Date: Sat, 29 Aug 2009 15:56:09 -0600
From: Dan Long
Subject: Re: 2.5m obslog 20090828 (MJD 55072)
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Hi Steph,
    If you see evidence of it not stopping (dumping liquid) that is
another matter.  What we've seen so far is it stopping short, and
from the logs it sounds like what you've seen as well.   The behavior
seems to indicate either a faulty ground (both stopping at once), or
an overly optimistic full sensor (one of them stopping).
    If you do see evidence of it spilling liquid in auto, then let me
know and leave it in the off position after satisfying yourself that
the dewars are topped off at the end of the night.
-Dan
>Okay, Dan. Our concern about leaving it in auto was that it is the
>weekend and staffing is minimal, and we didn't know if anyone would
>be around if a fill failed to stop. However, we'll leave it in auto
>at the end of tonight.
>
>Steph
>
>On Aug 29, 2009, at 8:54 AM, Dan Long wrote:
>
>>
>>   Please leave the fill system in auto.  This will allow us to see
>>if there are false starts as well as stops.  When preparing for
>>observing, please use the normal start fill with auto stop, then
>>top off in manual and note how much additional LN2 is used.  It
>>would also be useful information to know how it stops in auto.  The
>>usual behavior is for the lower dewar (sp1 with rotator at zero) to
>>stop well before sp2.  If they stop at the same time, this is an
>>indication of a grounding problem (lack of continuity indicates to
>>the autofill system that the hoses are not connected).
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Re: 2.5m obslog 20090828 (MJD
55072)
Hi Steph,
   If you see evidence of it not stopping (dumping
liquid) that is another matter.  What we've seen so far is it
stopping short, and from the logs it sounds like what you've seen as
well.   The behavior seems to indicate either a faulty
ground (both stopping at once), or an overly optimistic full sensor
(one of them stopping).
   If you do see evidence of it spilling liquid in
auto, then let me know and leave it in the off position after
satisfying yourself that the dewars are topped off at the end of the
night.
-Dan
Okay, Dan. Our concern about leaving it
in auto was that it is the weekend and staffing is minimal, and we
didn't know if anyone would be around if a fill failed to stop.
However, we'll leave it in auto at the end of tonight.
Steph
On Aug 29, 2009, at 8:54 AM, Dan Long
wrote:
  Please leave the fill system in auto.  This
will allow us to see if there are false starts as well as stops.
 When preparing for observing, please use the normal start fill
with auto stop, then top off in manual and note how much additional
LN2 is used.  It would also be useful information to know how it
stops in auto.  The usual behavior is for the lower dewar (sp1
with rotator at zero) to stop well before sp2.  If they stop at
the same time, this is an indication of a grounding problem (lack of
continuity indicates to the autofill system that the hoses are not
connected).
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