In order to access the core monitoring data (i.e. the raw data of each monitoring cycle) that PRTG Traffic Grapher acquires from a device you can export the data into CSV files.
If you enable the CSV export (in each sensor's settings) you will get a daily CSV logfile for each sensor with the results of each refresh cycle. The file is placed in the daily subfolders ("yyyymmdd") of your PRTG monitoring data folder named "{sensorid}.csv" (e.g. "{D7BB45A1-0550-4201-93AF-F6EADFEC2D05}.csv").
The file uses standard CSV format, can be loaded with e.g. Excel or Notepad and looks like this (note: the first line was wrapped):
"date","time","timecode (seconds since 2000/1/1)",
"kbits_per_sec_in","kbits_per_sec_out","bytes_in","bytes_out"
"2003-12-31","12:57:59","126190679",18,27,2014,2948
"2003-12-31","12:58:03","126190683",56,24,32843,11954
"2003-12-31","12:58:08","126190688",7,4,4325,2759
"2003-12-31","12:58:13","126190693",74,204,51161,140067
"2003-12-31","12:58:18","126190698",133,20,74608,11260
"2003-12-31","12:58:23","126190703",55,116,34203,72308
"2003-12-31","12:58:28","126190708",181,56,113430,34827
"2003-12-31","12:58:33","126190713",17,7,10415,4134
As usual for CSV files the first line contains a short description of the columns. The columns are:
For traffic sensors:
For other sensors: