Histogram Monitoring

Wire occupancy histograms are monitored using a bin by bin comparison to find bins with a large deviation representing a changing wire. Instead of reporting a whole histogram as changing, the statistically different wire (by default a False Alarm Probability less than 1 × 10^-4 ) is reported along with the corresponding histogram.

Many hot or dead wires are a persistent problem over multiple data taking runs. When the Reference histograms are written, these bad wires are included, and comparison of the Sample and Reference histograms will not report them. By taking a preliminary look at the Reference histograms the user is alerted to hot or dead wires. QOD quickly scans through the Reference wire occupancy histograms and reports wires whose neighbors (one wire to the left and right) have relatively high (a hot wire) or low (dead or dying wire) occupancies. By default the neighboring wires are required to have five times the number of hits on the wire in question (see Changing Default Analysis Parameters ). This process is only carried out once, at the completion of filling the Reference histograms.