Honeywell International Inc.
Apparatus and method for diagnosing faults in a fieldbus interface module

Abstract:

A method and system for detecting faults in a communication interface is disclosed. The communication interface is connected to a field device and a device bus comprising generating periodic diagnostic pulse by a programing unit. The programming unit is communicatively connected to the controller and a controller interface and provides the diagnostic pulse to a multiplexer to periodically apply the diagnostic pulses from the programming unit to a first winding of a transformer. The programming unit provides the diagnostic pulse to the isolation unit. A sensing unit senses a voltage drop across a sense resistor, the sensing unit having an input connected to the sense resistor and an output connected to the programming unit. The sensing unit communicates a sense signal based on the comparison to the programming unit, and switches from a primary or a secondary module to the other based on the sense signal.