How to determine the status of a HART circuit and its field interface

Abstract

This application discloses a HART circuit and a method for determining the state of its field interface, the HART circuit includes a control interface, an adjustable power module, a first HART module, an isolation module and a field interface, the first HART module is connected to the control interface and configured 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 configured 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 isolation module has a first end connected to the control interface and configured to isolate and couple the signal at the first end to a second end of the isolation module, and the field interface is connected to the second end of the isolation module.

Description

[Technical field]

[0001] This application claims priority to a Chinese patent application filed with the China Patent Office on May 11, 2022 and accepted under application number 202210511096.2, the entire contents of which are incorporated herein by reference.

[0002] TECHNICAL FIELD The present disclosure relates to measurement and control technology, for example, to a method for determining the state of a HART circuit and its field interface. [Background technology]

[0003] With the increasing automation level, the number of sensors used in industrial sites is also increasing. In high-risk production sites such as petroleum, chemical and natural gas, many sensors and positioning valves need to realize communication connection with the control system.

[0004] Because the production site is far away from the control room where the control system is located, and the sensors and positioning valves are distributed in a scattered manner, conventional communication connection devices often use 4 to 20 mA analog current signals to transmit signals to realize communication between the site and the control room.

[0005] The conventional communication connection device can only realize a single control or detection function, and cannot perform remote two-way interaction, and has the problems of single function and poor performance. Summary of the Invention

[0006] The present application provides a method for determining the status of a Highway Addressable Remote Transducer (HART) circuit and its field interface, which realizes two-way communication between a control room and a production site, diversifies the application scenarios of the communication function of the HART circuit, and improves the performance of the HART circuit.

[0007] In a first aspect, the present embodiment comprises: 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 configured to generate a first control signal when a first interrogation signal is input to the control interface; the adjustable power module is respectively connected to the control interface and the first HART module, and configured 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 isolation module has a first end connected to the control interface and is configured to isolate a signal at the first end and couple it to a second end of the isolation module; The field interface provides a HART circuit that is connected to a second end of the isolation module.

[0008] In a second aspect, the present embodiment comprises interposing a resistance measuring device between two interfaces of the control interface; measuring a resistance between two interfaces in the control interface using the resistance measuring device; and determining whether an open circuit fault has occurred in the field interface based on a relative relationship between a resistance value between two interfaces in the control interface and a preset resistance value. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a structural schematic diagram of a HART circuit according to an embodiment of the present application. [Diagram 2] FIG. 2 is a structural schematic diagram of another HART circuit according to an embodiment of the present application. [Diagram 3] FIG. 2 is a structural schematic diagram of a further HART circuit according to an embodiment of the present application. [Figure 4]FIG. 2 is a schematic diagram of a flow of a method for determining the state of a field interface of a HART circuit according to an embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application.

[0011] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the drawings are not necessarily used to describe a particular order or priority, but are merely used to distinguish between similar objects. It should be understood that the data used in this manner may be substituted where appropriate, such that the embodiments of the present application described herein can be performed in an order other than that shown or described herein. In addition, the terms "comprise" and "have" and any variations thereof are intended to cover a non-exclusive inclusion, for example, a process, method, system, product, or apparatus of a series of steps or units, and are not necessarily limited to those steps or units expressly recited, but may include other steps or units not expressly recited or inherent to the process, method, product, or apparatus.

[0012] An embodiment of the present application provides a HART circuit, and FIG. 1 is a structural schematic diagram of a HART circuit according to an embodiment of the present application. Referring to FIG. 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 configured 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 respectively connected to the control interface 101 and the first HART module 103 and configured to output a first power supply signal to the control interface 101 and modulate the first power supply signal into a first HART signal in response to the first control signal, the isolation module 104 has a first end connected to the control interface 101 and is configured to isolate and couple the signal at the first end to a second end, and the field interface 105 is connected to the second end of the isolation module 104.

[0013] The control interface 101 is an interface provided on the control room side, and may be connected to a transmitter monitoring device or a positioning valve monitoring device, or may be connected to a diagnostic device. The field interface 105 is an interface provided on the production site side, and may be connected to a transmitter or a positioning valve. The adjustable power supply module 102 is a power supply module built into the HART circuit 100, and can provide a variable power supply. The first HART module 103 is a communication module for realizing HART communication between the control interface 101 and the field interface 105, and can realize HART communication between the control interface 101 and the field interface 105 when an analog signal is input to the field interface 105. The first inquiry signal is a communication signal input by the diagnostic device to the control interface 101 to inquire about the operating state of the transmitter.

[0014] For example, the first interrogation signal includes first interrogation information, which is interrogation information that the control room sends to a transmitter connected to the field interface 105, and the transmitter can input corresponding reply information to the field interface 105 based on the first interrogation information. The adjustable power supply module 102 can provide a first power supply signal, and can further adjust the first power supply based on the first control signal of the first HART module 103. signal can be modulated into a first HART signal, in which the first HART signal is generated according to the first control signal of the first HART module 103, and the first HART signal also includes the first interrogation information. The isolation module 104 can realize isolation and coupling between the first end and the second end, and the isolation function can isolate the field interface 105 from the adjustable power supply module 102 and the control interface 101, ensure that the device connected to the field interface 105 is not affected by the adjustable power supply and the control interface 101, and further realize the mutual transmission of signals on both ends of the isolation module 104. Illustratively, the isolation module 104 may be a combination module of a coupling circuit, a transformer device, and a rectifier circuit.

[0015] For example, on the one hand, when a transmitter is connected to the field interface 105, the control room side may correspondingly connect a transmitter monitoring device to the control interface 101 to obtain measurement data of the transmitter. The transmitter monitoring device is capable of determining measurement data of the transmitter by detecting an electrical signal in the load resistor, with a load resistor connected to the control interface 101. With the transmitter connected to the field interface 105, the adjustable power supply module 102 in the HART circuit 100 outputs a first power supply signal, for example, the first power supply signal may be a DC voltage. The first power supply signal is transmitted to a first end of the isolation module 104 through the load resistor. A second end of the isolation module 104 is connected to the field interface 105. The transmitter can adjust a resistor connected to the field interface 105 based on the measurement data. The resistor connected to the field interface 105 affects the change of the electrical signal at the second end of the isolation module 104 and is coupled to the first end of the isolation module 104, whereby a transmitter monitoring device connected to the control interface 101 can realize a determination on the measurement data of the transmitter by detecting the electrical signal at the load resistor. For example, the resistance of the transmitter connected to the field interface 105 is 4 to 100 Ω between the second end of the isolation module 104 and the field interface 105. 20 The transmitter monitoring device, which is connected to the control interface 101, affects the change in the analog current signal of 4 to 10 mA and is coupled to the first end of the isolation module 104, where the 4 to 10 mA current flows through the load resistor. 20 By detecting the analog current in mA, a decision can be made on the measurement data of the transmitter.

[0016] In addition, when the transmitter transmits the measurement data to the control interface 101 through the HART circuit 100, if the control room side finds that an abnormality has occurred in the measurement data and needs to inquire about the transmitter status or other data at the field side, a diagnostic device may be connected to the control interface 101, and for example, the diagnostic device may be a HART communicator. The diagnostic device can input a first interrogation signal to the control interface 101, and the parameters of the first interrogation signal can be adjusted in real time by the diagnostic device. The first HART module 103 is connected to the control interface 101 and can generate a first control signal based on the first interrogation signal. The adjustable power supply module 102 modulates the first power supply signal into a first HART signal based on the first control signal generated by the first HART module 103 and outputs it to a first end of the isolation module 104. The second end of the isolation module 104 is connected to a field interface 105, and the transmitter connected to the field interface 105 can determine corresponding interrogation information based on the first HART signal output by the field interface 105. A transmitter connected to the field interface 105 can input a second reply signal to the field interface 105 in response to the first HART signal. The diagnostic device can obtain the transmitter status or other relevant data based on the second reply signal output by the control interface 101. Exemplarily, the first HART signal and the second reply signal may be current signals of ±0.5 mA.

[0017] On the other hand, when a positioning valve is connected to the field interface 105, the control room side will correspondingly connect a positioning valve monitoring device to the control interface 101 to control the specific parameters of the positioning valve. A variable power supply is connected between the positioning valve monitoring device and the control interface 101, for example, the variable power supply may be a DC current source. The variable power supply can input an opening control signal corresponding to the control parameters to the control interface 101. When the positioning valve is connected to the field interface 105, the adjustable power supply module 102 in the HART circuit 100 outputs a first power supply signal. The current signal obtained by superimposing the opening control signal on the first power supply signal may be the positioning valve control signal, and the positioning valve control signal is transmitted to a 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 specific parameters according to the positioning valve control signal output by the field interface 105, and the transmission of the signal in this process realizes the control room side to control the positioning valve at the field. For example, the positioning valve monitoring device can deliver a variable current signal to the control interface 101, and the first power signal can be a voltage signal, and the first power signal can ensure the transmission ability of the variable current signal. The variable current signal can be a 4-20mA analog current signal and transmitted to the field interface 105 through the isolation module 104. The positioning valve connected to the field interface 105 can adjust a specific parameter according to the 4-20mA analog current signal, for example, the specific parameter can be a parameter such as opening of the positioning valve, closing of the positioning valve, or / and opening amount of the positioning valve.

[0018] The HART circuit according to the present embodiment is provided with a control interface, an adjustable power module, a first HART module, an isolation module and a field interface, and the adjustable power module can provide a variable power supply for the HART circuit to form a circuit. The isolation module can form isolation and coupling between the control interface and the field interface to prevent the device and power supply connected to the control interface from affecting the safety of the device in the field, and can also complete the transmission of an analog signal between the control interface and the field interface, so that the device connected to the control interface can detect or control the device connected to the field interface. The first HART module can generate a first control signal according to a first interrogation signal input by the control interface. The adjustable power module can further modulate the first power signal into a first HART signal according to the first control signal. When the device connected to the control interface detects the device connected to the field interface, the first HART module realizes HART communication between the control interface and the field interface, and the HART signal is superimposed with the analog signal in the circuit to realize two-way communication between the control room and the production site based on the transmission of the analog signal, which further diversifies the application scenarios of the communication function of the HART circuit and improves the performance of the HART circuit.

[0019] For example, FIG. 2 is a structural schematic diagram of another HART circuit according to an embodiment of the present application. Referring to FIG. 2 and based on the above-mentioned embodiment, the HART circuit 100 further includes a second HART module 201, which is disposed between the field interface 105 and the second end of the isolation module 104, and is configured 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.

[0020] Among them, the second HART module 201 is a module that realizes HART communication between the control interface 101 and the field interface 105, and can realize HART communication between the control interface 101 and the field interface 105 when an analog signal is input to the control interface 101.

[0021] For example, the second HART module 201 can modulate the first reply signal input to the field interface 105 into a second HART signal and transmit it to the second end of the isolation module 104. The isolation module 104 couples the second HART signal at the second end to the first end of the isolation module 104 for control. Control Interface 101 can be transmitted to. Control Interface 101 The diagnostic device connected to the field end can determine feedback information of the positioning valve connected to the field end based on the second HART signal. For example, the first reply signal may include an AC voltage signal, and parameters such as a voltage level and a frequency of the AC voltage signal are related to real-time parameters of the positioning valve, and the real-time parameters may include status parameters such as an open / closed state and an opening degree.

[0022] Exemplarily, when the positioning valve monitoring device controls the positioning valve connected to the field interface 105 through the HART circuit 100, if the control room needs to determine 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 may be connected to the control interface 101. For example, the diagnostic device may be a HART communicator. The diagnostic device may include an AC current source, and the second interrogation signal may be an AC current signal. The AC current source may input the second interrogation signal to the control interface 101, and the parameters of the second interrogation signal may be adjusted in real time by the diagnostic device. The second interrogation signal may be transmitted to the field interface 105 via the coupling of the isolation module 104 and output to the positioning valve. After receiving the second interrogation signal, the positioning valve may reply with a corresponding first reply signal in response to the interrogation information in the second interrogation signal. The second HART module 201 may modulate the first reply signal into a second HART signal and transmit it to the second end of the isolation module 104. Through the coupling action, the isolation module 104 can transmit the second HART signal at the second end to the first end of the isolation module 104. Thus, the second HART signal can be outputted through the control interface 101. By way of example, the second interrogation signal and the second HART signal may be current signals of ±0.5 mA.

[0023] In the HART circuit of this embodiment, the second HART module is provided, so that when a first reply signal is accessed at the field interface, the first reply signal can be modulated into a second HART signal and transmitted to the control interface through the coupling and isolation of the isolation module, thereby realizing HART communication in multiple scenarios, which can be applied to the control circuit of the positioning valve and the monitoring circuit of the transmitter. Based on the transmission of the analog current signal, two-way HART communication is realized and the applicability of the HART circuit is improved.

[0024] For example, FIG. 3 is a structural schematic diagram of a further HART circuit according to an embodiment of the present application. Referring to FIG. 3, based on the above-mentioned embodiment, the second HART module 201 includes a first switch tube T21, a first resistor R21, a second resistor R22 and a first capacitor C22, the first end of the first switch tube T21 is connected to the field interface 105, the first end of the first switch tube T21 is further connected to the control end of the first switch tube T21 via the first capacitor C22, the second end of the first switch tube T21 is connected to the second end of the isolation module 104, the control end of the first switch tube T21 is connected to the second end of the isolation module 104 via the first resistor R21, and the control end of the first switch tube T21 is further connected to the second end of the first switch tube T21 via the second resistor R22.

[0025] For example, when a positioning valve is connected to the field interface 105, the control room side correspondingly connects a positioning valve monitoring device to the control interface 101 to control specific parameters of the positioning valve. An adjustable power supply is connected between the positioning valve monitoring device and the control interface 101, for example, the adjustable power supply may 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 positioning valve is connected to the field interface 105, the adjustable power supply module 102 in the HART circuit 100 outputs a first power supply signal. A current signal obtained by superimposing the opening control signal on the first power supply signal may be a positioning valve control signal, and the positioning valve control signal is transmitted to a first end of the isolation module 104. A second end of the isolation module 104 is connected to the field interface 105. The positioning valve can adjust specific parameters according to the positioning valve control signal output by the field interface 105, and the transmission of the signal in this process realizes the control room side to control the positioning valve at the field. For example, the positioning valve monitoring device can deliver a variable current signal to the control interface 101, and the first power signal can be a voltage signal and can ensure the transmission capability of the variable current signal. The variable current signal can be a 4-20mA analog current signal and can be transmitted to the field interface 105 through the isolation module 104. The positioning valve connected to the field interface 105 can adjust a specific parameter according to the 4-20mA analog current signal, for example, the specific parameter can be a parameter such as opening of the positioning valve, closing of the positioning valve, or / and opening amount of the positioning valve.

[0026] If there is a need to monitor or provide a positioning valve connected to the field interface 105, Communicatoris connected between the two interfaces 1+ and 1- of the control interface 101, and the AC current signal (i.e., the second interrogation signal) generated in the control interface 101 directly enters the first end of the isolation module 104. Through the coupling and isolation functions of the isolation module 104, the second interrogation signal is received by the positioning valve connected to the field interface 105. In response, the positioning valve connected to the field interface 105 inputs a first reply signal to the second interface 2- of the field interface 105, for example, the first reply signal is an AC voltage signal, which can form a voltage division at the control end of the first switch tube T21 by the first capacitor C22 and the second resistor R22. The AC voltage division signal makes the first switch tube T21 conduct or turn off, thereby generating an AC signal at the coupling power point, and finally the isolation module 104 isolates the AC signal. Module The HART signal transmitted from the positioning valve connected to the field interface 105 can be coupled to the first end of the field interface 104 for transmission and output from the control interface 101. Thus, the HART signal returned by the positioning valve connected to the field interface 105 is received by the diagnostic device, and based on the control of the positioning valve by the analog current signal, two-way HART communication between the control room and the positioning valve is realized, and the communication efficiency between the control room and the field positioning valve is improved.

[0027] For example, in light of the above-mentioned embodiment, still referring to FIG. 3 , the isolation module 104 includes an inverter unit 301, a transformer 302 and a rectifier unit 303, a first end of the inverter unit 301 is a first end of the isolation module 104, a second end of the inverter unit 301 is connected to a primary side T1 of the transformer 302, the inverter unit 301 is configured to convert a DC signal accessed at the first end of the inverter unit 301 into an AC signal, and transmit it from the second end of the inverter unit 301 to the primary side T1 of the transformer 302, the transformer 302 is configured to realize isolation and coupling between the primary side T1 and the secondary side T2, a first end of the rectifier unit 303 is connected to the secondary side T2 of the transformer 302, and a second end of the rectifier unit 303 is a second end of the isolation module 104, the rectifier unit 303 is configured to rectify the AC signal of the secondary side T2 of the transformer 302, and output the rectified electric signal from the second end of the rectifier unit 303.

[0028] For example, the first end of the inverter unit 301 includes a connection end and a first ground end GND3, of which the connection end is 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 accessed at the first end into an AC signal and transmit it to the primary side T1 of the transformer 302, which then passes through the coil of the primary side T1 back to the inverter unit 301 and is grounded through the first ground end GND3, thereby forming a circuit in the primary side T1 of the transformer 302. The transformer 302 can realize the isolation and coupling of electrical signals between the primary side T1 and the secondary side T2, and for example, the transformation ratio between the primary side T1 and the secondary side T2 of the transformer 302 may be 1:1. The second end of the rectifier unit 303 is the second end of the isolation module 104, and the rectifier unit 303 can rectify the AC signal of the secondary side T2 of the transformer 302 into a single-phase pulse signal and transmit it to the second end of the rectifier unit 303. The frequency of the single-phase pulse signal is smaller than the frequency of the AC signal of the secondary side T2 of the transformer 302. For example, the rectifier unit 303 may include a bridge rectifier circuit Q, and two input ends of the bridge rectifier circuit Q are respectively connected to both ends of the secondary side T2 of the transformer 302, and two output ends of the bridge rectifier circuit Q are respectively connected to two interfaces of the field interface. In addition, the two output ends of the bridge rectifier circuit Q may be the second power supply terminal VCC2 and the second ground terminal GND2, respectively, and the power supply of the second power supply terminal VCC2 is obtained by the coupling of the transformer 302. A first filter capacitor C23 and a second filter capacitor C21 may be further paralleled between the second power supply terminal VCC2 and the second ground terminal GND2. By installing the inverter unit 301, the transformer 302 and the rectifier unit 303, the isolation and coupling of signals between the field interface 105 side and the control interface 101 side can be realized, the stable transmission of electrical signals can be guaranteed, and the safety of operation of the equipment connected to the field interface 105 can be guaranteed.

[0029] For example, based on the above embodiment, still referring to FIG. 3, the first HART module 103 includes a second switch tube T8, the control end of the second switch tube T8 is connected to the control interface 101, the first end of the second switch tube T8 is respectively connected to the adjustable power module 102 and the first power supply terminal VCC3, and the second end of the second switch tube T8 is connected to the first ground terminal GND3. The adjustable power 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 end of the second switch tube T8, and is further connected to the set power supply terminal VAC through a resistor and a capacitor, wherein 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 end b is connected to the first power supply end VCC3, the comparison unit U1 is configured to output a corresponding second control signal according to the relative relationship of the electrical signals connected to the first comparison end a and the second comparison end b, the output end of the power supply unit 304 is connected to the control interface 101, the input end of the power supply unit 304 is connected to the first power supply end VCC3, and the control end of the power supply unit 304 is connected to the first output end c, and the power supply unit 304 is configured to output a first power signal or a first HART signal according to the second control signal.

[0030] For example, a third resistor R18 and a second capacitor C15 are further connected in series between the control end of the second switch tube T8 and the first interface 1+ of the control interface 101, and a fourth resistor is further connected in series between the control end of the second switch tube T8 and the second interface 1- of the control interface 101. When a first interrogation signal is input to the control interface 101, the first interrogation signal may be an AC voltage signal, and an AC voltage division is formed at the control end of the second switch tube T8, so that the second switch tube T8 can be controlled to be conductive or turned off according to the voltage division wave. When the second switch tube T8 is conductive, a path is formed between the first power supply end VCC3 and the first ground end GND3, and when the second switch tube T8 is turned off, the first power supply end VCC3 supplies power to the first comparison end a of the comparison unit U1, thereby realizing the access of the first comparison end a of the comparison unit U1 to the ground or the first power supply end VCC3. The comparison unit U1 can output a corresponding second control signal according to the relative relationship of the electrical signals connected to the first comparison terminal a and the second comparison terminal b, and 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", and if the voltage levels connected to the first comparison terminal a and the second comparison terminal b are not equal or the difference value exceeds a preset value, the comparison unit U1 outputs "1". The power supply unit 304 further includes a third switch tube T6, a first diode D5, a power filter inductor L1 and at least one power filter capacitor, and the first end of the third switch tube T6 is the input end of the power supply unit 304, the second end of the third switch tube T6 is the output end of the power supply unit 304, and the control end of the third switch tube T6 is the control end of the power supply unit 304. The first diode D5 is connected between the first ground terminal GND3 and the second end of the third switch tube T6 to determine the output direction of the power supply. The power supply filter inductor L1 is connected to the second end of the third switch tube T6 to perform a filtering function for the output power supply. The third switch tube T6 can be turned on or off according to the second control signal.When the control interface 101 does not receive a first interrogation signal, the second switch tube T8 is continuously turned off, and the third switch tube T6 is continuously conductive, and the adjustable power module 102 outputs a first power signal, which is an electrical signal output by the first power terminal. When the control interface 101 receives a first interrogation signal, the second switch tube T8 switches between a conducting and turned off state according to the frequency of the first interrogation signal, and the corresponding third switch tube T6 also switches between a conducting and turned off state according to the second control signal, so that the first power signal is modulated into a first HART signal and output through the second terminal of the third switch tube T6.

[0031] For example, when the HART circuit 100 realizes the access function of the analog current signal (i.e., the control room takes the measurement value of the transmitter), a load resistor is connected between the two interfaces 1+ and 1- of the control interface 101, and a field temperature or pressure transmitter (which may be regarded as a variable resistor whose resistance value is related to the measurement value) is connected to the two interfaces 2+ and 2- of the field interface 105. The transmission direction of the analog current signal is from the field interface 105 to the control interface 101 through the isolation module 104. At this time, since the second switch tube T8 is turned off, the comparison unit U1 outputs a high level to the control end of the third switch tube T6, ensuring the conduction of the third switch tube T6, so that the adjustable power supply module 102 outputs a first power supply signal to the first interface 1+ of the control interface 101, and the first power supply signal is a DC voltage signal output by the first power supply end. The first power signal is sequentially connected to a first ground terminal GND3 connected to the inverter unit 301 via a load resistor, the inverter unit 301, and the primary side T1 of the transformer 302, thereby forming a power circuit. The secondary side T2 of the transformer 302 supplies power to a temperature or pressure transmitter connected to the field interface 105, and a circuit is also formed on the secondary side T2 of the transformer 302. The measured value of the temperature or pressure transmitter affects the resistance value connected to the field interface 105, and the 4-phase current flowing through the field interface 105 is20 Changing the mA analog current signal changes the electrical signal flowing through the secondary side T2 of the transformer 302. Since the electrical signals of the primary side T1 and the secondary side T2 of the transformer 302 are coupled to each other, the 4 to 5 V current flowing through the load resistor is 20 The temperature or pressure transmitter measurements can be obtained by detecting the analog current signal in mA.

[0032] If the HART circuit 100 needs to monitor or provide a temperature or pressure transmitter connected to the field interface 105 while realizing the access function of the analog current signal, an adjustable AC voltage source may be connected between the two interfaces 1+ and 1- of the control interface 101, and the AC signal generated by the AC voltage source forms a voltage division through the third resistor R18, the second capacitor C15 and the fourth resistor. The AC voltage division signal can make the second switch tube T8 function, and the conduction and turn-off of the second switch tube 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 turn-off of the third switch tube T6. Adjustable power supply Module The HART output unit 302 outputs a voltage signal (i.e., the first HART signal) whose duty cycle is related to the AC voltage source, and can be transmitted to the inverter unit 301 by a load resistor. The first HART signal is transmitted to the field interface 105 via the transformer 302 and the rectifier unit 303, and thus the first HART signal is received by a field temperature or pressure transmitter. In response, the temperature or pressure transmitter can respond to the first HART signal by inputting an AC current signal to the field interface 105.

[0033] When the HART circuit 100 realizes the output function of the analog current signal (i.e., the control room is in a state of controlling the positioning valve at the field), an adjustable DC current source is connected between the two interfaces 1+ and 1- of the control interface 101, and a positioning valve is connected between the two interfaces 2+ and 2- of the field interface 105. The transmission direction of the analog current signal is from the control interface 101 to the positioning valve connected to the field interface 105 through the isolation module 104. At this time, since the second switch tube T8 is turned off, the comparison unit U1 outputs a high level to the control end of the third switch tube T6, ensuring the conduction of the third switch tube T6, so that the adjustable power supply module 102 outputs a first power supply signal to the first interface 1+ of the control interface 101, and the first power supply signal is a DC voltage signal output by the first power supply end, providing power for the adjustable DC current source. The current output by the DC current source is an analog current signal. The analog current signal is transmitted to a first end of the inverter unit 301, and after being regulated by the inverter unit 301, passes through the primary side T1 of the transformer 302 and returns to the first ground end GND3 connected to the inverter unit 301. 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.

[0034] When the HART circuit 100 realizes the output function of an analog current signal, if it is necessary to monitor or provide a positioning valve at the field side, an adjustable AC current source is connected to the control end. The AC signal generated by the AC current source directly enters the isolation module 104, and thus a second interrogation signal is received by the positioning valve connected to the field interface 105. The positioning valve inputs an AC voltage signal as a reply signal through the second interface in the field interface 105. The AC voltage signal forms a voltage division at the control end of the first switch tube T21 through the first capacitor C22 and the second resistor R22. The AC voltage division signal turns on and off the first switch tube T21, generating an AC signal at the third power supply end, and finally transmits the AC signal to the primary side T1 of the transformer 302 through the rectifier bridge and the transformer 302, and thus the control interface 101 can receive a second HART signal that replies to the second interrogation signal.

[0035] In the HART circuit of this embodiment, the adjustable power circuit is provided with a comparison unit and a third switch tube, the first HART module is provided with a second switch tube, and the connection between the switch tube and the comparison unit realizes the function of modulating the power supply according to the first interrogation signal, thereby completing the bidirectional HART communication between the control side and the transmitter connected to the field side. The second HART module is provided with a first switch tube that can be turned on or off according to the AC voltage signal input by the field interface, thereby realizing the function of modulating the second HART signal according to the first reply signal, thereby completing the bidirectional communication between the control side and the positioning valve connected to the field side, making the HART circuit suitable for various application scenarios, and improving the applicability of the HART circuit.

[0036] For example, in light of the above-described embodiment and still referring to FIG. 3 , the HART circuit 100 further includes an intrinsically safe energy limiting unit 305, which is disposed between the second HART module 201 and the field interface 105, and which is configured to limit a voltage or current level output to the field interface 105.

[0037] For example, HART circuit 100 is often applied in the production and processing of oil, natural gas, or other hazardous chemicals, where the transmission of electrical signals is likely to cause deflagration of the hazardous chemicals. However, the intrinsically safe energy limiting unit 305 can limit the voltage and current levels output by the field interface 105 to provide an explosion-proof effect and improve the safety of HART circuit 100.

[0038] For example, in light of the above embodiment, still referring to FIG. 3, the HART circuit 100 further 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 supply module 102, and the second filter inductor L3 is connected in series between the first interface 1+ of the control interface 101 and the adjustable power supply module 102. is connected between the second interface 1- of the control interface 101 and the first end of the isolation module 104, and 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, and 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.

[0039] For example, the first transient diode TVS2 and the second transient diode TVS10 can prevent the HART circuit 100 from being damaged by a surge signal in an externally connected electrical signal. The first fuse F10 can prevent the circuit from being damaged by an overcurrent. The first filter inductor L2, the second filter inductor L3, the third filter inductor L21, and the fourth filter inductor L22 can filter out clutter in the communication electrical signal to improve the clarity of the HART communication signal. In addition, a second fuse F11 is provided between the primary side T1 of the transformer 302 and the inverter unit 301. A third fuse F20 is provided between the intrinsically safe energy limiting unit 305 and the rectifier unit 303, which can prevent the circuit from being damaged by an overcurrent in the field side.

[0040] In the HART circuit of this embodiment, a transient diode, a filter inductor, and a fuse are respectively connected to the control interface and the field interface, which prevents damage caused by surges and overcurrents, and filters and removes signal clutter, thereby further improving the safety of the HART circuit, extending the service life of the HART circuit, and improving communication quality.

[0041] The present application further provides a method for determining the status of a field interface of a HART circuit, for determining whether an open circuit fault occurs in the field interface in any of the above-mentioned embodiments. Figure 4 is a schematic flow diagram of a method for determining the status of a field interface of a HART circuit according to an embodiment of the present application. Referring to Figure 4, the method for determining the status of a field interface of a HART circuit includes:

[0042] In S401, a resistance measuring device is interposed between two interfaces in a control interface.

[0043] For example, a resistance measuring device is interposed between two interfaces in the control interface, and the resistance measuring device can be integrated into a transmitter monitoring device or a positioning valve monitoring device, and can measure the resistance value between the two interfaces in the control interface in real time.

[0044] In S402, a resistance measuring device is used to measure the resistance between two interfaces in the control interface.

[0045] For example, a resistance measuring device is used to measure the resistance between two interfaces in the control interface, the resistance value being related to resistors, inductors, capacitors and other devices connected between the two interfaces in the control interface, and also related to the resistance value of the circuit formed on the secondary side of the transformer.

[0046] In S403, it is determined whether an open circuit fault occurs in the field interface based on the relative relationship between the resistance between the two interfaces in the control interface and the preset resistance value.

[0047] For example, the preset resistance value may be one value, or different preset values ​​may be set according to the state of the HART circuit. When the connection between the field interface and the transmitter or the positioning valve is disconnected, that is, when the two interfaces in the field interface are in a disconnected state, there is no current in the secondary side of the transformer, so there is no current in the coil in the secondary side. At this time, the two interfaces in the control interface will be in a high resistance state, and the resistance between the two interfaces in the control interface at this time is greater than the preset resistance value, so the current source cannot input to the control interface, so it can be known that there is a problem with the connection of the field interface.

[0048] Illustratively, if the resistance between the two interfaces in the control interface is greater than or equal to a preset resistance value, it is determined that an open fault occurs in the field interface, and if the resistance between the two interfaces in the control interface is less than a preset resistance value, it is determined that the field interface is in a normal state.

[0049] The HART circuit and its field interface status determination method according to the embodiment of the present application can provide a variable power supply to the HART circuit so that the adjustable power supply module forms a circuit. The isolation module can prevent the device and power supply connected to the control interface from affecting the safety of the field device by forming isolation and coupling between the control interface and the field interface, and can also complete the transmission of analog signals between the control interface and the field interface, so that the device connected to the control interface can detect or control the device connected to the field interface. The first HART module can generate a first control signal according to a first interrogation signal input by the control interface. The adjustable power supply module can further modulate the first power supply signal into a first HART signal according to the first control signal. When an equipment connected to the control interface detects an equipment connected to the field interface, the first HART module realizes HART communication between the control interface and the field interface, and by superimposing the HART signal and the analog signal in the circuit, it realizes two-way communication between the control room and the production site and judges the status of the interface based on the transmission of the analog signal, avoids checking the status of the interface at the site, makes the communication function of the HART circuit more diversified, improves the performance of the HART circuit, and improves the work efficiency at the site.

Claims

1. 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 configured to generate a first control signal when a first interrogation signal is input to the control interface; the adjustable power supply module is respectively connected to the control interface and the first HART module, and configured to output a first power supply signal to the control interface and modulate the first power supply signal into a first HART signal in response to the first control signal; the isolation module has a first end connected to the control interface and is configured to isolate a signal at the first end and couple it to a second end of the isolation module; the field interface is connected to a second end of the isolation module; The first HART module includes: a second switch tube having a control end connected to the control interface, a first end connected to the adjustable power supply module and a first power supply end respectively, and a second end connected to the first ground end; Highway addressable remote transducer HART circuit.

2. and a second HART module disposed between the field interface and a second end of the isolation module, the second HART module being configured to, when the field interface receives a first reply signal, modulate the first reply signal into a second HART signal and transmit the second reply signal to the second end of the isolation module.

2. The HART circuit of claim 1.

3. the second HART module comprises a first switch tube, a first resistor, a second resistor and a first capacitor; The first switch tube has a first end connected to the field interface, a first end further connected to a control end of the first switch tube via the first capacitor, a second end connected to a second end of the isolation module, a control end connected to the second end of the isolation module via the first resistor, and a control end further connected to the second end of the first switch tube via the second resistor; 3. The HART circuit of claim 2.

4. The isolation module comprises an inverter unit, a transformer and a rectifier unit; The inverter unit has a first end which is the first end of the isolation module and a second end which is connected to the primary side of the transformer, and is configured to convert a DC signal accessed at the first end of the inverter unit into an AC signal and transmit the AC signal from the second end of the inverter unit to the primary side of the transformer; The transformer is configured to provide isolation and coupling between a primary side and a secondary side; the rectifier unit has a first end connected to the secondary side of the transformer and a second end corresponding to the second end of the isolation module, and is configured to rectify an AC signal from the secondary side of the transformer, and output the rectified electrical signal from the second end of the rectifier unit; 3. The HART circuit of claim 2.

5. The rectifier unit comprises a bridge rectifier circuit.

5. The HART circuit of claim 4.

6. and an intrinsically safe energy limiting unit disposed between the second HART module and the field interface and configured to limit a voltage or current level output to the field interface.

3. The HART circuit of claim 2.

7. The adjustable power supply module includes: a comparison unit including a first comparison end connected to the second end of the second switch tube, a second comparison end connected to the first power supply end, and a first output end, and configured to output a corresponding second control signal according to a relative relationship between the electrical signals connected to the first comparison end and the second comparison end; a power supply unit having an output end connected to the control interface, an input end connected to the first power supply end, and a control end connected to the first output end, configured to output the first power supply signal or the first HART signal according to the second control signal; 2. The HART circuit of claim 1.

8. The power supply unit includes: a third switch tube having a first end corresponding to the input end of the power supply unit, a second end corresponding to the output end of the power supply unit, and a control end corresponding to the control end of the power supply unit; 8. The HART circuit of claim 7.

9. a first interface protection unit, comprising: a first transient diode, a first filter inductor, a second filter inductor and a first fuse, the first transient diode being connected between two interfaces of the control interface, the first filter inductor and the first fuse being serially connected between the first interface of the control interface and the adjustable power supply module, and the second filter inductor being connected between the second interface of the control interface and a first end of the isolation module; a second interface protection unit including a second transient diode, a third filter inductor and a fourth filter inductor, the second transient diode being connected between two interfaces of the field interface, the third filter inductor being connected between a first interface of the field interface and a second end of the isolation module, and the fourth filter inductor being connected between the second interface of the field interface and the second end of the isolation module.

2. The HART circuit of claim 1.

10. interposing a resistance measuring device between two interfaces of the control interface; measuring a resistance between two interfaces in the control interface using the resistance measuring device; and determining whether an open-wire fault occurs in the field interface based on a relative relationship between a resistance value between two interfaces in the control interface and a preset resistance value. A method for determining a state of a field interface of a HART circuit according to any one of claims 1 to 9.

11. Determining whether an open circuit fault occurs in the field interface based on the relative relationship between the resistance value between the two interfaces in the control interface and a preset resistance value as described above, determining that an open wire fault has appeared in the field interface in response to determining that a resistance between two interfaces in the control interface is greater than or equal to the preset resistance value; determining that the field interface is in a normal state in response to determining that a resistance between two interfaces in the control interface is less than the preset resistance value. The method of claim 10.

Images