Patent Publication Number: US-11650582-B2

Title: Gated asynchronous multipoint network interface monitoring system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/947,716 filed on Apr. 6, 2018, entitled “Gated Asynchronous Multipoint Network Interface Monitoring System, which is hereby incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Many industries, such as hydrocarbon refining and power generation, can rely heavily upon operation of machinery, and in some instances, continuous operation of machinery. In these environments, failure of one or more machines can incur significant costs due to repair expenses as well as loss of production and potential injury to workers. Given these risks, it can be common to monitor certain operating parameters of one or more machine components. Measurements of the operating parameters can provide an indication of the mechanical condition of a machine component, allowing preventative maintenance (e.g., repair, replacement, etc.) to be performed on the machine component prior to failure. This monitoring can provide one or more long term benefits, such as lower production costs, reduced equipment down time, improved reliability, and enhanced safety. 
     SUMMARY 
     Systems, devices, and methods for monitoring operating conditions of machines are provided. In one embodiments, a monitoring system is provided that includes a bus having a plurality of coupling elements in electronic communication with at least one data lane. The monitoring system can also include at least one slave circuit that can be detachably coupled to at least one of the plurality of coupling elements. The at least one slave circuit can be configured to deliver data to the at least one data lane. The slave circuit can have at least one first gate configured to enable electronic communication between the slave circuit and the at least one data lane. The at least one first gate can be configured to operate in a first operating mode and in a second operating mode. The at least one first gate can configured to allow data to be transferred from the slave circuit to the at least one data lane when in the first operating mode, and the at least one first gate can be configured to prevent data from being transferred from the slave circuit to the at least one data lane when in the second operating mode. The monitoring system can also include a master circuit that can be detachably coupled to at least one of the plurality of coupling elements. The master circuit can be configured to deliver data to the at least one data lane. The master circuit can have a first schedule controller configured to generate a first schedule and deliver data characterizing the first schedule to the at least one data lane. The first schedule can specify when the at least one first gate is in the first operating mode and when the at least one first gate is in the second operating mode. 
     The monitoring system can vary in a number of ways. One or more of the following features can be included in any feasible combination. For example, in one embodiments, the at least one slave circuit can include at least one first gate controller in electronic communication with the at least one first gate. The at least one first gate controller can be configured to receive data characterizing the first schedule and to control operation of the at least one first gate based on the data that characterizes the first schedule. 
     In some embodiments, the at least one slave circuit can include a second schedule controller that can be configured assume arbitration responsibilities, thereby enabling the second schedule controller to generate a second schedule that defines when the at least one first gate is in the first operating mode and when the at least one first gate is in the second operating mode. 
     In some embodiments, the master circuit can include at least one second gate that can be configured to enable electronic communication between the master circuit and the at least one data lane. The at least one second gate can be configured to operate in a third operating mode and in a fourth operating mode. The at least one second gate can be configured to allow data to be transferred from the master circuit to the at least one data lane when in the third operating mode, and the at least one second gate can be configured to prevent data from being transferred from the master circuit to the at least one data lane when in the fourth operating mode. The master circuit can also include at least one second gate controller in electronic communication with the first schedule controller and the at least one second gate. The at least one second gate controller can be configured to receive data that characterizes the first schedule, and to control operation of the at least one second gate based on the first schedule. 
     In some embodiments, the at least one slave circuit can include a plurality of slave circuits. Each slave circuit of the plurality of slave circuits can be configured to receive data from the at least one data lane of the bus. 
     In some embodiments, the monitoring system can include a sensor that can be electrically coupled to the at least one slave circuit. The sensor can be configured to measure operating parameters of a machine and to deliver data characterizing the measured operating parameters the at least one slave circuit. 
     In some embodiments, the monitoring system can include a sensor in electronic communication with the master circuit. The sensor can be configured to measure operating parameters of a machine and to deliver an analog sensor signal to the master circuit. The analog sensor signal can characterizing the measured operating parameters of the machine. 
     In some embodiments, the slave circuit can be configured to receive a discrete signal from at least one sensor measuring operating parameters of a machine, generate a digital signal based on the discrete signal, and deliver the digital signal to the at least one data lane. 
     In some embodiments, the master circuit can include an analog to digital converter configured to receive the analog sensor signal and convert the analog sensor signal to a digital sensor signal. 
     In some embodiments, the at least one data lane can include a plurality of parallel data lanes. 
     In some embodiments, the at least first one gate can include a 16 lane bidirectional differential transceiver. 
     In some embodiments, the at least one second gate can include a 16 lane bidirectional differential transceiver. 
     In some embodiments, the at least one data lane can include 16 data lanes. Each of the 16 data lanes can be a low voltage signaling pair. 
     In another aspect, a method is provided that includes generating a first schedule for a first frame that includes at least one first time sliced. The first schedule can identify the at least one first time slice and at least one slave circuit to which the at least one first time slice is assigned. The at least one slave circuit can be configured to provide a data packet to a bus of a monitoring system during the at least one first time slice. The method can also include generating a first beacon packet that includes the first schedule, delivering the first beacon packet to the bus of the monitoring system, and receiving the first beacon packet at the at least one slave circuit. The method can also include generating a first set of instructions for controlling operation of at least one gate of the at least one slave circuit based on the at least one first time slice that is assigned to the at least one slave circuit. The at least one gate can be configured to operate in a first operating mode and in a second operating mode. The at least one gate can be configured to allow data to be transferred from the at least one slave circuit to the bus when in the first operating mode, and the at least one gate can be configured to prevent data from being transferred from the at least one slave circuit to the bus when in the second operating mode. The method can also include providing the first set of instructions to a gate controller of the at least one slave circuit, thereby configuring the gate controller to operate the at least one gate in the first operating mode during the at least one first time slice. 
     The method can vary in a number of ways. One or more of the following features can be included in any feasible combination. For example, in some embodiments, the first schedule can be generated by a schedule controller of a master circuit that is coupled to the bus. 
     In some embodiments, the method can include providing a data packet from the at least one slave circuit to the bus during the at least one first time slice. 
     In some embodiments, the method can also include determining that the at least one slave circuit failed to provide a data packet to the bus during the at least one first time slice. 
     In some embodiments, the method can also include generating a beacon response packet based on the first schedule received with the first beacon packet. The beacon response packet can include a request for at least one second time slice to be assigned to the at least one slave circuit during a second frame. The method can also include delivering the beacon response packet to the bus of the monitoring system, and receiving the beacon response packet at a master circuit, the master circuit being configured to generate a second schedule for the second frame. 
     In some embodiments, the method can include generating the second schedule for the second frame based on the beacon response packet. The second frame can include the at least one second time slice. The second schedule can identify the at least one second time slice and the at least one slave circuit to which the at least one second time slice is assigned. 
     In some embodiments, the method can include generating a second beacon packet that includes the second schedule. The method can also include delivering the second beacon packet to the bus of the monitoring system, receiving the second beacon packet from the bus of the monitoring system, and generating a second set of instructions for controlling operation of the at least one gate of the slave circuit based on the at least one second time slice that is assigned to the slave circuit. 
     In some embodiments, the method can include delivering the second set of instructions to the gate controller of the slave circuit, thereby configuring the gate controller to operate the at least one gate in the first operating mode during the at least one second time slice. 
     In one embodiment, a system can include a bus and a master circuit detachably coupled to the bus. The master circuit can include a manager bus node configured to interface with a first data lane of the bus. The system can also include a plurality of slave circuits detachably coupled to the bus. A first slave circuit of the plurality of slave circuits can include a first slave bus node configured to interface with the first data lane. The master circuit can be configured to broadcast a first beacon packet during a first time slice of a first plurality of time slices to the bus. The first beacon packet can include a first system frame schedule indicative of an assignment of the first plurality of time slices of a first system frame to one or more of the plurality of slave circuits. The first plurality of time slices can be temporally arranged relative to a first system frame reference time. The master circuit can also be configured to receive one or more beacon response packets from one or more of the plurality of slave circuits during a second time slice of the first plurality of time slices. The first time slice can be temporally adjacent to the first system frame reference time and the second time slice can be temporally adjacent to the first time slice. 
     In one embodiment, the first slave circuit can be configured to receive the first beacon packet and configure the first slave bus node to transmit data packets to the first data lane during a third time slice of the first plurality of time slices. The first system frame schedule can be indicative of assignment of the third time slice to the first slave circuit. 
     In one embodiment, the master circuit can be further configured to determine a set of valid beacon response packets from the one or more beacon response packets received during the second time slice. The master circuit can also be configured to generate a second beacon packet including a second system frame schedule indicative of assignment of a second plurality of time slices of a second system frame to one or more of the plurality of slave circuits. Assignment of the second plurality of time slices can be based on time slice requests in the set of valid beacon response packets. 
     In one embodiment, the determination of the set of valid beacon response packets can be based on transmission collisions of the one or more beacon response packet in the first data lane of the bus. In another embodiment, the second plurality of time slices can be temporally arranged relative to a second system frame reference time. In yet another embodiment, the first slave bus node can include a first node controller, a first gate controller and a first plurality of gates. The first gate controller can configure one or more gates of the first plurality of gates to transmit data packets from the first node controller to the first data lane. 
     In one embodiment, the master circuit can assign of a fourth time slice of the second plurality of time slices to a second slave circuit of the plurality of slave circuits based on a unique identification of the second slave circuit in a second beacon response packet broadcasted on the first data lane by the second slave circuit. In another embodiment, the master circuit can be further configured to cancel the assignment of the fourth time slice to the second slave circuit based on inactivity of the second slave circuit during one or more time slices assigned to the second slave circuit. 
     In one embodiment, the second beacon packet can be generated at an application layer executed in a slave circuit controller in the second slave circuit. In another embodiment, the second slave circuit can include a second slave circuit clock, and the second slave circuit can be configured to synchronize the second slave circuit clock based on one or both of the first system frame reference time and the second system frame reference time. In another embodiment, the first slave bus node can be further configured to maintain a copy of the first beacon packet. In yet another embodiment, the first time slice can include a dead band and a usable time slice period. 
     In one embodiment, the master circuit can be configured to broadcast the first beacon packet during the usable time slice period, and configured to prevent broadcast of the first data packet during the dead band. In another embodiment, the first plurality of time slices can include one or both of an unassigned time slice and a best-effort time slice. The master circuit can be configured to discard data packets broadcasted by one or more slave circuits of the plurality of slave circuits during the unassigned time. The one or more slave circuits of the plurality of slave circuits can broadcast an asynchronous application layer event during the best-effort time slice. 
     In one embodiment, a method can include broadcasting a first beacon packet during a first time slice of a first plurality of time of a first system frame slices to a first data lane of a bus. The first beacon packet can include a first system frame schedule indicative of assignment of the first plurality of time slices to one or more of a plurality of slave circuits coupled to the bus. The first plurality of time slices can be temporally arranged relative to a first system frame reference time. The method can also include receiving one or more beacon response packets from one or more of the plurality of slave circuits during a second time slice of the first plurality of time slices. The first time slice can be temporally adjacent to the first system frame reference time and the second time slice can be temporally adjacent to the first time slice. The method can further include generating a second beacon packet including a second system frame schedule indicative of assignment of a second plurality of time slices of a second system frame to one or more of the plurality of slave circuits. The method can also include providing the second beacon packet to the one or more of the plurality of slave circuits. The broadcasting, the receiving, the generating and the providing can be by a master circuit detachably coupled to the bus, the master circuit can include a manager bus node configured to interface with the first data lane of the bus. 
     In one embodiment, the method can further include determining a set of valid beacon response packets from the one or more beacon response packets received during the second time slice. Assignment of the second plurality of time slices can be based on time slice requests in the set of valid beacon response packets. In another embodiment, determination of the set of valid beacon response packets can be based on transmission collisions of the one or more beacon response packet in the first data lane of the bus. In yet another embodiment, the second plurality of time slices can be temporally arranged relative to a second system frame reference time. 
     In one embodiment, the method can further include receiving the first beacon packet by a first slave circuit of the plurality of slave circuits. The first slave circuit can include a first slave bus node configured to interface with the first data lane. The method can also include configuring the first slave bus node to transmit data packets to the first data lane during a third time slice of the first plurality of time slices. The first system frame schedule can include assignment of the third time slice can be to the first slave circuit. In another embodiment, the method can further include the first slave bus node can include a first node controller, a first gate controller and a first plurality of gates. In yet another embodiment, configuring the first slave bus node to transmit data packets can include configuring one or more gates of the first plurality of gates, by the first gate controller, to transmit the data packets from the node controller to the first data lane. 
     In one embodiment, the method can further include assignment of a fourth time slice of the second plurality of time slices to a second slave circuit of the plurality of slave circuits based on a unique identification of the second slave in a beacon response packet received from the second slave circuit. In one embodiment, the method can further include cancelling the assignment of the fourth time slice to the second slave circuit based on inactivity of the second slave circuit during one or more time slices assigned to the second slave circuit. 
     In one embodiment, a monitoring system can include a first backplane having at least one first data lane. The monitoring system can also include at least one second data lane in parallel with the at least one first data lane. The monitoring system can also include at least one first port in electronic communication with the at least one first data lane and the at least one second data lane. The monitoring system can also include at least one second port in electronic communication with the at least one first data lane and the at least one second data lane. The monitoring system can further include a first functional circuit detachably coupled to the at least one first port. The first functional circuit can be configured to receive a sensor signal from a sensor. The sensor signal can characterize measured operating parameter of a machine. The functional circuit can be configured to generate a first digital signal based on the sensor signal, and deliver the first digital signal to the at least one first data lane. The monitoring system can also include a second functional circuit detachably coupled to the at least one second port. The second functional circuit can be configured to receive the first digital signal from the at least one first data lane. The second functional circuit can also be configured to determine an operating status of the machine based on the received first digital signal and a predetermined operating threshold. The second functional circuit can further be configured to generate a second digital signal based on the first digital signal and the predetermined operating threshold. The second digital signal characterizing the operating status of the machine, and deliver the second digital signal to the at least one second data lane. 
     In one embodiment, the monitoring system can include at least one third data lane in parallel with the at least one first data lane and the at least one second data lane. The monitoring system can also include at least one third port in electronic communication with the at least one first data lane, the at least one second data lane, and the at least one third data lane. The monitoring system can also include a third functional circuit detachably coupled to the at least one third port. The third functional circuit can be configured to receive the second digital signal from the at least one second data lane, and actuate a relay based the operating status of the machine. 
     In one embodiment, the first functional circuit not in electronic communication with the at least one second data lane. In another embodiment, the at least one first data lane can be a dedicated data lane and can be configured to receive data from only the first functional circuit. In yet another embodiment, the second functional circuit may not be in electronic communication with the at least one first data lane. 
     In one embodiment, the at least one second data lane can be a dedicated data lane and can be configured to receive data from only the second functional circuit. In another embodiment, the first functional circuit can include a first unidirectional gate configured to allow the first functional circuit to deliver the first digital signal to the at least one first data lane. In yet another embodiment, the first functional circuit can include a gate pair which can include a transmitter and a receiver. The transmitter can be configured to deliver a third digital signal from the at least one third data lane, and the receiver can be configured to receive a fourth digital signal from the at least one third data lane. 
     In one embodiment, the second functional circuit can include a gate pair comprising a transmitter and a receiver, the transmitter can be configured to deliver a third digital signal to the at least one third data lane, and the receiver can be configured to receive a fourth digital signal from the at least one third data lane. In another embodiment, the second functional circuit can include a second unidirectional gate configured to allow the second functional circuit to receive the first digital signal from the at least one first data lane. In yet another embodiment, the at least one third data lane can be a bi-directional serial data lane. 
     In one embodiment, the at least one first data lane can be a unidirectional serial data lane. In another embodiment, the at least one second data lane can be a unidirectional serial data lane. In yet another embodiment, the at least one first data lane comprises a plurality of first data lanes. 
     In one embodiment, the at least one second data lane comprises a plurality of second data lanes. In another embodiment, the at least one first port can be electrically decoupled from the at least one second data lane, thereby preventing electronic communication between the first functional circuit and the at least one second data lane. In yet another embodiment, the monitoring system can further include at least one fourth port in electronic communication with the at least one third data lane and a fourth functional circuit coupled to the at least one fourth port. The fourth functional circuit can be configured to deliver a third digital signal to the second functional circuit via the at least one third data lane. The third signal can characterize updated operating thresholds. 
     In one embodiment, the at least one fourth port can be electrically decoupled from the at least one first data lane, thereby preventing electronic communication between the fourth functional circuit and the at least one first data lane. In another embodiment, the fourth functional circuit can include a schedule controller configured to generate a first schedule. 
     In one embodiment, a method, can include delivering, from a first functional circuit of a monitoring system, a first digital signal to a first data lane of a backplane of a monitoring system. The first digital signal can characterize a measured operating parameter of a machine. The method, can include receiving the first digital signal from the first data lane, at a second functional circuit of the monitoring system. The method, can also include determining an operating status of the machine based on the received first digital signal and a predetermined operating threshold. The method, can further include generating a second digital signal based on the first digital signal and the predetermined operating threshold, the second digital signal characterizing the operating status of the machine. The method can also include delivering the second digital signal to a second data lane of the backplane, receiving the second digital signal from the second data lane at a third functional circuit, and actuating a relay based the operating status of the machine. 
     In one embodiment, the method can include receiving, at the first functional circuit, an analog signal from a sensor, the analog signal characterizing the measured operating parameter of the machine. The method can also include converting the analog signal to the first digital signal. In another embodiment, the method can include generating a third digital signal characterizing updated operating thresholds, and delivering the third digital signal to a third data lane of the backplane. The third signal can characterize updated operating thresholds. 
     In one embodiment, the analog signal can be converted to the first digital signal at a fixed rate. In another embodiment, the method can further include filtering the analog signal. In yet another embodiment, the method can further include delivering a signal to a control system upon actuation of the relay to stop operation of the machine. 
     Systems, devices, and methods for monitoring operating conditions of machines are provided. In one embodiment, a monitoring system is provided that includes a first backplane having a first set of data lanes and a first set of ports. Each port of the first set of ports can be in electronic communication with at least one data lane of the first set of data lanes. The monitoring system can include a second backplane having a second set of data lanes and a second set of ports. Each of the second set of ports can be in electronic communication with at least one data lane of the second set of data lanes. The monitoring system can further include a first bridge circuit that can be detachably coupled to at least one of the first set of ports, and a second bridge circuit detachably coupled to at least one of the second set of ports. The second bridge circuit can be in electronic communication with the first bridge circuit. The first bridge circuit can be configured to receive a first set of data from the first set of data lanes, convert the first set of data to a first serial data stream, and to deliver the first serial data stream to the second bridge circuit, thereby delivering the first set of data to the second backplane. The second bridge circuit can be configured to receive a second set of data from the second set of data lanes, convert the second set of data to a second serial data stream, and to deliver the second serial data stream to the first bridge circuit, thereby delivering the second set of data to the first backplane. 
     The monitoring system can vary in a number of ways. One or more of the following features can be included in any feasible combination. For example, in some embodiments, the first bridge circuit can include at least one first gate configured to facilitate electronic communication between the first bridge circuit and at least one data lane of the first set of data lanes. The at least one first gate can be configured to operate in a first operating mode and in a second operating mode. The at least one first gate can be configured to allow data to be transferred from the first bridge circuit to the at least one data lane of the first set of data lanes when in the first operating mode. The at least one first gate can be configured to prevent data from being transferred from the first bridge circuit to the at least one data lane of the first set of data lanes when in the second operating mode. The monitoring system can also include at least one first gate controller in electronic communication with the at least one first gate. The at least one first gate controller can be configured control operation of the at least one first gate. 
     In some embodiments, the second bridge circuit includes the second bridge circuit can include at least one second gate configured to facilitate electronic communication between the second bridge circuit and at least one data lane of the second set of data lanes. The at least one second gate can be configured to operate in a third operating mode and a fourth operating mode. The at least one second gate can be configured to allow data to be transferred from the second bridge circuit to the at least one lane of the second set of data lanes when in the third operating mode. The at least one second gate can be configured to prevent data from being transferred from the second bridge circuit to the at least one lane of the second set of data lanes when in the fourth operating mode. The second bridge circuit can also include at least one second gate controller in electronic communication with the at least one second gate and the at least one first gate controller. The at least one second gate controller can be configured control operation of the at least one second gate. 
     In some embodiments, the monitoring system can also include a first set of functional circuits. Each functional circuit of the first set of functional circuits can be detachably coupled to at least one port of the first set of ports. The first set of functional circuits can be configured to deliver the first set of data to the first backplane and to selectively receive any data delivered to the first backplane. The monitoring system can also include a second set of functional circuits. Each functional circuit of the second set of functional circuits can be detachably coupled to at least one port of the second set of ports. The second set of functional circuits can be configured to deliver a second set of data to the second backplane and to selectively receive any data delivered to the second backplane. 
     In some embodiments, the first set of functional circuits can include at least one first functional circuit. The first functional circuit can include at least one second gate configured to facilitate electronic communication between the at least one first functional circuit and at least one of the first set of data lanes. The at least second one gate being configured to operate in a first operating mode and a second operating mode. The at least one second gate can be configured to allow data to be transferred from the at least one first functional circuit to the at least one lane of the first set of data lanes when in the first operating mode. The at least one second gate can be configured to prevent data from being transferred from the at least one first functional circuit to the at least one lane of the first set of data lanes when in the second operating mode. 
     In some embodiments, the first set of data lanes can include a plurality of data lanes. 
     In some embodiments, the second set of data lanes can include a plurality of data lanes. 
     In some embodiments, the monitoring sensor can include a sensor in electronic communication with a functional circuit of at least one of the first set of functional circuits and the second set of functional circuits. The sensor can be configured to measure operating parameters of a machine and to deliver data characterizing the measured operating parameters to the functional circuit. 
     In some embodiments the first set of functional circuits can include a plurality of functional circuits. Each functional circuit of the plurality of functional circuits can be configured to receive data from at least one data lane of the first set of data lanes. 
     In some embodiments, the first backplane and the second backplane can be passive backplanes that not include active switches. 
     In another aspect, a method is provided that includes receiving a first identification data at a first bridge circuit coupled to a first backplane of a first monitoring subsystem. The first identification data can characterize information identifying hardware of a second monitoring subsystem. The method can also include receiving a second identification data at a second bridge circuit coupled to a second backplane of the second monitoring subsystem. The second identification data can characterize information identifying hardware of the first monitoring subsystem. The method can further include determining, using the first identification data and the second identification data, that first monitoring subsystem is compatible with the second monitoring subsystem. The method can also include receiving a first schedule at the second bridge circuit. The first schedule can characterize a first communication schedule for a first set of functional circuits that are in electronic communication with the first backplane. The method can further include receiving a second schedule at the first bridge circuit. The second schedule can characterize a second communication schedule for a second set of functional circuits that are in electronic communication with the second backplane. The method can further include comparing the first communication schedule to the second communication schedule and determining that the first schedule is compatible with the second schedule. The method can further include providing a first signal to at least one first gate of the first bridge circuit and providing a second signal to at least one second gate of the second bridge circuit, thereby activating the at least one first gate and the at least one second gate, and facilitating electronic communication between the first backplane and the second backplane. 
     The method can vary in a number of ways. One or more of the following features can be included in any feasible combination. For example, the method can include delivering, from the first set of functional circuits, a first set of parallel data streams to a first set of parallel data lanes of the first backplane. The method can also include receiving, at the first bridge circuit, the first set of parallel data streams from the first set of parallel data lanes of the first backplane, converting the first set of parallel data streams to a first serial data stream, and delivering the first serial data stream to the second bridge circuit. The method can further include expanding the first serial data stream to a second set of parallel data streams, and delivering the second set of parallel data streams to a second set of parallel data lanes. 
     In some embodiments, the method can include amplifying a power of the first serial data stream based on a distance between the first bridge circuit and the second bridge circuit. 
     In some embodiments, the method can include delivering, from the second set of functional circuits, a third set of parallel data streams to the second set of parallel data lanes of the second backplane. 
     In some embodiments, the method can include receiving, at the second bridge circuit, the third set of parallel data streams from the second set of parallel data lanes of the second backplane, converting the third set of parallel data streams to a second serial data stream, and delivering the second serial data stream to the first bridge circuit. The method can also include expanding the second serial data stream to a fourth set of parallel data streams, and delivering the fourth set of parallel data streams to the first set of parallel data lanes. 
     In some embodiments, the method can include generating a third schedule using at least one functional circuit of the first set of functional circuits. The third schedule can include data that determines when each functional circuit of the first set of functional circuits delivers data to the first set of parallel data lanes and when each functional circuit the second set of functional circuits delivers data to the second set of parallel data lanes. 
     In some embodiments, the third set of parallel data streams can include sensor data characterizing measured operating values of a machine. The sensor data can be measured by sensors coupled to the machine. 
     In some embodiments, the method can include amplifying a power of the second serial data stream based on a distance between the first bridge circuit and the second bridge circuit. 
     In some embodiments, the method can include determining an estimated delay time that can characterize an estimated amount of time required to transfer data between the first bridge circuit and the second bridge circuit. The method can also include determining a dead band period based on at least one of the first communication schedule and the second communication schedule. The dead band time can characterize a total amount of time available to absorb delays in communication between one or more backplane. The method can further include determining an amount of the dead band time that is available based on at least one of the first communication schedule and the second communication schedule, and comparing the estimated delay time to the amount of dead band time that is available. 
     In some embodiments, the method can include receiving a first network identification data at the first bridge circuit. The first network identification data can characterize a first network configuration. The method can also include receiving a second network identification data at the second bridge circuit. The second network identification data can characterize a second network configuration. The method can further include comparing the first network identification data with the second network identification data. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       These and other features will be more readily understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1 A  is a block diagram illustrating one exemplary embodiment of an operating environment containing an existing monitoring system; 
         FIG.  1 B  is a block diagram illustrating one exemplary embodiment of a backplane of the monitoring system of  FIG.  1 A ; 
         FIG.  2    is a block diagram illustrating one exemplary embodiment of an operating environment containing a flexible monitoring system configured to monitor a machine; 
         FIG.  3    is a diagram illustrating families of various types of functional circuits that can be used with the scalable monitoring system shown in  FIG.  2   ; 
         FIG.  4    is block diagram of a portion of an exemplary embodiment of a monitoring system; 
         FIG.  5    is a block diagram of an exemplary embodiment of a functional circuit that includes two nodes; 
         FIG.  6    is block diagram of an exemplary embodiment of a functional circuit that does not include transmitters; 
         FIG.  7    is a diagram illustrating components of system frames; 
         FIG.  8    is an exemplary data structure of a beacon packet; 
         FIG.  9    is an exemplary structure of system frame schedule; 
         FIG.  10    is an exemplary data structure of a beacon response packet; 
         FIG.  11    is an exemplary communication protocol between a master circuit and a slave circuit; 
         FIG.  12    is an exemplary structure of a data packet that can be delivered to the backplane of a monitoring system during operation; 
         FIG.  13    is flow diagram that illustrates an exemplary initialization process; 
         FIG.  14    is flow diagram that illustrates an exemplary method of generating a schedule based on the communication requests from slave circuits; 
         FIG.  15    is a flow diagram illustrating an exemplary method of processing time slice requests from beacon response packets and generating a schedule entry array; 
         FIG.  16    is a flow diagram of an exemplary traffic monitoring process that can be used to recover unused time slices; 
         FIG.  17    is shown an exemplary of a schedule entry array that includes a time slice array, an assignment array, a length array, and a counter array; 
         FIG.  18    is a flow diagram illustrating exemplary operation of a node of a slave circuit of a monitoring system; 
         FIG.  19    is a block diagram of an exemplary embodiment of a bridge circuit that can be configured to facilitate electronic communication between backplanes of a monitoring system; 
         FIG.  20    is a block diagram of an exemplary embodiment of a monitoring system that includes two monitoring subsystems that are coupled using bridge circuits; 
         FIG.  21    is a magnified view of the block diagram of the monitoring system shown in  FIG.  20   ; 
         FIG.  22    is a data flow diagram illustrating exemplary communication between various components of the monitoring system illustrated in  FIG.  20   ; 
         FIG.  23    is a flow chart illustrating an exemplary method of determining compatibility of backplanes; 
         FIG.  24    is a block diagram of another exemplary monitoring system that includes two monitoring subsystems that are coupled using bridge circuits; 
         FIG.  25    is block diagram of another exemplary monitoring system that includes two monitoring subsystems that are coupled using bridge circuit; 
         FIG.  26    is a block diagram of an exemplary monitoring system that utilizes a time-sensitive networking (TSN) Ethernet protocol to facilitate communication between functional circuits of the monitoring system; 
         FIG.  27    is a detailed view of a portion of the monitoring system shown in  FIG.  27   ; 
         FIG.  28    is block diagram of another exemplary monitoring system that utilizes TSN Ethernet protocol to facilitate communication between functional circuits of the monitoring system; 
         FIG.  29    is a block diagram of a portion of an exemplary embodiment of a monitoring system utilizes dedicated data lanes to facilitate communication between functional circuits; 
         FIG.  30    is a magnified view input circuits of the monitoring system shown in  FIG.  30   ; 
         FIG.  31    is a magnified view of a system interface circuit of the monitoring system shown in  FIG.  29   ; 
         FIG.  32    is a magnified view of protection circuit of the monitoring system shown in  FIG.  29   ; 
         FIG.  33    is a magnified view of relay circuits of the monitoring system shown in  FIG.  30   ; 
         FIG.  34    shows a magnified view of the gateway circuit of the monitoring system shown in  FIG.  29   ; 
         FIG.  35    is a magnified view of a 4-20 output circuit of the monitoring system shown in  FIG.  29   ; 
         FIG.  36    is a block diagram of an exemplary backplane of the monitoring system shown in  FIG.  29   ; 
         FIG.  37    is a data flow diagram illustrating exemplary communication between various components of the monitoring system shown in  FIG.  29   ; 
         FIG.  38    is a block diagram another exemplary embodiment of a monitoring system that utilizes dedicated data lanes; 
         FIG.  39    shows a magnified view of input circuits and a system interface circuit of the monitoring system shown in  FIG.  38   ; 
         FIG.  40    is a magnified view of protection circuits of the monitoring system shown in  FIG.  38   ; 
         FIG.  41    is a magnified view of a relay circuit, a 4-20 output circuit, and a condition monitoring circuit of the monitoring system shown in  FIG.  38   ; and 
         FIG.  42    is a block diagram of an exemplary backplane of the monitoring system shown in  FIG.  38   . 
     
    
    
     DETAILED DESCRIPTION 
     Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the systems, devices, and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. 
     Industrial monitoring systems, such as wind turbines, can be used to monitor operating conditions of industrial systems. Although industrial monitoring systems can provide users with useful information regarding operation of industrial systems, some monitoring systems can be limited in terms of flexibility and/or scalability. Additionally, costs and complexity of installation can create a significant barrier to entry for some users that want to monitor low cost and/or low priority components/systems. Systems, methods, and devices are provided that improve flexibility and scalability of monitoring systems. In one embodiment, a monitoring system is provided that includes a passive backplane and one or more functional circuits that can couple to the backplane. Each of the functional circuits has access to all data that is delivered to the backplane. Therefore, resources (e.g., computing power) from each functional circuit can be shared by all active functional circuit that are coupled to the backplane. Because resources from each functional circuit can be shared, and because the functional circuits can be detachably coupled to the backplane, performance of the monitoring systems adjusted and/or scaled to fit individual monitoring needs. For example, processing power can be increased by coupling additional processing circuits to the backplane. The shared data and detachable functional circuits also allow for multiple backplanes to be coupled using bridges. Bridging can allow multiple backplanes to share common resources, which can provide flexibility when designing and installing monitoring systems. For example, monitoring subsystems can be installed remotely near industrial equipment such that the functional circuits can receive sensor data, while other monitoring subsystems can be installed at another location that may be more convenient, easier to access, or more cost effective. 
     Embodiments of systems and corresponding methods for monitoring industrial machines are discussed herein. However, embodiments of the disclosure can be employed with other machines without limit. 
     An operating environment  100  containing an existing monitoring system is illustrated in  FIG.  1   . The operating environment  100  can include a target  102 , at least one sensor  104 , and a monitoring system  106  in communication with the sensor  104 , an internal network  110   a , and an external network  110   b.    
     The target  102  can be any component of any machine. Examples of the target  102  can include gears, bearings, and shafts, amongst others. Examples of machines can include turbomachines, turbines (e.g., hydro, wind), generators, and reciprocating compressors. 
     The sensor  104  can be configured to sense an operating parameter of the target  102 , to generate at least one sensor signal  104   s  representing the measured operating parameter, and to transmit the sensor signal  104   s  to the monitoring system  106  (e.g., via field wiring). As an example, the sensor  104  can include a probe, a transducer, and a signal conditioning circuit (not shown). The probe can interact with the target  102  for measurement of the operating parameter. The transducer can convert measurements of the operating parameter into an electrical signal (e.g., a voltage). The signal conditioning circuit can condition and/or amplify the electrical signal to generate the sensor signal  104   s  (e.g., a voltage ranging between a minimum and maximum). Thus, in one aspect, the sensor signal  104   s  can contain the direct or raw measurement made by the sensor transducer. The sensor signal  104   s  can be an analog signal or a digital signal. 
     In another aspect, the sensor signals  104   s  can also include an enhanced data set, in addition to the direct measurements of the operating parameter. The enhanced data set can contain a variety of measured variables that depend upon the type of operating parameter being measured. As an example, the target  102  can be a rotating component, such as a shaft, and radial vibration can be a variable measured by a sensor  104  in the form of a proximity sensor. Under these circumstances, the enhanced data set can include one or more of a gap voltage, a 1× filtered amplitude, a 2× filtered amplitude, a 1× filtered phase, a 2× filtered phase, Not 1× amplitude, and maximum shaft displacement (Smax). Gap voltage is the voltage output by the probe and represents the physical distance between the target  102  and a tip of the probe. 1× amplitude is the amplitude of vibrations having the same frequency as the shaft rotation, while 2× amplitude is the amplitude of vibrations having a frequency twice that of the shaft rotation. For instance, a rotation speed of 1480 revolutions per minute corresponds to a frequency of 24.6 6  cycles per second (Hz). Phase is the time delay between a vibration measured at a predetermined measurement location with respect to a reference location. Thus, 1× phase refers to phase of vibrations having the same frequency as the shaft rotation, while 2× phase refers to phase of vibrations having a frequency twice that of the shaft rotation. Not 1× amplitude refers to all amplitudes except for the 1× amplitude. In other embodiments, the enhanced data set can include metadata regarding one or more components of the sensor  104 , such as the transducer. Examples of metadata can include one or more of a serial number, revision number, operating temperature, and state of health. 
     The number and type of sensor  104  can be dictated by the operating parameter(s) that are intended to be measured. In one aspect, the sensor  104  can take the form of one or more proximity probes for measurement of vibration, position, speed, direction of motion, and eccentricity. In another aspect, the sensor  104  can take the form of one or more accelerometers for measurement of seismic vibration and acceleration. In a further aspect, the sensor  104  can take the form of one or more temperature probes or pressure probes for measurement of temperature and pressure, respectively. It can be understood that the sensor types and corresponding operating parameters listed above are not exhaustive and embodiments of the sensor  104  can include any sensor or combination of sensors suitable for measurement of operating parameters of interest. 
     In use, the monitoring system  106  can be configured to process the received sensor signals  104   s  and output monitoring signals  106   s ,  108   s . As an example, the monitoring system  106  can be configured to determine a value characterizing an operating parameter measurement. The monitoring system  106  can also compare this determined value, and/or any measured variables of the enhanced data set, to one or more corresponding predetermined alarm conditions in real-time and determine an alarm status (e.g., OK, not OK, alert, danger, etc.). For instance, when the target  102  is a rotating shaft and the measured operating parameter is radial vibration of the shaft, the sensor signal  104   s  can include measurements of displacement of the shaft as a function of time. From the sensor signal  104   s , the monitoring system  106  can determine the value of vibration amplitude from the peak-to-peak displacement. 
     The monitoring system  106  can also be configured to output monitoring signals  106   s ,  108   s  to the internal network  110   a  and/or the external network  110   b . The output monitoring signals  106   s ,  108   s  can include one or more of the measured variables of the enhanced data set, the determined values, and the determined status. Alarm statuses, such as alert and danger, can be annunciated via physical relays on the monitoring system  106  or to the external systems  110  by the monitoring signals  106   s ,  108   s . In another aspect, the monitoring system  106  can additionally or alternatively store the sensor signals  104   s  for later processing. 
     The internal network  110   a  can be a plant network that is in communication with a machine control system  112 . The machine control system  112  can be configured to provide commands to a machine operative to control one or more operating parameters of the target  102 . The internal network  110   a  can also be in communication with other systems, such as computing devices executing configuration software (not shown), human-machine interfaces (HMIs)  114  and/or a customer historian  116 . The configuration software can be used to provide configuration information, such as the pre-determined alarm conditions, to the monitoring system  106 . The HMI  114  can be one or more computing devices in communication with user interface devices (e.g., displays) allowing an operator of the machine to review measured operating parameters and/or provide instructions to the machine control system  112 . 
     So configured, the monitoring system  106  can facilitate protection of a machine containing the target  102 . As an example, in response to annunciation of an alarm status, the machine control system  112  can be utilized to control operation of the target  102  (e.g., automatically according to programmed logic or manually using the HMI  114 ) to cause the measured operating parameters to change and move out of the alarm status. Under extreme circumstances, the machine control system  112  can be employed to shut down operation of the machine to protect the target  102  from damage and/or workers from injury. The historian  116  can store any of the data contained within the monitoring signals  106   s.    
     The external network  110   b  can be a business network that is in communication with a diagnostic system  120 . The diagnostic system  120  can analyze any of the data contained within the monitoring signals  108   s  received from the monitoring system  106  to diagnose improper operation of the target  102  and/or predict improper operation of the target  102  before it occurs. Thus, by providing monitoring signals  108   s  to the external network  110   b , the monitoring system  106  can facilitate condition monitoring of the target  102 . 
     The monitoring system  106  is illustrated in greater detail in  FIG.  1 B . As shown, the monitoring system  106  includes a backplane  150  that can be configured to allow communication between different components coupled thereto. The components can include a measurement processing circuit  152   a , a relay output circuit  154   a , a measurement output circuit  156   a , a configuration and diagnostic circuit  160   a , and corresponding interface circuits  152   b ,  154   b ,  156   b ,  160   b . The interface circuits  152   b ,  154   b ,  156   b ,  160   b  can provide hardware interfaces for communication to and from their respective circuits  152   a ,  154   a ,  156   a ,  160   a . The individual circuits  152   a ,  154   a ,  156   a ,  160   a  can communicate selected information on the backplane  150  using protocols running on busses formed from passive traces extending across the backplane  150 . 
     In one aspect, the measurement processing circuit  152   a  can be coupled to an interface circuit  152   b  such that sensor signals  104   s  received by the interface circuit  152   b  are transmitted directly to the measurement processing circuit  152   a . That is, the sensor signals  104   s  are not transmitted to the backplane  150 . The sensor signals  104   s  can be accessed by an operator through an output port  162 . Multiple measurement processing circuits  152   a  and interface circuit  152   b  can be present, on a one-to-one basis, for receipt of the sensor signals  104   s . As discussed above, the measurement processing circuit  152   a  can be configured to determine one or more values for the operating parameter measurements contained within the received sensor signal  104   s . The measurement processing circuit  152   a  can also compare determined values, and/or measured variables of the enhanced data, to pre-determined alarm conditions in real-time and determine a status for the target  102 . The measurement processing circuit  152   a  can further output signals representing the measured variables of the enhanced data, the determined values, and the determined statuses to the backplane  150 . 
     The measurement processing circuit  152   a  can also format process variables (e.g., determined values, measured variables of the enhanced data set, annunciated alarms, etc.) for output to the machine control system  112 . As an example, the format can be a current that ranges between about 4 mA to about 20 mA (also referred to as 4-20) and is proportional to the determined values and/or measured variable as compared to a corresponding scale. The machine control system  112  can utilize the process variables for process control of the target  102 . 
     The statuses determined by the measurement processing circuits  152   a  can be retrieved by the relay processing circuit  154   a  from the backplane  150 . The relay processing circuit  154   a  can include relays that are programmed to actuate based upon received alarm statuses to annunciate an alarm. In one example, relays can actuate based upon a single status. In another example, relays can actuate based upon Boolean expressions (e.g., AND or voting) that combine two or more statuses. The relay processing circuit  154   a  can also output signals representing annunciated alarms directly to the machine control system  112  for process control of the target  102 . As an example, the machine control system  112  can shut down operation of the target  102  upon receipt of an alarm annunciation. Annunciated alarms can also be used to provide indications and/or to drive into digital input of the machine control system  112 , the HMI  114 , or historian  116 . 
     The measurement output circuit  156   a  can retrieve data such as determined values, measured variables of the enhanced data, determined statuses, and annunciated alarms from the backplane  150  for transmission to the internal network  110   a . Upon receipt, the retrieved data can be stored by the historian  116  and/or reviewed by an operator using the HMI  114 . 
     The configuration and diagnostic circuit  160   a  can receive first configuration commands from the internal network  110   a  and transmit the first configuration commands to the backplane  150  for use by the circuits  152   a ,  154   a ,  156   a ,  160   a . The first configuration commands can provide one or more set points for use by the measurement processing circuit  152   a  in determining statuses. The first configuration commands can also provide logic instructions and identify statuses to be used by the relay output circuit  154   a  for alarm annunciation. The first configuration commands can further identify data such as determined values, measured variables of the enhanced data, determined statuses, and/or annunciated alarms to be retrieved from the backplane  150  by the measurement output circuit  156   a  and transmitted to the internal network  110   a.    
     The configuration and diagnostic circuit  160   a  can also receive second configuration commands from the internal network  110   a . The second configuration commands can identify data such as determined values, measured variables of the enhanced data, determined statuses, and annunciated alarms to be retrieved from the backplane  150  and transmitted to the external network  110   b  for use by the diagnostic system  120 . 
     While capable of facilitating protection monitoring and condition monitoring of the target  102 , in some instances, the architecture of monitoring systems such as monitoring system  106  can lack flexibility. In one aspect, placement of the configuration and diagnostic circuit  160   a  in communication with both the internal and external networks  110   a ,  110   b  can cause delays when updating the second configuration commands. When diagnosing machine problems, it can be desirable to change the data received by the diagnostic system  120 . However, transmissions to or from components in communication with the internal network  110   a  can be strictly regulated in order to protect the machine control system  112  from unauthorized access. This regulation can include permitting the configuration and diagnostic circuit  160   a  to transmit data to the external network  110   b  for condition monitoring but prohibiting transmission of changes to the second commands from the external network  110   b  to the configuration and diagnostic circuit  160   a . Instead, an authorized operator of the machine control system  112  can be required to approve any changes to the second configuration commands and transmit the updated second conditioning commands from the internal network  110   a  to the configuration and diagnostic circuit  160   a.    
     In another aspect, directly coupling the interface circuit  152   b  receiving the sensor signals  104   s  to the measurement processing circuit  152   a  can limit access of the sensor signal  104   s  to only the measurement processing circuit  152   a . As a result, the other circuits  154   a ,  156   a ,  160   a  of the monitoring system  106 , as well as the diagnostic system  120 , cannot utilize the raw operating parameter measurements transmitted by the sensor signal  104   s . Furthermore, should a second measurement processing circuit (not shown) be added to the monitoring system for receipt of additional sensor signals from another sensor, each measurement processing circuit could utilize the operating parameter measurements it receives but not operating parameters received by the other. 
     In a further aspect, process variables output by the measurement processing circuit  152   a  to the machine control system  112  can be limited. In general, for each sensor signal  104   s  received by the measurement processing circuit  152   a , there can be a variety of possible process variables (e.g., determined values and/or measured variables of the enhanced data set). As an example, there can be 8 possible process variables determined by the measurement processing circuit  152   a  from a sensor signal  104   s  measuring radial vibration (vibration amplitude, gap voltage, 1× filtered amplitude, 2× filtered amplitude, 1× filtered phase, 2× filtered phase, Not 1× amplitude, and Smax. However, the measurement processing circuit  152   a  can possess the ability to output a single process variable for each sensor  104  from which it receives sensor signals  104   s.    
     One or more of these limitations can be addressed by embodiments of a flexible monitoring system of the present disclosure.  FIG.  2    illustrates an exemplary embodiment of an operating environment  200  including a flexible monitoring system  202 . The operating environment  200  can be similar to the operating environment  100 , except that the monitoring system  106  is replaced with the flexible monitoring system  202 . The flexible monitoring system  202  can include a base  204  containing a backplane  206 , and one or more circuits  210 . The backplane  206  can be configured to communicatively couple with two or more circuits  210  and receive data from at least one circuit  210  coupled thereto. As discussed herein, data transmitted to the backplane  206  can be referred to as monitoring data. In one aspect, monitoring data can include information contained within the sensor signals  104   s , such as measured operating parameters of the target  102  and measured variables of the enhanced data set. Monitoring data can also include any values, statuses, and/or annunciated alarms that are determined based upon the measured operating parameters of the target  102  and/or measured variables of the enhanced data set. Circuits  210  coupled to the backplane  206  can retrieve monitoring data from the backplane  206 . In certain embodiments, the backplane  206  can be passive. A passive backplane can contain substantially no or no logical circuitry that performs computing functions. Desired arbitration logic can be placed on daughter cards (e.g., one or more of the circuits  210 ) plugged into or otherwise communicatively coupled to the passive backplane. 
     In contrast to the circuits  152   a ,  154   a ,  156   a ,  160   a  of the monitoring system  106 , the circuits  210  can be designed with a common architecture that is programmable to perform different predetermined functions of the flexible monitoring system  202 . Sensor signals  104   s  received by one or more of the circuits  210  can be transmitted to the backplane  206  and monitoring data represented by the sensor signals  104   s  can be accessed by any circuit  210 . Furthermore, the flexible monitoring system  202  can communicatively couple multiple bases in a manner that forms a common backplane  206 ′ from the individual backplanes  206  of each base  204  (e.g., a logical backplane). Thus, circuits  210  can retrieve monitoring data from any backplane  206  forming the common backplane  206 ′, rather than just from the backplane  206  to which they are physically coupled. 
     In certain embodiments, the circuits  210  of the flexible monitoring system  202  can be configured to provide at least functionality similar to that of circuits  152   a ,  154   a ,  156   a ,  160   a  of the monitoring system  106 . Exemplary embodiments of circuits  210  are illustrated in  FIGS.  2 - 3    and discussed in detail below. As an example, circuits  210  can include input circuits  210   i , processing circuits  210   p , output circuits  210   o , and infrastructure circuits  210   n . It can be understood, however, that the circuits  210  can be programmed to perform other functions. Accordingly, the flexible monitoring system  202  can be configured to receive sensor signals  104   s  and output monitoring signals  206   s ,  208   s  to the internal and external networks  110   a ,  110   b , respectively. As discussed in detail below, embodiments of the flexible monitoring system  202  can receive command signals  209   s ,  211   s  from the internal and external networks  110   a ,  110   b , respectively, without compromising security of the machine control system  112 . As a result, the flexible monitoring system  202  can be a suitable replacement for existing deployments of monitoring systems  106  while providing improved flexibility and functionality. 
     With this architecture, the circuits  210  can be combined in various ways on one or more backplanes  206  to form different implementations of the flexible monitoring system  202 . The number of bases  204 , input circuits  210   i , processing circuits  210   p , output circuits  210   o , and infrastructure circuits  210   n  included in a given implementation of the flexible monitoring system  202  can also be varied independently of one another. In some implementations, the flexible monitoring system  202  can be in the form of a single base  204  including circuits  210  configured to provide signal input, signal output, protection monitoring, condition monitoring, and combinations thereof. In other implementations, the flexible monitoring system  202  can be in the form of at least two bases  204  and circuits  210  configured to perform any combination of signal input, signal output, protection monitoring, and condition monitoring can be distributed between the at least two bases  204 . In this manner, the input, processing, and output capabilities of the flexible monitoring system  202 , as well as the physical location of different circuits  210  of the flexible monitoring system  202 , can be tailored to specific monitoring applications. 
     Furthermore, implementations of the flexible monitoring system  202  can be modified after initially deployed to modify the circuits  210  coupled to a given base  204  in the event that the intended monitoring application changes. Given their common architecture, circuits  210  can be easily added to a base  204  having capacity to couple to a new circuit  210 . Alternatively, one or more new bases  204  can be communicative coupled to an existing base  204 , allowing one or more new circuits  210  to be couple to respective backplane(s)  206  of the new base(s)  204  and expanding the monitoring capabilities of the flexible monitoring system  202 . In some instances, circuits  210  removed from one base  204  of the flexible monitoring system  202  can be stored in reserve as spares or redeployed to another base  204  of the same or a different implementations of the flexible monitoring system  202 , which may be beneficial. 
     In certain embodiments, input circuits  210   i  can be configured to receive sensor signals  104   s , perform signal conditioning on the sensor signals  104   s , and output the conditioned sensor signals  104   s  to the backplane  206 . In contrast to the monitoring system  106  of  FIGS.  1 A- 1 B , the input circuits  210   i  can be decoupled from processing circuits  210   p , allowing the number of input circuits  210   i  of the flexible monitoring system  202  to be varied independently of the number of processing circuits  210   p.    
     The sensor signals  104   s  can be received from a variety of different types of sensor  104 . Examples of sensor types can include, but are not limited to, vibration sensors, temperature sensors (e.g., resistance temperature detectors or RTD), position sensors, and pressure sensors. 
     Embodiments of the flexible monitoring system  202  can include one or more input circuits  210   i . As shown in the  FIG.  2   , the flexible monitoring system  202  includes two input circuits  210   i . Each of the input circuits  210   i  can be in communication with a respective sensor  104  for receipt of a corresponding sensor signal  104   s . As an example, one sensor signal  104   s  can represent first monitoring data including measurements of a first operating parameter of a first machine component (e.g., acquired by a first sensor). The other sensor signal  104   s  can represent second monitoring data including measurements of a second operating parameter of a second machine component (e.g., acquired by a second sensor, different from the first sensor). In certain embodiments, the first and second machine components can be the same (e.g., the target  102 ). In other embodiments, the first and second machine components can be different (e.g., the target  102  and a different target [not shown]). Similarly, in some embodiments, the first and second operating parameters can be the same operating parameter. In one aspect, this configuration can provide redundancy in case of failure of one of the sensors  104 . In another aspect, this configuration can be utilized where a desired measurement (e.g., shaft rotation speed) is derived from two sensor measurements coordinated in time (phase). In additional embodiments, the first and second operating parameters can be different. While two input circuits  210   i  have been illustrated and discussed, other embodiments of the monitoring system can include greater or fewer input circuits. 
     Different types of sensors  104  can generate sensor signals  104   s  in different formats, and input circuits  210   i  can be programmed to perform signal conditioning appropriate to the different sensor signals  104   s  before transmitting conditioned sensor signals to the backplane  206 . Examples of various types of inputs are illustrated in  FIG.  3   . In one instance, a sensor signal  104   s  received from a position sensor can be received by a position input circuit  250 . In another instance, a sensor signal  104   s  received from a vibration sensor can be received by a vibration input circuit  252 . In an further instance, a sensor signal  104   s  received from a temperature sensor can be received by a temperature input circuit  254 . In an additional instance, a sensor signal  104   s  received from a pressure sensor can be received by a pressure input circuit  256 . 
     In other embodiments, the input circuit  210   i  can be in the form of a discrete contact circuit  260 . The discrete contact circuit  260  can include a pair of contacts that can be closed by an external switch or relay. The pair of contacts can be closed by the machine control system  112  or by an operator of the machine control system  112  closing a switch. The discrete contact circuit  260  can be used to change the behavior of the flexible monitoring system  202 . Examples of behavior changes can include, but are not limited to, a different mode of machine operation, causing the flexible monitoring system  202  to inhibit alarm determination, and resetting alarm states. 
     While the monitoring system  106  can include a discrete contact, it can lack specificity. As an example, changes effected by closing a discrete contact in the measurement system  106  can be effected upon all alarms generated by the measurement system  106 . In contrast, because the discrete contact circuit  260  of the flexible monitoring system  202  can be separate from the protection processing circuit  264 , the discrete contact circuit  260  can be configured to effect only selected alarm determinations and/or reset alarm states, or effect all alarms. 
     In further embodiments, the input circuit  210   i  can be in the form of a digital data stream input circuit  262 . As an example, the digital data stream input circuit  262  can be configured to receive digital data streams from the sensor  104 , the machine control system  112 , and/or a trusted third-party system, as opposed to an analog data stream (e.g., from sensor  104 ). 
     Processing circuits  210   p  can be configured to retrieve any data from the backplane  206 , analyze the retrieved operating parameters, and output the results of such analysis. As illustrated in  FIG.  3   , certain embodiments of the processing circuits  210   p  can be configured to perform protection functions and can be referred to as protection processing circuits  264  herein. In other embodiments, the processing circuits  210   p  can be configured to retrieve selected data from the backplane  206  and transmit the retrieved information to the diagnostic system  120  for performing diagnostic and/or predictive functions (e.g., condition monitoring) and can be referred to as condition processing circuits  266  herein. 
     The number of processing circuits  210   p  and input circuits  210   i  included in a given implementation of the flexible monitoring system  202  can be varied independently of the one another. In certain embodiments, processing circuits  210   p  can be added to the backplane  206  or removed from the backplane to tailor the amount of computing resources available for protection monitoring and/or condition monitoring. In other embodiments, a given processing circuit  210   p  can be replaced by another processing circuit  210   p  having greater or less computing power. 
     Any of these scenarios can be beneficial under certain circumstances, providing computational flexibility to the flexible monitoring system  202  that can be tailored to a given application and/or modified as needed. In one instance, machines having relatively low importance can have higher cost pressures and lower processing requirements. In this circumstance, an implementation of the flexible monitoring system  202  can include processing circuits  210   p  having processing resources tailored for cost. In another instance, a particular monitoring application can require high processing requirements (e.g., for determining values characterizing the measured parameters, for output of monitoring data, etc.). In this circumstance, an implementation of the flexible monitoring system  202  can include processing circuits  210   p  having processing resources tailored for processing resources. Thus, the architecture of the flexible monitoring system  202  can allow adaptation for different use cases depending upon the priorities of the intended monitoring application. 
     The protection processing circuits  264  and the condition processing circuits  266  are discussed below with reference to different functionalities. However, protection processing circuits  264  can be programmed to perform any function of the condition processing circuits  266 . Condition processing circuits  266  can be programmed to perform functions of the protection processing circuits  264 , except for transmitting data to the backplane  206  and providing local storage. The ability to inhibit the condition processing circuit  266  from transmitting data to the backplane  206  can inhibit unauthorized intrusion and facilitate protection of the internal network  110   a  and machine control system  112 . 
     Protection processing circuits  264  can be configured to retrieve selected monitoring data from the backplane  206  in response to receipt of a protection command. As an example, one or more protection commands can be transmitted to protection processing circuits  264  in the form of protection command signal  209   s  received from the internal network  110   a  (e.g., from an operator of the machine control system  112 ). The selected monitoring data can include at least a portion of the monitoring data transmitted to the backplane  206 . The monitoring data transmitted to the backplane can be received from an input circuit  210   i  or another protection processing circuit  264 . The protection processing circuits  264  can also be configured to determine a value characterizing the selected monitoring data and transmit the determined value to the backplane  206  as additional monitoring data. 
     The protection processing circuit  264  can be configured to determine a status for the selected monitoring data based upon a comparison of the determined value, another determined value retrieved from the backplane  206  (e.g., from another protection processing circuit  264 ), and combinations thereof, with one or more predetermined set points. Predetermined set points can correspond to respective alarm conditions (e.g., an Alert condition, a Danger condition, etc.). Continuing the example above, where the determined value is an amplitude of a radial vibration, the one or more set points can include an Alert set point, a Danger set point that is greater than the Alert set point, and combinations thereof. In certain embodiments, a single set point can be employed. Assuming the use of Alert and Danger set points, if the radial vibration amplitude value is less than the Alert set point, the status of the radial vibration amplitude can be determined as “OK.” If the radial vibration amplitude value is greater than or equal to the Alert set point, the status of the radial vibration amplitude can be determined as “Alert.” If the radial vibration amplitude value is greater than the Danger set point, the status of the operating parameter can be determined as “Danger.” After the status of the selected monitoring data is determined in this manner, the protection processing circuit  264  can transmit the determined status to the backplane  206 . The condition processing circuit  266  can be configured to retrieve selected monitoring data from the backplane  206  and to provide the retrieved monitoring data to the external network  110   b  for use by diagnostic system  120 . In certain embodiments, the selected monitoring data can be retrieved by the condition processing circuit  266  in response to receipt of a conditioning command. As an example, one or more conditioning commands can be transmitted to condition processing circuits  266  in the form of conditioning command signals  211   s  can be received from the external network  110   b . (e.g., from an operator of the diagnostic system  120 ). In turn, the diagnostic system  120  can utilize the retrieved monitoring data to determine the cause of statuses and/or alarm conditions. Alternatively or additionally, the diagnostic system  120  can also employ the retrieved monitoring data to predict the development of statuses and/or alarm conditions before they arise. In further embodiments, the diagnostic system  120  can store the retrieved monitoring data for subsequent analysis. In additional embodiments, the diagnostic system  120  can transmit the retrieved monitoring data to another computing device for analysis. 
     In further embodiments, the condition processing circuit  266  can retrieve selected monitoring data from the backplane  206  based upon detection of a pre-determined status. As an example, the condition processing circuit  266  can retrieve and review statuses generated by the protection processing circuit  264  to identify a status matching the pre-determined status. The identified status can also include a status time characterizing the time when the status was determined. Upon identification of a match, the condition processing circuit  266  can retrieve selected monitoring data including operating parameter measurements corresponding to the pre-determined status for time durations before and/or after the status time. In this manner, the diagnostic system  120  can be provided with operating parameter information relevant to determining the cause of the status. The pre-determined statuses and selected monitoring data can be contained within the one or more conditioning commands. 
     The number of condition processing circuits  266  present in the flexible monitoring system  202  can be varied independently of the number of input circuits  210   i . In certain embodiments, condition processing circuit  266  can be added to increase the ability of the flexible monitoring system  202  to output monitoring data. As an example, when two or more condition processing circuits  266  are present in the flexible monitoring system  202 , each can tasked with output of different measured operating parameters. In another example, two or more condition processing circuits  266  can output the same measured operating parameters in order to provide redundancy. Each can be beneficial under certain circumstances, providing computational flexibility to the flexible monitoring system  202 . In a further example, condition processing circuits  266  can be added to implement custom analytics without interfering with standard operation (e.g., when beta-testing a new analytic). 
     Output circuits  210   o  can be configured to obtain any monitoring data contained on the backplane  206  in response to receipt of output commands (e.g., contained in the one or more protection command signal  209   s  received from the internal network  110   a ). The output circuits  210   o  can further output the retrieved monitoring data to the internal network  110   a  in the form of output monitoring signals  206   s . Examples of monitoring data retrieved by output circuits  210   o  can include, but are not limited to, operating parameter measurements, the determined values, variables of the enhanced data set, statuses, and alarms. 
     With continued reference to  FIG.  3   , embodiments of the output circuits  210   o  can be in the form of proportional output circuits  270 . The proportional output circuits  270  can be configured to output monitoring signals  206   s  in the form of process control signals (not shown). The process control signals can be proportional to process variables, such as direct measurement values or variables of the enhanced data set, as compared to a predetermined scale. As an example, a current output can be a 4-20 mA output. The process control signals can be provided to the machine control system  112 , either directly or via the internal network  110   a , to facilitate control of operating parameters of the target  102 . The process variables included in the process control signals can be specified by the protection command signal  209   s.    
     In further embodiments, output circuits  210   o  can be in the form of one or more relay circuits  272  configured to retrieve selected status data from the backplane  206  and to actuate based upon received alarm statuses to annunciate an alarm. Annunciated alarms can be output in the form of alarm signals (not shown). In one example, relays can actuate based upon a single status. In another example, relays can actuate based upon predetermined Boolean expressions (e.g., AND or voting) that combine two or more statuses. The alarm signals can be provided to the machine control system  112  via the internal network  110   a , or directly to the machine control system  112 , to facilitate control of operating parameters of the target  102 . As an example, the machine control system  112  can shut down operation of the target  102  in response to receipt of an alarm signal. The selected status data and the logic employed for actuation of a relay can be specified by the protection command signal  209   s    
     In other embodiments, output circuits  210   o  can be in the form of at least one communication interface circuits  274 . The communication interface circuit  274  can be configured to retrieve selected monitoring data from the backplane  206  in response to receipt of the protection command signal  209   s . The selected monitoring data can include one or more of the measured operating parameters, the measured variables of the enhanced data set, determined statuses, and determined alarms. The retrieved data can be transmitted to the internal network  110   a  in one or more output monitoring signals  206   s  for use by machine control system  212  (e.g., for process control), the HMI  114  (e.g., display to an operator) and/or stored by the historian  116 . 
     Infrastructure circuits  210   n  can be configured to perform functionality required for the flexible monitoring system  202  to operate. As shown in  FIG.  3   , embodiments of the infrastructure circuits  210   n  can take the form of a system interface circuit  276 . The system interface circuit  276  can function as an access point for transmission of protection command signals  209   s  from the internal network  110   a  to the monitoring system  220 , facilitating configuration of the circuits involved in protection monitoring (e.g., protection processing circuit  264 , output circuits  210   i ). The protection command signals  209   s  can include one or more signals including any of the following in any combination: identification of selected monitoring data for each of the protection processing circuit  264  and output circuits  210   i  to retrieve and/or output, alarm set points for the protection processing circuit  264 , and logic for annunciation of relays by relay output circuits  272 . 
     It can be appreciated that, in contrast to the monitoring system  106 , embodiments of the flexible monitoring system  202  can separate the circuits  210  that configure protection monitoring functions (e.g., the system interface circuit  276 ) and condition monitoring functionality (e.g., the condition processing circuit  266 ). As a result, protection monitoring configuration can be performed entirely on the internal network  110   a  while condition monitoring configuration can be performed entirely on the external network  110   b . That is, the internal network  110   a  is not communicatively coupled to the external network  110   b . As a result, conditioning command signals  211   s  can be provided to the condition processing circuit  266  without the need to obtain approval from an authorized operator of the machine control system  112 . 
     In appreciation of cybersecurity risks inherent in allowing the condition processing circuit  266  to communicate with the external network  110   b  and the backplane  206 , the condition processing circuit  266  can be limited to unidirectional communication with the backplane  206  for data retrieval only. Such unidirectional communication can be established by any combination of hardware (e.g., data diodes), firmware, and/or software. In certain embodiments, this unidirectional communication is provided at least through hardware. As a result, the flexible monitoring system  202  can be kept secure from malicious actors while facilitating rapid configuration of the condition processing circuit  266 . 
     In another aspect, infrastructure circuits  210   n  can take the form of power input circuits  280 . Power input circuits  280  can provide the ability to connect one or more power sources to the flexible monitoring system  202 . 
     In a further aspect, infrastructure circuits  210   n  can take the form of bridge circuits  282 . The bridge circuits  282  can provide the ability to connect the backplanes  206  of two or more bases  204  together and to form the common backplane  206 ′ for communication therebetween. 
     So configured, embodiments of the circuits  210  can be arranged in any combination distributed amongst one or more bases  204  to form implementations of the flexible monitoring system having desired monitoring capabilities (e.g., input, processing, output, etc.). 
       FIG.  4    shows a detailed block diagram of a portion of an exemplary embodiment of a monitoring system  300  that can be configured to monitor operating parameters of industrial equipment. The monitoring system  300  can include any number of functional circuits  310 , which can be detachably coupled to a backplane  306  via ports  308  of the backplane  306 . The backplane  306  can be, include, or form part of, a physical bus. In some embodiments, the backplane  306  can have a unique ID that can be used to identify the backplane  306 . The backplane  306  can be a passive backplane  306  configured to facilitate multipoint asynchronous electronic communication between the functional circuits  310  that are coupled to the backplane  306 . Therefore, all data that is delivered to the backplane  306  can be received by all functional circuits  310  that are coupled to the backplane  306 . In the illustrated example, the backplane  306  includes a number of data lanes  312  that are in electronic communication with ports  308  that are configured to receive functional circuits  310 . Each port  308  is configured to facilitate electronic communication between a functional circuit  310  coupled to the port  308 , and all of the data lanes  312  of the backplane  306 . 
     As shown in  FIG.  4   , each data lane can include a transmitting portion  314  and a receiving portion  316 . Ends of the transmitting and receiving portions can be coupled with resistors  318  that extend between the transmitting and receiving portions  314 ,  316 . The resistors  318  can function to prevent, or mitigate, signal reflections that can be caused by unused energy associated with pulsed signals delivered to the data lanes  312  and/or noise due to inductance and capacitance effects associated with the data lanes  312 . The transmitting and receiving portions  314 ,  316  of each data lane  312  can be coupled to each port  308  to facilitate electronic communication between the functional circuits  310  and the data lanes  312 . Therefore, each port  308  facilitates delivery of data (e.g., data packets) to all data lanes  312 , and retrieval of data from all data lanes  312 . 
     There are a number of different types of functional circuits  310  that can be coupled do the backplane  306 . For example, one or more of the functional circuits  310  can be an input circuit, a processing circuit, an output circuit, and/or an infrastructure circuit, as described with regard to  FIGS.  2 - 3   . In some embodiments, each functional circuit  310  can have a unique ID (e.g., a MAC address) that can be used to identify the functional circuit  310 . The monitoring system  300  provides a high degree of flexibility and scalability by allowing a user to adjust performance of the monitoring system by attaching different functional circuits  310  to the backplane. For example, processing power can be increased by coupling additional processing circuits to the backplane  306 . As another example, the monitoring system  300  can be expanded by coupling additional input circuits to the backplane  306  such that the monitoring system  300  can receive and process sensor data from additional sensors (e.g., sensors  104 ) used for monitoring the industrial equipment. 
     As shown in the illustrated example, each functional circuit  310  can include a circuit controller  320  and a node  322  configured to facilitate and control electronic communication between the circuit controller  320  and the backplane  306 . For example, the node  322  can control delivery of data from the circuit controller  320  to the data lanes  312  of the backplane  306 . The nodes  322  can also control which data is delivered from the data lanes  312  to the circuit controllers  320  of the functional circuits  310 . 
     The circuit controllers  320  can include memory, at least one data processor, and/or other circuitry configured facilitate operation as described herein. The circuit controllers  320  can be configured to perform specific operations corresponding to desired functionality of the functional circuit  310 . In some embodiments, the circuit controllers  320  can be configured to receive data from an external source (e.g., a sensor, or a user device), process the data, and provide the data to the node  322 . For example, if a given functional circuit is an input circuit, as described herein with regard to  FIGS.  2 - 3   , the circuit controller  320  can include an analog-to-digital (A/D) converter that can be configured to receive analog signals from sensors and convert the analog signals to digital signals. Each of the circuit controllers can be configured to receive data from all data lanes of the backplane (e.g., via the node  322 ) and process the data. 
     In some embodiments, circuit controllers  320  of functional circuits  310  such as, e.g., protection circuits, can be configured to retrieve any data packets (e.g., data packets corresponding to sensor measurements) from data lanes  312  of the backplane  306  (e.g., via the node), analyze the retrieved data packets, and provide the results of such analysis to the data lanes  312  of the backplane  306  (e.g., via the node). For example, circuit controllers  320  of protection circuits can also be configured to compare data received from the backplane to pre-determined alarm conditions in real-time and determine a status (e.g., OK, alert, danger, etc.) for any measured operational parameter or variable, alone or in combination. The determined status can be subsequently output to the data lanes  312  of the backplane  306 . Circuit controllers  320  of condition monitoring circuits can generally function similarly to circuit controllers of protection circuits. However, nodes of condition monitoring circuits can prevent the circuit controllers  320  of the condition monitoring circuits from delivering data to data lanes  312  of the backplane  306 , as described in more detail below. 
     In some embodiments, circuit controllers  320  of output circuits (e.g., output circuits  210   o ) can be configured to obtain any data packets delivered to the data lanes  312  of the backplane  306 , and output monitoring signals (e.g., monitoring signals  106   s ) to any external systems (e.g., external systems  110 ). Examples can include, but are not limited to, the direct measurement values, variables of an enhanced data set, and statuses, 4-20 mA recorder outputs, voltages of direct measurement values, as described herein with regard to output circuits  210   i . In some embodiments, circuit controllers  320  of output circuits such as, e.g., relays, can be configured to retrieve status data from data lanes  312  of the backplane  306  (e.g., via the node) and to actuate based upon received data characterizing alarm statuses. In one example, circuit controllers  320  of relay circuits can actuate based upon a single status. In another example, relay circuits can actuate based upon Boolean expressions (e.g., AND or voting) that combine two or more statuses. In some embodiments, upon actuation, relay circuits can be configured to deliver a monitoring signal (e.g., monitoring signal  106   s ) to a control system (e.g., customer control system  212 ). The control system can then stop operation of the equipment being monitored to prevent damage or failure. 
     Circuit controllers  320  of infrastructure circuits (e.g., infrastructure circuits  210   n ) can be configured to perform operations required for the monitoring system to function. For example, circuit controllers  320  of system interface circuits can function as an access point for configuration of any of the functional circuits, alarm conditions for protection of the industrial equipment, and conditions for actuation of relay circuits. In some embodiments, circuit controllers  320  of system interface circuits can be coupled to the control system and/or a HMI (e.g., HMI  220 ). A trusted user, such as, e.g., a plant operator, can provide configuration data to the circuit controller  320  of the system interface circuit via the control system and/or the HMI, and the system interface circuit can provide data packets characterizing the configuration data to data lanes  312  of the backplane  306 . 
     As described herein, the circuit controllers  320  can be configured to provide data to the nodes  322 , but the circuit controllers do not have direct control of data delivery to the data lanes  312 . The nodes  322  of the functional circuits  310  can control data flow between the circuit controllers  320  and the data lanes  312 . Each node  322  can include a node controller  324 , a gate controller  326 , as well as an array of gate pairs  328 . The gate pairs  328  can be configured to facilitate electronic communication between the functional circuits  310  and the data lanes  312  of the backplane  306 . Each gate controller  326  can be configured to control operation of transmitters  330  and receivers  332  of the corresponding functional circuit  310 , thereby controlling data flow between the functional circuit  310  and the data lanes  312  of the backplane  306 . The transmitters  330  and receivers  332  can be referred to as gates. The transmitters  330  and receivers  332  are described in more detail below. 
     The node controllers  324  can include memory, at least one data processor, and/or other circuitry configured facilitate operation as described herein. Each node controller  324  can be in electronic communication with the circuit controller  320  gate controller  326  of the corresponding functional circuit  310 . The node controller  324  can function as an interface between the circuit controller  320  and the gate controller  326  and/or the transmitters  330  and receivers  332 . For example, the node controller  324  can be configured to control which data is transferred from the data lanes  312  to the circuit controller  320  using, e.g., packet filtering techniques. As an example, a circuit controller  320  of a functional circuit  310  such as, e.g., a protection circuit, can send a signal to the node controller  324  to instruct the node controller to provide specific data from the backplane  306 . The node controller  324  can monitor data lanes  312  of the backplane  306 , identify the desired data packets, and deliver the data packets and/or, data corresponding to the data packets, to the circuit controller  320  for processing. In some embodiments, the node controllers  324  can use information provided with data packets delivered to the backplane to identify relevant data to provide to the circuit controller  320 . For example, the node controller can use IP addresses, MAC addresses, TCP/IP headers, UDP/IP headers, message headers, object headers, source information. destination information, and/or contents of the data packets to identify relevant data packets to provide to the circuit controller  320 . In some embodiments, the node controller  324  can be configured to receive signals from the circuit controller  320 , encode the signals into bits, and deliver signals (e.g., data packets) corresponding to the encoded bits to the gate controller  326  for the data to be delivered to data lanes  312  of the backplane  306 . The node controller  324  can also store a copy of a schedule that can be used to control operation of the transmitters  330  and receivers  332 . 
     The gate controllers  326  can include memory, at least one data processor, and/or other circuitry configured facilitate operation as described herein. Each gate controller  326  can be in electronic communication with the transmitters  330 , receivers  332 , and the node controller  324  of the corresponding functional circuit  310 . Each gate controller  326  can be configured to control operation of the transmitters  330  and the receivers  332  of the corresponding functional circuit  310 , thereby controlling data flow between the functional circuit  310  and the data lanes  312  of the backplane  306 . For example, the gate controllers  326  can control operating modes of the gate pairs  328 . In some embodiments, the gate controllers  326  can be configured to control operating modes of the transmitters  330  and receivers  332  based on a predetermined schedule and/or instruction provided by the node controller  324 . As an example, the gate controllers  326  can be configured to receive data from the node controller  324 , store the data, and deliver it to the data lanes  312  at a scheduled time. In some embodiments, the gate controller  326  can receive the schedule from the node controller  324 . The schedule, as well as operating modes of the transmitters  330  and receivers  332 , are described in more detail below. In some embodiments, each data lane  312  can have a corresponding schedule that defines when the various functional circuits  310  can deliver data packets to that particular data lane  312 . 
     As shown in the illustrated example, the gate pairs  328  can be electrically coupled to individual data lanes  312  via the ports  308 . In some embodiments, each gate pair  328  can be a half-duplex transceiver that includes a transmitter  330  and a receiver  332 . The transmitters and receivers can be referred to as gates. Each transmitter and receiver of each gate pair  328  can be electrically coupled to receiving and transmitting portions  316 ,  314  of a corresponding data lane  312 , respectively. In some embodiments, the node controller  324 , gate controller  326 , transmitters  330  and/or receivers  332  can be a field programmable gate array (FPGA). 
     The transmitters can be configured to facilitate delivering signals corresponding to data packets to data lanes of the backplane. Each transmitter can have first and second operating modes. When in the first operating mode, the transmitters are configured to allow data (e.g., data packets) to be transferred from the functional circuits  310  to the data lanes  312  of the backplane  306 . In some embodiments, the gate controller  326  can deliver control signals to the transmitters to set them to operate in the first operating mode. As an example, the control signal can be an electrical signal delivered to the transmitters. As another example, the control signal can be a change in a voltage and/or current of an electrical signal delivered to the transmitters. When in the second operating mode, the transmitters are configured to prevent data (e.g., data packets) from being transferred from the functional circuits  310  to the data lanes  312  of the backplane  306 . For example, when in the second operating mode, the transmitters can be logically disconnected from the port  308  and from the corresponding data lane  312  of the backplane  306 . When in the second operating mode, the transmitters can have a high impedance to prevent signals from being delivered to the data lanes  312  of the backplane  306 . For example, the gate controller  326  can deliver control signals to the transmitters such that the transmitters have a high impedance, thereby preventing the transmitters from delivering data packets to the data lanes  312 . As another example, the gate controller  326  can stop delivering electrical signals to the transmitters  330 , thereby placing the transmitters  330  in a state of high impedance. Operating modes of each transmitter can be controlled independently by the gate controllers  326  of the functional circuits  310 . 
     The receivers can facilitate receiving signals corresponding to data packets from data lanes  312  of the backplane  306 . In some embodiments, the receivers can be configured to modify and/or control signals delivered to the circuit controller  320  from the backplane. For example, the receivers can receive signals from the data lanes  312  of the backplane  306 , amplify the signals, and provide the signals to the circuit controller  320  (e.g., via the gate controller  326  and/or the node controller  324 ). 
     In some embodiments, the receivers can also have first and second operating modes. When in the first operating mode, the receivers can be configured to allow data (e.g., data packets) to be transferred from the attached data lane  312  to the node controller  324  and/or the circuit controller  320 . When in the second operating mode, the receivers can be configured to prevent data (e.g., data packets) from being transferred from the attached data lane  312  to the node controller  324  and/or circuit controller  320 . As an example, if the gate pairs  328  are half-duplex transceivers, when the transmitter is in the first operating mode, the receiver is in the second operating mode. In some embodiments, when the transmitter switches to the first operating mode, the transmitter can deliver a control signal to the receiver to switch the receiver to the second operating mode. Conversely, when the transmitter is in the second operating mode, the receiver is in the first operating mode. As an example, when the transmitter switches to the second operating mode, the transmitter can stop delivering the control signal to the receiver, thereby switching the receiver to the first operating mode. 
     In some embodiments, operating modes of the receivers can be controlled independently of the corresponding transmitter of the gate pair  328 . For example, the gate controller  326  can deliver a control signal to the receivers to put the receivers in the second operating mode. Periodically, at predetermined times, the gate controller  326  can stop delivering the control signal to the receivers, thereby switching the receivers to switch to the first operating mode. 
     In order to effectively manage communication between each of the functional circuits  310 , a communication schedule can be created and distributed among the functional circuits  310 . In an exemplary embodiment, at least one node  322  of one of the functional circuits  310  can include a schedule controller  334  that can be part of, and/or in electronic communication with, the node controller  324 . The schedule controller  334  can include memory, at least one data processor, and/or other circuitry configured facilitate operation as described herein. The schedule controller can be configured to generate schedules that can define when each of the transmitter and/or receivers are in the first or the second operating modes. Therefore, the schedule determines when each functional circuit  310  can deliver data to each data lane  312  of the backplane  306 . Controlling operating modes of the transmitters  330  and receivers  332  can be referred to as gating. Each schedule can include a frame that corresponds to a predetermined amount of time. The frame can be divided into a number of time slices. Each time slice can be assigned to a given functional circuit  310 , thereby allowing the functional circuit  310  to deliver data to the data lanes  312  during assigned time slice. Schedule generation can also be referred to as arbitration. Functional circuits  310  that are capable of generating schedules and delivering the schedules to the data lanes  312  can be referred to as arbitration capable functional circuits. The functional circuit  310  that is in control of generating the schedule can be referred to as a master circuit. The node  322  of the master circuit can be referred to as a master node, or a manager node. Other functional circuits  310  that are coupled to the backplane  306  can be referred to as slave circuits. The master circuit can be in a master/slave relationship with all other functional circuits (e.g., the slave circuits) that are coupled to the backplane  306 . Nodes  322  of the slave circuits can be referred to as slave nodes. 
     In some embodiments, gating can be autonomously arbitrated between functional circuits  310  of the monitoring system  300 . For example, upon initial system startup, the functional circuits  310  can wait for a predetermined period of time to receive a beacon packet indicating the presence of a master circuit. If the functional circuits  310  do not receive a beacon packet after the predetermined period of time, a functional circuit  310  that is capable of arbitration can deliver a beacon packet to the data lanes  312  indicating that it (the arbitration capable functional circuit  310 ) has assumed arbitration responsibilities, thereby becoming the master circuit. 
     To generate the schedule, the schedule controller  334  of the master circuit can start a schedule record in memory. The schedule controller  334  can then provide the node controller  324  with a signal to deliver a beacon packet to data lanes  312  of the backplane  306 . The beacon packet can contain information about the monitoring system  300  (e.g., unique IDs) schedule for the current frame. The beacon packet can also include time syncing information that each of the slave circuits can use to synchronize internal clocks with that of the master circuit. Time synchronization can allow functional circuits  310  to effectively communicate over shared data lanes  312  at predetermined scheduled times. The beacon signal can also trigger slave circuits to request time slices within the following frame. Each slave circuit can deliver a beacon response packet to the data lanes  312  to request certain time slices to deliver data to the backplane  306 . For example, node controllers  324  can generate beacon packets to request time slices based on requests received from the circuit controllers  320 . 
     The schedule controller  334  of the master circuit can receive the requests and can assign time slices to various nodes  322  and/or functional circuits  310 , thereby generating the schedule. The schedule controller  334  can deliver the schedule to the node controller  324 , which can provide the schedule to the gate controller  326 . The gate controller  326  can deliver the schedule to the data lanes  312  of the backplane  306  at predetermined time slices, which can be referred to as beacon time slices, via the transmitters. Each slave circuit can receive the schedule from the backplane  306 , and implement the schedule. For example, gate controllers  326  of each functional circuit  310  can receive the schedule and can enforce the schedule by controlling operating modes of the transmitters  330  and receivers  332  based on what is defined within the schedule. 
     In some embodiments, the gate controller  326  of each node  322  can logically disconnect the transmitters from the data lanes  312  during time slices that are not assigned to that particular node  322 . In this way, circuit controllers  320  of slave circuits can request certain time slices within the schedule, but the circuit controllers  320  have no direct control over the transmitters  330  and receivers  332  of the functional circuit  310 . As such, the circuit controllers  320  have no direct control over when data can be delivered to the data lanes  312 . Therefore, if a functional circuit is sending invalid data, e.g., due to accidental or intentional corruption, the functional circuit  310  only corrupt time slices that have been scheduled for that particular functional circuit  310 . 
     During normal operation, the gate controller  326  of a given functional circuit  310  can operate all of the transmitters  330  in the first operating mode during time slices that are assigned to that particular functional circuit  310 . During assigned time slices, the gate controller  326  can provide data to all of the data lanes simultaneously. For example, if the backplane  306  includes 16 data lanes, the gate controller  326  can transmit a 2 bytes of information by simultaneously transmitting 1 bit of information to each data lane via the transmitters  330 . 
     In some embodiments, one or more of the slave circuits can be configured to assume arbitration responsibilities if the master circuit is disabled or removed from the backplane. For example, if the slave circuits do not receive a beacon signal at the beginning of a frame, an arbitration capable slave circuit can wait for a period of time before delivering a beacon packet to the data lanes  312  indicating that it (the arbitration capable slave circuit) has assumed arbitration responsibilities, thereby becoming the master circuit. Methods of generating the schedule, and communication between master circuits and slave circuits, are discussed in more detail below. 
     Since arbitration can be performed by multiple functional circuits  310 , and gating can be managed by nodes  322  of each functional circuit  310  rather than by a centralize source on the backplane  306 , the monitoring system  300  provides robust communication between functional circuits  310  without a single point of failure. The method of arbitration is discussed in more detail below. 
     The functional circuits  310  can vary in a number of ways. For example, in some embodiments, one or more functional circuits can include multiple nodes for redundancy.  FIG.  5    shows an example of a functional circuit  310   a  that can generally be similar to the functional circuits  310  shown in  FIG.  4   , but that includes a primary node  322  and a secondary node  323 . The functional circuit  310   a  can include a circuit controller  320  that can be in electronic communication with node controllers  324  of the nodes  322 ,  323 . The primary and secondary nodes  322 ,  323  can include the node controllers  324 , schedule controllers  334 , gate controllers  326 , and gate pairs  328  that can include transmitters  330  and receivers  332 , which can be transmitters and receivers, respectively. The functional circuit  310   a  can be coupled to a port (e.g., port  308 ) of a backplane (e.g., backplane  306 ), and can function as described above with regard to the functional circuits  310  shown in  FIG.  4   . However, in this case, during operation one of the primary and secondary nodes  322 ,  323  can be disabled while the other of the primary and secondary nodes  322 ,  323  is operable. If the operable node  322 ,  323  fails, the other node  322 ,  323  can be activated to ensure that the functional circuit  310   a  can send data to, and receive data from, data lanes of the backplane. In some embodiments, the port of the backplane can couple corresponding gate pairs  328  of the individual nodes to the same data lane of the backplane, thereby allowing a seamless transition to the secondary node  323 , if the primary node  322  fails. 
     In some embodiments, a monitoring system can include functional circuits that can be prevented from delivering data to the data lanes of the backplane. As an example, a functional circuit such as, e.g., a condition monitoring circuit, can be configured to receive data from data lanes of a backplane, but can be prevented from delivering data to the data lanes of the backplane.  FIG.  6    shows an example of a functional circuit  310   b  that is configured to receive signals from data lanes of a backplane, but is prevented from delivering signals to the data lanes of the backplane. As shown in the illustrated example, the functional circuit that includes a circuit controller  320  and a node  325  that is configured to facilitate communication between the circuit controller  320  and data lanes of the backplane. The node  325  includes a node controller  324 , a gate controller  326 , receiver  332  such that it can receive signals from data lanes of a backplane, but does not include transmitters  330 , thereby preventing the functional circuit  310   b  from delivering signals to the data lanes of the backplane. 
     In some embodiments, the functional circuit  310   b  can allow an untrusted, or external, user to view information from the backplane and interact with the circuit controller  320 . An example of such a user can be, e.g., a remote maintenance engineer. As an example, the user can deliver data to the circuit controller  320  to request specific information (e.g., sensor data) from the data lanes for troubleshooting purposes. The circuit controller  320  can deliver the request to the node controller  324 , which can allow the desired data to be delivered from the data lanes to the circuit controller  320 . The user can review the data and assist a plant operator with troubleshooting, but cannot deliver any data to the data lanes of the backplane. Therefore, the user cannot make any changes to a monitoring system that employs the functional circuit  310   b . The user can only relay information to the plant operator which, as a trusted user, can make changes to the monitoring system. 
     Controlling when each circuit module can communicate can provide a high degree of synchronization and determinism, which can facilitate communication between functional circuits without centralized switching within the bus. By utilizing functional circuits that can generate communication schedules, in conjunction with one or more bus that allows each of the functional circuits to communicate information to each other, the monitoring system  300  provides a modular, flexible, and scalable solution for monitoring industrial equipment. 
     Traditional monitoring systems can be limited in terms of flexibility and scalability. Additionally, costs and complexity of installation can create a significant barrier to entry for users that want to monitor low cost and/or low priority components/systems. By utilizing functional circuits that can be detachably coupled to the backplane, performance of the monitoring systems described herein can be adjusted and/or scaled to fit individual monitoring needs. For example, processing power can be increased by coupling additional processing circuits to the backplane. As another example, the monitoring system can be expanded by coupling additional input circuits to the backplane to such that the monitoring system can receive and process sensor data from additional sensors. Additionally, by generating a schedule at a master circuit, and gating communications at slave circuits, the monitoring system can provide robust communication and/or eliminate centralized failure points associated with system that use centralized switching for communication. 
     Since functional circuits can send and receive signals via one or more data lanes in a bus, it can be desirable to configure functional circuits (e.g., functional circuits  310 ) to broadcast data based on a schedule. Doing so can prevent multiple functional circuits from broadcasting simultaneously resulting in reduction of collision between data packets broadcasted by different functional circuits.  FIG.  11    illustrates an exemplary time sequencing of communication between functional circuits of a monitoring system. The monitoring system time can be divided into system frames during which functional circuit communication can be carried out based on a system frame schedule. 
     As illustrated in  FIG.  7   , system time  402  can be divided into system frames  404 A-N. A system frame  404 A can extend over a period of time, for example, between a starting time  406  and an ending time  408 . The system frame can be divided into multiple time slices  410 A- 410 N that can be temporally contiguous. The first time slice  410 A can begin at the starting time  406  which can be used as a reference time for the system frame. A second time slice  410 B can be temporally adjacent to the first time slice  410 A. The first time slice  410 A can be referred to as a beacon time slice. The second time slice  410 B can be referred to as a beacon response time slice. Together, time slices  410 A and  410 B can constitute an arbitration period  411  during which a master circuit can interact with slave circuits for allocation of time slices for data communication over the data lanes of the bus. The remaining time slices  410 C- 410 N can constitute a data communication period during which slave circuit can broadcast data packets on the data lanes of the bus. 
     During the first time slice  410 A of the arbitration period  411 , the master circuit can broadcast a beacon packet on a data lanes of the bus to which the master circuit is communicatively coupled. The beacon packet can be received by the slave circuits (e.g., node controllers of the slave circuits) that are communicatively coupled to the data lane. The beacon packet can include a system frame schedule for the system frame  404 A that allocates time slices of the data communication period (e.g., time slices  410 C- 410 N) to slave circuits of the monitoring system. System frames can also be referred to as frames. 
     During the second time slice  410 B of the arbitration period  411 , one or more slave circuits can broadcast beacon response packet on the data lane of the bus. As an example, node controllers (e.g., node controller  324 ) can generate beacon response packets and deliver the beacon response packets to the data lane via transmitters (e.g., transmitters  330 ). The master circuit can receive the beacon response packets from the slave circuits. The beacon response packets can include requests for time slice assignment. The master circuit can generate schedules for future system frames (e.g., system frames  404 B-N) that can include time slice assignments based on the requests in the beacon response packets from the slave circuits. 
     During the data communication period (e.g.,  410 C- 410 N), the slave circuits can broadcast data packets on the data lane of the bus. A slave circuit can receive the beacon packet broadcasted by the master circuit during the arbitration period  411 , and can broadcast data packets during the time slice assigned to it in the system frame schedule of the beacon packet. 
     For example, the gate controller in the slave circuit can configure the slave bus node to transmit data packets during the time slice assigned to the slave circuit. This can be done by operating one or more transmitters in the slave bus node in a first operating mode where the transmitters allow data packets to be transferred from the slave circuit to one or more data lanes in the bus. 
     As illustrated by an expanded view of time slice  410 G, each time slice  410 A- 410 N can include a usable time slice period  420  temporally located prior to a dead band period  424 . A slave circuits can be configured to transmit data packets during the usable time slice period of the assigned time slice. As an example, the usable time slice period  420  can be used to transmit a data packet that includes a preamble  426 , headers  428 ,  430 ,  432 , a data payload  434 , a cyclic redundancy check (CRC)  436 , and an interpacket gap  438 . As an example, the headers  428 ,  430 ,  432  can be an Ethernet header, an IP header, and a UDP header, respectively. In some embodiments the preamble  426  can be 8 bytes, the data payload  434  can be 1476 bytes, the CRC  436  can be 4 bytes, and the interpacket gap  438  can be 12 bytes. Furthermore, in some embodiments, the headers  428 ,  430 ,  432  can be 14, 20, and 4 bytes, respectively. Information corresponding to sizes of preamble  126 , the data payload  134 , the CRC  436 , and the interpacket gap  438 , and the headers  428 ,  430 ,  432  can be distributed in schedules provided with beacon packets. The sizes of the various portions of data packets that can be transmitted during the useable time slice period can vary. Similarly, the duration of the useable time slice period  420  can vary. For example, the duration of the usable time slice period  420  can be determined based on the largest permissible data packet that can be broadcasted by a slave circuit and/or rates at which data can be transferred from functional circuits. The duration of the useable time slice period  420  can be at least as long as the amount of time required to transfer a data packet to the backplane. As an example, data packets can be in a range of approximately 56-65535 bytes. As another example, time slices have durations in the range of approximately 2500-13496 nanoseconds (ns). 
     The slave circuits may not transmit any data packets during the dead band period  424 . The dead band periods  424  at the end of each time slice  410 A- 410 N can facilitate seamless transitions between data delivery from functional circuits in communication data lanes of a backplane (e.g., backplane  306 ). For example, the dead band period  424  can function to mitigate data transmission timing errors due to inaccuracies in time synchronization between functional circuits, as well as minimize signal collisions that can result from latencies associated with data transmission between bridged backplanes. As an example, time synchronization errors can arise due to signal propagation delay along data lanes, propagation delay between bridged backplanes, time synchronization errors between functional circuits, bit error rate, and the like. Bridged backplanes are described in more detail below. 
     In some embodiments, the duration of the dead band period  424  can be determined based on a data communication protocol employed in the monitoring system. For example, an Ethernet communication protocol (e.g., TCP/IP, UDP/IP) can require that the dead band period  424  can allow for communication of a 12 byte data packet. In some implementations, the duration of the dead band period  424  can be determined based on expected and/or known time synchronization errors. 
       FIG.  8    illustrates an exemplary data structure of a beacon packet  500  broadcasted by the master circuit during the arbitration period. The beacon packet can include a preamble field  501 , which can function as a reference signal. The slave circuits of the monitoring use the preamble field  501  to identify the beginning of data within the beacon packet. The beacon packet can also include data fields such as a type field  502 , current time field  504 , network identification number (ID) field  505 , number of lanes field  507 , baud rate field  506 , schedule header  522 , and schedule entries array  524 , among others. The type field  502  can indicate that the data packet is a beacon packet  500 . In some embodiments, functional circuits coupled to the backplane can use the preamble field  501  and the type field  502  to identify data delivered to the backplane. For example, the preamble field  501  can include a data transmission clock, which functional circuits coupled the backplane can use to identify data transmitted from a given functional circuit. 
     The current time field  504  can function as a reference time to synchronize clocks of the slave circuits. The current time field  504  can be, e.g., one or more of time of transmission of the beacon packet, starting time  406 , ending time  408 , and the like. The network ID field can identify a network formed by one or more backplanes and functional circuits coupled thereto. In some embodiments, network IDs can be generated and/or assigned to the monitoring system upon startup. The network IDs can function to characterize hardware of the monitoring system (e.g., unique IDs of functional circuits and/or the backplane, number of data lanes on the backplane, etc.) as well as operating parameter such as e.g., communication schedules, the baud rate, etc. In some embodiments, network IDs can provide a means to identify and/or separate independent networks that get connected unintentionally. The baud rate field  506  can include data that characterizes a speeds of communication over the various data lanes of the backplane. 
     The beacon packet can also include the system frame schedule  520 . The system frame schedule  520  can include a schedule header  522  and a schedule entry array  524 . The schedule header  522  can include self-describing information about the schedule. For example, the schedule header  522  can include data characterizing a number of time slices included in the schedule, a duration of each time slice, a duration of a dead band within the time slice, and identification data that can be used by node controllers of functional circuits to parse time slice assignments within the schedule. 
       FIG.  9    illustrates an exemplary structure of system frame schedule  520 . The system frame schedule includes the schedule header  522  and the schedule entry array  524 . The schedule entry array  524  can include time slice assignments of time slices in the system frame (e.g., system frame  404 A). The data matrix of schedule entry array  524  can include a time slice array  602  and assignment array  604 . Fields of the time slice array can be identify the time slices and the fields of the assignment array can include the assignment data for the time slice arrays. For example, assignment field of a time slice that has been assigned to a slave circuit can include unique identification (ID) of the slave circuit. As an example a unique ID can be, e.g., MAC address. In some embodiments, the schedule entry array  524  can include time slices that are not be assigned to a slave circuit. The schedule entry array  524  can also include best-effort time slices in which multiple slave circuits can broadcast a data packet. An assignment field of an unassigned time slice can have a first predetermined value (e.g., 00-00-00-00-00-00). An assignment field of a best-effort time slice can include a second predetermined value (e.g., FF-FF-FF-FF-FF-FF, or 0xAA-AA-AA-AA-AA-AA). 
     In some embodiments, the master circuit can discard any data packets broadcasted by slave monitoring nodes during an unassigned time slice. During the best effort time slice any functional circuit coupled to the backplane of the monitoring system can broadcast a data packet. As an example, the best effort time slice can be used to communicate low priority traffic, asynchronous application layer events (e.g., events that are difficult to schedule). Because multiple functional circuits are broadcasting during the best effort time slice, data packets collisions can occur. These collisions can be resolved using, for example, a CSMA/CD algorithm. In some embodiments, each functional circuit can monitor data lanes of the backplane to determine if a collision has occurred. For example, during periods in which a functional circuit is transmitting data to data lanes of the backplane, a node controller and/or a gate controller of the functional circuit can monitor the data lanes to determine if data that exists on the backplane is the same as the data that was transmitted. If the data on the backplane is different than the data that was transmitted, then the node controller and/or gate controller can determine that a collision has occurred. 
       FIG.  10    illustrates an exemplary data structure of a beacon response packet  700  that can be provided to the backplane by a slave circuit during the second time slice (e.g.,  410 B) of the arbitration period  411 . The beacon response packet  700  can include type field array  701  and the value array  703  can include corresponding array  703  of values. The field array  701  can include a data field  702  indicating that data the beacon response packet  700  represents a beacon response packet. The field array  701  can also include a slave time fields  704  that can include data that characterizes an internal time of the slave circuit. The field array  701  can include a unique identification (ID) field  706  that can include data that characterizes a unique identification corresponding to the slave circuit. The field array  701  can also include a time slice request field  708  that can include data that characterizes a number of time slices needed by the slave circuit to broadcast its data packets. 
       FIG.  11    illustrates an exemplary communication protocol  800  between a master circuit  801  and a slave circuit  803 . The master circuit  801  can include data receivers  804 A and data transmitters  806 A. The slave circuit  803  can include data receivers  804 B and a data transmitters  806 B. During the time synchronization period  812 , nodes of the master circuit  801  and the slave circuit  803  can synchronized their time. For example, the master circuit  801  can include its reference time (e.g., reference time  504 ) in the beacon packet and transmit it to the slave circuit  803  during the arbitration period (e.g., first time slice of a system frame) of one or more system frames. The slave circuit can remain in a standby mode and receive the beacon packets in multiple system frames. The slave monitoring node can synchronize its internal time with the reference time of the received beacon packet. 
     During the arbitration period  814  of a system frame, the master circuit can transmit beacon packets to the slave monitoring nodes (e.g., during the first time slice  410 A), and can receive beacon response packet from the slave monitoring nodes (e.g., during the second time slice  410 B). During the data communication period  816 , the slave circuit can transmit data packets to the master circuit based on the system schedule transmitted in the beacon packet. 
       FIG.  12    shows an exemplary structure of a data packet  900  that can be delivered to the backplane (e.g., backplane  306 ) of a monitoring system (e.g., monitoring system  300 ) during operation. As shown in the illustrated example, the data packet  900  can include a packet header  902 , a communication header  904 , a protocol header  906 , a packetized message header  908 , an object message header  910 , an object header  912 , and an object body  914 . In some embodiments, node controllers (e.g., node controllers  324 ) and/or gate controllers (e.g., gate controllers  926 ) of functional circuits can use data within the packet header  902  and the communication header  904  to characterize and/or identify the data packet  900 . The protocol header  906 , packetized message header  908 , object message header  910 , object header  912 , and object body  914  can include data corresponding to a payload of the data packet  900 . In some embodiments, circuit controllers (e.g., circuit controllers  320 ) can used data within the protocol header  906 , packetized message header  908 , object message header  910 , and/or object header  912  to characterize and/or identify data within the data packet  900 . 
     The packet header  902  can include a packet preamble field  916 , a type field  918 , packet number fields  920 , a length field  922 , and a packet CRC field  924 . The preamble field  916  can include a data transmission clock, which functional circuit coupled the backplane can use to identify the data packet  900 . The type field  918  can include data that describes the type of data transmitted within the data packet  900 . For example, if the data packet was transmitted by an input circuit, the type field can indicate that the data packet includes sensor data. The packet number fields  920  can include data characterizing information for delivering the data packet. For example, the packet number fields  920  can include data characterizing source information and/or destination information. The length field  922  can include data describing a length (e.g., in bytes) of the data packet  900 . The packet CRC field  924  can include error checking information that can be used by other functional circuit to detect unintentional changes in raw data of the packet header  902 . 
     The communication header  904  can include an Ethernet header  926 , an IP header  928 , and a TCP/UDP header  930 . The Ethernet header  926  can include data characterizing MAC addresses of the functional circuit and/or the backplane. IP header  928  can include data describing a source IP address and/or a destination IP address. For example, the IP header  928  can include an IP address of the functional circuit that delivered the data packet  900  as well as an IP address of a functional circuit intended to receive the data packet  900 . The TCP/UDP header  930  can include data describing source and destination ports. For example, the TCP/UDP header  930  can include a port number identifying a port that the functional circuit that delivered the data packet  900  is coupled to. The TCP/UDP header  930  can also include a port number identifying a port corresponding to that functional circuit that is intended to receive the data packet  900 . 
     The protocol header  906  can include a message type field  932 , a message length field  934 , and a message CRC field  936 . The message type field  932  can include data that describes the type of data transmitted within the data packet  900 . In some embodiments, circuit controllers (e.g., circuit controller  320 ) of functional circuits that receive the data packet can use data within the message type field  932  to identify the type of data within the data packet  900 . The message length field  934  can include data describing a length (e.g., in bytes) of a message within the data packet  900 . The message CRC field  936  can include error checking information that can be used by other circuit controllers of functional circuits to detect unintentional changes in raw data of the message. 
     The packetized message header  908  can include a packet length field  938 , packet number fields  940 , and a packet CRC field  942 . The packet length field  938  can include data describing a length (e.g., in bytes) of the data packet  900 . The packet number fields  940  can include data characterizing information for delivering the data packet  900 . The packet CRC field  942  can include error checking information that can be used by circuit controllers that receive the data packet  900  to detect unintentional changes in raw data of the packet header  902 . 
     The object message header  910  can include an object number field  944 . The packet number fields  940  can include data describing a number of objects within the data packet  900 . 
     The object header  912  can include an object ID field  946 , an object type field  948 , an object length field  950 , a timestamp field  952 , a status field  954 , a configuration sequence number field  956 , and an object CRC field  958 . The object ID field  946  can include data identifying an object field  960  of the object body  914 . The object type field  948  can include data that describes the type of object transmitted within the data packet  900 . The object length field  950  can include data describing a length (e.g., in bytes) of the object within the data packet  900 . The timestamp field  952  can include data characterizing a time corresponding to when the data packet  900  was delivered to the backplane. The status field  954  can include data describing a status of the object within the data packet  900 . The configuration sequence number field  956  can include data describing a configuration of data within the data packet  900 . The object CRC field  958  can include error checking information that can be used by circuit controllers that receive the data packet  900  to detect unintentional changes in raw data of the object within the data packet  900 . 
     The object body  914  can include an object field  960 . The object field  960  can include a portion of the payload that corresponds to the object transmitted within the data packet  900 . For example, the object field can include data from sensors. 
     Initially, when a functional circuit of a monitoring system is powered on, the functional circuit (e.g., a node controller) can perform an initialization process to determine if a master circuit exists and/or to assume arbitration responsibilities to become the master circuit.  FIG.  13    shows an exemplary flow diagram  1100  that illustrates an initialization process that can occur when a functional circuit is powered on. The functional circuit can be powered on at step  1102 . As an example, the functional circuit can be powered on when the monitoring system powered on. As another example, the functional circuit can be powered on when it is coupled to an active monitoring system (e.g., via hot insertion). The functional circuit can wait for a period of time to detect a beacon signal and/or to receive a schedule. 
     After a period of time, at step  1104 , the functional circuit can determine that no beacon has been detected, that no schedule is available, and that the monitoring system does not include a master circuit. The functional circuit can also a link state. The link state can describe a state of connectivity to the backplane. If the link state indicates that there is no link, at step  1106 , the functional circuit can start a node (e.g., node  322 ) of the monitoring state to generate a positive link state. For example, a card controller of the functional circuit can deliver a signal to a node controller to start the node. In some embodiments, the node controller and/or gate controller can identify the link state. If there is no link, the node controller and/or gate controller can start the node. If the node is linked to the backplane, at step  1108 , the functional circuit can perform a self-evaluation to determine if it is arbitration capable. For example, the node controller of the functional circuit can determine if it includes, or is coupled to, a schedule controller. If the functional circuit is not arbitration capable, it can stop the initialization process at step  1110 . 
     If the functional circuit is arbitration capable, a schedule controller of the functional circuit can generate a beacon packet and provide the beacon signal to the data lanes of the backplane (e.g., via the node controller and transmitters). If the node controller detects a collision, or if the node controller detects a beacon signal from a different functional circuit, the schedule controller and/or node controller can enter a state of random back-off at step  1112 . At step  1112 , the schedule controller and/or node controller can wait for a period of time to receive a beacon signal from another functional circuit. 
     In some embodiments, functional circuits that are arbitration capable can each be configured to wait for random amounts of time during step  1112 . Waiting for random amounts of time can reduce the probability of multiple consecutive collisions, thereby allowing a functional circuit to assume arbitration capabilities more quickly. During step  1112 , if the functional circuit receives a valid beacon packet, the node can stop the initialization process. If, at any point during operation, a frame (e.g., the frames discussed above with regard to  FIG.  7   ) does not include a beacon packet, the functional circuit can restart the initialization process and attempt to become the master circuit. If each frame includes a beacon packet, the initialization process can remain stopped indefinitely. 
     If the functional circuit does not detect a beacon signal, at step  1114 , the functional circuit can assume arbitration responsibilities, thereby becoming the master circuit. After the functional circuit becomes the master circuit, the master circuit can generate, distribute, and maintain schedules that define when each slave circuit of the monitoring system can communicate. 
       FIG.  14    shows a flow diagram  1200  that illustrates a method of generating a schedule based on the communication requests from slave circuits. As shown in the illustrated example, the master circuit can assume arbitration capabilities at step  1202 . At step  1204 , the schedule controller of the master circuit can generate a schedule and assign beacon time slice and beacon response time slice (e.g., time slices  410 A,  410 B). The schedule controller can also store the schedule in memory. At this point, each time slice within the schedule can be unassigned, with the exception of the beacon time slice (e.g., time slice  410 A) and the beacon response time slice (e.g., time slice  410 B). As another example, the time slices can be assigned based on a previously available schedule. Alternatively, if the functional circuit is in a continued state of operation from a previous frame, the method can move directly to step  1206 . 
     At step  1206 , the master circuit can transmit a beacon packet during the first time slice (e.g., time slice  110 A). If the master circuit detect that there was a collision, at step  1207 , the master circuit can enter a state of random back-off in which it will wait for a period of time before attempting to transmit another beacon packet with an updated data transmission clock, or timer, which can be used for time synchronization across various functional circuits coupled to the backplane. 
     If a no collision is detected the schedule controller and/or node controller of the master circuit can wait for a beacon response packet from one or more slave circuits at step  1208 . If there is no beacon response packet, or if the beacon response packet is invalid, the master circuit can determine that no schedule update is necessary at step  1210 . 
     At step  1212 , if the master circuit receives a valid beacon response packet from a slave circuit, the schedule controller of the master circuit can process time slice requests from the beacon response packet. If there are no time slices available to be assigned, the schedule controller can generate an error signal at step  1214 . In some embodiments, the schedule controller can deliver the error signal to a plant operator via a gateway circuit. For example, the schedule controller can deliver the error signal to the backplane via the node controller and transmitters and receivers of the master circuit. The gateway circuit can receive the error signal from the data lane, and deliver the error signal to a user device to inform the user that the backplane has been overprovisioned. In some embodiments, a user can replace the backplane with a backplane that includes more data lanes, thereby facilitating a higher volume of data traffic. As another example, a user can replace the backplane with a backplane that is configured to transfer data at a higher rate. 
     If time slices are available for scheduling, at step  1216 , the schedule controller can update the schedule to accommodate communication requested within the beacon response packet. The schedule controller can deliver another beacon packet containing an updated schedule to the backplane. Slave circuits can receive the beacon packet from the backplane, and update their schedules. 
     At step  1218 , the schedule controller and/or node controller of the master circuit can transition to a traffic monitoring, or “garbage collection” phase, as described in more detail below. In some embodiments, the traffic monitoring phase can occur simultaneously with all scheduling and arbitration functions performed by the master circuit. 
     As mentioned above with regard to step  1212 , if the schedule controller of the master circuit receives a valid beacon response from a slave circuit, the schedule controller of the master circuit can process the time slice requests from the beacon response packet.  FIG.  15    shows a flow diagram  1300  illustrating an exemplary method of processing time slice requests from beacon response packets and generating a schedule entry array (e.g., schedule entry array  524 ). At step  1302 , the schedule controller of the master can receive a beacon response packet and begin processing time slice requests. 
     At step  1304 , the schedule controller can allocate memory for variable N and set a value for the variable within memory. The schedule controller can determine a number of time slices requested from the beacon response packet. For example, the schedule controller can evaluate a value (e.g., a value provided with the number of requested time slices field  708 ) corresponding to a time slice request field (e.g., time slice request field  708 ) to determine the number of time slices requested. The schedule controller can then set a value for the variable N to be equal to the number of time slices requested. If the value of N is zero, at step  1306 , the schedule controller can determine that there are no time slice requests to be processed. The schedule controller can then terminate processing time slice requests at step  1308 . 
     At step  1310 , the schedule controller can allocate memory for a schedule array (e.g., schedule entry array  524 ), which can include a time slice array (e.g., time slice array  602 ) and an assignment array (e.g., assignment array  604 ). Sizes of the time slice array and the assignment array can correspond to a predetermined number of time slices within a frame. For example, if there are 100 time slices per frame, the time slice array and the assignment array can each have 100 elements. The schedule controller can also allocate memory for an indexing variable M, and set the value of M to be 0. 
     At step  1312 , the schedule controller can check a value of the assignment array at index M, which corresponds to a time slice at index M of the time slice array. If the value of the assignment array at index M indicates that the corresponding time slice is unassigned, at step  1314 , the schedule controller can set the value of the assignment array at index M to be equal to a value of a unique ID (e.g., unique identification (ID) field  706 ) from the beacon response packet (e.g. beacon response packet  700 ). 
     At step  1316 , the schedule controller can decrement, or reduce, the value N by one. If the value of N is equal to zero after step  1316 , at step  1306 , the schedule controller can determine that there are no time slice requests to be processed. If there are no more time slice requests to be processed, the process can move to step  1320 , which is described in more detail below. If the value of N is not equal to zero after step  1316 , the schedule controller can increment, or increase, the value of M by one at step  1320 . 
     If the value of index M of the assignment array indicates that the corresponding time slice is not unassigned, or is a best effort time slice, at step  1318 , the schedule controller can determine that the time slice at index M of the time slice array is already assigned. The schedule controller can then increment, or increase, the value of M by one at step  1320 . 
     At step  1320 , the schedule controller can increment, or increase, the value of M by 1. If the value of M is less than the number of time slices within the frame minus one, the process can return to step  1312 . If the value of M is greater than the number of time slices within the frame, step  1322 , the schedule controller can determine that a schedule request failure has occurred. The schedule controller can then terminate processing time slice requests at step  1308 . 
     During operation, the master circuit can monitor traffic on the data lanes of the backplane to verify that data transmission is occurring during assigned time slices. If there is no data transmission during an assigned time slice, the master circuit can determine that the time slice has been abandoned. The master circuit can free, or unscheduled, a time slice and can reassign the time slice based on requests received during a subsequent beacon response time slice (e.g., beacon response time slice  410 B). 
       FIG.  16    shows a flow diagram  1400  of an exemplary traffic monitoring, or “garbage collection”, process that can be used to recover unused time slices so that they can be reassigned. At step  1402 , the schedule controller of the master can begin an iteration of the traffic monitoring process. At step  1404 , the schedule controller can allocate memory to for an indexing variable X and set a value for the variable within memory. For example, the value of the indexing variable can be set to be equal to a number of beacon time slices plus one. For example, if an assignment array (e.g., assignment array  604 ) includes a beacon time slice at index 0, and a beacon response time slice at index 1, the value of the indexing variable can be set to 2, which corresponds to the index of the first time slice that has potentially been assigned to a slave circuit. 
     At step  1404  the schedule controller can also allocate memory for a counter array. The counter array can be the same size as the assignment array. Values of elements of the counter array can be set to predetermined idle slice limit. The idle slice limit can describe an acceptable number of consecutive delivery opportunities in which a slave circuit can remain idle, i.e., not transmit data. A delivery opportunity can be a time slice to which the slave circuit has been assigned. For example, if each slave circuit can remain idle for two consecutive delivery opportunities, values of each element of the counter array can be set to two. In some embodiments, if the counter array already exists from a previous frame, the schedule controller can reference the existing counter array.  FIG.  17    shows an example of a schedule entry array  1500  that includes a time slice array  1502 , an assignment array  1504 , a length array  1506 , and a counter array  1508 . 
     At step  1406 , the schedule controller can determine a value of index X of the assignment array. If the value of index X of the assignment array indicates that a corresponding time slice has not been assigned, the schedule controller can increment, or increase, the value of X by one at step  1408 . 
     If the value of index X of the assignment array indicates that the corresponding time slice has been assigned, at step  1410 , the schedule controller can monitor one or more data lanes of the backplane for a signal from the slave circuit to which the time slice corresponding to index X of the time slice array has been assigned. If the master circuit does not detect a signal from the slave circuit to which the time slice has been assigned, at step  1412 , the schedule controller can decrement, or decrease, the value of index X of the counter array by one. If index X of the counter array is equal to zero, at step  1414 , the schedule controller can unscheduled the slave circuit from the time slot. The schedule controller can then increase the value of X by one at step  1408 . 
     After step  1412 , if the value of index X of the counter array is greater than zero, at step  1408 , the schedule controller can increase the value of X by one. If the master circuit detects a signal from the slave circuit to which the time slice has been assigned at step  1410 , the schedule controller of the master circuit can set the value of index X of the counter array to the idle slice limit (e.g., one) at step  1418 . The schedule controller can then increase the value of M by one at step  1408 . 
     After step  1408 , if the value of X is less than the number of time slices in the frame, the process can then return to step  1408 . If the value of X is equal to the number of time slices in the frame, at step  1416 , the schedule controller can terminate the traffic monitor process for the current frame. 
     By monitoring traffic on data lanes of the backplane, the master circuit can maximize efficiency of resource (e.g., time slice) utilization by identifying time slices in which the assigned slave circuit failed to communicate, unscheduling the assigned slave circuit, and reassigning the time slices based on communication requests received in beacon response packets. 
       FIG.  18    shows a flow diagram  1600  illustrating exemplary operation of a node of a slave circuit of a monitoring system (e.g., the monitoring system  300 ). The slave circuit can generally be similar to the functional circuit  310  described above with regard to  FIG.  4   . However, in some embodiments, the slave circuit may not include a schedule controller, or the schedule controller may be inactive. 
     At step  1602 , the slave circuit can be powered on. At step  1604 , a node controller can check to determine whether a circuit controller of the slave circuit has provided a request to deliver data to data lanes of a backplane to which the slave circuit is coupled to. 
     If the node controller determines that the circuit controller has not provided any additional requests to deliver data to the backplane, at step  1606 , the node controller can wait to receive a beacon packet from a master circuit. After a period of time, if the node controller does not receive a beacon packet, the process can return to step  1604  and the node controller can check to determine if the circuit controller has provided a request to deliver data to data lanes of the backplane. If the node controller receives a beacon packet during step  1606 , the node controller can update and/or generate an internal copy of a schedule stored in memory based on a schedule provided with the beacon packet at step  1608 . The node controller can also provide the updated/generated schedule to a gate controller of the slave circuit so that the gate controller can control operation of transmitters and/or receivers of the slave circuit to enforce the schedule. The process can then return to step  1604  and the node controller can check to determine if the circuit controller has provided a request to deliver data to data lanes of the backplane. 
     If the node controller detects that the circuit controller has requested that data be delivered to the backplane, at step  1610 , the node controller can prepare a beacon response packet to request time slices for communication based on the request from the circuit controller. For example, the circuit controller can provide one or more communication packets to the node controller to be delivered to the backplane. The node controller can determine the total size (e.g., in bytes), and can calculate a number of time slices required to transmit the communication packet based on a baud rate of the monitoring system. The node controller can generate the beacon response packet requesting the calculated number of time slices. As another example, in some embodiments, the circuit controller deliver a signal to the node controller to request a certain amount of bandwidth (e.g., in bytes per second) to deliver a desired payload that can be provided with the communication packets. 
     In some embodiments, at step  1612 , the node controller can enter a hold-off state in which the node controller waits for period of time. As an example, the node controller can enter the hold-off state to reduce simultaneous data delivery to the backplane, thereby reducing the risk of collisions between beacon response packets from different functional circuits. At step  1614 , the node controller can wait to receive a beacon packet. After the node controller receives the beacon packet from the master circuit, at step  1616 , the node controller can provide the beacon response packet to a data lane of the backplane. 
     If the node controller detects that the beacon response packet experienced a collision, the node controller can enter a hold-off state at step  1612 . After a period of time, the node controller can wait for a beacon packet (e.g., in a subsequent frame) at step  1614 . After the node controller receives the beacon packet, at step  1616 , the node controller can provide the beacon response packet to the data lane of the backplane. 
     At step  1618 , after the beacon packet is transmitted to the data lane, the node controller can wait to receive a beacon packet. The node controller can then receive the beacon packet from the master circuit. 
     At step  1620 , the node controller can check a schedule provided with the beacon packet to determine if the requested time were granted. If slave node was not assigned the time slices that were requested in the beacon response packet, the node controller can enter a hold-off state at step  1612 . The process can then proceed through steps  1614 ,  1616 ,  1618 . If the slave node was assigned the time slices that were requested in the beacon response packet, at step  1622 , the node controller can provide the schedule and/or instructions with the assigned time slices to the gate controller. The gate controller can control operation of the transmitters and/or receivers based on the schedule and/or instructions. For example, the gate controller can switch transmitters to the first operating mode during assigned time slices. The gate controller can switch the transmitters to the second operating mode during time slices in which the slave circuit is not assigned to communicate. 
     At step  1624 , the node controller can determine a link state of the node of the slave circuit. If the link state indicates that the node is coupled to the backplane, the process can then proceed to step  1606 , in which the node controller can wait to receive a beacon packet from a master circuit. The process can proceed from step  1606  as described above. 
     By generating a communication schedule at a master circuit, distributing the schedule to slave circuits, and enforcing the communication at the slave circuits, the monitoring system provides robust communication and eliminates centralized failure points associated with system that use centralized switching for communication. The scheduled communication can prevent multiple functional circuits from broadcasting simultaneously, which can mitigate or eliminate collisions between data packets broadcasted by different functional circuits. 
     Exemplary technical effects of the subject matter described herein can include the ability schedule communications between multiple functional circuits such that the functional circuits can effectively communicate over shared data lanes. Other exemplary technical effects include the ability to maximize utilization of a limited number of data lanes, and adapt to physical and/or operation changes of the monitoring system. For example, by monitoring traffic on data lanes of the backplane, the master circuit can adapt to physical and/or operation changes of the monitoring system and maximize efficiency of resource (e.g., time slice) utilization by identifying time slices in which assigned slave circuits failed to communicate, unscheduling the assigned slave circuits, and reassigning the time slices based on communication requests received in beacon response packets. 
     In some embodiments, multiple backplanes can be coupled using bridge modules. The coupled backplanes can form an extended logical bus such that all data is transferred between the backplanes. This allows monitoring systems to span across multiple locations while retaining the full functionality that is available when using monitoring systems that include a single backplane. 
       FIG.  19    shows an example of a bridge circuit  1710  that can be configured to facilitate electronic communication between backplanes of a monitoring system. The bridge circuit  1710  can include a bridge controller  1703  that is in electronic communication with a range extending element  1705  and a node  322 . The nodes  322  can be configured to facilitate and control electronic communication between the bridge controller  1703  and a first backplane of a first monitoring system. For example, the node  322  can control delivery of data from the bridge controller  1703  to the data lanes of the first backplane. 
     The node  322  can include a schedule controller  334 , node controller  324 , gate controller  326 , and a gate array that includes gate pairs  328 . The node controller  324  can include memory, at least one data processor, and/or other circuitry configured facilitate operation as described herein. The node controller can function as an interface between the bridge controller  1703  and the gate controller  326 , transmitters  330  and/or receivers  332  of the gate pairs  328 . For example, in some embodiments, the node controller  324  can be configured to receive signals from the bridge controller  1703 , encode the signals into bits, and deliver signals corresponding to the encoded bits to the gate controller  326  for the data to be delivered to data lanes of the first backplane. The node controller  324  can also store a copy of a schedule that can be used to control operation of the transmitters  330  and receivers  332 . The transmitters  330  receivers  332  and the gate controller  326  are described in more detail below. 
     The gate controller  326  can include memory, at least one data processor, and/or other circuitry configured facilitate operation as described herein. The gate controller  326  can be in electronic communication with the transmitters  330 , receivers  332 , and the node controller  324  of the bridge circuit  1710 . The gate controller  326  can be configured to control operation of the transmitters  330  and receivers  332  bridge circuit  1710 , thereby controlling data flow between the bridge circuit  1710  and the data lanes of the first backplane. For example, the gate controller  326  can control operating modes of the gate pairs  328 . In some embodiments, the gate controllers  326  can be configured to control operating modes of the transmitters  330  and receivers  332  based on a predetermined schedule and/or instruction provided by the node controller  324 . As an example, the gate controller  326  can be configured to receive data from the node controller  324 , store the data, and deliver it to the data lanes at a scheduled time. In some embodiments, the gate controller  326  can receive the schedule from the node controller  324 . 
     Each transmitter  330  and receiver  332  of each gate pair  328  can be electrically coupled to receiving and transmitting portions of a corresponding data lane, respectively. In some embodiments, the node controller  324 , gate controller  326 , transmitters  330 , and/or receivers  332  can be a field programmable gate array (FPGA). The transmitters  330  and receivers  332  can have first and second operating modes, as described above with regard to the transmitters and receivers shown in  FIG.  4   . 
     In some embodiments, the bridge circuit  1710  can include the schedule controller  334  such that the bridge circuit  1710  is arbitration capable. The schedule controllers  334  can allow the bridge circuit  1710  to assume arbitration responsibilities and become a master circuits of the monitoring system. The schedule controller  334  can include memory, at least one data processor, and/or other circuitry configured facilitate operation as described herein. The schedule controller  334  can be configured to generate schedules that can define when each of the transmitter and/or receivers of functional circuits and/or bridge circuits  1710  of the monitoring system are in the first or the second operating modes. As described here, the schedule identifies when each functional circuit and/or bridge circuit can deliver data to each data lane of the first backplane. 
     As shown in the illustrated example, the bridge controller  1703  can be electrically coupled to the range extending element  1705  as well as the node controller  324  of the node. The bridge controller  1703  can include memory, at least one data processor, and/or other circuitry configured facilitate operation as described herein. In some embodiments, the bridge controller  1703  can be, or can include, a FPGA. The bridge controller  1703  can be configured to receive data from the first backplane (e.g., via the node), process the data, and provide the data to another bridge circuit coupled to a second backplane. For example, the bridge controller  1703  can convert, or condense, parallel data flow from data lanes of first backplane to a serial data stream to deliver to the bridge circuit  1710  coupled to the second backplane, via the range extending element. As another example, the bridge controller  1703  can be configured to receive a serial data stream from the bridge circuit  1710  coupled to the second backplane, and convert serial data stream to parallel data streams to be delivered to data lanes of the first backplanes (e.g., via the node). 
     In some embodiments, the bridge controller  1703  and/or node controllers  324  of the bridge circuits  1710  can be configured to store information about the monitoring system in memory. For example, the bridge controller  1703  can store hardware data, schedules, network IDs, etc. As an example, hardware data can be, or can include, a unique ID (e.g., a MAC address) of the first backplane and/or functional circuits coupled thereto. As another example, the hardware data can include data describing the number of data lanes that the backplane includes. In some embodiments, the bridge controllers  1703  can receive data describing the number of data lanes from beacon packets (e.g., number of lanes field  207 ). 
     The range extending element  1705  can be, or can include, e.g., a signal amplifier and/or attenuator. The range extending element  1705  can be configured to facilitate communication between bridge circuits  1710  that are separated by a range of distances. For example, the range extending element  1705  can be configured to receive a signal from the bridge controller  1703 , amplify the signal, and provide the amplified signal to another bridge circuit  1710 . In some embodiments, the range extending element  1705  can be configured to amplify outgoing signals (e.g., signals delivered to another bridge circuit  1710 ) based on a known distance between the bridge circuits  1710 . Additionally, the range extending element  1705  can be configured to receive an amplified signal from another bridge circuit  1710 , attenuate the signal, thereby reducing a voltage and/or current of the signal, and provide the attenuated signal to the bridge controller  1703 . As an example, the range extending element  1705  can attenuate incoming signals (e.g., signals received from another bridge circuit) based on predetermined maximum voltage and/or current thresholds for signals that the bridge controller  1703  is configured to receive. 
     In some embodiments, the bridge circuit  1703  can be configured verify that the monitoring system that are being bridged are compatible. As an example, the bridge circuit  1703  can use hardware data, unique IDs, and schedules to determine that that monitoring systems are compatible. Once the bridge controllers  1703  of the bridge circuit  1710  determine that the monitoring systems are compatible, the bridge controllers  1703  can allow the monitoring systems to be connected, thereby facilitating communication between the backplanes of the monitoring systems. The bridge circuits  1710  are described in more detail below. 
       FIG.  20    shows a block diagram of an exemplary embodiment of a monitoring system  1800  that includes two monitoring subsystems  1801   a ,  1801   b  that are coupled using bridge circuits  1710   a ,  1710   b . The bridge circuits can be the same as the bridge circuits  1710 , as described herein. The monitoring system  1800  can be configured to monitor operating parameters of industrial equipment. 
     The monitoring subsystems  1801   a ,  1801   b  can generally be similar to the monitoring system  1800  described above with regard to  FIG.  4   , but each of the monitoring subsystems  1801   a ,  1801   b  can include a bridge circuit configured to facilitate communication between backplanes of the monitoring subsystems  1801   a ,  1801   b . Each monitoring subsystem can include any number of functional circuits  310   a ,  310   b  and bridge circuits that can be detachably coupled to backplanes  306   a ,  306   b  via ports  308   a ,  308   b  of the backplanes  306   a ,  306   b . The functional circuits  310   a ,  310   b  can be the same as the functional circuits  310 . 
     The backplanes  306   a ,  306   b  can be, include, or form part of, a physical bus. The backplanes  306   a ,  306   b  can be passive backplanes  306   a ,  306   b  that can be configured to facilitate multipoint asynchronous electronic communication between the functional circuits  310   a ,  310   b  and/or bridge circuits  1710   a ,  1710   b  that are coupled to the backplanes  306   a ,  306   b . Therefore, all data that is delivered to the backplanes  306   a ,  306   b  can be received by all functional circuits  310   a ,  310   b  and/or bridge circuits  1710  coupled to the backplanes. The backplane  306   a  can include data lanes  1812   a ,  1812   b ,  1812   c ,  1812   d - 1812   n , and the backplane  306   b  can include data lanes  1812   a ,  1813   b ,  1813   c ,  1813   d - 1813   n , as shown in  FIG.  21   . Referring to  FIGS.  20 - 21   , the data lanes  1812   a - 1812   n ,  1813   a - 1813   n  are in electronic communication with a number of ports  308   a ,  308   b  on the respective backplanes  306   a ,  306   b . The ports  308   a ,  308   b  can be configured to receive functional circuits  310   a ,  310   b  and/or bridge circuits  1710   a ,  1710   b . Each port  308   a ,  308   b  is configured to enable electronic communication between a functional circuit  310   a ,  310   b  or bridge circuit  1710   a ,  1710   b  coupled to the port, and all of the data lanes  1812   a - 1812   n ,  1813   a  of the respective backplanes  306   a ,  306   b.    
     There are a number of different types of functional circuits that can be coupled to ports of the backplanes  306   a ,  306   b . For example, one or more of the functional circuits can be an input circuit (e.g., input circuit  210   i ), an output circuit (e.g., output circuit  210   o ), a processing circuit (e.g., processing circuit  210   p ), and/or an infrastructure circuit (e.g., infrastructure circuit  210   n ). As shown in the illustrated example, each functional circuit  310   a ,  310   b  can include a circuit controller  320   a ,  320   b  and a node  322   a ,  322   b  configured to facilitate and control electronic communication between the circuit controller  320   a ,  320   b  and the backplane  306   a ,  306   b . As described herein, the node  322   a ,  322   b  can control delivery of data from the circuit controller  320   a ,  320   b  to the data lanes  312   a ,  312   b  of the backplane  306   a ,  306   b . The nodes  322   a ,  322   b  can also control which data is delivered from the data lanes  312   a ,  312   b  to the circuit controllers  320   a ,  320   b  of the functional circuits  310   a ,  310   b.    
     As shown in the illustrated example, the bridge circuits  1710   a ,  1710   b  can be detachably coupled to ports  308   a ,  308   b  of the backplanes  306   a ,  306   b . The bridge circuits  1710   a ,  1710   b  can be electrically coupled via a coupling element  1807  that can between the bridge circuits  1710   a ,  1710   b . Ends of the coupling element  1807  can be attached to range extending elements  1705   a ,  1705   b  of the bridge circuits  1710   a ,  1710   b . The coupling element  1807  can be e.g., electrical cabling and/or fiber optic cabling. In some embodiments, the bridge circuits  1710   a ,  1710   b  can communicate wirelessly. For example, the bridge circuits can include transceivers for communicating via Bluetooth protocol, cellular protocol, WI-FI protocol, near field communication (NFC), and/or a radio frequency identification (RFID) protocol. 
     In the illustrated example, the bridge circuits  1710   a ,  1710   b  can include bridge controllers  1703   a ,  1703   b  that are in electronic communication with the range extending elements  1705   a ,  1705   b  and nodes  322   a ,  322   b  of corresponding bridge circuits  1710   a ,  1710   b . The nodes  322   a ,  322   b  of the bridge circuits  1710   a ,  1710   b  can generally be similar to the nodes  322  of functional circuits  310 , as described above with regard to  FIG.  4   . The nodes  322   a ,  322   b  can be configured to facilitate and control electronic communication between the bridge controllers  1703   a ,  1703   b  and the backplanes  306   a ,  306   b . For example, the nodes  322   a ,  322   b  can control delivery of data from the bridge controllers  1703   a ,  1703   b  to the data lanes  1812   a - 1812   n ,  1813   a - 1813   n  of the backplanes  306   a ,  306   b . The nodes  322   a ,  322   b  can include schedule controllers  334   a ,  334   b , node controllers  324   a    324   b , gate controllers  326   a ,  326   b , and gate pairs  328   a ,  328   b.    
     As mentioned above, the bridge circuits  1710   a ,  1710   b  can be configured to facilitate electronic communication between backplanes  306   a ,  306   b  of monitoring subsystems. For example, the bridge circuit  1710   a  can be configured to receive all data delivered to the data lanes  1812   a - 1812   n  of the backplane  306   a , and provide the data to the bridge circuit  1710   b . The bridge circuit  1710   b  can receive the data, and can distribute the among data lanes  1813   a - 1813   n  of the backplane  306   b  that correspond to the data lanes  1812   a - 1812   n  backplane  306   a . For example, all data that is provided from functional circuits  310   a  to data lanes  1812   a ,  1812   b ,  1812   c , can be provided to corresponding data lanes  1813   a ,  1813   b ,  1813   c  via the bridge circuits  1710   a ,  1710   b . Therefore, the backplanes  306   a ,  306   b  form an extended logical bus, and the functional circuits  310   a ,  310   b  can function as if they were coupled to a single backplane. 
     As described herein, communication from functional circuits and/or bridge circuits is controlled using a schedule that can be generated by a master circuit. Since all data packets are shared between the backplanes  306   a ,  306   b , the bridge circuits  1710   a ,  1710   b  and the functional circuits  310   a ,  310   b  can share a schedule. The schedule can be generated using a single master circuit, which can be one of the functional circuits  310   a ,  310   b  coupled to either of the backplanes  306   a ,  306   b . The master circuit can generally function to generate and distribute the schedule, and monitor communication across the data lanes  1812   a - 1812   n ,  1813   a - 1813   n , as described herein with regard to  FIGS.  7 - 18   . 
       FIG.  22    shows a data flow diagram  1900  illustrating communication between various components of the monitoring system  1800  during an arbitration period (e.g., arbitration period  411 ). As an example, the master circuit can be one of the functional circuits  310   a  that is coupled to the backplane  306   a . At step  1902 , the master circuit can deliver a beacon packet that includes a schedule for a current time frame to data lanes  1812   a - 1812   n  of the backplane  306   a.    
     At step  1904 , functional circuits  310   a  coupled to the backplane  306   a  can receive the beacon packet from the backplane  306   a . At step  1906 , the node controller  324   a  of the bridge circuit  1710   a  can receive the beacon packet and store a copy of the schedule in memory. The node controller  324   a  can provide the schedule and/or instructions with the assigned time slices for the current frame to the gate controller  326   a . The gate controller  326   a  can use the schedule and/or instructions to control operation of the transmitters  330   a  and receivers  332   a , as described in more detail below. The node controller  324   a  can also provide the beacon packet to the bridge controller  1703   a . The bridge controller  1703   a  can receive the beacon packet and provide the beacon packet to the range extending element  1705   a  which can amplify the signal the beacon packet. 
     At step  1908  the bridge circuit  1710   a  can deliver the beacon packet to the bridge circuit  1710   a . The range extending element  1705   b  of the bridge circuit  1710   b  can receive the beacon packet and provide the beacon packet to the node controller  324   b , which can store a copy of the schedule in memory 
     At step  1910 , the node controller  324   b  can provide the beacon packet to the data lanes  1813   a - 1813   n  of the backplane  306   b  via the gate controller  326   b  and the transmitters of the gate pair  328   b . At step  1912 , the functional circuits  310   b  can receive the beacon packet from the backplane  306   b . Node controllers  324   b  of the functional circuits  310   b  can store a copy of the schedule corresponding to the current frame as well as check the schedule to determine if their previous communication requests were schedule. The node controllers  324   b  can also provide the schedule and/or instructions with the assigned time slices to the gate controllers  326   b . The gate controllers  326   b  can use the schedule and/or instructions to control operation of the transmitters  330   b  and receivers  332   b , as described in more detail below. 
     At step  1914 , the functional circuits can provide beacon response packets to the data lanes  1813   a - 1813   b . At step  1916 , the bridge controller  1703   b  of the bridge circuit  1710   b  can receive the beacon response packets from each of the data lanes  1813   a - 1813   n  via the receivers  332   b , gate controller  326   b , and node controller  324   b . Since the data lanes  1813   a - 1813   n  are in parallel, the bridge controller  1703   b  receives a parallel data stream that includes, or characterizes, the beacon response packets. The bridge controller  1703   b  can convert, or condense, the parallel data stream into a serial data stream, and provide the serial data stream to the range extending element  1705   b . The range extending element can amplify power (e.g., voltage and/or current) of the serial data stream. 
     At step  1918 , the bridge circuit  1710   b  provide the serial data stream to the bridge circuit  1710   a  via the range extending element  1705   b . The range extending element  1705   a  can receive the serial data stream, attenuate power (e.g., voltage and/or current) of the serial data stream and provide the serial data stream to the bridge controller  1703   a . The bridge controller  1703   a  can receive the serial data stream, expand the serial data stream into parallel data streams. 
     At step  1920 , the bridge controller  1703   a  can provide the parallel data streams to the data lanes  1812   a - 1812   n  of the backplane  306   a  via the node  322   a . At step  1922 , functional circuits  310   a  can deliver beacon response packets to the data lanes  1812   a - 1812   n  of the backplane  306   a . At step  1924 , the master circuit can receive the beacon response packets from the functional circuits  310   a ,  310   b , and generate a schedule for the following frame. 
     During normal operation (e.g., during time slices  410 C- 410 N), functional circuits  310   a ,  310   b  can communicate via data lanes  1812   a - 1812   n ,  1813   a - 1813   n  of the backplanes  306   a ,  306   b . For example, functional circuits  310   a ,  310   b  can deliver data packets to the data lanes  1812   a - 1812   n  of the backplane  306   a . The bridge controller  1703   a  of the bridge circuit  1710   a  can receive the data packets in a parallel data stream, convert, or condense, the parallel data stream into a serial data stream, and provide the serial data stream to the range extending element  1705   a . The range extending element  1705   a  can amplify power (e.g., voltage and/or current) of the serial data stream and provide the serial data stream to the bridge circuit  1710   b . The range extending element  1705   b  can receive the serial data stream, attenuate power (e.g., voltage and/or current) of the serial data stream and provide the serial data stream to the bridge controller  1703   b . The bridge controller  1703   b  can receive the serial data stream, expand the serial data stream into parallel data streams, and provide the parallel data streams to the data lanes  1813   a - 1813   n  via the node  322   b.    
     Similarly, functional circuits  310   b  can deliver data packets to the data lanes  1813   a - 1813   n  of the backplane  306   a . The bridge controller  1703   b  of the bridge circuit  1710   b  can receive the data packets in a parallel data stream, convert, or condense, the parallel data stream into a serial data stream, and provide the serial data stream to the range extending element  1705   b . The range extending element  1705   b  can amplify power (e.g., voltage and/or current) of the serial data stream and provide the serial data stream to the bridge circuit  1710   a . The range extending element  1705   a  can receive the serial data stream, attenuate power (e.g., voltage and/or current) of the serial data stream and provide the serial data stream to the bridge controller  1703   a . The bridge controller  1703   a  can receive the serial data stream, expand the serial data stream into parallel data streams, and provide the parallel data streams to the data lanes  1812   a - 1812   n  via the node  322   a . During operation the bridge circuits  1710   a ,  1710   b  are transparent to all the functional circuits  310   a    310   b  coupled to the backplanes  306   a ,  306   b  of the monitoring system. Therefore, the monitoring system  1800  functions it appears that the signals/data are all from the same base. 
     As mentioned above, the gate controllers  326   a ,  326   b  of the bridge circuits  1710   a ,  1710   b  can use the schedule and/or instructions to control operation of the transmitters  330   a ,  330   b  and receivers  332   a ,  332   b . For example, the gate controller  326   b  can set the transmitters  330   b  to operate in the first operating mode during time slices when the functional circuits  310   a  attached to the backplane  306   a  are scheduled to deliver data to the backplane  306   a  such that the data can be delivered to the backplane  306   b  via the bridge circuits  1710   a ,  1710   b . The gate controller  326   b  of the bridge circuit  1710   b  can set the transmitters  330   b  to operate in the second operating mode during time slices in which the functional circuits  310   a  are not schedule to deliver data to the backplane  306   a . Similarly, the gate controller  326   a  of the bridge circuit  1710   a  can set the transmitters  330   a  to operate in the first operating mode during time slices when the functional circuits  310   b  attached to the backplane  306   b  are scheduled to deliver data to the backplane  306   a  such that the data can be delivered to the backplane  306   a  via the bridge circuits  1710   a ,  1710   b . The gate controller  326   a  can set the transmitters  330   a  of the bridge circuit  1710   a  to operate in the second operating mode during time slices when the functional circuits  310   b  are not schedule to deliver data to the backplane  306   b.    
     In some embodiments, separation distances between the bridge circuits  1710   a ,  1710   b  can introduce non-negligible propagation delays in transmissions of data packets between the bridge circuits  1710   a ,  1710   b . The propagation delays can create time synchronization errors between functional circuits  310   a ,  310   b  of each monitoring subsystem  1801   a ,  1801   b . For example, when the master circuit (e.g., one of the functional circuits  310   a ) sends the beacon packet, functional circuits  310   a  that are coupled to the backplane  306   a  can receive the beacon packet before functional circuits  310   b  that are coupled to the backplane  306   b . Therefore, the time synchronization of functional circuits  310   b  can be delayed as compared to the time synchronization of the functional circuits  310   a . Additionally, in some cases, propagation delays can result in data packet transmissions that extend over multiple time slices, which can result in collisions. For example, if a data packet is transmitted from a functional circuit  310   b  coupled to the backplane  306   b  requires more time to travel to the backplane  306   a  than is allotted in a usable time slice period (e.g., usable time slice period  420 ), the data packet may still be in transit during a subsequent time slice. In that case, the data packet may collide with another data packet that is transmitted during the subsequent time slice. 
     Dead band periods (e.g., dead band period  424 ) can be built into time slices to absorb delays in communication between functional circuits coupled to a single backplane as well as delays in communication that result from bridge backplanes. The dead band periods can function to mitigate data transmission timing errors due to inaccuracies in time synchronization between functional circuits, as well as minimize signal collisions that can result from latencies associated with data transmission between bridged backplanes. 
     In order to ensure that the time slices include a sufficiently large dead band period, the bridge controllers  1703   a ,  1703   b  and/or node controllers  324   a ,  324   b  of the bridge circuits  1710   a ,  1710   b  can estimate delay times that can characterize an estimated amount of time required to transfer data packets between the bridge circuits  1710   a ,  1710   b . The bridge circuits  1710   a ,  1710   b  can then determine, identify, or calculate a current allotted dead band period based on information available in the schedule. The bridge circuits  1710   a ,  1710   b  can compare the estimated delay times with the allotted dead band period. In some embodiments, if the dead band period is insufficient, the bridge circuits  1710   a ,  1710   b  can deliver data packets to the master circuit to request adjustment of the dead band periods and/or adjustment of sizes of time slices in subsequent frames. 
     In some embodiments, when the monitoring subsystems  1801   a ,  1801   b  are powered on, the bridge circuits  1710   a ,  1710   b  can be configured prevent data transmission between the backplanes  306   a ,  306   b  until hardware and operating parameters (e.g., communication schedules, baud rates, etc.) of monitoring subsystems (e.g. monitoring subsystems  1801   a ,  1801   b ) are determined to be compatible. For example, the bridge circuits  1710   a ,  1710   b  can be configured to receive data from the backplanes  306   a ,  306   b , but can be prevented from delivering data to the backplanes  306   a ,  306   b . In some embodiments, the transmitters  330   a ,  330   b  can be set to the second operating mode such that they prevent data from being delivered to the data lanes  1812   a - 1812   n ,  1813   a - 1813   n . In some embodiments, the bridge circuits  1710   a ,  1710   b  can determine if hardware of the monitoring subsystem is compatible. The bridge circuits  1710   a ,  1710   b  can also determine if any preexisting schedules of the monitoring subsystems  1801   a ,  1801   b  are compatible. As an example, operating parameters can include schedules, baud rates, etc. 
     Upon startup, the bridge circuits  1710   a ,  1710   b  can determine if they include system data stored in memory of the node controllers  324   a ,  324   b  and/or the bridge controllers  1703   a ,  1703   b . As an example, system data can be, or can include, unique IDs (e.g., MAC addresses) corresponding to components of the monitoring subsystems, information describing how many data lanes each backplane includes, network IDs, etc.  FIG.  23    shows a flow chart  2000  illustrating an exemplary method of determining that hardware and operating parameters of monitoring subsystems (e.g. monitoring subsystems  1801   a ,  1801   b ) are compatible. 
     At step  2002 , the method can include receiving a first identification data at a first bridge circuit (e.g., bridge circuit  1710   a ) coupled to a first backplane (e.g., backplane  306   a ) of a first monitoring subsystem (e.g., monitoring subsystem  1801   a ). The first identification data can characterize information identifying hardware of a second monitoring subsystem (e.g., monitoring subsystem  1801   b ). As an example, the first identification data can be, or can include, a unique ID (e.g., a MAC address) of the second backplane (e.g., backplane  306   b ) and/or functional circuits  310   b  coupled thereto. As another example, the first identification data can be, or can include, data describing the number of data lanes that the second backplane includes, as well as a network ID corresponding to the second monitoring subsystem. In some embodiments, the first bridge circuit can receive unique IDs of the functional circuits from data packets delivered to the first backplane from the second monitoring subsystem during operation. As another example, the first bridge controller can receive data describing the number of data lanes from beacon packets (e.g., number of lanes field  507 ). The bridge controller and/or a node controller (e.g., bridge controller  1703   a  and node controller  324   a ) of the first bridge circuit can store the first identification data in memory during operation. The first identification data can remain in memory during a system shutdown, and can be used to confirm that the first monitoring subsystem and the second monitoring subsystem are during a subsequent system startup, as described herein. 
     At step  2004 , the method can include receiving a second identification data at a second bridge circuit (e.g., bridge circuit  1710   b ) coupled to a second backplane (e.g., backplane  306   b ) of the second monitoring subsystem. The second identification data can characterize information identifying hardware of the first monitoring subsystem. As an example, the second identification data can be, or can include, a unique ID (e.g., a MAC address) of the first backplane and/or functional circuits coupled thereto. As another example, the second identification data can be, or can include, data describing the number of data lanes that the first backplane includes, as well as a network ID corresponding the first monitoring subsystem. In some embodiments, the second bridge circuit can receive unique IDs of the functional circuits from beacon packets or other data packets delivered to the second backplane from the first monitoring subsystem during operation. As another example, the second bridge controller can receive data describing the number of data lanes from beacon packets (e.g., number of lanes field  507 ). The bridge controller and/or a node controller (e.g., node controller  324   b  and bridge controller  1703   b ) of the second bridge circuit can store the second identification data in memory during operation. The second identification data can remain in memory during a system shutdown, and can be used to confirm that the first monitoring subsystem and the second monitoring subsystem are compatible during a subsequent system startup, as described herein. 
     In some embodiments, the second identification data can be stored in memory of the node controller and/or bridge controller of the first bridge circuit, and the first bridge circuit can provide the second identification data to the second bridge circuit. Similarly, the first identification data can be stored in memory of the node controller and/or bridge controller of the second bridge circuit, and the second bridge circuit can provide the first identification data to the first bridge circuit. As another example, the first and second identification data can be stored in memory of node controllers and/or bridge controllers of the first and second bridge circuits. 
     At step  2006 , the first identification data and the second identification data can be used to determine that the first monitoring subsystem is compatible with the second monitoring subsystem. For example, the bridge controllers and/or node controllers of the first and second bridge circuits can confirm that the first backplane and the second backplane have the same number of data lanes. As another example, bridge controllers and/or node controller of can use the unique IDs of functional circuits and/or backplanes of the first and second monitoring subsystems to determine that the first and second monitoring subsystems are compatible. The bridge controllers and/or node controllers can also compare network IDs provided with the first and second identification data to determine that the first and second monitoring systems are compatible. For example, if the network IDs are the same, the monitoring system can be determined to be compatible. 
     At step  2008 , the method can include receiving a first schedule at the second bridge circuit. The first schedule can characterize a first communication schedule for a first set of functional circuits that are in electronic communication with the first backplane. In some embodiments, the first schedule can be stored in memory of the node controller and/or bridge controller of the first bridge circuit, and the first bridge circuit can provide the first schedule to the second bridge circuit. As another example, the bridge controller and/or a node controller of the second bridge circuit receive the first schedule in a beacon packet during operation. The bridge controller and/or a node controller of the second bridge circuit can store the first schedule in memory. The first schedule can remain in memory during a system shutdown, and can be available for use in a subsequent system startup, as described herein. 
     At step  2010 , the method can include receiving a second schedule at the first bridge circuit. The second schedule can characterize a second communication schedule for a second set of functional circuits that are in electronic communication with the second backplane. In some embodiments, the second schedule can be stored in memory of the node controller and/or bridge controller of the second bridge circuit, and the second bridge circuit can provide the second schedule to the first bridge circuit. As another example, the bridge controller and/or a node controller of the first bridge circuit receive the second schedule in a beacon packet during operation. The bridge controller and/or a node controller of the first bridge circuit and can store the second schedule in memory. The first schedule can remain in memory during a system shutdown, and can be available for use in a subsequent system startup, as described herein. 
     The first communication schedule can be compared to the second communication schedule at step  2012 . For example, the first and second bridge circuits can compare the first and second schedule to ensure that functional circuits of the first monitoring subsystem are not scheduled to deliver data to data lanes of the first backplane at the same time that functional circuits of the second monitoring subsystem are schedule to deliver data to corresponding data lanes of the second backplane. 
     At step  2014 , the method can include determining that the first schedule is compatible with the second schedule. For example, if the comparison indicates that functional circuits of the first monitoring subsystem are not scheduled to deliver data to data lanes of the first backplane at the same time that functional circuits of the second monitoring subsystem are schedule to deliver data to corresponding data lanes of the second backplane, the first and second bridge circuits can determine that the first and second schedule are compatible. 
     At step  2016 , the method can include providing a first signal to at least one first gate (e.g., transmitter  330   a ) of the first bridge circuit and providing a second signal to at least one second gate (e.g., the transmitter  330   b ) of the second bridge circuit, thereby activating the at least one first gate and the at least one second gate, and facilitating electronic communication between the first backplane and the second backplane. As an example, node controllers of the first and second bridge circuits can provide data to the gate controllers of the first and second bridge circuit to confirm that the schedules of the first and second monitoring subsystem are compatible. The gate controllers can activate gates (e.g., transmitters  330   a ,  330   b ) of the first and second bridge circuits by delivering signals to the gates to set the gates to operate in the first operating mode, thereby allowing data to be transmitted from the bridge circuits, and allowing data to be transferred between the first and second monitoring subsystems. 
     In some embodiments, network IDs of the first and second monitoring subsystems can be used to determine of the first and second monitoring subsystems are compatible. The network IDs can also be used to determine if the first and second schedules are compatible. 
     As an example, the first bridge circuit can provide the second bridge circuit with a first network ID that characterizes a configuration of the first monitoring subsystem. The second bridge circuit can provide the first bridge circuit with a second network ID that characterizes a configuration of the second monitoring subsystem. The first and second network IDs can include data such as, e.g., unique IDs of functional circuits and/or the backplane, number of data lanes on the backplane, etc. corresponds to hardware of the first and second monitoring subsystems as well as operating parameters such as e.g., communication schedules, the baud rate, etc. of the first and second monitoring subsystems. The bridge controllers and/or node controllers of the first and second bridge circuits can compare the first network ID with the second network ID to determine if the hardware and operating parameters of the first and second monitoring subsystems are compatible. If the network IDs indicate that the hardware and operating parameters of the first and second monitoring subsystem are compatible, node controllers of the first and second bridge circuits can provide data to the gate controllers of the first and second bridge circuit to confirm the compatibility of the first and second monitoring subsystems. The gate controllers can activate gates (e.g., transmitters  330   a ,  330   b ) of the first and second bridge circuits by delivering signals to the gates to set the gates to operate in the first operating mode, thereby allowing data to be transmitted from the bridge circuits, and allowing data to be transferred between the first and second monitoring subsystems. 
     After the gates first and second bridge circuit are set to operate in the first operating mode, functional circuits of the first and second monitoring subsystem can then execute an initialization process to select a master node, as described above with regard to  FIG.  13   . The master circuit can generate and distribute a third schedule, and monitor data delivered to the backplanes, as described above with regard to  FIGS.  14 - 17   . 
     In some embodiments, when the monitoring subsystems are powered, the first and second bridge circuits may not have access to preexisting data (e.g., identification data, network IDs, schedules, etc.) that can be used to determine if hardware and operating parameters of the first and second subsystems are compatible. In that case, the first and second bridge circuits can used data from beacon packets to determine if hardware and operating parameters of the first and second subsystems are compatible. 
     Initially, upon system startup one or more functional circuits coupled to each of the first and second backplanes (e.g., backplanes  306   a ,  306   b ) can begin an initialization process to assume arbitration responsibilities and become a master circuit, as described above with respect to  FIG.  13   . At the end of the initialization processes, the first monitoring subsystem (e.g., monitoring subsystem  1801   a ) can include a first master circuit, and the second monitoring subsystem (e.g., monitoring subsystem  1801   b ) can include a second master circuit. 
     The first and second master circuits can deliver first and second beacon packets to data lanes of the first and second backplanes, respectively. The beacon packets can generally be similar to the beacon packet  500 , describe with regard to  FIG.  8   . Each beacon packet can include a preamble, type, current time, number of lanes, baud rate, schedule header, and schedule entries fields. 
     The bridge controller (e.g., bridge controller  1703   a ) of the first bridge circuit can receive the first beacon packet, and the bridge controller (e.g., bridge controller  1703   b ) of the second bridge circuit can receive the second beacon packet. The bridge controller and/or node controller of the first bridge circuit can store data corresponding to the fields of the first beacon packet in memory. The bridge controller and/or node controller of the second bridge circuit can store data corresponding to the fields of the second beacon packet in memory. 
     The bridge controller of the first bridge circuit can deliver the first beacon packet to a range extending element (e.g., range extending element  1705   a ) of the first bridge circuit. The range extending element can amplify power (e.g., voltage and/or current) of a signal corresponding to the first beacon packet, and can provide the first beacon packet to the bridge controller and/or node controller of the second bridge circuit. The bridge controller of the second bridge circuit can deliver the second beacon packet to a range extending element (e.g., range extending element  1705   b ) of the second bridge circuit. The range extending element can amplify power (e.g., voltage and/or current) of a signal corresponding to the second beacon packet, and can provide the second beacon packet to the bridge controller and/or node controller of the first bridge circuit. 
     The bridge controllers and/or note controllers of the first and second bridge circuits can compare the data corresponding to the fields (e.g., preamble, type, current time, number of lanes, baud rate, schedule header, and schedule entries fields) provided within the first and second beacon packets to determine if the first and second monitoring subsystems are compatible. 
     If the first and second monitoring subsystems are determined to be compatible, node controllers of the first and second bridge circuits can provide data to the gate controllers of the first and second bridge circuit to confirm that the first and second monitoring subsystems are compatible. The gate controllers can activate gates (e.g., transmitters) of the first and second bridge circuits by delivering signals to the gates to set the gates to operate in the first operating mode, thereby allowing data to be transmitted from the bridge circuits, and allowing data to be transferred between the first and second monitoring subsystems. 
     After the monitoring subsystems are in electronic communication, one of the master circuits can relinquish arbitration capabilities such that only one master circuit is shared between the first and second backplane. For example, if one of the master circuits detects a beacon packet, the master circuit can enter a state of random back-off, as described above with regard to step  1112 , shown in  FIG.  13   . In some embodiments, the former master circuit can remain in a state of random back-off and function as a slave note until it does not receive a beacon packet during a beacon time slice (e.g., beacon time slice  410 A). If the former master circuit does not receive a beacon packet during beacon time slice, the former master circuit can assume arbitration responsibilities, thereby becoming the master circuit, as described with regard to step  1114 , shown in  FIG.  13   . 
     Bridge circuits can function to electrically couple backplanes to form an extended logical bus such that all data is transferred between the backplanes. This allows monitoring systems to span between multiple locations while retaining the full functionality that is available when using monitoring systems that include a single backplane. Additionally, since all data is shared between bridged backplanes, the bridges allow for resources (e.g., functional circuits) to be distributed between the backplanes as desired. 
       FIG.  24    shows block diagram of another exemplary monitoring system  2100 . As shown in the illustrated example, the monitoring system include monitoring subsystems  2101   a ,  2101   b  that can be electrically coupled using bridge circuits  1710   a ,  1710   b . Coupling elements  1807  can electrically couple the bridge circuits  1710   a ,  1710   b . The first and second monitoring subsystems  2101   a ,  2101   b  can include backplanes  2106   a ,  2106   b  that can generally be similar to the backplane  306   a ,  306   b.    
     The monitoring subsystems  2101   a ,  2101   b  can include various different functional circuits that can be coupled to ports of the backplanes  2106   a ,  2106   b . The backplanes  2106   a ,  2106   b  can be, include, or form part of, a physical bus. The backplanes  2106   a ,  2106   b  can generally be similar to the backplanes  306   a ,  306   b  described above with regard to  FIGS.  4 ,  20   . 
     The first monitoring subsystem  2101   a  include condition monitoring circuits  2102   a , gateway circuits  2104   a , system interface circuits  2108   a , power input circuits  2110   a , a discrete input circuit  2112   a , protection circuits  2114   a,  4-20 output circuits  2116   a , relay circuits  2118   a , and bridge circuits  1710   a . The second monitoring subsystem  2101   b  can include dynamic input circuits  2120   b , static input circuits  2122   b , relay circuits  2118   b , and PIM circuits  2110   b . As shown in the illustrated example, the monitoring subsystems  2101   a ,  2101   b  can be coupled via multiple bridge circuits  1710   a ,  1710   b  for the purpose of redundancy. If one of the bridge circuits fails, another pair of bridge circuits is available to bridge communications between the backplanes  2106   a ,  2106   b.    
     As shown in the illustrated example, the monitoring subsystem  2101   b  can primarily function receive analog sensor data, digitize the sensor data, and provide data packets corresponding to the sensor data to data lanes of the backplane  2106   b  using the various input circuits. The monitoring subsystem  2101   a  can primarily function to provide updates to the monitoring system (e.g., via the system interface circuit  2108   a ), process the sensor data (e.g., using the protection circuits  2114   a ), and provide processed data to users (e.g., via the gateway circuit  2104   a , condition monitoring circuit  2102   a ). 
     Bridging can allow for monitoring subsystem to share common resources (e.g., functional circuits), which can provide flexibility when designing and installing monitoring systems. For example, the monitoring subsystem  2101   b  can be installed remotely near industrial equipment such that the input circuits can receive sensor data, while the monitoring subsystem  2101   a  can be installed at another location that may be more convenient, or easier to access. Installing the monitoring subsystem near the industrial equipment to be monitored, can also reduce costs of running cables from the sensors to the input circuits, as well as improve the quality of the signals delivered from sensors to the input circuits by reducing exposure to noise and ground loops. As an example, ground loops be described as interference resulting from portions of a circuit that are at different ground reference voltages, rather than the same ground reference voltage. Ground loops can cause undesirable signal degradation and/or noise within signals. The monitoring subsystem  2101   b  can take advantage of resources (e.g., condition monitoring circuits  2102   a , gateway circuits  2104   a , system interface circuits  2108   a , PIM circuits  2110   a , a discrete input circuit  2112   a , protection circuits  2114   a,  4-20 output circuits  2116   a , relay circuits  2118   a ) installed on the monitoring subsystem  2101   a.    
       FIG.  25    shows block diagram of another exemplary monitoring system  2200 . As shown in the illustrated example, the monitoring system  2200  include monitoring subsystems  2201   a ,  2201   b ,  2201   c  that can be electrically coupled via bridge circuits  1701   a ,  1701   b ,  1701   c . The monitoring subsystems  2201   a ,  2201   b ,  2201   c  can include backplanes  2206   a ,  2206   b ,  2206   c  that can be coupled via the bridge circuits  1701   a ,  1701   b ,  1701   c . The backplanes  2206   a ,  2206   b ,  2206   c  can generally be similar to the backplanes  2106   a ,  2106   b . The coupled backplanes  2206   a ,  2206   b ,  2206   c  form an extended logical bus. 
     The monitoring subsystems  2201   a ,  2201   b ,  2201   c  can include various monitoring circuits that can be coupled to the respective backplanes. The monitoring subsystem  2201   a  can include a condition monitoring circuit  2102   a , a gateway circuit  2104   a , a system interface circuit  2108   a , a discrete input circuit  2112   a , a relay circuit  2118   a , PIM circuits  2110   a , and bridge circuits  1710   a . The monitoring subsystem  2201   b  can include a protection circuit  2114   b , dynamic input circuits  2120   b,  4-20 output circuits  2116   b , relay circuits  2118   b , power input circuits  2110   b , and bridge circuits  1710   b . The monitoring subsystem  2201   c  can include dynamic input circuits  2120   c , a PIM circuit  2110   c , a relay circuit  2118   c , and bridge circuits  1710   c.    
     In some embodiments, the monitoring subsystem  2201   b  can function as the primary monitoring subsystem. For example, the monitoring subsystem  2201   b  can be positioned locally near a critical piece of industrial equipment. The 4-20 output circuits  2116   b  can be configured to output analog sensor data, which can allow local users to troubleshoot operation of the dynamic input circuits and/or sensors coupled to the dynamic input circuits of the monitoring subsystem  2201   b  to ensure that the monitoring subsystem  2201   b  is functioning properly. In some embodiments, the monitoring subsystems  2201   c  can be installed remotely near another industrial system. The monitoring subsystem  2201   a  can primarily function to provide updates to the monitoring system (e.g., via the system interface circuit  2108   a ), and provide processed data to users (e.g., via the gateway circuit  2104   a , and the condition monitoring circuit  2102   a ). For example, the gateway circuit  2104   a  can function to provide data to, and receive data from, trusted users (e.g., plant operators). The condition monitoring circuit, which cannot deliver data packets to the backplane  2206   a , can function to provide untrusted users (e.g., remote technical support operators) with data characterizing operation of the industrial system. 
     Bridging can allow for monitoring subsystem to share common resources, which can provide flexibility when designing and installing monitoring systems. For example, monitoring subsystems (e.g., monitoring subsystem  2201   c ) can be installed remotely near industrial equipment such that the input circuits can receive sensor data, while other monitoring subsystems (e.g., monitoring subsystem  2201   b ) can be installed at another location that may be more convenient, or easier to access, or have a system that is more critical to monitor. Installing monitoring subsystems near the industrial equipment to be monitored, can also reduce costs of running cables from the sensors to input circuits, as well as improve the quality of the signals delivered from sensors to the input circuits by reducing exposure to noise and ground loops. Since monitoring system can share common resources, bridging can also allow monitoring systems to be expanded more cost effectively. For example, monitoring subsystems (e.g., monitoring subsystem XC) can be added to monitoring systems to monitor operation of industrial equipment that might not be critical, or might otherwise be cost prohibitive to monitor. 
     In some embodiments, rather than using passive backplanes (e.g., backplanes  306   a ,  306   b    2106   a ,  2106   b , etc.) to facilitate communication between functional circuits of a monitoring system, Ethernet networks can be used to facilitate communication between functional circuits. In some embodiments, Ethernet protocols such as, e.g., TCP/IP and/or TSN can be used to facilitate and control communication between functional circuits. 
       FIG.  26    shows a block diagram of an exemplary monitoring system  2300  that utilizes the TSN Ethernet protocol to facilitate communication between functional circuits of the monitoring system  2300 . As shown in the illustrated example, the monitoring system  2300  includes a sensor input subsystem  2302 , a marshalling cabinet  2304 , and an instrument cabinet  2306 . The sensor input subsystem  2302  can be configured to receive signals from sensors  2308  configured to measure operating parameters of an industrial system  2310 , and provide digital signals characterizing the sensor measurements to the marshalling cabinet  2304 . The marshalling cabinet  2304  can be configured provide alarm/alerts to a control system (e.g., customer control system  212 ), and to facilitate communication between the instrument cabinet  2306  and the sensor input subsystem  2302 . The instrument cabinet  2306  can be configured to process sensor data, receive and distribute updates to the monitoring system  2300 , and provide users with data characterizing operation of the industrial system  2310 . 
     As shown in  FIG.  26   , the sensor input subsystem  2302  can include junction  2312  boxes that are configured to receive the sensor signals, and a conduit  2314  that can house coupling elements  2316  (e.g., Ethernet cables) that extend between the junction boxes  2312  and to the marshalling cabinet  2304 . The junction boxes  2312  can be configured to receive signals from the sensors, condition the signals, and provide digital signals characterizing the sensor measurements to the marshalling cabinet  2304 . In some embodiments, sensors  2308  can be configured to provide analog signals, discrete signals, and/or digital signal streams. 
       FIG.  27    shown a detailed view of components within the junction boxes  2312 . As shown in  FIG.  27   , the junction boxes  2312  can include multiple signal conditioners  2318  that can be in electronic communication with the sensors  2308  and with input circuits  2320 . The junction boxes  2312  can also include a power supply  2319  that can be electrically coupled to the signal conditioners  2318  and to the input circuits  2320 . The power supply  2319  can be configured to power the signal conditioners  2318  and the input circuits  2320 . The signal conditioners  2318  can be configured to receive signals from the sensors  2308 , adjust a voltage and/or current of the signal, and provide the adjusted signal to the input circuits  2320 . 
     Depending on the type of signal provided by the sensors  2308  the input circuits  2320  can be configured to receive the adjusted signals from the signal conditioners  2318 , convert the signals to digital signals, adjust a voltage and/or current of a discrete signal, adjust a current and/or voltage of a digital signal stream, and provide adjusted digital signal to the marshalling cabinet  2304  via the coupling elements. 
     As shown in the illustrated example, the marshalling cabinet can include a relay circuit  2322 , power supplies  2324 , signal barriers  2326 , and cable couplings  2328   a . The power supplies  2324  can be electrically coupled to the relay circuit  2322 . The power supplies  2324  can be configured to provide power to the relay circuit  2322   a . The signal barriers  2326  can function to prevent potentially dangerous signals from being transmitted to the sensor input system  2302 . For example, if the sensor input subsystem  2302  is positioned within an environment that contains combustible gasses, the signal barriers  2326  can be configured to prevent signals that are beyond a predetermine voltage and/or current from being delivered to the sensor input subsystem  2302 . The relay circuit  2322   a  can be electrically coupled to the sensor input subsystem  2302  via the coupling elements  2327   a  and the signal barrier  2316 . The relay circuit  2322   a  can also be electrically coupled to the cable coupling  2328   a  such that it is in electrical communication with functional circuits within the instrument cabinet  2306 . 
     The instrument cabinet  2306  can include protection circuits  2330   a ,  2330   b  a relay circuit  2322   b , a 4-20 output circuit  2332 , a system interface circuit  2334 , gateway circuit  2336 , and cable couplings  2328   b . The power supplies  2324  can also provide power to the protection circuits  2330   a ,  2330   b , relay circuit  2322   b,  4-20 output circuit  2332 , system interface circuit  2334 , and gateway circuit  2336  within the instrument cabinet  2306 . The protection circuits  2330   a ,  2330   b , relay circuit  2322   b,  4-20 output circuit  2332 , system interface circuit  2334 , and gateway circuit  2336  can generally function similarly to other protection circuits, relay circuit, 4-20 output circuit, system interface circuit, and gateway circuits as described herein. Coupling elements  2327   b  can extend from the cable couplings  2328   b  to the protection circuit  2330   a  and the gateway circuit  2336 . Coupling elements  2327   b  can also extend between the protection circuits  2330   a ,  2330   b  the relay circuit  2322   b,  4-20 output circuit  2332 , system interface circuit  2334 , and gateway circuit  2336 , such that the protection circuits  2330   a ,  2330   b , relay circuit  2322   b,  4-20 output circuit  2332 , system interface circuit  2334 , and gateway circuit  2336  can be electrically coupled between the cable couplings  2328   b.    
     The instrument cabinet  2306  can be electrically coupled to the marshalling cabinet  2304  via coupling elements  2338 . In some embodiments, the coupling elements  2338  can be fiber optic cabling that can extend between cable couplings  2328   a ,  2328   b  of the marshalling cabinet  2304  and the instrument cabinet  2306 . The cable couplings  2328   a ,  2328   b  can be configured to function as an interface between coupling elements  2327   a ,  2327   b  within the marshalling cabinet  2304  and the instrument cabinet  2306 , and coupling elements  2338  that extend between the marshalling cabinet  2304  and the instrument cabinet  2306 . 
     In operation, the sensor input subsystem  2302  can provide digital signals characterizing sensor measurements to the marshalling cabinet  2304 . The digital signals can travel through the coupling elements  2327  within the marshalling cabinet  2304  to the relay circuit  2322 . The digital signals can also be provided to the instrument cabinet  2306  via the cable couplings  2328   a ,  2328   a , and the coupling elements  2338  that extend therebetween. Within the instrument cabinet  2306 , the digital signals can be provided to the protection circuits  2330 , the relay circuit  2322   b , the 4-20 output circuit  2332 , the system interface circuit  2334 , and gateway circuit  2336 . 
     In some embodiments, input circuits can be positioned within a marshalling cabinet of monitoring system that utilizes the TSN Ethernet protocol to facilitate communication between functional circuits of a monitoring system.  FIG.  28    shows a block diagram of another exemplary monitoring system  2400  that utilizes the TSN Ethernet protocol to facilitate communication between functional circuits of a monitoring system. The monitoring system  2400  can generally be similar to the monitoring system  2300  illustrated in  FIG.  26   , but can include input circuits positioned within a marshalling cabinet  2404 .] 
     As shown in the illustrated example, the monitoring system  2400  includes a sensor input subsystem  2402 , a marshalling cabinet  2404 , and an instrument cabinet  2406 . The sensor input subsystem  2402  can be configured to receive signals from sensors  2308  configured to measure operating parameters of an industrial system  2310 , condition the sensor signals, and provide conditioned sensor signals characterizing the sensor measurements to the marshalling cabinet  2404 . The marshalling cabinet  2404  can be configured receive the conditioned sensor signals and provide digital signals characterizing the sensor measurements to the instrument cabinet  2406 . The marshalling cabinet  2404  can also be configured provide alarm/alerts to a control system (e.g., customer control system  212 ), and to facilitate communication between the instrument cabinet  2306  and the sensor input subsystem  2302 . The instrument cabinet  2406  can be configured to process sensor data, receive and distribute updates to the monitoring system  24000 , and provide users with data characterizing operation of the industrial system  2310 . 
     The sensor input subsystem  2402  can include junction  2412  boxes that can be configured to receive the sensor signals, and a conduit  2414  that can house coupling elements  2416  (e.g., Ethernet cables) that extend between the junction boxes  2412  and to the marshalling cabinet  2404 . The junction boxes  2412  can generally be similar to the junction boxes  2312  but do not include input circuits. The junction boxes  2412  can be configured to receive signals from sensors  2308 , condition the sensor signals, and provide conditioned sensor signals characterizing the sensor measurements to the marshalling cabinet  2404  via the coupling elements  2416 . In some embodiments, the coupling elements  2416  can be analog field wires. 
     The marshalling cabinet  2404  can include input circuits  2320 , power supplies  2324 , a relay circuit  2322 , signal barriers  2326 , and cable couplings  2328   a . The power supplies  2324  can be electrically coupled to the input circuits  2320 , the relay circuits  2322   a , and other functional circuits within the instrument cabinet  2406 . The signal barrier  2326  can be coupled to the coupling elements  2416 . The input circuits  2320  can be coupled to the junction boxes  2412  via a coupling element  2417  that extends between each of the input circuits  2320  and the signal barrier  2326 . The input circuits  2320  and the relay circuit  2322   a  can be in electrically coupled via coupling elements  2327   a  that extend between each of the input circuits  2320   a , the relay circuit  2322   a , and the cable coupling  2328   a.    
     The instrument cabinet  2406  can include protection circuits  2330   a ,  2330   b  a relay circuit  2322   b , a 4-20 output circuit  2332 , a system interface circuit  2334 , gateway circuit  2336 , and a cable coupling  2328   b . The power supplies  2324  can provide power to the protection circuits  2330   a ,  2330   b , relay circuit  2322   b,  4-20 output circuit  2332 , system interface circuit  2334 , and gateway circuit  2336  within the instrument cabinet  2306 . Coupling elements  2327   b  can extend from the cable coupling  2328   b  to the protection circuit  2330   a  and the gateway circuit  2336 . Coupling elements  2327   b  can also extend between the protection circuits  2330   a ,  2330   b  the relay circuit  2322   b,  4-20 output circuit  2332 , system interface circuit  2334 , and gateway circuit  2336 , such that the protection circuits  2330   a ,  2330   b , relay circuit  2322   b,  4-20 output circuit  2332 , system interface circuit  2334 , and gateway circuit  2336  can be electrically coupled. 
     The instrument cabinet  2406  can be electrically coupled to the marshalling cabinet  2406  via coupling elements  2438 . In some embodiments, the coupling elements  2338  can be fiber optic cabling that can extend between cable couplings  2328   a ,  2328   b  of the marshalling cabinet  2404  and the instrument cabinet  2406 . The cable couplings  2328   a ,  2328   b  can be configured to function as an interface between coupling elements  2327   a ,  2327   b  within the marshalling cabinet  2404  and the instrument cabinet  2406 , and coupling elements  2438  that extend between the marshalling cabinet  2404  and the instrument cabinet  2406 . 
     In operation, the sensor input subsystem  2402  can provide conditioned signals characterizing sensor measurements to the marshalling cabinet  2304 . The input circuits  2320  can receive the conditioned signals. The input circuits  2320  can generate digital signals based on the conditioned signals, and provide the digital signals to the relay circuit  2322   a  and the he instrument cabinet  2406  via the cable couplings  2328   a ,  2328   a , and the coupling elements  2438  that extend therebetween. Within the instrument cabinet  2306 , the digital signals can be provided to the protection circuits  2330 , the relay circuit  2322   b , the 4-20 output circuit  2332 , the system interface circuit  2334 , and gateway circuit  2336 . 
     Traditional monitoring systems can be limited in terms of flexibility and scalability. Additionally, costs and complexity of installation can create a significant barrier to entry for users that want to monitor low cost and/or low priority components/systems. By utilizing functional circuits that can be detachably coupled to the backplane, performance of the monitoring systems described herein can be adjusted and/or scaled to fit individual monitoring needs. For example, processing power can be increased by coupling additional processing circuits to the backplane. Additionally, utilizing bridge circuits to facilitate communication between multiple backplanes can allow for monitoring subsystem of a monitoring system to share common resources, which can provide flexibility when designing and installing monitoring systems. For example, monitoring subsystems (e.g., monitoring subsystem  2101   b ) can be installed remotely near industrial equipment such that the input circuits can receive sensor data, while other monitoring subsystems (e.g., monitoring subsystem  2101   a ) can be installed at another location that may be more convenient, or easier to access. Installing monitoring subsystems near the industrial equipment to be monitored can also reduce costs of running cables from the sensors to input circuits, as well as improve the quality of the signals delivered from sensors to the input circuits by reducing exposure to noise and ground loops. Since monitoring system can share common resources, bridging can also allow monitoring systems to be expanded more cost effectively. For example, monitoring subsystems (e.g., monitoring subsystem  2201   c ) can be added to monitoring systems to monitor operation of industrial equipment that might not be critical, or might otherwise be cost prohibitive to monitor. 
     Exemplary technical effects of the subject matter described herein can include the ability to bridge multiple backplanes of a monitoring system to create an extended logical bus. The extended logical bus allows monitoring systems to span between multiple locations while retaining the full functionality that is available when using monitoring systems that include a single backplane. Additionally, since all data is shared between bridged backplanes, the bridges allow for resources (e.g., monitoring circuits) to be distributed between the backplanes as desired. For example, monitoring subsystems can be installed remotely near industrial equipment such that the input circuits can receive sensor data, while other monitoring subsystems can be installed at another location that may be more convenient, or easier to access. Installing monitoring subsystems near the industrial equipment to be monitored can also reduce costs of running cables from the sensors to input circuits, as well as improve the quality of the signals delivered from sensors to the input circuits by reducing exposure to noise and ground loops. 
     In some embodiments, a monitoring system can utilize a backplane that has dedicated data lanes that only receive data from one input circuit. Therefore, if a data lane fails during operation, the impact of that failure can be limited to a single monitoring circuit that is configured to deliver data to that particular data lane.  FIG.  29    shows a block diagram of a portion of an exemplary embodiment of a monitoring system  2500  utilizes dedicated data lanes to facilitate communication between monitoring circuits  2510 . 
     The monitoring system  2500  can include any number of monitoring circuits  2510 , which can be detachably coupled to a backplane  2506  via ports  2508  of the backplane  2506 . As shown in the illustrated example, the monitoring system includes input circuits  2550 , protection circuits  2552 , a system interface circuit  2554 , a condition monitoring circuit  2556 , a 4-20 output circuit  2561 , a relay circuit  2558 , and a gateway circuit  2559 . In some embodiments the input circuits  2550  can be, e.g., dynamic input circuits. The backplane can be, include, or form part of, a physical bus. In some embodiments, the backplane can have a unique ID that can be used to identify the backplane. The backplane can be a passive backplane configured to facilitate multipoint asynchronous electronic communication between the functional circuits that are coupled to the backplane. Therefore, all data that is delivered to the backplane can be received by all functional circuits  2510  that are coupled to the backplane  2506 . 
     In the illustrated example, the backplane includes a set of input data lanes  2512   a , a set of protection data lanes  2512   b , and at least one system data lane  2512   c . The protection data lanes  2512   b  and input data lanes  2512   a  can be single-direction serial communication lanes. Each of the input data lanes  2512   a  can be configured to receive data packets from an input circuits  2550  coupled to a port that can be configured to facilitate data delivery to the corresponding monitoring lane. As shown in the illustrated example, each input data lane  2512   a  can receive data packets from a single input circuit  2550 . Each input data lane  2512   a  can be in electronic communication with ports  2508  configured to receive input circuits  2550 , protection circuits  2552 , the system interface circuit  2554 , the condition monitoring circuit  2556 , the 4-20 output circuit  2561 , the relay circuit  2558 , and the gateway circuit  2559 . 
     In some embodiments, all of the input, protection, and system data lanes  2512   a ,  2512   b ,  2512   c  can be electrically coupled to each of the ports. However, for clarity, unused connections between the ports  2508  and the input, protection, and system data lanes  2512   a ,  2512   b ,  2512   c  are omitted in  FIGS.  29 - 34   . 
     The protection data lanes  2512   b  can function to provide trusted systems/users with alarms and/or other data characterizing operation of the industrial equipment being monitored. As shown in the illustrated example, each of the protection data lanes  2512   b  can be in electronic communication with a port configured to couple to a protection circuit such that the protection data lane is configured to receive data packets from the protection circuit. All of the protection data lanes  2512   b  can be in electronic communication with ports configured to receive relay circuits  2558  such that alarm signals provided by the protection circuits can be provided to trusted systems (e.g., customer control system  212 ). 
     Each of the input data lanes  2512   a  and protection data lanes  2512   b  can be dedicated data lanes, such that each of the input data lanes  2512   a  and protection data lanes  2512   b  are configured to receive data from one input circuit  2550  and one protection circuit  2552 , respectively. 
     The system data lane  2512   c  can be a bi-directional serial communication lane. The system data lane  2512   c  can function as a communication lane for the system interface circuit to perform update operating parameters, operating thresholds, or configurations, of any of the functional circuits. The system data lane  2512   c  can also allow the system interface circuit to adjust, or set, alarm conditions for protection circuits as well as conditions for actuation of relay circuits  2558 . The system data lane  2512   c  can be in electronic communication with all of the ports of the backplane, such that functional circuits coupled to each port can deliver data packets to, and receive data packets from, the system data lane  2512   c . In some embodiments, the system data lane  2512   c  can be a command/response lane that can be controlled by the system interface circuit  2554 , as described in more detail below. 
     Each input circuit  2550  can be in electronic communication with one of the input data lanes  2512   a , as well as with the system data lane  2512   c . The input circuits  2550  can be configured to receive sensor signals, perform signal conditioning on the sensor signals, and output the conditioned sensor signals to the input data lanes  2512   a  backplane. The input circuits  2550  can also be configured to receive data packets from the system data lane  2512   c , as well as provide data packets to the system data lane  2512   c  when commanded. In some embodiments, the input circuits can provide various coupling interfaces for different sensors supported by the monitoring system. 
       FIG.  30    shows a magnified view of the input circuits  2550 . As shown in the illustrated example, the input circuits  2550  can include a circuit controller  2520   a  and a node  2522   a  configured to facilitate and control electronic communication between the circuit controller and the backplane. The circuit controller  2520   a  can generally be similar to the circuit controller  320 . The circuit controller  2520   a  can be configured to receive analog sensor signals from the sensors and convert the analog sensor signals to digital signals at a fixed rate. The circuit controller  2520   a  can also be configured to normalize the digital signals and provide the normalized digital signals to a corresponding input data lane on the backplane (e.g., via the node  2522   a ). In some embodiments, the circuit controller  2520  can be configured to filter the analog sensor signals to provide aliasing protection for an output rate of the digitized sensor signal. The circuit controllers  2520   a  can also communicate with smart sensors (e.g., transducers) to receive asset data and to issue commands to the transducers. In some embodiments, the input circuits can also provide power to the sensors. 
     Each node  2522   a  of the input circuits  2550  can include schedule controller  2534 , a node controller  2524 , a gate controller  2526 , a gate pairs  2528 , as well as a transmitter  2530 . The schedule controller  2534 , a node controller  2524 , a gate controller  2526 , a gate pairs  2528 , as well as a transmitter  2530 , can generally be similar to the schedule controller  334 , node controller  324 , gate controllers,  326 , gate pairs  328 , and transmitter  330 . The gate pair  2528  can include a transmitter and a receiver. The node controller  2524  can function as an interface between the circuit controller  2520   a  and the gate controller  2526 , transmitters  330  and/or receivers  332 . For example, the node controller  2524  can be configured to control which data is transferred from the system data lane  2512   c  to the circuit controller  2520   a  using, e.g., packet filtering techniques. In some embodiments, the node controller  2524  can be configured to receive signals from the circuit controller  2520   a , encode the signals into bits, and deliver signals (e.g., data packets) corresponding to the encoded bits to the gate controller  2526  for the data to be delivered to the input data lane  2512   a  of the backplane  2506 . 
     In some embodiments, the schedule controller  2534  can be configured manage timing of communication from the input circuits  2550  to the input data lanes  2512   a  and/or the serial data lanes. For example, in some embodiments, data packets can be delivered to input data lanes  2512   a  using time division multiplexing. The schedule controllers  2534  can generate schedules and/or algorithms that can be managed by the node controllers  2524  and/or gate controllers  2526  to enable successful deliver of data packets. The schedules can generally be similar to the schedules described above with regard to  FIGS.  4 ,  7 - 9   . Utilizing time division multiplexing can allow multiple input circuits  2550  to deliver data to a single input data  2512   a  lane while eliminating, or mitigating, collisions between data packets. 
     The gate pair  2528  can be configured to facilitate electronic communication between the input circuit  2550  and the system data lanes  2512   c  of the backplane  306 . In some embodiments, the gate pair  2528  can be a half-duplex transceiver or a full-duplex transceiver. Each gate controller  2526  can be configured to control operation of the transmitter  2530  as well as a transmitter and receiver of the gate pair  2528 . 
       FIG.  31    shows a magnified view of the system interface circuit  2554 . The system interface circuit  2554  can be in electronic communication with one of the input data lanes  2512   a , as well as with the system data lane  2512   c . The system interface circuit  2554  can be configured to enable adjustment of operating parameters of functional circuits coupled to the backplane. As shown in the illustrated example, the system interface circuit  2554  can include a circuit controller  2520   b  and a node  2522   b  configured to enable and control electronic communication between the circuit controller  2520   b  and the system data lane  2512   c  of the backplane. Circuit controllers  2520   b  of system interface circuits can function to enable configuration of any of the functional circuits, alarm conditions for protection of the industrial equipment, and conditions for actuation of relay circuits  2558 . In some embodiments, the circuit controller  2520   b  of the system interface circuit  2554  can be coupled to the control system and/or a HMI (e.g., HMI  220 ). A trusted user, such as, e.g., a plant operator, can provide configuration data to the circuit controller  2520   b  of the system interface circuit  2554  via the control system and/or the HMI, and the system interface circuit  2554  can provide data packets characterizing the configuration data to the system data lane  2512   c  of the backplane  2506 . 
     The node  2522   b  of the system interface circuit  2554  can include schedule controller  2534 , a node controller  2524 , a gate controller  2526 , and a gate pair  2528 . The schedule controller  2534 , node controller  2524 , gate controller  2526 , gate pairs  2528 , and transmitters  2530 , can generally be similar to the schedule controller  334 , node controller  324 , gate controllers,  326 , gate pairs  328 . The gate pair  2528  can include a transmitter and a receiver. In some embodiments, the gate pair  2528  can be a half-duplex transceiver or a full-duplex transceiver. The node controller  2524  can function as an interface between the circuit controller  2520   b  and the gate controller  2526  and/or the gate pair  2528 . In some embodiments, the node controller  2525  be configured to receive signals from the circuit controller  2520   b , encode the signals into bits, and deliver signals (e.g., data packets) corresponding to the encoded bits to the gate controller  2526  for the data to be delivered to the system data lane  2512   c  of the backplane  2506 . 
     The gate pair  2528  can be configured to facilitate electronic communication between the system interface circuit and the system data lanes  2512   c  of the backplane. Each gate controller  2526  can be configured to control operation of the transmitter as well as the transmitter and receiver of the gate pair  2528 . 
     In some embodiments, the system interface circuit  2554  can be in a master/slave relationship with other monitoring circuits  2510  that are in electronic communication with the system data lane  2512   c . Therefore, the system interface circuit  2554  can deliver commands to the input circuits  2550 , protection circuits  2552 , relay circuit  2558 , gateway circuit  2559 , and 4-20 output circuit  2561 , thereby commanding responses from the input circuits  2550 , protection circuits  2552 , relay circuit  2558 , gateway circuit  2559 , and 4-20 output circuit  2561 . The input circuits  2550 , protection circuits  2552 , relay circuit  2558 , gateway circuit  2559 , and 4-20 output circuit  2561  can receive the command, and deliver data to the system data lane  2512   c  based on the response. As another example, in some embodiments, if the input data lanes  2512   a  and/or protection data lanes  2512   b  are configured to each receive data from more than one input circuit  2550  and protection circuit  2552 , respectively, the schedule controller  2534  can be configured to generate a communication schedule that determines when each of the input circuit  2550  and/or protection circuits  2552  can deliver data to the system data lane  2512   c . The schedules can generally be similar to the schedules described above with regard to  FIGS.  4 ,  7 - 9   . The schedule controller  2534  can generate a schedule and deliver the schedule to the system data lane  2512   c  via the node controller  2524  and/or the gate controller  2526 . Monitoring circuits  2510  that are in electronic communication with the system data lane  2512   c  can receive the schedule, and deliver data packets to the system data lane  2512   c  based on time slices that they have been assigned. 
     In some embodiments, if multiple monitoring circuits communicate over a single data lane (e.g., using time division multiplexing), the system interface circuit  2554  can be configured to monitor the all of the data lanes. 
       FIG.  32    shows a magnified view of the protection circuits  2552 . The protection circuits can be configured to monitor sensor data provided to the input data lanes  2512   a . The protection monitoring system can also be configured to determine a status (e.g., OK, alert, danger, etc.) of the industrial equipment that is being monitored based on the sensor data. As shown in the illustrated example, the protection circuit  2552  can include a circuit controller  2520   c  and a node  2522   c  configured to facilitate and control electronic communication between the circuit controller  2520   c  and the system data lane  2512   c , a protection data lane, and the input data lanes  2512   a  of the backplane  2506 . 
     The circuit controller  2520   c  can be configured to retrieve any data packets (e.g., data packets corresponding to sensor measurements) from the input data lanes  2512   a  of the backplane  2506  (e.g., via the node  2522   c ), analyze the retrieved data packets, and provide the results of such analysis to one of the protection data lanes  2512   b  of the backplane  2506  (e.g., via the node  2522   c ). For example, circuit controllers  2520   c  of protection circuits  2552  can also be configured to compare data received from the backplane  2506  to pre-determined alarm conditions in real-time and determine a status (e.g., OK, alert, danger, etc.) for any measured operational parameter or variable, alone or in combination. The determined status can be subsequently output to one or more of the protection data lanes  2512   b  of the backplane  2506 . The protection circuits  2552  can also be configured to receive data packets from the system data lane  2512   c , as well as provide data packets to the system data lane  2512   c , when commanded (e.g., when scheduled to communicate). 
     Each node  2522   c  of the protection circuit can include schedule controller  2534 , a node controller  2524 , a gate controller  2526 , and a gate pair  2528 , a transmitter  2530 , and receivers  2532 . The schedule controller  2534 , node controllers  2524 , gate controllers  2526 , gate pair  2528 , transmitters  2530 , and receivers  2532  can generally be similar to the schedule controller  334 , node controller  324 , gate controllers  326 , gate pairs  328 , transmitters  330 , and receivers  332 . The gate pair  2532  can include a transmitter and a receiver. In some embodiments, the gate pair  2528  can be a half-duplex transceiver or a full-duplex transceiver. The node controller  2524  can function as an interface between the circuit controller  2520   c  and the gate controller  2526  and/or gates and the gate pair. For example, the node controller  2524  can be configured to control which data is transferred from the input data lanes  2512   a  to the circuit controller  2520   c  using, e.g., packet filtering techniques. In some embodiments, the node controller  2524  can be configured to receive signals from the circuit controller  2520   c , encode the signals into bits, and deliver signals (e.g., data packets) corresponding to the encoded bits to the gate controller  2526  for the data to be delivered to the system data lane  2512   c  of the backplane  2506 . 
     The gate pairs  2528  can be configured to facilitate electronic communication between the protection circuit  2552  and the system data lane  2512   c . The receivers  2532  can be configured to facilitate communication between the protection circuits  2552  and the input data lanes  2512   a . The transmitter  2530  can be configured to facilitate deliver of data packets (e.g., corresponding to alarms) to one or more of the protection data lanes  2512   b . Each gate controller  2526  can be configured to control operation of the transmitter  2530 , the receivers  2532 , and the gate pair  2528 . 
     As shown in  FIGS.  29 ,  30 , and  32   , each input circuit  2550  is configured to deliver data to a different input data lane  2512   a , and each protection circuit  2552  is configured to deliver data to a different protection data lane  2512   b . Therefore, each of the input data lanes  2512   a  and protection data lanes  2512   b  is dedicated to a single input circuit  2550  and protection circuit  2552 , respectively. 
       FIG.  33    shows a magnified view of the relay circuit  2558 . The relay circuit  2558  can be configured to receive status data (e.g., data provided by the protection circuits) from the protection data lanes  2512   b  and deliver a signal to trusted system (e.g., customer control system  212 ) to alert plant operators of potential problems related to operation of industrial systems, and or trigger a shutdown of the industrial system. In some embodiments, the one or more of the relay circuit  2558  can be a protection fault relay and will also have provide an alert, or indication, when the user has placed the system in a mode of operation that compromises protection. 
     As shown in the illustrated example, the relay circuit  2558  can include a circuit controller  2520   d  and node  2522   d  configured to facilitate and control electronic communication between the circuit controller  2520   d  and the system data lane  2512   c  as well as each of the protection data lanes  2512   b . The circuit controller  2520   d  of the relay circuit  2558  can be configured to retrieve status data (e.g., data delivered by protection circuits) from protection data lanes  2512   b  of the backplane  2506  (e.g., via the node  2522   d ) and to actuate based on the system status. In one example, circuit controllers  2520   d  of relay circuit  2558  can actuate based upon a single status. In another example, relay circuit  2558  can actuate based upon Boolean expressions (e.g., AND or voting) that combine two or more statuses. In some embodiments, upon actuation, relay circuit  2558  can be configured to deliver a monitoring signal (e.g., monitoring signal  106   s ) to a control system (e.g., customer control system  212 ). The control system can then stop operation of the equipment being monitored to prevent damage or failure. 
     Each node  2522   d  of the relay circuit  2558  can include schedule controller  2534 , a node controller  2524 , a gate controller  2526 , and a gate pair, a transmitter  2530 , and receivers  2532 . The schedule controller  2534 , node controllers  2524 , gate controllers  2526 , gate pair  2528 , transmitters  2530 , and receivers  2532  can generally be similar to the schedule controller  334 , node controller  324 , gate controllers  326 , gate pairs  328 , transmitters  330 , and receivers  332 . In some embodiments, the gate pair  2528  can be a half-duplex transceiver or a full duplex transceiver. The node controller  2524  can function as an interface between the circuit controller  2520   d  and the gate controller  2526 , transmitter  2530 , receivers  2532  and/or the gate pair  2528 . For example, the node controller  2524  can be configured to control which data is transferred from the protection data lanes  2512   b  to the circuit controller  2520   d  using, e.g., packet filtering techniques. In some embodiments, the node controller  2524  can be configured to receive signals from the circuit controller  2520   d , encode the signals into bits, and deliver signals (e.g., data packets) corresponding to the encoded bits to the gate controller  2526  for the data to be delivered to the system data lane  2512   c  of the backplane  2506 . 
       FIG.  34    shows a magnified view of the gateway circuit  2559 . As shown in the illustrated example, the gateway circuit  2559  can include a circuit controller  2520   e  and a node  2522   e  configured to enable and control electronic communication between the circuit controller  2520   e  and the system data lane  2512   c  as well as each of the protection data lanes  2512   b . The gateway circuit  2559  can enable communication between the flexible monitoring system  202  and trusted system such as, e.g., the HMI  220 , customer historian  216 , and customer control systems  212 . For example, the protection circuits  2552  can deliver data characterizing operation of a machine (e.g., machine  102 ) to the gateway circuit  2559 . The gateway circuit  2559  can provide the data to a trusted user and/or system (e.g., HMI  220 , customer historian  216 , and customer control systems  212 ). In some embodiments, the gateway circuit  2559  can also functions as input circuit. For example, a trusted user and/or system such as, e.g., the HMI  220 , customer historian  216 , and customer control systems  212 , can provide data to the gateway circuit, and the gateway circuit  2559  can deliver the data to the backplane  2506  such that the data is available to other functional circuits. For example, a trusted user can deliver data to the gateway circuit  2559  to request that the protection circuit  2552  perform certain analyses on sensor data. In some embodiments, if the gateway circuit  2559  can include a transmitter such that the gateway circuit can receive the request and deliver the data characterizing the request to the backplane  2506 . 
     Each node  2522   e  of the gateway circuit  2559  can include schedule controller  2534 , a node controller  2524 , a gate controller  2526 , and a gate pair  2528 , and receivers  2532 . The schedule controller  2534 , node controllers  2524 , gate controllers  2526 , gate pair  2528 , transmitters  2530 , and receivers  2532  can generally be similar to the schedule controller  334 , node controller  324 , gate controllers  326 , gate pairs  328 , transmitters  2530 , and receivers  2532 . The gate pair  2528  can include a transmitter and a receiver. In some embodiments, the gate pair can be a half-duplex transceiver or a full-duplex transceiver. The node controller  2524  can function as an interface between the circuit controller  2520   e  and the gate controller  2526 , receivers  2532 , and/or the gate pair  2528 . For example, the node controller  2524  can be configured to control which data is transferred from the protection data lanes  2512   b  to the circuit controller  2520   e  using, e.g., packet filtering techniques. In some embodiments, the node controller  2524  can be configured to receive signals from the circuit controller  2520   e , encode the signals into bits, and deliver signals (e.g., data packets) corresponding to the encoded bits to the gate controller  2526  for the data to be delivered to the system data lane  2512   c  of the backplane  2506 . 
       FIG.  35    shows a magnified view of the condition monitoring circuit  2556  and the 4-20 output circuit  2561 , both of which can be configured to output 4-20 mA record outputs. The condition monitoring circuit  2556  and the 4-20 output circuit  2561  can be configured to output monitoring signals as 4-20 mA recorder outputs. The condition monitoring circuit  2556  can be configured to receive all data delivered to the input data lanes  2512   a , protection data lanes  2512   b , and system data lane  2512   c.    
     As shown in the illustrated example, the condition monitoring circuit  2556  can include a circuit controller  2520   f  and a node  2522   f  configured to enable and control electronic communication between the circuit controller  2520   f  and the system data lane  2512   c  as well as each of the input data lanes  2512   a . The node  2522   f  of the condition monitoring circuit  2556  can include a node controller  2524 , a gate controller  2526 , and receivers  2532 . However the node  2522   f  of the condition monitoring circuit  2556  does not include transmitters. Due to the lack of transmitters, nodes  2522  of 4-20 functional circuit  2556  can is unable to deliver data to the input data lanes  2512   a , protection data lanes  2512   b , and the system data lane  2512   c.    
     The 4-20 output circuit  2561  can be configured to receive all data delivered to the protection data lanes  2512   b  and the system data lane  2512   c . As shown in the illustrated example, the 4-20 output circuit  2561  can include a circuit controller  2520   g  and a node  2522   g  configured to enable and control electronic communication between the circuit controller  2520   g  and the system data lane  2512   c  as well as each of the protection data lanes  2512   b . The node  2522   g  of the 4-20 output circuit  2561  can include a node controller  2524 , a gate controller  2526 , and receivers  2532 . The node controllers  2524 , gate controllers  2526 , and receiver  2532  can generally be similar to the node controller  324 , gate controllers  326 , and receivers  332 . 
     As shown in  FIGS.  29 - 34   , transmitters  2530  of each of the input circuits  2550  is electrically coupled to a different input data lane  2512   a . Therefore, each of the input circuits  2550  delivers data packets to a different input data lane  2512   a  than the other input circuits  2550 . Similarly, transmitters  2530  of protection circuits  2552  are electrically coupled to different protection data lanes  2512   b . Therefore, each of the protection circuits  2552  delivers data packets to a different protection data lane  2512   b  than the other input circuits  2550 . By coupling different input data lanes  2512   a  and protection data lanes  2512   b  to each input circuit  2550  and protection circuit  2552  respectively, there is no risk of collisions when delivering data to the backplane  2506 . Since the input data lanes  2512   a  and protection data lanes  2512   b  do not receive inputs from multiple input circuits  2550  and protection circuits  2552 , respectively, a communication protocol governing data delivery to the backplane  2506  can be simplified. For example, in some embodiments, there is no need to schedule communication from input circuits  2550  and protection circuits  2552 . 
     In some embodiments, the data lanes that receive data packets from input circuit  2550  and protection circuit  2552  can be determined by the ports  2508  of the backplane  2506 .  FIG.  36    shows a top view of the backplane  2506  of the monitoring system  2500 . As shown in the illustrated example, each port includes first and second input links  2562 ,  2564 . Each of input links  2562  can be in electronic communication with a different input data lane  2512   a  than the other input links  2562 . Each port can also include first and second sets of output links  2566 ,  2568 , and system links  2570 . In  FIG.  36   , the first and second sets of output links  2566 ,  2568  are illustrated along the input data lanes  2512   a  and the protection data lanes  2512   b , respectively. Each of the output links  2566 ,  2568  can be in electronic communication with a corresponding input data lane  2512   a  and protection data lane  2512   b , respectively. Therefore, all functional circuits  2510  coupled to the ports  2508  can receive data from all of the data lanes  2512   a ,  2518   b ,  2512   c . The system links  2570  can be in electronic communication with the system data lane  2512   c  and can be configured to facilitate bi-directional serial communication with the system data lane  2512   c.    
     Referring to  FIGS.  29 - 36   , in the illustrated example, the input circuits are  2512  coupled to ports  2508   a , the protection circuits  2552  are coupled to ports  2508   b , the relay circuit  2558 , the gateway circuit  2559 , and the 4-20 output circuit are coupled to ports  2508   c , the condition monitoring circuit  2556  is coupled to port  2508   d , and the system interface circuit is coupled to port  2508   e . However, since each port  2508  includes input links  2562 ,  2564 , output links  2566 ,  2568 , and system links  2570 , functional circuits  2510  can be coupled to any given port  2508  of the backplane  2506 . In  FIGS.  29 - 36    transmitters  2530  of the input circuits  2550  can be electrically coupled to input links  2562  of the ports  2508   a , and transmitters  2530  of the protection circuits  2552  can be electrically coupled to the input links  2564  of the ports  2508   b.    
       FIG.  37    shows a data flow diagram  2600  illustrating exemplary communication between various components of the monitoring system  2500 . At step  2602 , the input circuits can deliver data packets characterizing sensor measurements to respective input data lanes  2512   a  (e.g., via the first input links  2562  of the ports  2508   a ). At step  2604 , the protection circuits  2552  can receive the data packets from the input data lanes  2512   a . At step  2606 , the condition monitoring circuit  2556  can receive the data packets from the input data lanes  2512   a.    
     The protection circuits  2552  can analyze and process the data from the input data lanes. For example, the protection circuits  2552  can determine an operating status of a machine based on the sensor measurements. At step  2608 , the protection circuits  2552  can provide the results of such analyses to the protection data lanes  2512   b  (e.g., via the second input links  2564  of the ports  2508   b ). At steps  2610 ,  2612 ,  2614 ,  2616 ,  2618 , the relay circuit  2558 , gateway circuit  2559 , 4-20 output circuit  2561 , and condition monitoring circuit  2556  can receive the data from the protection data lanes  2512   b , respectively. 
     Based on the status of the machine, the relay circuit  2558  can deliver a signal to a control system (e.g., customer control system  212 ). The control system can then stop operation of the equipment being monitored to prevent damage or failure. In some embodiments, the condition monitoring circuit  2556  can perform further analysis on data received from the input data lanes  2512   a  and the protection data lanes  2512   b . The condition monitoring circuit  2556  can provide data from the input data lanes  2512   a  and the protected data lanes  2512   b  to untrusted users or systems (e.g., remote technical support operators and condition monitoring system  214 ). The gateway circuit  2559  can provide data from the protection data lanes  2512   b  to trusted system such as, e.g., the HMI  220 , customer historian  216 , and customer control systems  212 . The 4-20 output circuit can provide from the protection data lanes  2512   b  to a trusted user (e.g., a plant operator). During operation, the system interface circuit  2554  can deliver data packets to the system data lane  2512   c  to adjust operating parameters of functional circuits  2510  coupled to the backplane and/or request status updates from each of the other functional circuits  2510  coupled to the backplane  2506 . A trusted user, such as, e.g., a plant operator, can provide configuration data to the circuit controller  2520   b  of the system interface circuit  2554  via the control system and/or the HMI, and the system interface circuit  2554  can provide data packets characterizing the configuration data to the system data lane  2512   c  of the backplane  2506 . The input circuits  2550 , protection circuits  2552 , relay circuit  2558 , gateway circuit  2559 , 4-20 output circuit  2561 , and the condition monitoring circuit  2556  can receive the data from the system data lane  2512   c , update operating parameters based on the received data, and/or provide status responses to the system data lane  2512   c  if requested. 
     Periodically, each functional circuit  2510  of the monitoring system  2500  can perform self-tests to evaluate a status of internal processors, memory, and/or other circuitry. The functional circuit can also determine a current operating status. Each of the functional circuit can deliver the results of the self-test to the system data lane  2512   c  to be provided to the statuses will be sent on the system data lane  2512   c  and can be sent over the various data lanes. The system interface circuit  2554  can also provide an additional level of analysis at a system level. Included in the health analysis with telemetry data (system temperature, hours in use, supply voltage), configuration changes, network performance information. The system interface circuit  2554  can deliver data characterizing results of the health analysis to the system data lane  2512   c  such that each functional circuit can receive the data. 
     In some embodiments, the monitoring system can be configured to deliver data to a local displays such that the data can be displayed for a plant operator. In other embodiments, data can be transmitted using industrial protocols such that it is available for presentation on HMIs. The data can include current values, status, and/or trends of measure values. 
     In some embodiments, the system interface circuit  2554 , a gateway circuit  2559 , and/or a condition monitoring circuit  2556  can include a short range wireless communication components such that each of the system interface circuit  2554 , a communication gateway, and/or a condition monitoring circuit  2556  can be configured to communicate wirelessly with a user device. In some embodiments, the system interface circuit  2554 , a communication gateway, and/or a condition monitoring circuit can provide health information to a user device such as, e.g., a tablet, laptop, smartphone, etc. In some embodiments, the system can include a 4-20 mA recorder output. 
     By utilizing different input data lanes  2512   a  and protection data lanes  2512   b  to receive data from each input circuit  2550  and protection circuit  2552  respectively, there is no risk of collisions when delivering data to the backplane  2506 . Since the input data lanes  2512   a  and protection data lanes  2512   b  do not receive inputs from multiple input circuits  2550  and protection circuits  2552 , respectively, a communication protocol governing data delivery to the backplane  2506  can be simplified. For example, in some embodiments, there is no need to schedule communication from input circuits  2550  and protection circuits  2552 . Additionally, by separating functionality of input data lanes  2512   a  and protection data lanes  2512   b , circuitry of nodes  2522  of each functional circuit  2510  can be simplified such that it can be designed and constructed more efficiently. 
     In some embodiments, a backplane of a monitoring systems can include dedicated data lanes that are not separated by functionality, but which are still configured to receive data input from a single monitoring circuit.  FIG.  38    shows block diagram of a portion of another exemplary embodiment of a monitoring system  2700 . 
     The monitoring system  2700  can include any number of functional circuits  2710 , which can be detachably coupled to a backplane  2706  via ports  2708  of the backplane  2706 . As shown in the illustrated example, the monitoring system  2700  includes input circuits  2750 , protection circuits  2752 , a system interface circuit  2754 , a relay circuit  2758 , a 4-20 output circuit  2761 , and a condition monitoring circuit  2756 . The input circuits  2750 , protection circuits  2752 , a system interface circuit  2754 , relay circuit  2578 , a 4-20 output circuit  2761 , and condition monitoring circuit  2756  can generally be similar to the protection circuits  2552 , system interface circuit  2554 , relay circuit  2558 , 4-20 output circuit  2561 , and condition monitoring circuit  2556  describe herein with regard to  FIGS.  29 - 36   , with the exception of some slight difference between nodes of each, as described in more detail below. 
     In the illustrated example, the backplane includes a set of data lanes  2712   a , and at least one system data lane  2712   c . The data lanes  2712   a  can serve the same functions as the input data lanes  2512   a  and the protection data lanes  2512   b . The system data lane  2712   c  can generally function similarly to the system data lane  2512   c . Each of the input data lanes  2712   a  can be configured to receive data packets from an input circuits  2750  coupled to a port  2708  that can be configured to facilitate data delivery to the corresponding data lane  2712   a . As shown in the illustrated example, each data lane  2712   a  can receive data packets from a single input circuit  2550  or a single protection circuit  2752 . All of the data lanes  2712   a  and system data lanes  2712   c  can be electrically coupled to each of the ports  2708 . However, for clarity, unused connections between the ports  2708  and data lanes  2712   a  and/or system data lanes  2712   c  are omitted in  FIGS.  38 - 42   . 
     The backplane  2706  can be a passive backplane configured to facilitate multipoint asynchronous electronic communication between the functional circuits that are coupled to the backplane. Therefore, all data that is delivered to the backplane  2706  can be received by all functional circuits  2710  that are coupled to the backplane  2706 . 
       FIG.  39    shows a magnified view of the input circuits  2750  and the system interface circuit  2754 . As shown in the illustrated example, the input circuits  2750  can include a circuit controller  2720   a  and a node  2722   a  configured to facilitate and control electronic communication between the circuit controller and the backplane  2706 . The circuit controller  2720   a  can generally be similar to the circuit controller  2520   a . Each node  2722   a  of the input circuits  2750  can include a schedule controller  2534 , a node controller  2524 , a gate controller  2526 , a gate pairs  2528 , and a transmitter  2530 . Each of the transmitters  2530  of the input circuits  2750  can be in electronic communication with one data lane  2712   a . The transmitters  2530  can be configured to deliver data to one corresponding data lane  2712   a . Each gate pair  2528  of the input circuits  2750  can be in electronic communication with the system data lane  2712   c.    
     The system interface circuit  2754  can include a circuit controller  2720   b  and a node  2722   b  configured to facilitate and control electronic communication between the circuit controller and the backplane  2706 . The circuit controller  2720   b  can generally be similar to the circuit controller  2520   b . The node  2722   b  of the system interface circuit  2754  can include a schedule controller  2734 , a node controller  2724 , a gate controller  2726 , and gate pairs  2728 . The gate pair  2528  of the system interface circuit  2754  can be in electronic communication with the system data lane  2712   c.    
       FIG.  40    shows a magnified view of the protection circuits  2752 . As shown in the illustrated example, the protection circuits  2752  can include a circuit controller  2720   c  and a node  2722   c  configured to facilitate and control electronic communication between the circuit controller  2720   c  and the backplane  2706 . The circuit controller  2720   c  can generally be similar to the circuit controller  2520   c . Each node  2722   c  of the protection circuits  2752  can include a schedule controller  2534 , a node controller  2524 , a gate controller  2526 , a gate pairs  2528 , a transmitter  2530 , and receivers  2532 . Each of the transmitters  2530  of the protection circuits  2752  can be in electronic communication with one data lane  2712   a . The transmitters  2530  can be configured to deliver data to one corresponding data lane  2712   a . Each gate pair  2528  of the input circuits  2750  can be in electronic communication with the system data lane  2712   c . The receivers  2532  can be in electronic communication with the data lanes  2712   a , and can be configured to receive data from the data lanes  2712   a . The protection circuits  2752  can include a sufficient number of receivers  2532  to be able to receive data from all of the data lanes  2712   a.    
       FIG.  41    shows a magnified view of the relay circuit  2758 , 4-20 output circuit  2761 , and a condition monitoring circuit  2756 . The relay circuit  2758 , 4-20 output circuit  2761 , and a condition monitoring circuit  2756  can include circuit controllers  2720   d ,  2720   g ,  2720   f , and nodes  2722   d ,  2722   g ,  2722   f . The nodes  2722   d ,  2722   g ,  2722   f  can be configured to facilitate and control electronic communication between the circuit controllers  2720   d ,  2720   g ,  2720   f  and the backplane  2706 . The circuit controllers  2720   d ,  2720   g ,  2720   f  can generally be similar to the circuit controllers  2520   d ,  2520   g ,  2520   f . Each of the nodes  2722   d ,  2722   g ,  2722   f  can include a schedule controller  2534 , a node controller  2524 , a gate controller  2526 , a gate pairs  2528 , and receivers  2532 . The gate pairs  2528  of the relay circuit  2758 , 4-20 output circuit  2761 , and a condition monitoring circuit  2756  can be in electronic communication with the system data lane  2712   c . The receivers  2532  can be in electronic communication with the data lanes  2712   a , and can be configured to receive data from the data lanes  2712   a . The relay circuit  2758 , 4-20 output circuit  2761 , and a condition monitoring circuit  2756  can each include a sufficient number of receivers  2532  to be able to receive data from all of the data lanes  2712   a.    
     In some embodiments, the data lanes  2712   a  that receive data packets from input circuit  2750  and protection circuit  2752  can be determined by the ports  2708  of the backplane  2706 .  FIG.  42    shows a top view of the backplane  2706  of the monitoring system  2700 . As shown in the illustrated example, each port  2706  includes an input link  2762 . Each of input links  2762  can be in electronic communication with a different data lane  2712   a  than the other input links  2762 . Each port  2706  can also include a sets of output links  2766 , and system links  2570 . In  FIG.  42   , the output links  2766  are illustrated along the data lanes  2712   a . Each of the output links  2766  can be in electronic communication with a corresponding data lane  2712   a . Therefore, all functional circuits  2710  coupled to the ports  2708  can receive data from all of the data lanes  2712   a . The system links  2770  can be in electronic communication with the system data lane  2712   c  and can be configured to facilitate bi-directional serial communication with the system data lane  2512   c.    
     Referring to  FIGS.  38 - 42   , in the illustrated example, the input circuits  2750  are coupled to ports  2708   a , the protection circuits  2752  are coupled to ports  2708   b , relay circuit  2758 , 4-20 output circuit  2761 , and a condition monitoring circuit  2756  are coupled to ports  2708   c , and the system interface circuit is coupled to port  2708   e . However, since each port  2708  includes input links  2762 , output links  2766 , and system links  2770 , functional circuits  2710  can be coupled to any given port  2708  of the backplane  2706 . In  FIGS.  38 - 42   , transmitters  2730  of the input circuits  2750  and protection circuits  2752  can be electrically coupled to input links  2762  of the ports  2708   a ,  2708   b . Any receivers of the functional circuits  2710  can be coupled to the output links  2766 . 
     Traditional monitoring systems can be limited in terms of flexibility and scalability. Additionally, costs and complexity of installation can create a significant barrier to entry for users that want to monitor low cost and/or low priority components/systems. By utilizing functional circuits that can be detachably coupled to the backplane, performance of the monitoring systems described herein can be adjusted and/or scaled to fit individual monitoring needs. For example, processing power can be increased by coupling additional processing circuits to the backplane. As another example, the monitoring system can be expanded by coupling additional input circuits to the backplane to such that the monitoring system can to receive and process sensor data from additional sensors. 
     Exemplary technical effects of the subject matter described herein can include the ability to customize and adjust capabilities of a monitoring system through selection and application of various different types of functional circuits, as described here. Another exemplary technical effect includes the ability to share all data delivered to a backplane of a monitoring system, thereby allowing for resources (e.g., functional circuits) to be distributed between the backplanes as desired. For example, monitoring subsystems can be installed remotely near industrial equipment such that the input circuits can receive sensor data, while other monitoring subsystems can be installed at another location that may be more convenient, or easier to access. Installing monitoring subsystems near the industrial equipment to be monitored can also reduce costs of running cables from the sensors to input circuits, as well as improve the quality of the signals delivered from sensors to the input circuits by reducing exposure to noise and ground loops. Additionally, utilizing backplanes that have dedicated data lanes can minimize disruption associated with hardware failure while maintaining flexibility and scalability of the monitoring system. 
     One skilled in the art will appreciate further features and advantages of the subject matter described herein based on the above-described embodiments. Accordingly, the present application is not to be limited specifically by what has been particularly shown and described. All publications and references cited herein are expressly incorporated herein by reference in their entirety. 
     Other embodiments are within the scope and spirit of the disclosed subject matter. Those skilled in the art will understand that the systems, devices, and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention. 
     Further, in the present disclosure, like-named components of the embodiments generally have similar features, and thus within a particular embodiment each feature of each like-named component is not necessarily fully elaborated upon. Additionally, to the extent that linear or circular dimensions are used in the description of the disclosed systems, devices, and methods, such dimensions are not intended to limit the types of shapes that can be used in conjunction with such systems, devices, and methods. A person skilled in the art will recognize that an equivalent to such linear and circular dimensions can easily be determined for any geometric shape 
     In the descriptions above and in the claims, phrases such as “at least one of” or “one or more of” may occur followed by a conjunctive list of elements or features. The term “and/or” may also occur in a list of two or more elements or features. Unless otherwise implicitly or explicitly contradicted by the context in which it is used, such a phrase is intended to mean any of the listed elements or features individually or any of the recited elements or features in combination with any of the other recited elements or features. For example, the phrases “at least one of A and B;” “one or more of A and B;” and “A and/or B” are each intended to mean “A alone, B alone, or A and B together.” A similar interpretation is also intended for lists including three or more items. For example, the phrases “at least one of A, B, and C;” “one or more of A, B, and C;” and “A, B, and/or C” are each intended to mean “A alone, B alone, C alone, A and B together, A and C together, B and C together, or A and B and C together.” In addition, use of the term “based on,” above and in the claims is intended to mean, “based at least in part on,” such that an unrecited feature or element is also permissible. 
     The subject matter described herein can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structural means disclosed in this specification and structural equivalents thereof, or in combinations of them. The subject matter described herein can be implemented as one or more computer program products, such as one or more computer programs tangibly embodied in an information carrier (e.g., in a machine-readable storage device), or embodied in a propagated signal, for execution by, or to control the operation of, data processing apparatus (e.g., a programmable processor, a computer, or multiple computers). A computer program (also known as a program, software, software application, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file. A program can be stored in a portion of a file that holds other programs or data, in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub-programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network. 
     The processes and logic flows described in this specification, including the method steps of the subject matter described herein, can be performed by one or more programmable processors executing one or more computer programs to perform functions of the subject matter described herein by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus of the subject matter described herein can be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). 
     Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processor of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, (e.g., EPROM, EEPROM, and flash memory devices); magnetic disks, (e.g., internal hard disks or removable disks); magneto-optical disks; and optical disks (e.g., CD and DVD disks). The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry. 
     To provide for interaction with a user, the subject matter described herein can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user and a keyboard and a pointing device, (e.g., a mouse or a trackball), by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well. For example, feedback provided to the user can be any form of sensory feedback, (e.g., visual feedback, auditory feedback, or tactile feedback), and input from the user can be received in any form, including acoustic, speech, or tactile input. 
     The techniques described herein can be implemented using one or more modules. As used herein, the term “module” refers to computing software, firmware, hardware, and/or various combinations thereof. At a minimum, however, modules are not to be interpreted as software that is not implemented on hardware, firmware, or recorded on a non-transitory processor readable recordable storage medium (i.e., modules are not software per se). Indeed “module” is to be interpreted to always include at least some physical, non-transitory hardware such as a part of a processor or computer. Two different modules can share the same physical hardware (e.g., two different modules can use the same processor and network interface). The modules described herein can be combined, integrated, separated, and/or duplicated to support various applications. Also, a function described herein as being performed at a particular module can be performed at one or more other modules and/or by one or more other devices instead of or in addition to the function performed at the particular module. Further, the modules can be implemented across multiple devices and/or other components local or remote to one another. Additionally, the modules can be moved from one device and added to another device, and/or can be included in both devices. 
     The subject matter described herein can be implemented in a computing system that includes a back-end component (e.g., a data server), a middleware component (e.g., an application server), or a front-end component (e.g., a client computer having a graphical user interface or a web browser through which a user can interact with an implementation of the subject matter described herein), or any combination of such back-end, middleware, and front-end components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (“LAN”) and a wide area network (“WAN”), e.g., the Internet. 
     Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.