Date: Sun, 7 Nov 2010 12:31:00 -0500 (EST)
From: jegunn
Subject: Re: [SDSS3-infrastructure 4098] Re: questions
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I suspect this is the pressure issue again. The LN2 can temperatures
should be correlated with the LN2 pressure.
--jim
On Sun, 7 Nov 2010, David Kirkby wrote:
> I attached a plot of the SP1 LN2 temperatures from last night for reference.
> Both spectrographs dipped lower than usual at the time of the critical
> alert. 
> (This plot is also a sanity check that the archiver timestamps behaved
> normally, as expected, when crossing the local DST transition at 8h UTC).
>
> David
>
> On Sun, Nov 7, 2010 at 6:01 AM, Dan Long  wrote:
>          Cameras look okay now (temperatures all at nominal, 10L
>       pressure 10 psi in both).  It looks like from the dewar plots
>       that the fill at the start of the night and during observing
>       were considerably shorter than normal (10-15 lbs instead of 25).
>        Since both spectrographs stopped short, it looks like possibly
>       a grounding issue.  Bob, could you take a look today?
>
>          If by "green dewars", you are referring to the grade 5
>       nitrogen bottles next to the windbaffle controller, yes they are
>       supposed to be shut off.  With the imager gone, there is no need
>       for them to be open except when using the vacuum pump.
>
>                                      Cheers,
>
>                                        Dan
>
>
>             Corrections:
>             There was critical alert for ln2 zero pressure for
>             sp1.
>             And now, after small time, there is sp1 ln2 low
>             pressure again.
>
>
>             On Nov 7, 2010, at 5:50 AM//Nov 7, 2010,
>             alaina@apo.nmsu.edu wrote:
>
>                    Hello all
>
>                    There are 2 green dewars in the lower
>                   enclosure.  Normally one is
>                    connected at all times and reads some
>                   pressure.  Tonight it looks like one
>                    is empty and one is full, but the full
>                   one is not connected.  Is this on
>                    purpose?  If so, we won't worry about
>                   it.
>
>                    Also, we had to fill the BOSS
>                   spectrographs in the middle of the
>                   night,
>                    specifically sp2.  It was ok for a few
>                   hours, and now it is reading low
>                    again.  In the camera monitor, it reads
>                   between 4 and 5 when it should
>                    read 10.  Could someone please have a
>                   look at it?
>
>                    Thanks
>                    Alaina and Elena
>
>
>
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