Subject: Re: [sloan-25mlog 4353] 2.5m obslog 20190122 (SJD 58506)
From: jdowney
Date: Wed, 23 Jan 2019 16:53:19 -0700
> 2. We noticed that temperatures of SP1 and SP2 differ by more than 2 C. Checking
> records in  past 10 days, the difference run for 0.2C to 2.4 C. An sensor issue?
>
The last time we had this problem, it was the IC that drives the
sensors.  There are six temperature sensors per spectrograph, and when
James checked their readings, all six in each were of approximately the
same order of magnitude, indicating that the higher ones probably have
an in correct or wandering reference signal from the IC.
The earliest we should repair this is the next engineering time, as it
requires powering off the specmech box, which will then require homing
the collimator and re-collimating.  If the difference remains as slight
as this, we could consider putting it off until summer if the night
staff prefer that.