FIELD

The present disclosure relates generally to industrial process control and automation systems. More specifically, this disclosure relates to the diagnosis of faults in the fieldbus interface module of a process control system.

BACKGROUND

In an industrial process control system, an interface module is incorporated to communicate between the control system and plurality of field devices. Interface modules communicate in different protocols. Different protocols are suitable for different purposes. Protocols are widely used for industrial process control and automation, such as to interconnect sensors, actuators, and input/output (I/O) of controllers in an industrial facility. Different protocol systems are often deployed as digital I/O networks for proprietary controllers. This protocol enables two-way communication between field devices and the control system. One such protocol used for communication in an industrial control system is Foundation Fieldbus. Interface modules used in the Foundation Fieldbus protocol are generally known as fieldbus interface modules (FIM). The FIM integrates the Foundation Fieldbus to the field devices connected with a control system. In some instances, these interface modules can become faulty and fail to communicate in the desired manner. There may be various reasons for faults originating at the FIM including faulty internal hardware or external factors such as connectors, cables or terminations. Loss of control of field devices is an important concern in a Foundation Fieldbus system design. An important area where loss of control occurs is in the redundancy function of a FIM.

FIMs are typically implemented in redundant pairs. In redundant pair configuration, one of the FIM performs the functions as a primary FIM and the other functions as the secondary. In this redundancy configuration, the primary and the secondary FIM work in sync. The primary FIM is responsible to communicate the instructions from the control system to the field devices. The secondary FIM is disposed to take charge of the communication in the field link between the control system and the field devices if the primary FIM fails. Accordingly, it becomes imperative to ascertain any potential fault in a FIM in order to trigger the changeover to its redundant partner. However, in existing FIMs, it is difficult to differentiate between hardware failures in the FIM from failures induces by noise on the field link. Thus, it becomes difficult to ascertain the actual origin of the fault.

Therefore, there arises a need for diagnostics, that can be embedded in the FIM, to determine a FIM hardware fault. This fault detection would ensure seamless and reliable communications between the FIM and the field devices.

SUMMARY

In accordance with an embodiment, the present disclosure relates to an apparatus for detecting faults in a fieldbus interface module. The fieldbus interface module is connected to a field device and a device bus. The interface module comprises, a controller configured to generate a device bus communication signal TXE, and a programming unit communicatively connected to the controller and a controller interface. The programming unit is configured to detect faults in the fieldbus interface module and generate periodic diagnostic pulses. A transformer has a first winding connected to the controller interface and a second winding connected to the device bus. A multiplexer is connected to the programming unit and configured to periodically apply the diagnostic pulses from the programming unit to the first winding of the transformer. An isolation unit is also connected to the programming unit that is configured to periodically apply the diagnostic pulses from the programming unit to the transformer's second winding. A sense resistor is connected in series between the first winding of the transformer and a sensing unit. The sensing unit connects to the programming unit and is arranged to determine the voltage across the sense resistor whereby the sensed voltage is communicated to the programming unit.

