Abstract: A fieldbus device within a fieldbus network segment comprises a functional layer and includes an integral physical layer diagnostic (PhLD) element for measuring an electrical parameter of the fieldbus network segment. Placing the PhLD element within the fieldbus device itself provides for greater accuracy in monitoring electrical characteristics of the segment.

Abstract: A process control system for a fieldbus network includes field devices having function blocks. Some distributed control systems access the standard parameters of the function blocks but cannot access manufacturers' non-standard parameters. Such parameters are placed in shared transducer blocks in the field devices where they are accessed by an alternate system for configuration and for collecting and monitoring data. This enables use by the function blocks of both standard and manufacturers' specific parameters and enables function blocks with only standard parameters to facilitate non-standard inter-function block communication connections using the shared transducer block parameters.

Abstract: A short circuit detector for a fieldbus network which includes power/data wires that are typically positive and negative, respectively, and a shield conductor connected to a ground includes first and second high-impedance semiconductor circuits coupled between each of the leads and the shield conductors. Both circuits may either have a dedicated alarm indicator which indicates the presence of a short circuit between that conductor and the shield and/or may be coupled together to an alarm circuit which activates an alarm whenever a short circuit exists between either of the power/data leads and the shield conductor. The alarm circuit may have a ground which is isolated from the shield ground and may thus employ an isolation device such as an opto-isolator.

Abstract: The circuit of the invention provides protection for both a spur circuit and the network while allowing other spurs on the network to continue operation and is applicable to any type of fieldbus network including both FF and ASi type networks. A control circuit monitors a current limiter coupled to each spur circuit. If the spur circuit goes into an overcurrent condition for a preset period of time, the control circuit turns it off. After a second period of time has elapsed, the control circuit turns the current limiter back on permitting current to flow in the spur once again while continuing to monitor the current limiter.

Abstract: Fieldbus is a digital, two-way communication link for remotely located sensors, controllers and actuators used in industrial applications. The fieldbus simultaneously carries a digital signal for communication with devices attached to the bus and DC power to operate those devices. Unless isolated from the fieldbus, the constant voltage DC power supply would prevent the propagation of the varying voltage of the digital communication signals on the fieldbus. An adaptive current source is provided between the output the constant voltage power supply and the fieldbus wiring to isolate the power supply. The adaptive current source can also be used to isolate the input of DC/DC voltage converters providing power to devices attached to the fieldbus.

Abstract: A current limiter is provided to protect a fieldbus network from electrical shorts in the wiring of the spur cables and network devices attached to the spur cables. In the event of an electrical short, the impedance of the current limiter and the spur connection increases permitting the remainder of the network to continue to function. To facilitate repairs, the current limiter includes an indicator that signals excessive current in the spur.

Abstract: A current limiter is provided to protect a fieldbus network from electrical shorts in the wiring of the spur cables and network devices attached to the spur cables. In the event of an electrical short, the impedance of the current limiter and the spur connection increases permitting the remainder of the network to continue to function. To facilitate repairs, the current limiter includes an indicator that signals excessive current in the spur.

Abstract: A current limiter is provided to protect a fieldbus network from electrical shorts in the wiring of the spur cables and network devices attached to the spur cables. In the event of an electrical short, the impedance of the current limiter and the spur connection increases permitting the remainder of the network to continue to function. To facilitate repairs, the current limiter includes an indicator that signals excessive current in the spur.

Abstract: An interface circuit for coupling a drop port to a trunk line carrying data processing signals, includes a transformer network connected between the trunk line and that drop port and a resistor network connected between the trunk line and the drop port wherein the resistor network includes a non-linear switching circuit for attenuating high amplitude data processing signals from the drop port and for isolating the resistor network thereby permitting data processing signals carried by the trunk line to be routed directly to the drop port without attenuation.