Lynn's Industrial Protocols over IP

Saturday, January 06, 2007

Real Numbers (Part 2) - Modbus/RTU over cellular

My previous post covered Modbus/RTU polls once per 30 seconds. Here is a second set of results for 24 hours with polling once every 60 seconds.
  • Of 1440 polls, only 3 failed responses with a 30 sec timeout.
  • Fastest poll was 451 msec round-trip (1/2 sec)
  • Slowest poll was 10,407 msec round-trip (10.5 sec)
  • Statistical average of successful polls was 1748 msec
  • In chart below, white dots are round-trip times and black line is the moving average over a 15-minute period.
  • Notice a few interesting trends; such as the very fast response around 11am and again around 3am the next morning.
24 hours chart
(Click the image to see a large version)
(Click here to download ZIP file with Excel and OpenOffice spreadsheet of times)

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