Reports until 18:30, Thursday 28 April 2016
H1 CDS
patrick.thomas@LIGO.ORG - posted 18:30, Thursday 28 April 2016 - last comment - 10:35, Friday 29 April 2016(26866)
Corner Station Beckhoff down
Patrick, Matt, Kiwamu, Vern

We tried testing some code changes for the rotation stage. They didn't seem to work, so I reverted the change to the Laser Power library and went through the GUI to start afresh (copy new code from target directory, compile, run, etc.). Now everytime I do this I get a divide by zero error. (see attached).

Did someone change the code in PLC1 that introduced a divide by zero error, and not run it until we tried to now? Or did I somehow do this?
Images attached to this report
Comments related to this report
patrick.thomas@LIGO.ORG - 19:10, Thursday 28 April 2016 (26869)
Seem to be fixed by recompiling PLC1. I've burtrestored PLC1, PLC2 and PLC3 to 6:10 this morning (local time).
sheila.dwyer@LIGO.ORG - 19:37, Thursday 28 April 2016 (26870)

Here are two examples of locklosses when powering up from the last 24 hours.  The first one shows the rotation stage moving in a jerky way, this was an example of a time when the velocity was changed before the request was made, but is worse than the normal "moving in the wrong direction" problem.  You can see that the accelerometers on the PSL all have glitches when the rotation stage angle encoder records a change in angle. 

In the second example the rotation stage velocity moves smoothly, and the power changes smoothly, but we have a lockloss which could be ASC related.  

Images attached to this comment
daniel.sigg@LIGO.ORG - 08:01, Friday 29 April 2016 (26873)

One thing to remember is that TwinCAT will try to reuse its previously stored values of variables, when you log in with a slightly modified code. Generally, this is a good thing, but it can fail with an internal variable restored to a value which leads to a divide by zero error. You need to login and use the Reset (clear all variables except the persistant ones), or Reset All  (clear all variables). In the later case, you definitely need a SDF/burt restore.

patrick.thomas@LIGO.ORG - 10:35, Friday 29 April 2016 (26878)
I had tried logging in with the PLC and resetting the variables.