|Start Date||Start Time||End Date||End Time|
SGP/RL/C1 - Bad shot count data
|DataStreams:||sgprlprofmerge1turnC1.c0, sgp10rlprofdep1turnC1.c1, sgp10rlprofasr1ferrC1.c1,|
sgp10rlprofmr1turnC1.c1, sgprlC1.a0, sgp10rlprofext1ferrC1.c1
The number of laser pulses averaged per profile, or shot count, exhibited erratic behavior during the periods in question. The values reported in the sgprlC1.a0 datastream were incorrect and varied radically from profile to profile. Shot counts are used in the Merge VAP to compute photon count rates, which are then used by all the other RL VAPs. Thus, the shot count problem renders all of the RL VAPs bad or suspect during the periods in question. It appears that the problem was caused as the signal on the line between two triggering units got noisier over time, causing the second unit to occasionally trigger on noise. The second unit triggers the Licel electronics. So the false triggering on the second unit caused false shot count readings. On 6 October 2011 the trigger level was adjusted by the on-site technician, and this solved the problem. On 3 May 2012 the DG535 pulse generator, which is used to trigger the Licel data recorders, was swapped out with a spare. After installation of the spare, the system started recording erroneous values of shot counts. The problem was fixed on 12 June 2012 when the on-site tech increased trigger level on the DG535.