A chart in an excursion report is a display of raw readings; its appearance changes with scale and summarisation. Before interpreting an event, check which data produced the chart and how it was plotted.
Read the chart settings
Note the time-axis start and end, temperature-axis range, logging interval and any averaging window. A wide axis can compress small changes; averaging can smooth a brief peak. An undisclosed recording interval or data gap also makes event duration harder to interpret.
Compare the summary with raw data
Review the same period first as raw readings and then in the summary chart. Check that sensor identity and timestamps are consistent. If calculating time above a threshold, account for the logging interval and gaps; do not present a missing interval as continuous measurement.
Keep the supporting information
Retain the raw file, unit, logging interval, sensor details, chart-axis limits and averaging settings. Match the graph to the product lot and operating records. This preserves the basis for interpretation if the same event is later plotted at another scale.
