There is a limit to how many devices you can fit on a FOUNDATION Fieldbus network. This article will tell you about how to calculate your limit. To calculate the number of devices you can have in your segment, you need to guarantee at least nine volts at the end of the cable. If you push past that, you may start having problems getting your field devices to communicate with the control room.

RID14 Indication of up to 8 process or calculated values for FOUNDATION Fieldbus or PROFIBUS PA protocol
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What is needed?

  • The maximum current of each device
  • The length of the segment (and voltage drops along the cable)

Then you use Ohm’s law. The device needs at least nine volts sent to the back end of the segment. Theoretically, the segment can power 32 devices that pull 10 milliamps each, but now it can only support 23 devices. Some users avoid current limiting couplers, and most would limit each segment to 16 devices to prevent large scale failures.

To know more about FOUNDATION Fieldbus, please ask our engineers!

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