Date: Tue, 3 Aug 2004 17:32:44 -0700 (PDT)
From: Constance Rockosi
Subject: Re: 2.5m obslog 20040802 (MJD 53220)
Below are responses to some of the issues from last night's log.
On Tue, 3 Aug 2004, Pete Newman wrote:
> Spectro camera r2, which was working during the afternoon, started
> delivering all pixels reading 65535.  We power-cycled all components of sp2,
> then issued an iack.  The next bias showed b2 messed up by the power cycle and
> r2 now reading all zeros.  Another bias showed b2 looking close to normal and
> r2 still zeros.  We issued another iack and tried again, recalling the the day
> crew recently required several iack's on the imager to get its cameras back to
> normal.
This multiple-iacks-required incident turned out to be user error after
re-setting the voltages once the powersupply was fixed.  It takes of
order 5 minutes for the imager to get done checking all its voltages and
replacing the bad values with the new, good ones.  During that time,
it still reports errors on the bad values.  So you have to be patient
when checking after fixing something.  But there is no evidence that
anything was or is wrong.
> The imager coughed and spluttered before starting.  The first goDrift of the
> night complained that amplifier voltages were not at their nominal operating
> values, despite watcher and cc nn vcheck's showing they were.  That goDrift was
There is some nomenclature confusion here.  The "nominal" VDD values for
taking data are about 24.3V.  When they are in the "low" state, the VDDs
are set close to the VRD values, at about 15.4V. The 31 VCHECK recorded
in the log says that the VDDs (amplifier) voltages were, indeed, in their
low state, and that they were measured to be where the imager thought
they were set (no "*" by the measured value").
VRD2          223      13.99 V       14.02 V        870
VRD1          223      13.99 V       13.95 V        870
VDD2          150      15.43 V       15.39 V        772
VDD1          150      15.43 V       15.46 V        772
However, I can understand where the confusion comes from given the other
common use of the word "nominal," the value of the voltage that
the imager expects to measure (and which you see plotted and displayed by
the watcher).  That "nominal" value for VDD, in this case, is 15.43 volts,
but the "nominal" value for taking data is 24.3V.  So, sorry.  But
goDrift was correct -- the amplifiers were off, so you couldn't have taken
useful data.
> quit without resetting anything.  However, on issuing an iack, the imager
> immediately began spewing forth data.
That is because goDrift issues a STOPSCAN before it gets to the point
where it checks the amplifier voltages.  An iack issues a STARTSCAN, so
the camera then started sending pixels to the DA.
> another started with the same result.  Eventually, we decided the imager's
> amplifiers hadn't been "turned on" following the most recent PSU failure, so
> we issued a setImagerAmpsOn command, and the next goDrift started correctly
> (and with clearly different gains judged from the noise seen on the monitors)
hooray for the new and improved scrolling display stretch!
I hope tonight is considerably less exciting than last.
--connie