January/February 2011

ISA Certified Automation Professional (CAP) program

Certified Automation Professionals (CAPs) are responsible for the direction, design, and deployment of systems and equipment for manufacturing and control systems.

CAP question

Which H1 Level Fieldbus topology (shown here) reflects a "Tree Topology"?

A. Topology A

B. Topology B

C. Topology C

D. Topology D

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CAP answer

The correct answer is C. Tree Topology concentrates the connection of several field devices to couplers/junction boxes. Tree topology is also known as "Chickenfoot" or "Star" configuration.

A, End-to-End Topology, is used to directly connect two devices. The connection may be entirely located in the field (a transmitter and a valve with no other devices connected) or to connect a field device (a transmitter) to the Host Device.

B, Bus with Spurs Topology, uses a single bus to which devices and spurs are directly connected. Several devices may be connected to each spur. The total spur length is limited according to the number of spurs and the number of devices per spur.

D, Point-to-Point (or Daisy Chain) Topology, has all devices used in the application connected in series. The Fieldbus trunk is routed from one device to the next, being interconnected to the terminals of each Fieldbus device.

References: Ian Verhappen, CAP, P.E., and Augusto Pereira; Foundation Fieldbus, 3rd Edition, ISA, 2009.