from 26 to 40 mins: pcounter at MC1_IOOC location, not clamped, seated on 2" foam, counting 20s and holds for 2 mins
Rana won the bet
| Quote: | I'll bet Steve a dollar that it is mechanical. The attached PDF compares all of the accelerometers from right now.
You can see that the RMS in MC2 is way bigger than MC1.
In the second PDF file you can see the time series. I had to play around a lot with DTT to get it to work. The DTT/Foton
combo on Allegra is not stable, so make sure your work early and often.
In the plots shown, I am bandpassing the time series from 600-700 Hz. I found that doing so allowed the burp in MC1 to remain
large and reduce the extraneous fuzz in MC2. As you can see there is no such noise in MC2.
So its a noise around 600-700 Hz that comes on quickly and then shuts off after several seconds. Its also very periodic in that
it comes on around every 20 minutes. Steve also tells me (although he refuses to put in the elog) that it started up around
August 20th (?). I feel like someone in the 40m lab ought to be able to guess what this is at this point.
Please convince Steve to elog his findings about when the noise started.
If one goes out there and stands next to it when the trend predicts its happening it becomes clear what it is. |
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