Detecting and locating process control communication line faults from a hand-held maintenance tool

Abstract

A method of detecting a location of a fault in a process control network communication bus of a process control system of a process plant is presented, comprising: generating, at a first time, a pulse signal on a communication line via a handheld device connected to the communication line; detecting, at a second time, a reflected pulse signal on the communication line at the handheld device, the reflected pulse signal being a reflection of the pulse signal at the fault; determining, via a computer processor in the handheld device, a location of the fault on the communication line based on the detected reflected pulse signal; and displaying, via a user interface of the handheld device, the determined location of the fault in relation to a location of at least one of the process control devices based on an awareness of the process control network.

Description

[0001] This application is a continuation-in-part of patent application number 201710121078.2, filed March 2, 2017, entitled "Detecting and Locating Process Control Communication Line Faults from a Handheld Maintenance Tool." TECHNICAL FIELD

[0002] The present application relates to a diagnostic handheld maintenance tool that selectively provides power and communication signals to one or more field devices on a communication line, and more particularly, to a handheld maintenance tool that is capable of detecting and locating faults in a communication line. BACKGROUND

[0003] Process control systems, like those used in chemical and oil processes, typically include one or more process controllers communicatively coupled to at least one host or operator workstation and to one or more field devices via analog, digital or combined analog / digital buses. The field devices, which can be, for example, valves, valve positioners, switches and transmitters (e.g., temperature, pressure, and flow rate sensors), perform functions within the process plant such as opening or closing valves and measuring process parameters. The process controller receives signals from the field devices indicative of process measurements and / or other information relating to the field devices, uses the signals to perform control routines, and generates control signals based on the execution of the control routines. The control signals are transmitted to the field devices to control the operation of the process. Using information from the field devices and the process controller, an operator or a technician can employ one or more applications at the operator workstation to configure the process, to view the current state of the process, and / or to simulate the operation of the process.

[0004] In many cases, field devices can need to be set up, configured, tested, and maintained in the field. For example, a field device can need to be programmed before it can be installed at a particular location in the process control plant, and then can need to be tested before and after the field device is installed. Field devices that have already been installed can also need to be checked periodically for maintenance reasons, or diagnosed for repair or repair when a fault is detected, for example. Generally, handheld, portable maintenance tools are used to perform the configuration and testing of field devices in the field. Because many field devices are installed in remote, hard-to-reach locations, it is more convenient for a user to use a handheld, portable tool to test installed devices in such remote locations rather than using a full-blown configuration and testing device, which can be heavy, bulky, and non-portable, often requiring the installed field device to be transported to the location of the diagnostic device.

[0005] In the case where the field device is at least partially operable and powered via a local bus, a hand-held maintenance tool or portable test device ("PTD") can be connected to a communication terminal of the field device to run diagnostic routines. Typically, the field device and the PTD communicate over a two-wire or four-wire communication connection or line, often referred to as a bus. For example, when installed in a plant environment, Field bus devices and Devices are typically connected to a two-wire (or in some cases four-wire) connection line or bus. It is known to use a hand-held device to connect to, for example, a Foundation field bus or a HART communication line or other communication bus to communicate with devices connected to the communication line or bus.

[0006] In some cases, intrinsic safety ("IS") standards limit the manner in which power and other communication signals can be provided to field devices, particularly when the field devices are installed in critical or hazardous process control systems in the field. Typically, a higher voltage is used to provide power to the field devices, rather than the voltage used to communicate with the field devices. In addition, certain safety measures must be implemented before power is provided to the field devices in the field. Specifically, according to IS guidelines, a technician cannot turn on power to the field device within the field device itself, and cannot use a device that generates a voltage at certain predetermined levels. The IS guidelines prohibit internal power switching and generation of larger voltages because the field devices are typically installed in close proximity to volatile substances or volatile processes, and thus the potential for an explosion through arcing or generation of sparks is higher when a high voltage or power connection is applied to the field device. For reference, an internal switch can be considered any switch that is integrally connected within or physically housed within and / or affixed to the field device.

[0007] Related IS guidelines also suggest that power should not be turned on within a PTD that is connected to and located in close proximity to the field device. IS standards typically require manual intervention when applying power to a non-operational or unpowered field device installed in the field. Although it can be desirable to configure existing PTDs to have an automatic power supply function in order to power the field device, this configuration is typically prohibited under IS standards, particularly when a higher power signal is provided to the field device in order to power the field device or for testing purposes.

[0008] To comply with IS standards, some existing PTDs include an interface having four connection ports for coupling four lines or conductors between the PTD and the field device under test. Typically, a first pair of lines is used to transmit communication signals at a first voltage range, and a second pair of lines is used to power the field device at a second and higher voltage or voltage range. The first pair of lines is primarily used whenever the field device is under test, and the second pair of lines / conductors is used only when power needs to be provided to the field device to enable the field device to perform a function (e.g., a test function or a configuration function). In this manner, additional power to the field device under test always requires manual intervention, including connecting additional conductors between the field device and the PTD. In short, IS standards have generally limited the development of portable field device test devices, requiring two separate sets of lines or conductor sets and three or four ports for connecting the field device to the portable test device.

[0009] In any case, if the communication lines or bus has a fault (e.g., a short (low impedance) fault or an open (high impedance) fault), it is difficult, if not impossible, to use the handheld device to communicate with the field devices via the installed communication lines or bus. Moreover, when such a fault is present in the communication bus, it can be difficult to detect the presence of the fault in the bus or communication lines in the first instance. For example, when the bus experiences a high impedance fault, the handheld device is able to connect to the bus and operate on the bus, and even able to communicate with some of the devices on the bus. In these cases, it is difficult for the operator to know whether the inability to communicate with the field devices on the bus is caused by a fault in the bus or by a fault within the devices on the bus. Moreover, even if the operator knows that there is a fault in the communication lines or bus, it is difficult for the operator to know where the fault exists so that the fault can be easily found and repaired. In some cases, the communication and power lines of a process control communication bus can span great distances within a plant, and as installed in a plant, these lines can be hidden, covered, or otherwise difficult to see. Thus, even if the operator knows that there is a fault in the lines, it can take a long time to visually inspect the lines to discover the fault. SUMMARY

[0010] The handheld maintenance tool operates to detect the presence of a fault in the communication lines or bus of a process control network, and additionally can operate to detect the location or approximate location of the fault within the lines or bus. The handheld maintenance tool can detect various types of line or communication bus network faults, such as short or other low impedance faults, open or other high impedance faults, etc. Additionally, the handheld maintenance tool can operate in a second mode to detect the approximate location of the fault relative to the handheld device, thereby enabling the operator or maintenance personnel to more easily find and repair the detected fault.

[0011] In some cases, the handheld maintenance tool can be used to supply power as well as control and communication signals on a control loop using one or more known process control communication protocols, such as HART and Foundation Fieldbus protocols, to one or more field devices connected to a set of communication lines. Additionally, as part of the process, the handheld maintenance tool can implement diagnostic hardware and software that can be used to verify that the handheld device is successfully supplying power or communication signals to one or more field devices within the control loop. In one example, the handheld device can provide power on the loop (e.g., in the form of a voltage signal), and after the power supply has stabilized for a few seconds, the diagnostic hardware and software can measure the voltage across the loop and the current on the loop. If the measured voltage is the same as the supplied voltage, but there is no or only limited measured current, meaning that the power is not being consumed, then the device can detect an open circuit fault in the control loop or bus. This technique can be aided by providing a dummy load to the loop (e.g., near the connection to the handheld device).

[0012] In another case, the handheld tool can supply power to a control loop having a specific low current and high current input. The high current threshold can be, for example, 40 mA. In some cases where the number of devices on the loop is known not to exceed a certain limit, the handheld device can detect whether the current drawn exceeds the upper limit. If so, then a short or other low impedance fault can be detected. In other cases where the number of active field devices on the loop is unknown, the handheld device can limit the current draw to a certain limit, and if the current draw reaches or exceeds that limit, the handheld device can increase the limit to a new upper limit in one or more steps. If the current reaches the new upper limit, then a short or other low impedance fault condition can be detected. Thus, in this case, the high current limit can be based on the number of loads or active devices connected to the loop. In any case, if the current reaches or exceeds a predetermined or preset upper limit threshold, the handheld device can cut off the power supply and detect a short condition on the bus or loop.

[0013] In yet another case, the handheld maintenance tool can use electromagnetic pulse signals to detect the location of a fault (e.g., an open circuit fault). For example, the handheld device can generate an electromagnetic pulse or series of electromagnetic pulses and send the pulses over the communication line. The handheld maintenance tool can, for example, include circuitry that uses one or more operational amplifiers to generate a pulse current output of, for example, up to 250 mA. Of course, because the handheld device is typically battery operated, the number of such pulses that can be generated during any particular battery recharge cycle is limited, and the handheld device can inform the user of the user's usage status of the pulse signal generator via the user interface (e.g., an indication of the number of such tests available based on the current battery charge). In any case, the handheld device can generate a pulse and then detect a reflection or echo of the pulse on the communication line to determine the location of an open circuit or other high impedance fault. In particular, the handheld device can detect the time at which a return or echo pulse is received compared to the time at which the initial pulse was placed on the communication line, and the handheld device can determine an approximate distance to the fault based on the time difference. In another case, the handheld maintenance device can detect the signal power or amplitude of the return or echo pulse and determine the distance to the fault based on a drop in the amplitude of the echo pulse compared to the amplitude of the original pulse placed on the communication line. In some cases, such a method of determining the distance from the handheld device to the fault can operate better if (or even possibly require that) any unused node or device connections on the communication line are covered with a predetermined type of terminator having a particular input impedance so as to eliminate or at least limit electromagnetic reflections at these points in response to the generation of the test pulse. This additional feature thereby enables such detection of any reflections from terminal nodes.

[0014] Furthermore, because in some cases electromagnetic pulses can not be suitable for intrinsic safety (IS) applications (because the method can involve generating large amounts of power or voltage), the handheld maintenance device can operate to limit the electromagnetic pulses to a particular power or voltage level so that the hardware can be incorporated into an intrinsically safe application with appropriate power modulation so that the method will not cause any sparking. In other cases where generating electromagnetic pulses is not allowed in an intrinsically safe environment, the circuitry that generates the electromagnetic pulses can be housed in a removable or separate enclosure that can be easily connected to the handheld device. This configuration enables the fault detection circuitry to be attached to the handheld device and used to detect fault locations in a non-intrinsically safe environment, and removed from the handheld device so that other functions of the handheld device can be used in an intrinsically safe manner in an intrinsically safe environment.

[0015] In one embodiment, a method of detecting a fault in a process control communication network having a communication line and one or more devices connected to the communication line includes providing a first electrical signal on the communication line from a handheld device, measuring a second electrical signal on the communication line at the handheld device in response to the first electrical signal on the communication line, and analyzing the measured second electrical signal at a computer processor within the handheld device to determine a high impedance fault in the communication line. The method can also include indicating the presence of the detected high impedance fault to a user via a user display on the handheld device. If desired, measuring the second electrical signal on the communication line can include measuring a current on the communication line, and analyzing the measured second electrical signal can include determining whether the measured current on the communication line is below a threshold (e.g., zero or near zero), or less than a threshold of current draw expected for a particular number of devices on the communication line. In the latter case, the method can include storing an indication of the number of devices known to be attached to the communication line in a memory of the handheld device, and using the stored indication of the number of devices known to be attached to the communication line as the particular number of devices. Still further, the method of detecting a fault in a process control communication network can include connecting a known load across the communication line, and analyzing the measured second electrical signal can include determining whether the measured current on the communication line is equal to a current drawn by the known load. Likewise, the method of detecting a fault in a process control communication can also include storing an indication of an expected current draw of a number of devices known to be attached to the communication line in a memory of the handheld device, and using the stored indication of the expected current draw of the number of devices known to be attached to the communication line to determine the threshold.

[0016] Further, the method of detecting a fault in a process control communication network can also include detecting a location of the fault on the communication line by generating a pulse signal on the communication line at a first time at the handheld device, detecting a reflected pulse signal on the communication line at a second time at the handheld device, the reflected pulse signal being a reflection of the pulse signal at the fault, and using the reflected pulse signal to determine the location of the fault on the communication line. In one case, using the reflected pulse signal to determine the location of the fault on the communication line can include determining a time difference between the first time and the second time, and using the time difference to determine a distance to the fault. In other cases, using the reflected pulse signal to determine the location of the fault on the communication line can include determining an amplitude of the reflected pulse signal, and using the determined amplitude of the reflected pulse signal to determine a distance to the fault. More specifically, using the determined amplitude of the reflected pulse signal to determine a distance to the fault can include comparing the amplitude of the reflected pulse signal to an amplitude of the pulse signal to determine a drop in amplitude, and using the drop in amplitude to determine the distance to the fault. Additionally, using the determined amplitude of the reflected pulse signal to determine a distance to the fault can include storing one or more signal propagation factors in a memory of the handheld device, and using the one or more stored signal propagation factors in addition to the drop in amplitude to determine the distance to the fault.

[0017] Further, the method of detecting a fault in a process control communication network can include generating a first pulse signal on the communication line having a first amplitude, detecting whether a reflected pulse signal is received in a particular time period in response to the first pulse signal, and if the reflected pulse signal is not received in the particular time period, generating a second pulse signal on the communication line having a second amplitude greater than the first amplitude, and detecting whether a reflected pulse signal is received in a second time period in response to the second pulse signal. Still further, the method of detecting a fault in a process control communication network can also include tracking battery usage of the handheld device resulting from generating the pulse signals, and alerting a user of the handheld device of a power status related to usage of the pulse signals for detecting the fault location.

[0018] In another case, a handheld maintenance tool for detecting a fault in a communication line of a process control system includes an input / output interface configured to be electrically connected to the communication line, a power supply for setting a power and communication signal on the communication line, one or more electrical signal sensors, a user interface such as an electronic display and / or a sound generating interface, a processor, and a computer readable memory storing a program to be executed on the processor. The program, when executed on the processor, measures electrical signals on the communication line in response to the power signal set on the communication line, analyzes the measured electrical signals to determine a high impedance fault in the communication line, and indicates the presence of the detected high impedance fault to a user via the user interface.

[0019] The one or more electrical signal sensors can include a voltage sensor, and can include a current sensor that measures current on the communication line. The program can analyze the measured electrical signals by determining whether the measured current on the communication line is below a threshold, such as near zero, or less than a threshold of expected current draw for a particular number of devices connected to the communication line. In this case, the computer readable memory can store an indication of a number of devices known to be attached to the communication line, and in particular, the program can use the stored indication of the number of devices known to be attached to the communication line as the particular number of devices. Likewise, the computer readable memory can store an indication of expected current draw for a number of devices known to be attached to the communication line, and the program can use the stored indication of expected current draw for the number of devices known to be attached to the communication line to determine the threshold. The program can also determine whether the measured current on the communication line is equal to a current drawn by a known dummy load connected across the wires of the communication line.

[0020] The handheld maintenance tool can also include a pulse signal generator adapted to generate a pulse signal on the communication line, and the program can further cause the pulse signal generator to set the pulse signal on the communication line at a first time, use the one or more electrical signal sensors to detect a reflected pulse signal on the communication line at a second time at the handheld device, the reflected pulse signal being a reflection of the pulse signal at the fault, and use the reflected pulse signal to determine a location of the fault on the communication line. In particular, the program can determine the location of the fault on the communication line using the reflected pulse signal by determining a time difference between the first time and the second time and using the time difference to determine a distance to the fault. Additionally or alternatively, the program can determine an amplitude of the reflected pulse signal and use the determined amplitude of the reflected pulse signal to determine a distance to the fault. For example, the program can compare the amplitude of the reflected pulse signal to an amplitude of the pulse signal to determine a drop in amplitude, and can use the drop in amplitude to determine a distance to the fault. Additionally, the program can track battery usage of the handheld maintenance tool resulting from the generation of the pulse signal, and can alert a user of the handheld maintenance tool regarding a power status related to the use of the pulse signal via the user interface.

[0021] According to another embodiment, a method of detecting a location of a fault in a process control network communication bus having a set of communication lines and one or more devices connected to the set of communication lines includes generating a pulse signal on a communication line via a handheld device connected to the communication line at a first time, detecting a reflected pulse signal on the communication line at a second time at the handheld device, the reflected pulse signal being a reflection of the pulse signal at the fault, and determining a location of the fault on the communication line based on the detected reflected pulse signal via a computer processor in the handheld device.

[0022] According to yet another embodiment, a handheld maintenance tool for detecting a fault in a set of communication lines of a process control system includes an input / output interface configured to connect to a communication line, a pulse signal generator configured to generate a pulse signal to be set on the communication line, one or more electrical signal sensors, a user interface, a processor, and a computer readable memory storing a program to be executed on the processor. The program operates to measure an electrical signal on the communication line in response to the pulse signal on the communication line, analyze the measured electrical signal to determine a location of a fault in the communication line, and indicate the presence of the determined location of the fault to a user via the user interface. If desired, the one or more electrical signal sensors include a current sensor or a voltage sensor that detects a reflected pulse signal on the communication line. The program can also cause the pulse signal generator to set the pulse signal on the communication line at a first time, the one or more electrical signal sensors can be used to detect a reflected pulse signal on the communication line at a second time at the handheld device, the reflected pulse signal being a reflection of the pulse signal at the fault, and the reflected pulse signal can be used to determine the location of the fault on the communication line. In particular, the program can determine the location of the fault on the communication line using the reflected pulse signal by determining a time difference between the first time and the second time and using the time difference to determine a distance to the fault. Additionally or alternatively, the program can determine an amplitude of the reflected pulse signal and use the determined amplitude of the pulse signal to determine a distance to the fault. For example, the program can compare the detected amplitude of the reflected pulse signal to an amplitude of the pulse signal to determine a drop in amplitude and can use the drop in amplitude to determine a distance to the fault. Likewise, the program can track battery usage of the handheld device resulting from the generation of the pulse signal and can alert a user of the handheld device about a power status related to the use of the pulse signal via the user interface. Still further, the handheld device can include a first housing and a second housing removably connected to the first housing, wherein the processor, the one or more electrical signal sensors, and the user interface are disposed in the first housing and wherein the pulse signal generator is disposed in the second housing.

[0023] In another embodiment, a method of detecting a fault in a process control network having a communication line and one or more devices connected to the communication line includes providing a first power signal (such as a voltage or current limited power signal) at a first amplitude level on the communication line from a handheld device connected to the communication line, measuring a current signal on the communication line at the handheld device in response to the first power signal on the communication line, and analyzing the measured current signal via a processor within the handheld device to determine the presence of a low impedance fault in the communication line in response to the first power signal. If a low impedance fault condition is not determined in response to the first power signal on the communication line, the method provides a second power signal (such as a voltage signal or current limited power signal) at a second amplitude level higher than the first amplitude level on the communication line, measures a further current signal on the communication line in response to the second power signal on the communication line, and analyzes the measured further current signal to determine the presence of a low impedance fault in the communication line. If a low impedance fault is determined for either the first power signal or the second power signal, the method indicates the presence of the detected fault to a user via a user interface on the handheld device. The method of detecting a fault in a process control network can also include removing the first power signal or the second power signal from the communication line if a low impedance fault is determined for either the first power signal or the second power signal. Further, the method of detecting a fault in a process control network can analyze the measured current signal by determining whether the measured current signal is above a threshold value to determine the presence of a low impedance fault in the communication line in response to the first power signal. Likewise, the method of detecting a fault in a process control network can analyze the measured current signal by determining whether the measured current signal is above a first threshold value to determine the presence of a low impedance fault in the communication line in response to the first power signal, and can analyze the measured further current signal by determining whether the measured further current signal is above a second threshold value to determine the presence of a low impedance fault in the communication line in response to the second power signal, where the second threshold value is greater than the first threshold value. Still further, the method of detecting a fault in a process control network can also include storing an indication of an expected current draw from the one or more devices on the communication line in a memory of the handheld device, and can analyze the measured current signal by determining whether the measured current signal is above a first threshold value obtained from the indication of the expected current draw from the one or more devices on the communication line to determine the presence of a low impedance fault in the communication line in response to the first power signal. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Prior art systems for supplying power and communication signals to field devices under test are illustrated.

[0025] Figure 2 An example handheld communication device with fault detection capability when connected to a plant communication network is illustrated.

[0026] Figure 3 A handheld communication and maintenance device connected to a plant communication network with an open circuit fault is illustrated.

[0027] Figure 4 A handheld communication and maintenance device connected to a plant communication network with a short circuit fault is illustrated.

[0028] Figure 5 A block diagram of an example fault detection circuit within a handheld communication and maintenance device in Figure 2 is depicted.

[0029] Figure 6A and Figure 6B A pulse generation and reflection diagram illustrating the reflection of a pulse signal on a plant communication line that can be used to detect the location of a fault on the communication line is depicted.

[0030] Figure 7 A block diagram of an example pulse generation circuit that can be used in the fault detection circuit of the system in Figure 5 is illustrated.

[0031] Figure 8 A signal diagram associated with a method of generating a pulse signal that can be used by the circuit in Figure 7 is illustrated.

[0032] Figure 9 A handheld communication and maintenance device with a removably attached fault detection and fault location detection unit is illustrated. DETAILED DESCRIPTION

[0033] The devices and methods as described herein generally enable detection of faults within a communication network such as a process control communication network, including for example, short circuit (low impedance) faults and open circuit (high impedance) faults. More specifically, in one example, a handheld device and method of using a portable or handheld device is connected to a field device within a network such as a hardwired communication network and provides power and / or communication signals over, for example, a two-wire conductor set or two-wire communication line, while in some cases also complying with intrinsic safety ("IS") standards, in order to perform protocol communications with one or more devices on the network and diagnostics or other operations with respect to the devices on the communication network. The handheld device and method of using the device provides many safety features and advantages over current systems that communicate with and supply power to field devices, and therefore a brief description of these known systems will be provided.

[0034] Portable configuration and calibration tools often require a two-wire connection between a hand-held maintenance tool or portable test device ("PTD") and a field device, where the two-wire connection is used to provide communication between the two devices. For example, Fieldbus devices often require a two-wire communication line or two-wire conductor set to be connected between a PTD and a fieldbus device to set up, configure, or diagnose the field device. When the field device is already powered, a two-wire communication line is often sufficient to complete configuration and testing of the field device. On the other hand, when the field device (e.g. fieldbus device) requires power for testing and / or configuration, it is sometimes more convenient or necessary to use a PTD that provides the necessary power during configuration or testing. However, IS standards do not allow power to be turned on from within the PTD or from within the field device itself (e.g., when an auxiliary or redundant power line is available), because such PTDs are often used in hazardous and explosive environments.

[0035] Figure 1 An existing system is illustrated that includes a field device 10 and a PTD 12 that both communicates with and supplies power to the field device 10 in a configuration, operation, and testing situation. Typically, a first pair of conductors 14 from the PTD 12 is connected to a pair of input terminals 18 and output terminals 20 of the field device 10 to communicate with the field device 10. For example, the PTD 12 can perform a diagnostic routine that extracts information from the field device 10, and / or the PTD 12 can configure the field device 10 by sending program instructions to the field device 10 across the first pair of conductors 14. In Figure 1 the existing system in, when the PTD 12 fails to obtain a reading from the field device 10, a technician can determine that the field device 10 is not powered. In some cases, the technician can confirm the power status of the field device 10 from a visual inspection or from an indicator on the field device 10 itself. If the field device is in an unpowered state, the technician can then connect a second pair of conductors 16 between the PTD 12 and the field device 10 under test to supply power to the field device 10. Typically, the PTD 12 has an input / output interface 23 that provides a receptacle, jack, or any other type of electrical receptacle for connecting two double-prong plugs 30, 32 to the PTD 12. As used herein, a prong can refer to any type of male connector that couples to an electrical receptacle or female connector (e.g. Figure 1 the jack of the PTD input / output or communication interface 23). Each double-prong plug 30, 32 is connected to one of the two-wire pairs 14, 16, respectively, where each conductor of the pair of conductors 14, 16 is connected to a separate prong of each plug 30, 32.

[0036] The input / output communication interface 23 of the PTD 12 includes four jacks 41, 42, 43, 44. A first pair of jacks 41, 42 can be used to electrically couple to the first two-prong plug 30 to provide communication signals to the field device 10. As used herein, electrically coupling two or more elements can refer to a connection that allows power to be conducted between two or more elements. A second pair of jacks 43, 44 can be used to electrically couple the second two-prong plug 32 to provide power to the field device 10 via the second pair of wires 16. A general safety rule (e.g., IS standard) dictates that all power circuits carrying power must be connected to the field device 10 before power is applied to the power circuit. This rule can extend to low voltage communication signals (e.g., communication signals transmitted along the first pair of wires 14) as well as the higher power supply voltage on the second pair of wires 16. Any system that does not perform this directive can be in violation of the IS standard. Furthermore, according to the IS standard, any power switching device must be located outside of the field device 10. Figure 1 The configuration in FIG. 1 is in compliance with existing IS standards because power cannot be turned on within the field device 10 itself. Furthermore, Figure 1 The configuration in FIG. 1 allows a user to manually connect the terminals 18, 20 of the connector assembly to the field device 10 before connecting the plugs 30, 32 to the corresponding jacks 41, 42, 43, 44 of the PTD interface 23. Although Figure 1 The system in FIG. 1 illustrates the PTD 12 directly connecting to the terminals of the field device 10, the PTD 12 can instead connect to the terminals of a communication line or bus (e.g., a Foundation fieldbus or a HART communication line) and communicate with one or more devices on the bus or network line.

[0037] Figure 2 An example handheld communication device or maintenance tool 100 having fault detection and fault location detection capabilities is illustrated. The handheld communication device 100 can connect to a plant communication network that uses, for example, a two-wire or four-wire communication line or bus, and the device 100 can provide communication signals between devices on the bus, such as controllers, field devices, input / output devices, or other types of devices on the bus or network. Furthermore, the device 100 can provide auxiliary power to one or more field devices on the bus or network when needed.

[0038] Figure 2The example handheld device 100 includes a body or housing 102 with a user interface display 104 and various user interface buttons 106. The user interface buttons 106 can be used to scroll through a screen displayed on the display 104 and / or enable the user to take other actions regarding information displayed on the display 104 and / or to implement the functions of the handheld device 100. Furthermore, the handheld device 100 includes a communication and power signal input / output interface 110, which includes a series of ports that can be used to connect the handheld device 100 to various types of field devices or buses (such as…). Fieldbus devices or buses (Field devices or buses, CAN field devices or buses, Profibus field devices or buses, etc.). In some cases, different port configurations can be provided in the input / output interface 110, including various pins, jacks, or other types of connectors that can be used to electrically connect the device 100 to different types of field devices or communication lines or buses associated with different process control network communication protocols (such as any of the communication lines or buses mentioned above). Furthermore, the input / output interface 110 can enable the device 100 to provide power from the handheld device 100 to field devices on a communication bus or line for testing purposes. The pin or port connections of the interface 110 can include, for example, two-pin connections, three-pin connections, four-pin connections, etc. For illustrative purposes only, a three-pin connector consisting of two interlocked two-pin connectors 120 and 121 is used in... Figure 2 The handheld device 100 is illustrated as a three-port connector arrangement that can be removably connected to the interface 110 of the device 100. Additionally, the handheld device 100 includes various electronic components and circuitry, including a processor 190, one or more computer-readable memories 191, signal generation and detection circuitry 194, and other associated circuitry (which may be hardware, firmware, etc.) connected to the processor 190, memory 191, and signal generation and detection circuitry 194. The memory 191 and processor 190 can store and execute software (or firmware) that performs computational functions to control the power and signal generation circuitry 194, to perform configuration, message transmission, analysis, and to provide user input / output access and user display functions via the display 104 of the handheld device 100. Although... Figure 2 Although not explicitly shown, the handheld device 100 may include a user interface with audio-based interface components (such as one or more buzzers, speakers, audio sirens, etc.) that can be used to communicate with the user.

[0039] Circuitry 194 can include various power, voltage, and / or current signal generating circuitry and various sensors (such as voltage sensors, current sensors, etc.) configured to operate to place power and communication signals onto the communication lines connected via interface 110, to measure or detect power signals and communication signals on the communication lines connected via interface 110, and to perform various tests and analyses on signals received from the bus or network connected to interface 110 to perform diagnostics on the network such as detecting the presence and location of low impedance or high impedance faults. More particularly, circuitry 194 can be coupled to and controlled by processor 190 (operating under computer instructions stored in memory 191) and can provide information to processor 190 to enable the functionality of device 100, for example, to drive outputs of handheld device 100 to perform protocol-based communications and power functions on the bus or network (as defined by one or more process control communication protocols such as any of the process control communication protocols mentioned above) to perform communication line fault presence and location detection, to perform user interface input / output operations via user interface display 104, user interface buttons 106, and user interface audio components (not shown), and to perform other functions of device 100. Still further, memory 191 can store programming (e.g., one or more programs) to be executed on processor 190 and data to be used by the programs to perform the various functions described herein. In particular, the programs, when executed on processor 190 and used to control power and signal generating circuitry 194, can operate to perform various open circuit, short circuit, or other types of fault detection and fault location detection capabilities within a control loop implemented on a communication bus or line connected to one or more field devices. These tests can be performed while power is being supplied to the control loop or otherwise while communication signals are being provided via the communication bus or line in the control loop.

[0040] By way of example, Figure 3 A handheld device 100 (which can be the device 100 in Figure 2 connected to a communication network 300 (illustrated as a two-wire network) having three field devices 302, 304, 306 connected thereto and having one or more terminal devices 308 connected to terminals of network 300. Communication network 300 is illustrated in Figure 3 as a hardwired communication network, in this case having a cable pair (e.g., twisted pair cable) providing the backbone of network 300 and connected with the three field devices 302, 304, and 306. In this case, an open circuit fault, illustrated as a dashed circle 310, is illustrated as existing in the twisted pair cable of network 300. Open circuit faults can also exist at connections with field devices, at one of the terminals of the network where a terminal terminator is not connected, etc. However, in this example, the open circuit fault is illustrated as existing in the twisted pair cable of network 300.Figure 3 In this case, one or both of the twisted-pair cables or lines of 300 are separated or disconnected, thus creating an open circuit between device 304 and device 306. Furthermore, in Figure 3 In the example, handheld device 100 is illustrated as being connected to network bus 300, but may alternatively be directly connected to the appropriate terminal of one of field devices 302, 304, 306. In any case, device 100 may be used to detect open circuit condition 310 or other high impedance faults, and may also be used to detect the relative or approximate location of such open circuit.

[0041] As another example, Figure 4 An example is shown of a handheld device 100 connected to network 300, in which network 300 has a short-circuit fault illustrated by the dashed circle 320. Specifically, besides Figure 4 In addition to short-circuit conditions 320, network 300 includes short-circuit conditions 320 but not open-circuit conditions or faults 310. Figure 4 The network 300 in the middle can be with Figure 3 The network illustrated is the same as the network in this example. In this case, the handheld device 100 can supply power to the network 300, but in the process, it can also be operated to detect the presence of a short circuit 320 or other low-impedance fault within the network 300.

[0042] Figure 5 A block diagram of an example circuit is shown, which can be used as... Figure 2 The handheld device 100 contains a portion of signal generation and detection circuitry 194 and processor 190 to perform standard protocol communication, bus and device power supply functions, as well as fault detection, fault location determination, and other operations described herein. Figure 5As illustrated in FIG. 3, the handheld device 100 is connected to the network 300 via the communication interface 110, and specifically includes two ports that are directly connected to two lines or cables of the network 300. The handheld device 100 also includes a physiologic process signal block 402 that includes one or more voltage sensors 402A, current sensors 402B, resistance detection circuits 402C, impedance detection circuits 402D, etc. that can measure voltage, current, power, and / or other electrical signals or properties of the network 300. The physiologic process block 402 can include, for example, any number of voltage detection circuits or sensors 402A, current detection circuits or sensors 402B, impedance detection or resistance detection circuits or sensors 402C, 402D, etc. that can operate in known manners to measure voltage, current, impedance, resistance, or other electrical characteristics of or on the network 300. Signals generated by the various sensors 402A-402D within the signal block 402 can be provided to one or more amplifiers 404 that can amplify the received signals and provide the amplified signals to an analog-to-digital conversion circuit 406. The analog-to-digital conversion circuit 406 can include one or more analog-to-digital converters that convert the analog signals received from the amplifiers 404 into digital signals. The digital signals generated by the analog-to-digital converter 406 can then be provided to the memory 191 and / or a signal processing block 408 that can be implemented in the processor 190 in Figure 2 .

[0043] Further still, Figure 5 The system in FIG. 3 includes an analysis block 410 coupled to the signal processing block 408, a control and interface circuit 415, a power and communication signal generation circuit 420 coupled to the control and interface circuit 415 and to the network lines 300, a pulse generation circuit 430, and a timing circuit 432. In this case, the power and signal generation circuit 420 and the pulse generation circuit 430 can be connected to or include a battery 440 that provides energy for generating the power signals and / or communication signals to be placed on the communication network 300. The power and / or communication signals can be voltage signals, current signals, etc., and thus the power circuit 420 can include a voltage source, a current source, or some combination of the two. Further still, the power and communication signal generation circuit 420 can have outputs that are connected to the network 300 and provide the power signals and / or communication signals on the same set of wires (e.g., in a two-wire network), or can provide the power and communication signals on different sets of wires of the network 300 (e.g., in a four-wire network). Figure 5(In a four-wire network not shown). Similarly, the power and communication signal generation circuit 420 may be driven by the control and interface circuit 415 to provide various different power and / or communication signals on the bus or network 300 at various times as specified by the control and interface circuit 415, operating to control communication and testing performed by the device 100 on the network 300. Similarly, as will be described in more detail, the pulse generation circuit 430 may be operated according to the control and interface circuit 415 to generate one or more pulses (e.g., voltage pulses or current pulses) on the network line 300, and the timer circuit 432 may include a clock or other timer that tracks the precise time when a signal is set on the network 300 and / or received from the network 300.

[0044] As will be understood, control circuit 415 (which can be implemented, for example, in...) Figure 2 One or more programs executing on the processor 190 can implement configuration, communication, testing, and power supply features associated with one or more process control communication protocols (such as Foundation Fieldbus, HART, CAN, Profibus, etc.), or configuration, communication, testing, and power supply features defined for such one or more process control communication protocols. Thus, the memory 191 can store data and information, and the control circuit 415 can use this data to operate and perform communication with one or more devices on the communication line 300 conforming to a specific process control communication protocol. Therefore, for example, via... Figure 2 Upon receiving instructions from user interfaces 104 and 106, control circuit 415 can execute any pre-stored configuration and communication procedures on a device connected to the communication network or line 300, in a manner defined by or according to one or more specific process control protocols. However, control circuit 415 can also execute various communication line fault detection and fault location routines or procedures as described in more detail herein.

[0045] Specifically, it can be provided as standalone hardware or firmware, or it can be executed as... Figure 2 The software or programmed signal processing block 408 within the processor 190 performs signal processing on the digital signal received from the analog-to-digital converter 406, such as smoothing the signal, filtering the signal, adjusting the level, amplitude, frequency, etc., detecting the signal, and timing the individual signals of the received signal by comparing them based on the output from the timing circuit 432. It can also be implemented as standalone hardware or firmware, or as part of... Figure 2the processor 190 in the handheld device 100, or by a software or programming executing within the processor 190, receives the signals generated by the signal processing block 408 and performs analysis on these signals (under the control of the control block 415) to detect the presence and potential location of a fault within the network 300. In addition, the control block 415 can perform control of other elements in the handheld device 100 to implement one or more fault detection processes with respect to the network 300, particularly to detect a short circuit or other low impedance fault condition on the network 300, to detect an open circuit or other high impedance fault condition on the network 300, to detect the location of a fault, etc. Still further, the control and interface circuit 415 can interface with a user via the display 104 and interface buttons 106 in the handheld device 100 to enable the user to initiate various fault detection processes and to be informed of the results of these processes. Figure 5 the processor 190 in the handheld device 100, or by a software or programming executing within the processor 190, receives the signals generated by the signal processing block 408 and performs analysis on these signals (under the control of the control block 415) to detect the presence and potential location of a fault within the network 300. In addition, the control block 415 can perform control of other elements in the handheld device 100 to implement one or more fault detection processes with respect to the network 300, particularly to detect a short circuit or other low impedance fault condition on the network 300, to detect an open circuit or other high impedance fault condition on the network 300, to detect the location of a fault, etc. Still further, the control and interface circuit 415 can interface with a user via the display 104 and interface buttons 106 in the handheld device 100 to enable the user to initiate various fault detection processes and to be informed of the results of these processes. Figure 2

[0046] In particular, to detect an open circuit condition on the network 300, the analysis block 410 can compare the measured voltage to one or more predetermined stored voltage levels (e.g., stored in the memory 191) to determine whether the voltage supplied on the network 300 is at the maximum voltage as supplied by the power circuit 420 within the device 100 (or as otherwise supplied by an external power source on the network 300), and can detect current flow on the network 300. If the nominal voltage is on the network, e.g., the network voltage is at or near the nominal voltage, and there is no current flow, then the analysis block 410 can determine that there is an open circuit on the network 300. However, under an open circuit network condition, depending on the location of the open circuit, some devices connected to the network can still receive the supplied voltage and thus can draw current. In particular, devices on the network 300 disposed upstream of the open circuit (such as the devices 302 and 304 in the network 300) can still draw current. In this case, the analysis block 410 can be programmed to know the number of devices known to be on the network 300 or connected to the network 300 (i.e., store an indication of this number) and / or the expected current draw of each device on the network 300 (or the expected current draw of all devices on the network), and can operate to detect whether each device on the network appears to be functioning on the network according to its expected current draw. In these cases, the analysis block 410 can in effect compare the expected current draw to the actual measured current draw to detect whether one or more devices is not drawing current from the network 300, i.e., to detect the fact that one or more devices expected to draw current on the network 300 is not doing so, and thus is not connected to the network 300 as seen by the handheld device 100. This condition can indicate a high impedance fault within the network 300 with respect to one or more devices on the network 300. Figure 3

[0047] ​​To perform this analysis, the handheld device 100 (and specifically the control circuit 415) can cause the power supply 420 to provide a known power signal on or across the loop or network 300. After the power supply 420 has stabilized the power for a period of time, such as a few seconds, the diagnostic hardware and software (e.g., blocks 402, 404, 406, and 408 and analysis block 410) can detect the measured voltage across the network wires and the current on the network wires (e.g., as measured by block 402 and conditioned by signal processing blocks 406 and 408). If the measured voltage is the same voltage as the supplied voltage, but there is no or only limited measured current, meaning that the power is not being consumed, then the analysis block 410 can detect an open circuit fault in the control loop or bus of the network 300. This technique can be aided by providing a dummy load across the wires of the control loop (e.g., near the connection of the handheld device 100) to determine if the current drawn from the power supply 420 is equal to the expected current drawn through the dummy or known load at the supplied voltage. If the measured current from the device is equal to or nearly equal to the known current through the dummy or known load at the supplied voltage, then the analysis block 410 can detect an open circuit or other high impedance fault.

[0048] Likewise, by determining if there is a high current draw detected on the network 300 when the power supply 420 (under control of the control circuit 415) sets a voltage across the cables or wires of the network 300, the analysis block 410 can detect a short circuit in the network 300, such as Figure 4the network 300. In this case, the control circuit 415 can operate such that it uses a feedback system to control the power circuit 420 to repeatedly provide a certain level of voltage and / or current on the lines of the network 300 in order to prevent damage to the network 300 from high currents due to the presence of a power source connected to a short circuit. Specifically, the control circuit 415 can cause the power source 420 to first provide a small voltage across the network cable to first detect the possibility of a low impedance or short circuit condition on the network 300, but in such a way that limits damage to the network 300 in the form of very high current draws. For example, the control circuit 415 can cause the power source 420 to supply power via a current limiter or via a current source to supply a known or limited amount of current onto the communication line 300. The control circuit 415 can detect the measured current draw on the network (from the analysis block 410 or the signal processing block 408) in response to the supplied power signal, and then can step up the voltage (or maximum allowed current) provided by the power source 420 depending on the expected number of devices on the network 300. Thus, when the power source 420 first provides a voltage to the network 300, the power source 420 can be controlled to provide a very low voltage and / or a low and limited current signal onto the network 300. Here, the analysis block 410 can immediately detect, based on the incoming detected current signal, whether there is a high current draw across the lines of the network 300 (i.e., whether the current draw in the network 300 reaches the current limit imposed by the power source 420) to detect whether there can be a low impedance or short circuit condition. In one case, if no high current draw is detected at the current (low) voltage amplitude level, the analysis block 410 can step up the voltage in various iterative steps to determine whether there is a low impedance or short circuit condition at higher voltages, resulting in excess current beyond what is expected to be drawn by the various devices on the network 300. That is, the analysis block 410 can compare the measured current actually provided (or as drawn by the devices on the network 300) as across the network lines to the expected current draw based on the number of devices actually connected to the network 300. If the current draw is higher (e.g., higher than the expected current draw by some threshold amount), the analysis block 410 can detect the presence of a short circuit or other low impedance condition on the network 300, and the control and interface block 415 can cause the display 104 Figure 2) to the user as well. In addition, the control circuit 415 can shut off the power supply 420 to remove power from the network 300. In another case, the control circuit 415 can cause the power supply 420 to provide a current-limited voltage across the network line 300, and iteratively increase the current magnitude limit applied by the power supply 420 over time in steps. The control circuit 415 can measure the current draw in the network and compare that draw to the current limit applied by the power supply 420. When the current draw does not reach the limit, then the shorted condition is not detected. However, if the current draw reaches the current limit applied by the power supply 420, then the control circuit 415 can increase the current limit to see if the newly drawn current reaches or equals the current limit. This process can be repeated until the current limit is set to some maximum threshold, at which point the control circuit 415 or the analysis block 410 detects that a short circuit exists in the communication line 300.

[0049] Thus, in this case, the hand-held tool 100 can utilize a specific low current and high current input to provide power to the control loop. The high current threshold can be, for example, 40 mA. In some cases where the number of devices on the loop is known to not exceed a certain limit, the tool 100 can detect whether the current actually drawn on the network exceeds the upper limit. If so, a short circuit or other low impedance fault can be detected. In other cases where the number of active devices on the loop is unknown, the device 100 can limit the current draw to a certain limit, and if the current draw reaches or exceeds that limit, the hand-held device can increase the limit to a new upper limit in one or more steps. If the current reaches the new upper limit, a short circuit or other low impedance fault condition can be detected. Thus, in this case, the high current limit can be based on the number of loads or active devices connected to the loop. In any case, if the current reaches or exceeds a predetermined or preset upper limit threshold, the control circuit 415 can detect a shorted condition on the bus or loop, shut off the power supply 420, and alert the user via the display 104. Using this stepped current limiting method protects the communication network 300, and in some cases, the process plant in which the network 300 is installed, from severe damage that can result from high currents in a shorted condition.

[0050] Still further, as Figure 5As illustrated in the middle, the device 100 can use the pulse generator 430 and timer 432, along with other measurement and processing blocks 402-410, to detect the location of an open circuit and / or short circuit within the network 300 upon detecting a fault where an open circuit and / or short circuit is present. In many cases, the location detected will be relative to the location of the handheld device 100, i.e., the distance measured from the location where the handheld device 100 is attached to the network 300 to the fault, specifically, the distance along the wire of the communication network from the location where the handheld device 100 is attached to the network 300 to the fault. Specifically, during operation, the pulse generator 430 can generate one or a series of electronic pulses (e.g., voltage pulses) and can place these pulses on the network 300 at a known or measured time. Upon or immediately after placing the pulses on the network 300, the timer 432 can start a counter to determine the time that elapses since the pulse was placed on the line of the network 300. After the pulse is placed on the line, the analysis block 410 can begin receiving or detecting a current or voltage signal on the line of the network 300 (e.g., a voltage or current signal measured by the process block 402 and converted to a digital signal indicative of the current or voltage measurement as performed by blocks 404, 406, and 408). At some time after the pulse is placed on the network line, the analysis block 410 can detect a pulse received on the network line that is a reflection of the original pulse from a high impedance or open circuit fault. This reflected pulse is sometimes referred to herein as a ping pulse. The analysis block 410 can also receive the output of the timer 435 and determine the time difference between the placement of the original pulse on the network 300 at a first time and the receipt of the reflected or ping pulse at a second and later time. The occurrence of such a ping pulse is due to the open circuit condition and more specifically due to the lack of a terminator 308 at the open circuit location. Specifically, an open circuit condition is a fault on which there is no terminator, which causes the termination to match the impedance of the line, which means that when a pulse signal encounters an open circuit fault the electronic pulse signal will typically create a significant reflected component. In other words, due to the impedance mismatch at the open circuit location, a reflection of the original pulse will be generated and will be transmitted along the wire of the network 300 back to the handheld device 100.

[0051] To illustrate this point, Figure 6A A timing diagram is depicted in which the pulse signal generator 430 generates and places a series of pulses 500 on the network 300 at periodic times or potentially non-periodic times, if desired. Figure 6B The timing diagram of FIG. 5 illustrates a ping pulse 502 that can be received from the pulse 500 in FIG. 4 based on the presence of an open circuit condition (i.e., an open circuit or high impedance fault where there is a lack of a proper termination that matches the impedance of the connection) in the network 300. Figure 6A in FIG. 4.Figure 6B A time difference At between transmitting the pulse 500 and receiving the echo pulse 502 is also illustrated. Further, Figure 6B An amplitude difference between the pulse 500 and the received echo pulse 502 is illustrated. At a particular time or offset time At between the time the pulse 500 is transmitted that generates the echo pulse 502, the echo pulse 502 is detected at block 402. Figure 6B The echo pulse 502 illustrated in the graph.

[0052] This offset time (i.e., the time between when the pulse 500 is placed on the line (e.g., the leading edge of the pulse, the trailing edge of the pulse, the center of the pulse, etc.) and when the echo pulse 502 is received on the line (e.g., the leading edge of the pulse, the trailing edge of the pulse, the center of the pulse, etc.)) can be used as a basis for a method to determine the location of a short circuit within the network 300. Specifically, the analysis block 410 can detect the time difference At based on the timer output 432 when the leading edge of the pulse 500 is generated and the leading edge of the echo pulse 502 is received or when the trailing edge of the pulse 500 is generated and the trailing edge of the echo pulse 502 is received. Because, in general, electromagnetic waves such as those associated with the pulse 500 travel at a known speed (the speed of light) along the conductive line, the distance between the location of the handheld device that generated the pulse 500 and the short circuit (i.e., that generated the echo pulse) can be determined based on the time difference between when the pulse 500 is generated and when the echo pulse 502 is received. In this case, the analysis block 410 can calculate this distance based on the time difference and provide an estimated distance to the fault (e.g., along the conductive line) to assist the user in narrowing down the location of the fault (e.g., the open circuit 310 in FIG. 3). Figure 3 The control circuit 415 can then display the calculated distance to the detected fault via the user interface 104.

[0053] Further, if desired, the analysis block 410 can store (e.g., in the memory 191) or can be provided with a map of the entire network 300 (including where the devices are located on or attached to the network 300 relative to the handheld device 100 are typically located in the network 300). In this case, the analysis block 410 can provide or illustrate the location of the suspected fault or the approximate location of the suspected fault on the user interface display 104 based on its knowledge of the entire network 300 and the devices on it. Thus, in this case, the analysis block 410 can operate to determine the location of the fault based on the time at which the echo is received compared to or relative to other devices that are connected to the network 300 or that are known to be on the network 300.

[0054] In another example, the analysis block 410 can determine the location of a fault (e.g., an open circuit fault) based on the size of the detected echo pulse 502 compared to the size of the transmitted pulse 500. In this case, the measurement circuit 402 can also detect the amplitude of the signal (e.g., the voltage signal) at the time the echo pulse 502 is detected. The amplifier 404 and the signal processing block 408 can amplify the measured signal, reduce noise, filter out ripples, etc., and the analog-to-digital converter 406 can convert the analog signal to a digital format to generate a digitized signal that can be analyzed on the analysis block 410 (e.g., executed on the processor 190) as soon as the signal comes in, thereby performing online processing. In this case, the amplitude of the pulse signal can be characterized in some format from the digital value, and preferably, the amplitude of the received pulse signal is converted to mV (peak-to-peak) format.

[0055] In any case, the analysis block 410 can compare the detected amplitude of the received echo pulse signal 502 to the amplitude of the original pulse signal 500 set onto the network 300 to determine a drop in amplitude. For example, the analysis block 410 can determine a difference in amplitude, a ratio of amplitudes, etc. The analysis block 410 can store or know the overall resistance and propagation properties of the signal on the network 300 and the amount of power necessary to transmit a signal through a known distance along the network 300. This information can be determined in a base or test network and can be stored in the memory 191 of the handheld device 100, or can be estimated based on known electrical signal propagation properties, or can alternatively be experimentally determined for the network 300 by measuring the drop in a pulse on the network 300 between two known locations on the network 300. Such experimentally determined values can be determined when the network 300 is known to be free of any faults, and can be measured by setting a pulse on the network 300 and receiving an echo pulse from a known terminal location on the network (e.g., a terminal point not connected to a terminator). With such a system, the difference or change in amplitude of the generated pulse and the detected echo pulse can be used to obtain or determine the relative distance from the handheld device 100 at which the fault is located. Still further, if desired, the analysis block 410 can determine the location of the fault using both or any combination of the amplitude and time difference methods discussed above.

[0056] Figure 7 One possible structure of the pulse signal generator 430 is illustrated in Figure 5 Specifically, the pulse signal generator 430 can include a triangular signal generator (or a sine wave generator or other ramped or alternating periodic signal) 550 and a DC level voltage signal generator 552, which provide their outputs to the positive and negative inputs, respectively, of an operational amplifier (op-amp) 554. Thus, asFigure 7 As illustrated in FIG. 6, the positive input of operational amplifier 554 receives the output of triangle or sine wave generator 550, and the negative input of operational amplifier 554 receives the output of DC level 552. During operation, operational amplifier 554 generates a pulse width modulated signal output based on receiving these two inputs. The duration (and possibly the amplitude) of the created pulse (e.g., the width and amplitude of the pulse) is determined by the level or amplitude of the output of DC level generator 552, and can be changed or varied by changing the amplitude of the DC level generator output. The specific operation of operational amplifier 554 is illustrated in Figure 8 as using two signal graphs. Figure 8 The signal graphs above in FIG. 6 illustrate the output 650 of triangle signal generator 550 overlapping the output 652 of DC voltage level generator 552. Whenever signal 650 is below DC level signal 652, operational amplifier 554 essentially generates a zero output voltage, and, whenever the output 650 of triangle signal generator 550 is greater than DC level signal 652, operational amplifier 554 outputs a positive steady or constant level voltage. The pulse width modulated signal generated by operational amplifier 554 is illustrated as pulse width modulated signal 664 in the following signal graph in FIG. 7. Figure 8 Thus, Figure 8 The graph in FIG. 6 illustrates the manner in which ramped waveform 650 is compared to DC level 652 to generate the pulse width modulated waveform signal needed for diagnostic purposes. As will be appreciated, increasing the DC level used increases the width of the pulse created by generator 430. The DC level as the demand signal can be varied between the minimum and maximum voltages of the triangle wave to generate pulses of different widths. As will be seen, the output 654 of operational amplifier 554 swings high when triangle waveform voltage 650 is greater than DC level 652, and swings low when triangle waveform voltage 650 is less than DC level 652. Of course, the amplitude of the pulses of pulse width modulated signal 654 can be set at a particular level, can be equal to or can be set by the level of DC voltage 652, or can be set in any other manner.

[0057] Furthermore, using operational amplifier 554 to generate the pulses on the communication line makes it Figure 5The control circuit 415 in the handheld device 100 can vary the pulse strength (power or amplitude) of the output pulses to enable detection of the echo pulse. Specifically, the strength (amplitude) of the echo pulse decreases as the pulse travels from the fault location. At times, the control unit 415 can need to increase the generated electromagnetic pulse strength or amplitude, thereby increasing the strength of the echo pulse (e.g., when the control system sends a first pulse of a first strength but does not detect an echo pulse in response to the first pulse). The control circuit 415 can repeatedly increase the pulse strength until the control circuit 415 (or the analysis block 408) detects an echo pulse (or until a certain high-level threshold has been reached). In one embodiment, the pulse signal generator 430 can include a series of operational amplifiers to generate an output that can be increased from one minimum level to another maximum level (e.g., from 100 mA to 250 mA). Moreover, as will be appreciated, the strength of the echo pulse is inversely proportional to the distance of the fault location. The calculations that can be used to calculate the coefficient of the distance to the fault location depend primarily on the various signal propagation factors associated with the network 300. As an example, the following signal propagation factors can be used Fieldbus line.

[0058] Cable impedance: 100 & ± 20%

[0059] Attenuation: 3 dB / km

[0060] Shielding capacitance: < 4 nF / km

[0061] Similar signal propagation factors can be considered for other communication protocols or lines (e.g., for HART control lines), and the calculated coefficient can be used with the determined amplitude drop to calculate the distance from the handheld device generating the pulse to the fault.

[0062] Figure 9 Another example of a handheld device 700 is illustrated, which can include most of the circuits and functions of the handheld device 100 in Figure 2 but does not include the pulse signal generator circuit in the same housing. Rather, this circuit is provided in a separate or second housing or casing 710, which can be removably connected to the first housing of the device 700 via, for example, a pin that couples to an input of an input / output interface 720 of the device 700 (which can be part of the interface 110 in Figure 2 Specifically, the pulse signal generation circuit 420 (e.g., as illustrated in Figure 5 and the control circuit 415 in the handheld device 100 in Figure 5The potential entirety or portions of the measurement block 402, amplifier 404, signal processing block 408, and analysis block 410 in the handheld device 700 can be provided within the housing 710 and can be connected to the processor 410 of the device 700 via a connection through the input / output interface 720 of the handheld device 700. If desired, the pulse generator circuit 420 can be powered by a separate battery within the housing 710 or can be powered by a battery within the handheld device 700. In some cases, it is desirable to use a separate housing 710 to encase or hold the pulse generator circuit 430 because the pulse width generator circuit 430 can not be suitable for use in intrinsically safe environments because the pulse generator circuit 430 can generate pulses at a certain voltage level that can induce or can cause a potential spark. Thus, when the pulse generator circuit 430 is provided in a separate housing or module 710, the module 710 can be removed from the housing of the device 700 as needed so that the handheld device 700 can be used in intrinsically safe environments without the pulse signal generation circuit 430. However, when needed, such as in a non-intrinsically safe environment, the pulse generation functionality can simply be added to the diagnostic capabilities of the device 700 by connecting the module 710 to the device 700 via the input / output connection 720. Of course, if desired, the module 710 can include a separate input / output interface 740 that can provide a standard connection interface to a field device or network (such as the network 300) using any standard or known interface connection circuit. In this case, the device 710 can provide all of the signals or have all of the connections necessary to connect the device 700 to the network 300 or field devices within the network 300 in order to form a complete diagnostic system including the pulse signal generator 430 that can be used to determine the location of a fault within the network 300. In another embodiment, the module 710 can connect to the device 700 via a separate or dedicated input / output connection designed to enable the pulse generator circuit 430 to be integrated into the diagnostic capabilities of the device 700, but the input / output connection to the network 300 or field devices within the network 300 can be provided via other input / output connections 110 on the device 700. In other cases, the power output (or maximum voltage level) of the pulse generator circuit 430 can be limited to a power acceptable in an intrinsically safe environment to enable the pulse signal generator 430 to be used in an intrinsically safe manner.

[0063] In any case, the use of block 710 makes it easy for the user to see whether the pulse signal generation circuit 430 is present, and therefore whether the associated fault location detection circuitry is being used with device 700. This indication makes it easy to understand whether device 700 includes pulse generation functionality when used, and thus makes it easy to determine whether handheld device 700 can be used in an intrinsically safe environment. Furthermore, if desired, all the fault detection circuitry and functionality described herein (including fault detection and location functions and components as described herein) can be provided in removable module 710 to enable handheld device 700 to be transformed from a typical device into a device including fault detection and fault location determination functionality.

[0064] Furthermore, it will be understood that the pulse signal generation circuit 430 can use a significant amount of battery power to generate the pulses required to perform fault location detection. Therefore, the control circuit 415 can track the battery usage relative to the pulse generator function (e.g., Figure 5 The control circuit 415 can track the number of times the pulse signal generation circuit 430 operates (e.g., the number of pulses generated during a battery charge, the duration the pulse generation circuit 430 has been used, etc.) to perform diagnostics or some other status indicator of the battery, at least in a coarse manner, to determine the remaining battery charge. In other cases, the control circuit 415 can directly monitor the battery charge at any given time to determine the remaining battery charge in the battery 440 and can be operated to estimate the number or quantity of pulses that can be generated during that charge as a status indicator. The control circuit 415 can, for example, provide an indication of the number of times the user can use the pulse generator 430 to detect fault locations before the battery is depleted, or it can warn the user whether using the pulse signal generator 430 may result in the battery 440 being depleted or nearing depletion.

[0065] Therefore, as described above, handheld maintenance tools are used to detect the presence of faults in communication lines or buses, and additionally to detect the location or approximate location of the fault. Handheld maintenance tools can detect various types of line or communication network faults (such as short circuits or other low-impedance faults, and open circuits or other high-impedance faults). Furthermore, handheld maintenance tools can detect the approximate location of the fault, making it easier for operators or maintenance personnel to locate and repair it.

[0066] Although the foregoing text describes specific implementations of many different embodiments, it should be understood that the scope of this patent is defined by the language of the claims set forth herein. The specific implementations are to be interpreted as merely exemplary and do not describe every possible embodiment. Furthermore, although specific references have been made to… Field buses and HART type field devices are connected, but the components and devices described can be used with other process control systems and field devices and communication bus types. Numerous alternative embodiments could be implemented using current technology or technology developed after the filing date of this application that would still fall within the scope of the claims.

[0067] Many modifications and variations of the techniques and structures described and illustrated herein can be made in the context of the present claims without departing from their spirit or scope. Therefore, it should be understood that the methods and apparatus described herein are merely exemplary and not limiting as to the scope of the claims.

Claims

1. A method for detecting the location of a fault in the process control network communication bus of a process control system in a process plant, the method comprising: A pulse signal is generated on the communication line at the first moment via a handheld device connected to at least one communication line, the communication line being included in the process control network communication bus and communicatively coupled between process control devices of the process control system, the process control devices being installed in the process control network of the process plant, wherein the process control devices include a process controller and field devices, wherein the process controller, when fully operable and communicatively coupled via the communication line, operates to receive signals indicating process measurement results obtained by the field devices or information related to the field devices and generate control signals, the control signals being transmitted via the communication line to control the operation of the field devices and the processes within the process plant; At a second time, an echo pulse signal on the communication line is detected at the handheld device, the echo pulse signal being a reflection of the pulse signal at the fault location; Based on the detected echo pulse signal, the location of the fault on the communication line is determined via a computer processor in the handheld device; and Based on knowledge of the process control network, the determined location of the fault, related to the location of at least one of the process control devices, is displayed via the user interface of the handheld device.

2. The method for locating faults in the process control network communication bus of a process control system in a process plant according to claim 1, wherein, Determining the location of the fault includes: determining the time difference between the first time and the second time, and using the time difference to determine the distance to the fault.

3. The method for locating faults in the process control network communication bus of a process control system in a process plant according to claim 1, wherein, Determining the location of the fault on the communication line includes: determining the amplitude of a detected echo pulse signal, and using the determined amplitude of the detected echo pulse signal to determine the distance to the fault.

4. The method for locating faults in the process control network communication bus of a process control system in a process plant according to claim 3, wherein, Determining the distance to the fault using the determined amplitude of the detected echo pulse signal includes: comparing the amplitude of the detected echo pulse signal with the amplitude of the pulse signal to determine a decrease in amplitude, and using the decrease in amplitude to determine the distance to the fault.

5. The method for locating faults in the process control network communication bus of a process control system in a process plant according to claim 4, wherein, Determining the distance to the fault using the amplitude of the detected echo pulse signal includes: storing one or more signal propagation factors in the memory of the handheld device, and using the stored one or more signal propagation factors in addition to the decrease in amplitude to determine the distance to the fault.

6. The method for locating a fault in the process control network communication bus of a process control system in a process plant according to claim 1, wherein, Generating a pulse signal on the communication line includes: generating a first pulse signal with a first amplitude on the communication line; detecting whether an echo pulse signal is received in response to the first pulse signal during a specific time period; and if no echo pulse signal is received during the specific time period, generating a second pulse signal with a second amplitude greater than the first amplitude on the communication line; and detecting whether an echo pulse signal is received in response to the second pulse signal during a second time period.

7. The method for locating faults in the process control network communication bus of a process control system in a process plant according to claim 1, further comprising: The system tracks the battery usage of the handheld device caused by the generation of the pulse signal, and warns the user of the handheld device about the power status related to the use of the pulse signal generator within the handheld device for detecting fault locations.

8. The method for locating a fault in the process control network communication bus of a process control system in a process plant according to claim 7, wherein, The battery is located inside the casing.

9. A handheld maintenance tool for detecting faults in the process control network communication bus of a process control system in a process plant, comprising: An input / output interface is configured to connect to at least one communication line, the at least one communication line being included in the process control network communication bus and communicatively coupled between process control devices of the process control system, the process control devices being installed in the process control network of the process plant, wherein the process control devices include a process controller and field devices, wherein the process controller, when fully operable and communicatively coupled via the communication line, operates to receive signals indicating process measurement results obtained by the field devices or information related to the field devices and to generate control signals, the control signals being transmitted via the communication line to control the operation of the field devices and the processes within the process plant; A pulse signal generator, configured to generate a pulse signal to be applied to the communication line; One or more electrical signal sensors; processor; A computer-readable storage device storing a program that executes on the processor to measure electrical signals on the communication line in response to pulse signals on the communication line, analyze the measured electrical signals to determine the location of a fault in the communication line, and indicate the presence of the determined fault location to a user via a user interface; and A user interface, based on knowledge of the process control network, displays the determined location of the fault in relation to the location of at least one process control device in the process control equipment.

10. The handheld maintenance tool according to claim 9, wherein, The one or more electrical signal sensors include a voltage sensor that detects echo pulse signals on the communication line.

11. The handheld maintenance tool according to claim 9, wherein, The procedure also causes the pulse signal generator to set a pulse signal on the communication line at a first time, and uses the one or more electrical signal sensors to detect echo pulse signals on the communication line at a second time at the handheld maintenance tool. The echo pulse signals are reflections of the pulse signals at the fault location, and the echo pulse signals are used to determine the location of the fault on the communication line.

12. The handheld maintenance tool according to claim 11, wherein, The program determines the location of the fault on the communication line using the echo pulse signal by determining the time difference between the first time and the second time and using the time difference to determine the distance to the fault.

13. The handheld maintenance tool according to claim 11, wherein, The program determines the amplitude of the echo pulse signal and uses the determined amplitude of the pulse signal to determine the distance to the fault.

14. The handheld maintenance tool according to claim 13, wherein, The program compares the amplitude of the detected echo pulse signal with the amplitude of the pulse signal to determine the decrease in amplitude, and uses the decrease in amplitude to determine the distance to the fault.

15. The handheld maintenance tool according to claim 11, wherein, The program tracks the battery usage of the handheld maintenance tool caused by the generation of the pulse signal and alerts the user of the handheld maintenance tool via the user interface about the power status related to the use of the pulse signal.

16. The handheld maintenance tool of claim 9, comprising a first housing and a second housing, the second housing being removably connected to the first housing, wherein... The processor, the one or more electrical signal sensors, and the user interface are disposed in the first housing, and the pulse signal generator is disposed in the second housing.

17. The handheld maintenance tool according to claim 16, wherein, The pulse signal generator is powered by a battery within the handheld maintenance tool.

18. The handheld maintenance tool according to claim 17, wherein, The battery is located inside the first casing.

19. The handheld maintenance tool according to claim 17, wherein, The battery is located inside the second casing.

20. A method for detecting faults in the process control network of a process control system in a process plant, comprising: A handheld device connected to at least one communication line provides a first power signal at a first amplitude level on the at least one communication line, the communication line being included in the process control network and communicatively coupled between process control devices of the process control system, the process control devices being installed in the process control network of the process plant, wherein the process control devices include a process controller and field devices, wherein the process controller, when fully operable and communicatively coupled via the communication line, operates to receive signals indicating process measurement results obtained by the field devices or information related to the field devices and to generate control signals, the control signals being transmitted via the communication line to control the operation of the field devices and the processes within the process plant; At the handheld device, the current on the communication line is measured in response to the first power signal on the communication line; The measured current signal is analyzed by a processor within the handheld device to determine the presence of a low-impedance fault in the communication line in response to the first power signal. If a low-impedance fault condition is not determined in response to the first power signal on the communication line, the following steps are performed: (1) Provide a second power signal at a second amplitude level higher than the first amplitude level on the communication line; (2) In response to the second power signal on the communication line, measure another current signal on the communication line; (3) Analyze the measured additional current signals to determine the presence of a low-impedance fault in the communication line; and If a low-impedance fault is determined for either the first power signal or the second power signal, the location of the detected fault, related to the location of at least one process control device, is displayed to the user via a user interface on the handheld device, based on the knowledge of the process control network.

21. The method for detecting faults in the process control network of a process control system in a process plant according to claim 20, further comprising: If a low-impedance fault is determined for either the first power signal or the second power signal, then the first power signal or the second power signal is removed from the communication line.

22. The method for detecting faults in the process control network of a process control system in a process plant according to claim 20, wherein, Analyzing the measured current signal to determine the presence of a low-impedance fault in the communication line in response to the first power signal includes determining whether the measured current signal is higher than a threshold.

23. The method for detecting faults in the process control network of a process control system in a process plant according to claim 20, wherein, Analyzing the measured current signal to determine the presence of a low-impedance fault in the communication line in response to the first power signal includes: determining whether the measured current signal is higher than a first threshold, and wherein analyzing another measured current signal to determine the presence of a low-impedance fault in the communication line in response to the second power signal includes: determining whether the other measured current signal is higher than a second threshold, wherein the second threshold is greater than the first threshold.

24. The method for detecting faults in the process control network of a process control system in a process plant according to claim 20, further comprising: The indication of expected current draw from at least one of the process control devices on the communication line is stored in the memory of the handheld device, and wherein analyzing the measured current signal to determine the presence of a low impedance fault in the communication line in response to the first power signal includes: determining whether the measured current signal is higher than a first threshold, the first threshold being obtained from the indication of expected current draw from at least one of the process control devices on the communication line.

25. A method for detecting the location of a fault in the process control network communication bus of the process control system of the process plant, comprising: A pulse signal is generated on at least one communication line via a pulse signal generator connected to at least one communication line at a first time. The handheld device includes a first housing and a second housing, the second housing being removably connected to the first housing. The pulse signal generator is disposed in the second housing and powered by a battery within the handheld device. The communication line is included in the process control network communication bus and communicatively coupled between process control devices of the process control system. The process control devices are installed in the process plant, wherein the process control devices include a process controller and field devices. When fully operable and communicatively coupled via the communication line, the process controller operates to receive signals indicating process measurement results obtained by the field devices or information related to the field devices and generate control signals, which are transmitted via the communication line to control the operation of the field devices and the processes within the process plant. At a second time, an echo pulse signal on the communication line is detected at the handheld device, the echo pulse signal being a reflection of the pulse signal at the fault location; Based on the detected echo pulse signal, the location of the fault on the communication line is determined via a computer processor in the handheld device; and Based on knowledge of the process control network, the location of the detected fault, related to the location of at least one of the process control devices, is displayed to the user via a user interface on the handheld device.

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