A hart circuit and a state determination method of a field interface thereof

Abstract

This invention discloses a HART circuit and a method for determining the status of its field interface. The HART circuit includes: a control interface, an adjustable power supply module, a first HART module, an isolation module, and a field interface. The first HART module is connected to the control interface and is used to generate a first control signal when a first interrogation signal is input to the control interface. The adjustable power supply module is connected to both the control interface and the first HART module, and is used to output a first power signal to the control interface and modulate the first power signal into a first HART signal in response to the first control signal. The first end of the isolation module is connected to the control interface, and the isolation module is used to isolate the signal at its first end and couple it to its second end. The field interface is connected to the second end of the isolation module. This invention enables bidirectional communication between the control room and the production site, diversifies the application scenarios of the communication function of the HART circuit, and optimizes the performance of the HART circuit.

Description

Technical Field

[0001] The embodiments of the present invention relate to measurement and control technology, and in particular to a method for determining the status of a HART circuit and its field interface. Background Technology

[0002] With increasing automation, the number of sensors used in industrial settings is also increasing. In high-risk production sites such as oil, chemical, and natural gas industries, many sensors and positioning valves need to communicate with control systems.

[0003] Because the production site and the control room of the control system are far apart, and the sensors and positioning valves are scattered, traditional communication connection devices mostly use 4-20mA analog current signals to transmit signals in order to achieve communication between the field and the control room.

[0004] Traditional communication connection devices can only achieve single control or detection functions and cannot perform remote two-way interaction, resulting in problems of limited functionality and poor performance. Summary of the Invention

[0005] This invention provides a method for determining the status of a HART circuit and its field interface to achieve bidirectional communication between the control room and the production site, thereby diversifying the application scenarios of the communication function of the HART circuit and optimizing the performance of the HART circuit.

[0006] In a first aspect, embodiments of the present invention provide a HART circuit, which includes: a control interface, an adjustable power supply module, a first HART module, an isolation module, and a field interface;

[0007] The first HART module is connected to the control interface and is used to generate a first control signal when a first interrogation signal is input to the control interface;

[0008] The adjustable power module is connected to the control interface and the first HART module respectively, and is used to output a first power signal to the control interface and modulate the first power signal into a first HART signal in response to the first control signal.

[0009] The first end of the isolation module is connected to the control interface, and the isolation module is used to isolate the signal at its first end and couple it to its second end.

[0010] The field interface is connected to the second end of the isolation module.

[0011] Optionally, the HART circuit further includes a second HART module, which is disposed between the field interface and the second end of the isolation module, and is used to modulate the first reply signal into a second HART signal and transmit it to the second end of the isolation module when the field interface receives the first reply signal.

[0012] Optionally, the second HART module includes a first switch, a first resistor, a second resistor, and a first capacitor. The first end of the first switch is connected to the field interface. The first end of the first switch is also connected to the control end of the first switch via the first capacitor. The second end of the first switch is connected to the second end of the isolation module. The control end of the first switch is connected to the second end of the isolation module via the first resistor. The control end of the first switch is also connected to the second end of the first switch via the second resistor.

[0013] Optionally, the isolation module includes an inverter unit, a transformer, and a rectifier unit; the first end of the inverter unit serves as the first end of the isolation module, and the second end of the inverter unit is connected to the primary side of the transformer. The inverter unit is used to convert the DC signal input at the first end into an AC signal and transmit it to the primary side of the transformer through its second end.

[0014] The transformer is used to achieve isolation and coupling between the primary and secondary sides;

[0015] The first end of the rectifier unit is connected to the secondary side of the transformer, and the second end of the rectifier unit serves as the second end of the isolation module. The rectifier unit is used to rectify the AC signal on the secondary side of the transformer and output the rectified electrical signal from its second end.

[0016] Optionally, the rectifier unit includes a bridge rectifier circuit.

[0017] Optionally, the HART circuit further includes an intrinsically safe power limiting unit, which is disposed between the second HART module and the field interface, and is used to limit the voltage or current level output to the field interface.

[0018] Optionally, the first HART module includes a second switch transistor, the control terminal of the second switch transistor is connected to the control interface, the first terminal of the second switch transistor is connected to the adjustable power supply module and the first power supply terminal respectively, and the second terminal of the second switch transistor is connected to the first ground terminal.

[0019] Optionally, the adjustable power supply module includes a comparison unit and a power supply unit.

[0020] The comparison unit includes a first comparison terminal, a second comparison terminal, and a first output terminal. The first comparison terminal is connected to the second terminal of the second switching transistor, and the second comparison terminal is connected to the first power supply terminal. The comparison unit is used to output a corresponding second control signal according to the relative relationship between the electrical signals connected to the first comparison terminal and the second comparison terminal.

[0021] The output terminal of the power supply unit is connected to the control interface, the input terminal of the power supply unit is connected to the first power supply terminal, and the control terminal of the power supply unit is connected to the first output terminal. The power supply unit is used to output a first power signal or a first HART signal according to the second control signal.

[0022] Optionally, the power supply unit further includes a third switching transistor;

[0023] The first terminal of the third switch is used as the input terminal of the power supply unit, the second terminal of the third switch is used as the output terminal of the power supply unit, and the control terminal of the third switch is used as the control terminal of the power supply unit.

[0024] Optionally, the HART circuit further includes: a first interface protection unit and a second interface protection unit. The first interface protection unit includes a first transient diode, a first filter inductor, a second filter inductor, and a first fuse. The first transient diode is connected between the two interfaces of the control interface. The first filter inductor and the first fuse are connected in series between the first interface of the control interface and the adjustable power module. The second filter inductor is connected between the second interface of the control interface and the first end of the isolation module.

[0025] The second interface protection unit includes a second transient diode, a third filter inductor, and a fourth filter inductor. The second transient diode is connected between the two interfaces of the field interface. The third filter inductor is connected between the first interface of the field interface and the second terminal of the isolation module. The fourth filter inductor is connected between the second interface of the field interface and the second terminal of the isolation module.

[0026] Secondly, embodiments of the present invention also provide a method for determining the state of a field interface of a HART circuit as described in any of the first aspects. The method for determining the state of a field interface of a HART circuit includes:

[0027] A resistance measuring device is connected between the two interfaces in the control interface;

[0028] The resistance value between the two interfaces in the control interface is measured using the resistance measuring device.

[0029] The relative relationship between the resistance values ​​of the two interfaces of the control interface and the preset resistance value is used to determine whether the field interface has a disconnection fault.

[0030] Optionally, determining whether a disconnection fault has occurred at the field interface based on the relative relationship between the resistance values ​​of the two interfaces of the control interface and a preset resistance value includes:

[0031] If the resistance between the two interfaces of the control interface is greater than or equal to the preset resistance value, it is determined that the field interface has a disconnection fault.

[0032] If the resistance between the two interfaces of the control interface is less than the preset resistance value, the field interface is determined to be in a normal state.

[0033] This embodiment provides a HART circuit and its field interface status determination method. The HART circuit includes a control interface, an adjustable power supply module, a first HART module, an isolation module, and a field interface. The adjustable power supply module provides variable power to the HART circuit to form a loop. The isolation module isolates and couples the control interface and the field interface, preventing the devices connected to the control interface and the power supply from affecting the safety of the field devices, while also enabling the transmission of analog signals between the control interface and the field interface. This allows the devices connected to the control interface to detect or control the devices connected to the field interface. The first HART module generates a first control signal based on a first interrogation signal input from the control interface. The adjustable power supply module can also modulate the first power signal into a first HART signal based on the first control signal. When the devices connected to the control interface detect the devices connected to the field interface, the first HART module enables HART communication between the control interface and the field interface. The HART signal is superimposed on the analog signal in the circuit, achieving bidirectional communication between the control room and the production site based on the transmission of analog signals. This diversifies the application scenarios of the HART circuit's communication function and optimizes the performance of the HART circuit. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the structure of a HART circuit provided in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of another HART circuit provided in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of another HART circuit provided in an embodiment of the present invention;

[0038] Figure 4 This is a flowchart illustrating a method for determining the status of a field interface of a HART circuit, as provided in an embodiment of the present invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0040] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0041] This invention provides a HART circuit. Figure 1 This is a schematic diagram of a HART circuit provided in an embodiment of the present invention, with reference to... Figure 1 The HART circuit 100 includes: a control interface 101, an adjustable power supply module 102, a first HART module 103, an isolation module 104, and a field interface 105; the first HART module 103 is connected to the control interface 101 and is used to generate a first control signal when a first interrogation signal is input to the control interface 101; the adjustable power supply module 102 is connected to both the control interface 101 and the first HART module 103, and is used to output a first power signal to the control interface 101 and modulate the first power signal into a first HART signal in response to the first control signal; the first end of the isolation module 104 is connected to the control interface 101, and the isolation module 104 is used to isolate the signal at its first end and couple it to its second end; the field interface 105 is connected to the second end of the isolation module 104.

[0042] Among them, control interface 101 refers to the interface located on the control room side, which can connect to transmitter monitoring devices or positioning valve monitoring devices, and can also connect to diagnostic devices. Field interface 105 refers to the interface located on the production site side, which can connect to transmitters or positioning valves. Adjustable power module 102 is a power module built into HART circuit 100, providing variable power. First HART module 103 is a communication module that enables HART communication between control interface 101 and field interface 105, allowing HART communication between the two interfaces even when there is an analog signal input to field interface 105. First interrogation signal refers to the communication signal input from the diagnostic device to control interface 101 to inquire about the transmitter's operating status.

[0043] Specifically, the first interrogation signal includes first interrogation information, which refers to the interrogation information sent from the control room to the transmitter connected to the field interface 105. The transmitter can input corresponding response information to the field interface 105 according to the first interrogation information. The adjustable power module 102 can provide a first power signal and can also modulate the first power supply into a first HART signal according to the first control signal of the first HART module 103. The first HART signal is generated according to the first control signal of the first HART module 103 and also includes the first interrogation information. The isolation module 104 can realize the isolation and coupling between the first end and the second end. The isolation function can isolate the field interface 105 from the adjustable power module 102 and the control interface 101, which can ensure that the device connected to the field interface 105 is not affected by the adjustable power supply and the control interface 101. It can also realize the mutual transmission of signals between the two ends of the isolation module 104. For example, the isolation module 104 can be a combination module of coupling circuit, transformer and rectifier circuit.

[0044] For example, when the transmitter is connected to the field interface 105, in order to obtain the transmitter's measurement data, the control room side can connect a corresponding control interface 101 to the transmitter monitoring device. The transmitter monitoring device connects a load resistor to the control interface 101 and can determine the transmitter's measurement data by detecting the electrical signal on the load resistor. When the transmitter is connected to the field interface 105, the adjustable power module 102 in the HART circuit 100 outputs a first power signal, for example, a DC voltage. The first power signal is transmitted to the first terminal of the isolation module 104 via the load resistor. The second terminal of the isolation module 104 is connected to the field interface 105. The transmitter can adjust the resistor connected to the field interface 105 according to the measurement data. The resistor connected to the field interface 105 affects the change in the electrical signal at the second terminal of the isolation module 104, thereby coupling to the first terminal of the isolation module 104. Therefore, the transmitter monitoring device connected to the control interface 101 can determine the transmitter's measurement data by detecting the electrical signal on the load resistor. Preferably, the resistance of the transmitter connected to the field interface 105 affects the change of the 4-12mA analog current signal between the second terminal of the isolation module 104 and the field interface 105, thereby coupling to the first terminal of the isolation module 104. Then, the transmitter monitoring device connected to the control interface 101 can determine the measurement data of the transmitter by detecting the 4-12mA analog current flowing through the load resistor.

[0045] Furthermore, while the transmitter transmits measurement data to the control interface 101 via the HART circuit 100, if the control room detects an anomaly in the measurement data and needs to query the transmitter status or other data on the field side, a diagnostic device can be connected to the control interface 101. For example, the diagnostic device can be a HART protocol handheld device. The diagnostic device can input a first query signal to the control interface 101, and the parameters of the first query signal can be adjusted by the diagnostic device in real time. The first HART module 103 is connected to the control interface 101 and can generate a first control signal based on the first query signal. The adjustable power module 102 modulates the first power signal into a first HART signal based on the first control signal generated by the first HART module 103 and outputs it to the first terminal of the isolation module 104. The second terminal of the isolation module 104 is connected to the field interface 105. The transmitter connected to the field interface 105 can determine the corresponding query information based on the first HART signal output by the field interface 105. The transmitter connected to the field interface 105 can respond to the first HART signal and input a second response signal to the field interface 105. The diagnostic device can obtain the transmitter status or other relevant data based on the second response signal output from the control interface 101. For example, the first HART signal and the second response signal can be ±0.5mA current signals.

[0046] On the other hand, when the field interface 105 is connected to the positioning valve, in order to control the specific parameters of the positioning valve, the control room side is connected to the positioning valve monitoring device via the control interface 101. The positioning valve monitoring device is connected to a variable power source between the control interface 101 and the control interface 101. For example, the variable power source can be a DC current source. The variable power source can input an opening control signal corresponding to the control parameters to the control interface 101. When the field interface 105 is connected to the positioning valve, the adjustable power module 102 in the HART circuit 100 outputs a first power signal. The current signal obtained by superimposing the opening control signal on the first power signal can be used as the positioning valve control signal, which is transmitted to the first end of the isolation module 104. The second end of the isolation module 104 is connected to the field interface 105. The positioning valve can adjust its specific parameters according to the positioning valve control signal output by the field interface 105. The signal transmission in this process realizes the control of the field positioning valve by the control room side. Preferably, the positioning valve monitoring device can send a variable current signal to the control interface 101. The first power signal can be a voltage signal, and the first power signal can ensure the transmission capability of the variable current signal. The variable current signal can be a 4-20mA analog current signal, which is transmitted to the field interface 105 via the isolation module 104. The positioning valve connected to the field interface 105 can adjust specific parameters according to the 4-20mA analog current signal. For example, the specific parameters can be parameters such as positioning valve opening, positioning valve closing, and / or the opening amount of the positioning valve.

[0047] The HART circuit provided in this embodiment includes a control interface, an adjustable power supply module, a first HART module, an isolation module, and a field interface. The adjustable power supply module provides variable power to the HART circuit to form a loop. The isolation module isolates and couples the control interface and the field interface, preventing the devices and power supply connected to the control interface from affecting the safety of the field devices, while also enabling the transmission of analog signals between the control interface and the field interface. This allows the devices connected to the control interface to detect or control the devices connected to the field interface. The first HART module generates a first control signal based on the first interrogation signal input from the control interface. The adjustable power supply module can also modulate the first power signal into a first HART signal based on the first control signal. When the devices connected to the control interface detect the devices connected to the field interface, the first HART module enables HART communication between the control interface and the field interface. The HART signal is superimposed on the analog signal in the circuit, achieving bidirectional communication between the control room and the production site based on the transmission of analog signals. This diversifies the application scenarios of the HART circuit's communication function and optimizes the performance of the HART circuit.

[0048] Optionally, Figure 2 This is a schematic diagram of another HART circuit provided in an embodiment of the present invention, referred to... Figure 2Based on the aforementioned embodiments, the HART circuit 100 further includes a second HART module 201. The second HART module 201 is disposed between the field interface 105 and the second end of the isolation module 104, and is used to modulate the first reply signal into a second HART signal and transmit it to the second end of the isolation module 104 when the field interface 105 receives the first reply signal.

[0049] The second HART module 201 is a module that enables HART communication between the control interface 101 and the field interface 105. It can enable HART communication between the control interface 101 and the field interface 105 when there is an analog signal input to the control interface 101.

[0050] Specifically, the second HART module 201 can modulate the first response signal input from the field interface 105 into a second HART signal and transmit it to the second terminal of the isolation module 104. The isolation module 104 can then couple the second HART signal from the second terminal to the first terminal of the isolation module 104, and transmit it to the field interface 105. The diagnostic device connected to the field interface 105 can determine the feedback information of the positioning valve connected to the field terminal based on the second HART signal. For example, the first response signal may include an AC voltage signal, the voltage level and frequency of which are related to the real-time parameters of the positioning valve, and the real-time parameters may include status parameters such as switch status and opening degree.

[0051] For example, while the positioning valve monitoring device controls the positioning valve connected to the field interface 105 via the HART circuit 100, if the control room needs to determine the specific operating parameters of the field positioning valve to judge whether the operating parameters of the positioning valve meet the preset conditions, a diagnostic device can be connected to the control interface 101. For example, the diagnostic device can be a HART protocol handheld device. The diagnostic device can include an AC current source, and the second interrogation signal can be an AC current signal. The AC current source can input the second interrogation signal to the control interface 101, and the parameters of the second interrogation signal can be adjusted by the diagnostic device in real time. The second interrogation signal can be transmitted to the field interface 105 via the coupling of the isolation module 104, and then output to the positioning valve. After receiving the second interrogation signal, the positioning valve can respond to the interrogation information in the second interrogation signal and reply with the corresponding first response signal. The second HART module 201 can modulate the first response signal into a second HART signal and transmit it to the second end of the isolation module 104. Due to its coupling effect, the isolation module 104 can transmit the second HART signal from the second end to the first end of the isolation module 104. Then the second HART signal can be output via the control interface 101. For example, the second interrogation signal and the second HART signal can be current signals of ±0.5mA.

[0052] The HART circuit provided in this embodiment is equipped with a second HART module. When the first response signal is received at the field interface, the first response signal can be modulated into a second HART signal and transmitted to the control interface through coupling and isolation of the isolation module. This realizes HART communication in multiple scenarios. It can be applied to the control circuit of the positioning valve and the monitoring circuit of the transmitter. It realizes bidirectional HART communication based on analog current signal transmission, which improves the applicability of the HART circuit.

[0053] Optionally, Figure 3 This is a schematic diagram of another HART circuit provided in an embodiment of the present invention, with reference to... Figure 3 Based on the aforementioned embodiments, the second HART module 201 includes a first switch T21, a first resistor R21, a second resistor R22, and a first capacitor C22. The first end of the first switch T21 is connected to the field interface 105. The first end of the first switch T21 is also connected to the control end of the first switch T21 via the first capacitor C22. The second end of the first switch T21 is connected to the second end of the isolation module 104. The control end of the first switch T21 is connected to the second end of the isolation module 104 via the first resistor R21. The control end of the first switch T21 is also connected to the second end of the first switch T21 via the second resistor R22.

[0054] For example, when the field interface 105 is connected to a positioning valve, in order to control the specific parameters of the positioning valve, the control room side is connected to a control interface 101 to a positioning valve monitoring device. The positioning valve monitoring device is connected to an adjustable power supply between the control interfaces 101; for example, the adjustable power supply can be a DC current source. The adjustable power supply can input an opening control signal corresponding to the control parameters to the control interface 101. When the field interface 105 is connected to the positioning valve, the adjustable power supply module 102 in the HART circuit 100 outputs a first power signal. The current signal obtained by superimposing the opening control signal on the first power signal can be used as the positioning valve control signal, which is transmitted to the first end of the isolation module 104. The second end of the isolation module 104 is connected to the field interface 105. The positioning valve can adjust its specific parameters according to the positioning valve control signal output by the field interface 105. This signal transmission process enables the control room side to control the field positioning valve. Preferably, the positioning valve monitoring device can transmit a variable current signal to the control interface 101. The first power signal can be a voltage signal, and the first power signal can ensure the transmission capability of the variable current signal. The variable current signal can be a 4-20mA analog current signal, which is transmitted to the field interface 105 via the isolation module 104. The positioning valve connected to the field interface 105 can adjust specific parameters according to the 4-20mA analog current signal. For example, the specific parameters can be parameters such as positioning valve opening, positioning valve closing, and / or the opening amount of the positioning valve.

[0055] When monitoring or setting the positioning valve connected to field interface 105 is required, the handheld device is connected between the two ports 1+ and 1- of control interface 101. The AC current signal (i.e., the second interrogation signal) generated by control interface 101 directly enters the first terminal of isolation module 104. After coupling and isolation by isolation module 104, the positioning valve connected to field interface 105 receives the second interrogation signal. In response, the positioning valve connected to field interface 105 inputs a first response signal to the second port 2- of field interface 105. For example, the first response signal is an AC voltage signal. This first response signal can form a voltage divider at the control terminal of the first switch transistor T21 through the first capacitor C22 and the second resistor R22. This AC voltage divider signal causes the first switch transistor T21 to turn on or off, thereby causing the coupling power point to generate an AC signal. Finally, isolation module 104 can couple and transmit this AC signal to the first terminal of the isolation unit, and output it from control interface 101. As a result, the diagnostic device received the HART signal from the positioning valve connected to the field interface 105. Based on the control of the positioning valve using analog current signals, bidirectional HART communication between the control room and the positioning valve was realized, improving the communication timeliness between the control room and the field positioning valve.

[0056] Optionally, based on the foregoing embodiments, refer to... Figure 3 The isolation module 104 includes an inverter unit 301, a transformer 302, and a rectifier unit 303. The first end of the inverter unit 301 serves as the first end of the isolation module 104, and the second end of the inverter unit 301 is connected to the primary side T1 of the transformer 302. The inverter unit 301 is used to convert the DC signal input to the first end into an AC signal and transmit it to the primary side T1 of the transformer 302 through its second end. The transformer 302 is used to achieve isolation and coupling between the primary side T1 and the secondary side T2. The first end of the rectifier unit 303 is connected to the secondary side T2 of the transformer 302, and the second end of the rectifier unit 303 serves as the second end of the isolation module 104. The rectifier unit 303 is used to rectify the AC signal on the secondary side T2 of the transformer 302 and output the rectified electrical signal through its second end.

[0057] Specifically, the first end of the inverter unit 301 includes a connection terminal and a first ground terminal GND3. The connection terminal serves as the first end of the isolation module 104 and is connected to the control interface 101. The second end of the inverter unit 301 is connected to the primary side T1 of the transformer 302. The inverter unit 301 can convert the DC signal input to the first end into an AC signal and transmit it to the primary side T1 of the transformer 302. The signal then returns to the inverter unit 301 via the coil of the primary side T1 and is grounded via the first ground terminal GND3, thus forming a circuit on the primary side T1 of the transformer 302. The transformer 302 can achieve isolation and electrical signal coupling between the primary side T1 and the secondary side T2. For example, the turns ratio of the primary side T1 to the secondary side T2 of the transformer 302 can be 1:1. The second end of the rectifier unit 303 serves as the second end of the isolation module 104. The rectifier unit 303 can rectify the AC signal from the secondary side T2 of the transformer 302 into a single-phase pulsating signal and transmit it to the second end of the rectifier unit 303. The frequency of the single-phase pulsating signal is lower than the frequency of the AC signal on the secondary side T2 of transformer 302. For example, rectifier unit 303 may include a bridge rectifier circuit Q. The two input terminals of bridge rectifier circuit Q are respectively connected to the two ends of the secondary side T2 of transformer 302, and the two output terminals of bridge rectifier circuit Q are respectively connected to the two interfaces of the field interface. Furthermore, the two output terminals of bridge rectifier circuit Q can serve as the second power supply terminal VCC2 and the second ground terminal GND2, respectively. The power supply for the second power supply terminal VCC2 is obtained through coupling from transformer 302. A first filter capacitor C23 and a second filter capacitor C21 can also be connected in parallel between the second power supply terminal VCC2 and the second ground terminal GND2. The configuration of inverter unit 301, transformer 302, and rectifier unit 303 can achieve signal isolation and coupling between the field interface 105 side and the control interface 101 side, ensuring stable transmission of electrical signals and the safe operation of the equipment connected to the field interface 105.

[0058] Optionally, based on the foregoing embodiments, refer to... Figure 3The first HART module 103 includes a second switching transistor T8. The control terminal of the second switching transistor T8 is connected to the control interface 101. The first terminal of the second switching transistor T8 is connected to the adjustable power supply module 102 and the first power supply terminal VCC3, respectively. The second terminal of the second switching transistor T8 is connected to the first ground terminal GND3. The adjustable power supply module 102 includes a comparison unit U1 and a power supply unit 304. The comparison unit U1 includes a first comparison terminal a, a second comparison terminal b, and a first output terminal c. The first comparison terminal a is connected to the second terminal of the second switching transistor T8. The first comparison terminal a is also connected to the set power supply terminal VAC via a resistor and a capacitor. The voltage level of the set power supply terminal VAC is not equal to the voltage level of the first power supply terminal VCC3. The second comparison terminal b is connected to the first power supply terminal VCC3. The comparison unit U1 is used to output a corresponding second control signal according to the relative relationship between the electrical signals connected to the first comparison terminal a and the second comparison terminal b. The output terminal of the power supply unit 304 is connected to the control interface 101, the input terminal of the power supply unit 304 is connected to the first power supply terminal VCC3, and the control terminal of the power supply unit 304 is connected to the first output terminal c. The power supply unit 304 is used to output a first power signal or a first HART signal according to the second control signal.

[0059] Specifically, a third resistor R18 and a second capacitor C15 are connected in series between the control terminal of the second switch T8 and the first interface 1+ of the control interface 101, and a fourth resistor is connected in series between the control terminal of the second switch T8 and the second interface 1- of the control interface 101. When the first interrogation signal is input to the control interface 101, the first interrogation signal can be an AC voltage signal, which can form an AC voltage divider at the control terminal of the second switch T8, thereby controlling the second switch T8 to turn on or off according to the voltage divider fluctuation. Because when the second switch T8 is on, a path is formed between the first power supply terminal VCC3 and the first ground terminal GND3, and when the second switch T8 is off, the first power supply terminal VCC3 supplies power to the first comparison terminal a of the comparison unit U1, thereby realizing the grounding or connection of the first comparison terminal a of the comparison unit U1 to the first power supply terminal VCC3. The comparison unit U1 can output a corresponding second control signal based on the relative relationship between the electrical signals connected to the first comparison terminal a and the second comparison terminal b. The second control signal can be a digital signal, i.e., "1" or "0". For example, if the voltage levels connected to the first comparison terminal a and the second comparison terminal b are equal, the comparison unit U1 outputs "0"; if the voltage levels connected to the first comparison terminal a and the second comparison terminal b are unequal or the difference exceeds a preset value, the comparison unit U1 outputs "1". The power supply unit 304 also includes a third switch transistor T6, a first diode D5, a power supply filter inductor L1, and at least one power supply filter capacitor. The first terminal of the third switch transistor T6 serves as the input terminal of the power supply unit 304, the second terminal of the third switch transistor T6 serves as the output terminal of the power supply unit 304, and the control terminal of the third switch transistor T6 serves as the control terminal of the power supply unit 304. The first diode D5 is connected between the first ground terminal GND3 and the second terminal of the third switch transistor T6, which can determine the power output direction. The power supply filter inductor L1 is connected to the second terminal of the third switch transistor T6, which can filter the output power. The third switch T6 can be turned on or off according to the second control signal. When the control interface 101 is not connected to the first interrogation signal, the second switch T8 remains off and the third switch T6 remains on, and the adjustable power module 102 outputs a first power signal, which is an electrical signal output from the first power supply terminal. When the control interface 101 is connected to the first interrogation signal, the second switch T8 switches between on and off states according to the frequency of the first interrogation signal, and the corresponding third switch T6 also switches between on and off states according to the second control signal, thereby modulating the first power signal into a first HART signal, which is then output through the second terminal of the third switch T6.

[0060] For example, when the HART circuit 100 implements the analog current signal input function (i.e., the control room acquires the measured value of the transmitter), a load resistor is connected between the two interfaces 1+ and 1- of the control interface 101, and the two interfaces 2+ and 2- of the field interface 105 are connected to the field temperature or pressure transmitter (which can also be regarded as a variable resistor whose resistance is related to the measured value). The analog current signal is transmitted from the field interface 105 to the control interface 101 via the isolation module 104. At this time, the second switch T8 is turned off, so the comparison unit U1 outputs a high level to the control terminal of the third switch T6, ensuring that the third switch T6 is turned on. Then the adjustable power supply module 102 outputs a first power signal to the first interface 1+ of the control interface 101. The first power signal is a DC voltage signal output from the first power supply terminal. The first power signal is connected to the first ground terminal GND3 of the inverter unit 301 via the load resistor, the inverter unit 301, and the primary side T1 of the transformer 302 in sequence, forming a power circuit. The secondary side T2 of transformer 302 supplies power to the temperature or pressure transmitter connected to field interface 105, forming a loop on the secondary side T2 of transformer 302. The measured value of the temperature or pressure transmitter affects the resistance value connected to field interface 105, changing the 4-12mA analog current signal flowing through field interface 105, thereby changing the electrical signal flowing through the secondary side T2 of transformer 302. The electrical signals on the primary side T1 and the secondary side T2 of transformer 302 are coupled, allowing the measured value of the temperature or pressure transmitter to be obtained by detecting the 4-12mA analog current signal flowing through the load resistor.

[0061] While the HART circuit 100 implements the analog current signal input function, if it is necessary to monitor or configure the temperature or pressure transmitter connected to the field interface 105, an adjustable AC voltage source can be connected between the two interfaces 1+ and 1- of the control interface 101. The AC signal generated by the AC voltage source is divided by the third resistor R18, the second capacitor C15, and the fourth resistor. The AC voltage divider signal can activate the second switch T8. The conduction and cutoff of the second switch T8 affect the voltage level connected to the first comparison terminal a of the comparison unit U1. The comparison unit U1 compares the relative relationship between the first comparison terminal a and the second comparison terminal b to control the conduction and cutoff of the third switch T6. The adjustable power supply unit can then output a voltage signal (i.e., the first HART signal) with a duty cycle related to the AC voltage source, and transmit it to the inverter unit 301 through the load resistor. After passing through the transformer 302 and the rectifier unit 303, it is transmitted to the field interface 105, so that the temperature or pressure transmitter in the field receives the first HART signal. In response, the temperature or pressure transmitter can reply with the first HART signal by inputting an AC current signal to the field interface 105.

[0062] When the HART circuit 100 implements the analog current signal output function (i.e., the control room controls the state of the field positioning valve), an adjustable DC current source is connected between the two interfaces 1+ and 1- of the control interface 101, and the positioning valve is connected between the two interfaces 2+ and 2- of the field interface 105. The analog current signal is transmitted from the control interface 101 through the isolation module 104 to the positioning valve connected to the field interface 105. At this time, the second switch T8 is turned off, so the comparison unit U1 outputs a high level to the control terminal of the third switch T6, ensuring that the third switch T6 is turned on. Then, the adjustable power supply module 102 outputs a first power signal to the first interface 1+ of the control interface 101. The first power signal is the DC voltage signal output from the first power supply terminal, which provides power to the adjustable DC current source. The current output by the DC current source is the analog current signal. The analog current signal is transmitted to the first terminal of the inverter unit 301, and after being adjusted by the inverter unit 301, it returns to the first ground terminal GND3 connected to the inverter unit 301 via the primary side T1 of the transformer 302. In this way, the analog current signal is coupled to the rectifier unit 303 connected to the secondary side T2 of the transformer 302, and flows into the positioning valve through the field interface 105 to complete the transmission.

[0063] While the HART circuit 100 outputs analog current signals, if monitoring or setting of the positioning valve on the field side is required, the control terminal is connected to an adjustable AC current source. The AC signal generated by the AC current source directly enters the isolation module 104, so the positioning valve connected to the field interface 105 receives the second interrogation signal. The positioning valve inputs an AC voltage signal through the second interface in the field interface 105 as a reply signal. This AC voltage signal is divided by the first capacitor C22 and the second resistor R22 at the control terminal of the first switch transistor T21. The AC voltage divider causes the first switch transistor T21 to turn on and off, causing the third power supply terminal to generate an AC signal. Finally, the AC signal is transmitted to the primary side T1 of the transformer 302 through the rectifier bridge and transformer 302, so the control interface 101 can receive the second HART signal replying to the second interrogation signal.

[0064] The HART circuit provided in this embodiment includes a comparator unit and a third switch in the adjustable power supply circuit, and a second switch in the first HART module. Through the connection between the switch and the comparator unit, the power supply is modulated according to the first interrogation signal, enabling bidirectional HART communication between the control side and the field-side transmitter. A first switch is included in the second HART module. This first switch can be turned on or off according to the AC voltage signal input from the field interface, enabling the modulation of the second HART signal according to the first response signal. This also completes bidirectional communication between the control side and the field-side positioning valve, making the HART circuit suitable for various application scenarios and improving its applicability.

[0065] Optionally, based on the foregoing embodiments, refer to... Figure 3 The HART circuit 100 also includes an intrinsically safe power limiting unit 305, which is located between the second HART module 201 and the field interface 105. The intrinsically safe power limiting unit 305 is used to limit the voltage or current level output to the field interface 105.

[0066] Specifically, since HART circuit 100 is often used in the production and processing sites of oil, natural gas or other hazardous chemicals, the transmission of electrical signals can easily cause the combustion and explosion of hazardous chemicals. Intrinsically safe energy limiting unit 305 can limit the voltage and current level output by field interface 105, play an explosion-proof role, and improve the safety of HART circuit 100.

[0067] Optionally, based on the foregoing embodiments, refer to... Figure 3 The HART circuit 100 also includes a first interface protection unit 306 and a second interface protection unit 307. The first interface protection unit 306 includes a first transient diode TVS2, a first filter inductor L2, a second filter inductor L3, and a first fuse F10. The first transient diode TVS2 is connected between the two interfaces 1+ and 1- of the control interface 101. The first filter inductor L2 and the first fuse F10 are connected in series between the first interface 1+ of the control interface 101 and the adjustable power module 102. The second filter inductor L3 is connected to the control interface 1+. The second interface 1- of 01 is connected to the first end of the isolation module 104; the second interface protection unit 307 includes a second transient diode TVS10, a third filter inductor L21 and a fourth filter inductor L22. The second transient diode TVS10 is connected between the two interfaces 2+ and 2- of the field interface 105. The third filter inductor L21 is connected between the first interface 2+ of the field interface 105 and the second end of the isolation module 104. The fourth filter inductor L22 is connected between the second interface 2- of the field interface 105 and the second end of the isolation module 104.

[0068] Specifically, the first transient diode TVS2 and the second transient diode TVS10 prevent surge signals from external electrical signals from damaging the HART circuit 100. The first fuse F10 prevents circuit damage caused by overcurrent. The first filter inductor L2, the second filter inductor L3, the third filter inductor L21, and the fourth filter inductor L22 filter out noise in the communication signal, improving the clarity of the HART communication signal. In addition, a second fuse F11 is installed between the primary side T1 of the transformer 302 and the inverter unit 301. A third fuse F20 is installed between the intrinsically safe energy limiting unit 305 and the rectifier unit 303 to prevent circuit damage caused by overcurrent on the field side.

[0069] The HART circuit provided in this embodiment is equipped with transient diodes, filter inductors, and fuses at both the control interface and the field interface. These components serve to prevent surge damage, overcurrent damage, and filter out signal noise, thereby further improving the safety and lifespan of the HART circuit and enhancing communication quality.

[0070] The present invention also provides a method for determining the status of a field interface of a HART circuit, used to determine whether a disconnection fault has occurred in the field interface in any of the foregoing embodiments. Figure 4 A flowchart illustrating a method for determining the status of a field interface of a HART circuit according to an embodiment of the present invention is shown below. Figure 4 The methods for determining the status of the field interface of a HART circuit include:

[0071] S401. Connect a resistance measuring device between the two interfaces in the control interface.

[0072] Specifically, a resistance measuring device is connected between the two interfaces of the control interface. This resistance measuring device can be integrated into the transmitter monitoring device or the positioning valve monitoring device, and can measure the resistance value between the two interfaces of the control interface in real time.

[0073] S402. Measure the resistance between two interfaces in the control interface using a resistance measuring device.

[0074] Specifically, the resistance between two interfaces in the control interface is measured using a resistance measuring device. This resistance value is related to the resistance, inductance, capacitance and other devices connected between the two interfaces in the control interface, as well as the resistance value of the circuit formed by the secondary side of the transformer.

[0075] S403. Determine whether there is a disconnection fault in the field interface based on the relative relationship between the resistance between the two interfaces of the control interface and the preset resistance value.

[0076] Specifically, the preset resistance value can be a single value or different preset values ​​can be set according to the different states of the HART circuit. When the field interface is disconnected from the transmitter or positioning valve, that is, when the two interfaces of the field interface are in an open state, there is no current on the secondary side of the transformer, resulting in no current in the secondary coil. At this time, the two interfaces of the control interface present a high resistance state. Since the resistance between the two interfaces of the control interface is greater than the preset resistance value, the current source cannot be input to the control interface, indicating that there is a problem with the wiring of the field interface.

[0077] For example, if the resistance between the two interfaces of the control interface is greater than or equal to a preset resistance value, a disconnection fault is determined to have occurred at the field interface. If the resistance between the two interfaces of the control interface is less than the preset resistance value, the field interface is determined to be in a normal state.

[0078] The HART circuit and its field interface status determination method provided in this invention embodiment utilizes an adjustable power supply module to provide variable power to the HART circuit, forming a loop. An isolation module creates isolation and coupling between the control interface and the field interface, preventing the control interface-connected devices and power supply from affecting the safety of the field devices, while also enabling the transmission of analog signals between the control interface and the field interface. This allows the control interface-connected device to detect or control the field interface-connected device. The first HART module can generate a first control signal based on a first interrogation signal input from the control interface. The adjustable power supply module can also modulate the first power signal into a first HART signal based on the first control signal. When the control interface-connected device detects the field interface-connected device, the first HART module enables HART communication between the control interface and the field interface. The HART signal is superimposed on the analog signal in the circuit. Based on the transmission of analog signals, bidirectional communication and interface status determination between the control room and the production site are achieved, avoiding the need for on-site inspection of the interface status. This diversifies the communication functions of the HART circuit, optimizes its performance, and improves on-site work efficiency.

[0079] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A HART circuit, characterized in that, include: Control interface, adjustable power supply module, first HART module, isolation module and field interface; The first HART module is connected to the control interface and is used to generate a first control signal when a first interrogation signal is input to the control interface; The adjustable power module is connected to the control interface and the first HART module respectively, and is used to output a first power signal to the control interface and modulate the first power signal into a first HART signal in response to the first control signal. The first end of the isolation module is connected to the control interface, and the isolation module is used to isolate the signal at its first end and couple it to its second end. The field interface is connected to the second end of the isolation module.

2. The HART circuit according to claim 1, characterized in that, It also includes a second HART module, which is located between the field interface and the second end of the isolation module. When the field interface receives the first reply signal, it modulates the first reply signal into a second HART signal and transmits it to the second end of the isolation module.

3. The HART circuit according to claim 2, characterized in that, The second HART module includes a first switch, a first resistor, a second resistor, and a first capacitor. The first end of the first switch is connected to the field interface. The first end of the first switch is also connected to the control end of the first switch via the first capacitor. The second end of the first switch is connected to the second end of the isolation module. The control end of the first switch is connected to the second end of the isolation module via the first resistor. The control end of the first switch is also connected to the second end of the first switch via the second resistor.

4. The HART circuit according to claim 2, characterized in that, The isolation module includes an inverter unit, a transformer, and a rectifier unit; the first end of the inverter unit serves as the first end of the isolation module, and the second end of the inverter unit is connected to the primary side of the transformer. The inverter unit is used to convert the DC signal input at the first end into an AC signal and transmit it to the primary side of the transformer through its second end. The transformer is used to achieve isolation and coupling between the primary and secondary sides; The first end of the rectifier unit is connected to the secondary side of the transformer, and the second end of the rectifier unit serves as the second end of the isolation module. The rectifier unit is used to rectify the AC signal on the secondary side of the transformer and output the rectified electrical signal from its second end.

5. The HART circuit according to claim 4, characterized in that, The rectifier unit includes a bridge rectifier circuit.

6. The HART circuit according to claim 2, characterized in that, It also includes an intrinsically safe power limiting unit, which is disposed between the second HART module and the field interface. The intrinsically safe power limiting unit is used to limit the voltage or current level output to the field interface.

7. The HART circuit according to claim 1, characterized in that, The first HART module includes a second switch transistor. The control terminal of the second switch transistor is connected to the control interface. The first terminal of the second switch transistor is connected to the adjustable power supply module and the first power supply terminal, respectively. The second terminal of the second switch transistor is connected to the first ground terminal.

8. The HART circuit according to claim 7, characterized in that, The adjustable power supply module includes a comparison unit and a power supply unit. The comparison unit includes a first comparison terminal, a second comparison terminal, and a first output terminal. The first comparison terminal is connected to the second terminal of the second switching transistor, and the second comparison terminal is connected to the first power supply terminal. The comparison unit is used to output a corresponding second control signal according to the relative relationship between the electrical signals connected to the first comparison terminal and the second comparison terminal. The output terminal of the power supply unit is connected to the control interface, the input terminal of the power supply unit is connected to the first power supply terminal, and the control terminal of the power supply unit is connected to the first output terminal. The power supply unit is used to output a first power signal or a first HART signal according to the second control signal.

9. The HART circuit according to claim 8, characterized in that, The power supply unit also includes a third switching transistor; The first terminal of the third switch is used as the input terminal of the power supply unit, the second terminal of the third switch is used as the output terminal of the power supply unit, and the control terminal of the third switch is used as the control terminal of the power supply unit.

10. The HART circuit according to claim 1, characterized in that, Also includes: A first interface protection unit and a second interface protection unit. The first interface protection unit includes a first transient diode, a first filter inductor, a second filter inductor, and a first fuse. The first transient diode is connected between the two interfaces of the control interface. The first filter inductor and the first fuse are connected in series between the first interface of the control interface and the adjustable power supply module. The second filter inductor is connected between the second interface of the control interface and the first end of the isolation module. The second interface protection unit includes a second transient diode, a third filter inductor, and a fourth filter inductor. The second transient diode is connected between the two interfaces of the field interface. The third filter inductor is connected between the first interface of the field interface and the second terminal of the isolation module. The fourth filter inductor is connected between the second interface of the field interface and the second terminal of the isolation module.

11. A method for determining the status of a field interface of a HART circuit as described in any one of claims 1-10, characterized in that, include: A resistance measuring device is connected between the two interfaces in the control interface; The resistance value between the two interfaces in the control interface is measured using the resistance measuring device. The relative relationship between the resistance values ​​of the two interfaces of the control interface and the preset resistance value is used to determine whether the field interface has a disconnection fault.

12. The method for determining the field interface status of a HART circuit according to claim 11, characterized in that, Determining whether a disconnection fault has occurred at the field interface based on the relative relationship between the resistance values ​​between the two interfaces of the control interface and a preset resistance value includes: If the resistance between the two interfaces of the control interface is greater than or equal to the preset resistance value, it is determined that the field interface has a disconnection fault. If the resistance between the two interfaces of the control interface is less than the preset resistance value, the field interface is determined to be in a normal state.

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