Make New Entry, Make Followup Entry
User name R. Michaels
Log entry time 15:05:13 on April23,2014
Entry number 388835
keyword=deadtime in datamon from Trig. Super.Onboard the trigger supervisors (TS) there are 2 scalers which provide a
measure of the DAQ deadtime.
To each scaler is sent an onboard pulser; one of the scalers is ungated while the
other is gated by the system Busy. I believe this works and is accurate as long as
the busy is random, but if the triggers are not random in time it is subtlely wrong.
However, it is still better than trying to use our scalers without accounting for the
correlations between triggers, something we can do offline but not online.
Now, datamon displays BOTH kinds of online deadtime, and the user can ponder what
it means. They may disagree by a bit, but the "Deadtime from Trigger Supervisor"
is supposed to be better. I think the DVCS trigger will eventually provide another
deadtime for the L-HRS. We can display that, too, when it is available.
Fig 1 and Fig 2 are for cosmics runs on L-HRS and R-HRS. Deadtime is very small.
Technical scheme: At vxWorks boot, define 2 global variables TSLive1 and TSLive2.
These are the 2 TS scalers. The CRL code writes to these periodically (every
synch event if buffered or every 200 events if not buffered). The scaler server
code picks up these global variables and makes them available to clients like
datamon.
FIGURE 1
FIGURE 2
