A safety instrument system

Abstract

This invention provides a safety instrumented system, comprising: a controller, a primary working module, and a backup working module; both the primary and backup working modules include a safety circuit and a HART circuit, wherein the channel selection switch unit in the HART circuit has signal transmission channels corresponding to the number of transmission paths required by the safety circuit, and the on / off state of each signal transmission channel is controlled by the selection switch; the primary and backup working modules exchange data through the central processing unit in their respective safety circuits, and the safety circuit and HART circuit are powered independently; the controller is communicatively connected to both the primary and backup working modules, and switches to the backup working module when the primary working module fails, thus solving the problem that the failure of the HART circuit in the safety instrumented system can easily affect the operating safety functions and cause a shutdown.

Description

Technical Field

[0001] This invention relates to the field of safety technology, and more specifically to a safety instrumented system. Background Technology

[0002] HART (Highway Addressable Remote Transducer) is capable of transmitting both 4-20mA analog and digital signals over a single cable and is widely used in industry. Safety instrumented systems (VIS) are control systems specifically designed for safety. They are designed to respond to potential equipment malfunctions and must be able to respond quickly and accurately to accidents, ultimately preventing accidents altogether or at least minimizing the harm caused to equipment, the environment, and personnel.

[0003] However, failure of the HART circuit in a safety instrumented system can affect the safety functions that are in operation, leading to a shutdown. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a safety instrumented system to solve the problem that failure of the HART circuit in the safety instrumented system can easily affect the operating safety functions and cause a shutdown.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0006] This invention discloses a safety instrumented system, comprising: a controller, a main working module, and a backup working module;

[0007] Both the primary working module and the backup working module include a safety circuit and a HART circuit. The channel selection switch unit in the HART circuit is provided with a signal transmission channel corresponding to the number of transmission paths required by the safety circuit. The on / off state of each signal transmission channel is controlled by a selection switch.

[0008] The primary working module and the backup working module exchange data through the central processing unit in their respective security circuits. The security circuits and the HART circuits are powered independently.

[0009] The controller is communicatively connected to both the primary working module and the backup working module, and switches to the backup working module to operate when the primary working module fails.

[0010] Optionally, in the above-described safety instrumented system, the signal input / output ports of the safety circuit and / or the signal input / output ports of the HART circuit are further provided with EMC protection unit circuits.

[0011] Optionally, in the above-described safety instrumented system, the EMC protection unit circuit includes: a diode, a first capacitor, and a first resistor;

[0012] One end of the diode is connected to the signal input / output port, and the other end of the diode is connected to one end of the first capacitor and one end of the first resistor, respectively, with the connection point connected to signal ground;

[0013] The other end of the first capacitor is connected to the other end of the first resistor, and the connection point is connected to the protective ground.

[0014] Optionally, in the above-described safety instrumented system, the HART circuit includes: a signal coupling unit, a channel selection switch unit, a modulation and demodulation unit, a first power supply unit, and a central processing unit of the HART circuit;

[0015] The first power supply unit is used to supply power to the signal coupling unit, the channel selection switch unit, the modulation and demodulation unit, and the central processing unit of the HART circuit.

[0016] Optionally, in the above-described safety instrumented system, the signal coupling unit includes: a second capacitor, a third capacitor, a second resistor, a third resistor, and a fourth resistor;

[0017] One end of the second capacitor serves as the input terminal of the signal coupling unit and is connected to the signal input / output port of the HART circuit; the other end of the second capacitor is connected to one end of the second resistor through the third capacitor, and the other end of the second resistor is connected to one end of the third resistor and one end of the fourth resistor respectively, with the connection point serving as the output terminal of the signal coupling unit.

[0018] Optionally, in the above-described safety instrumented system, the central processing unit of the HART circuit is used to receive control commands sent by the central processing unit in the safety circuit, control the operation of the selection switch in its own channel selection switch unit according to the control commands, and report the current status of the HART circuit to the central processing unit in the safety circuit.

[0019] The controller is used to determine whether the working module of the safety circuit and the HART circuit in the working module are faulty based on the data of the central processing unit in the safety circuit, and to generate a fault alarm when the determination result is that a fault has occurred.

[0020] Optionally, in the above-described safety instrumented system, the control commands include signal transmission commands and fault commands;

[0021] The central processing unit in the HART circuit is used to control the gating switch to enable the corresponding transmission channel according to the signal transmission command.

[0022] The central processing unit in the HART circuit is used to control the gating switch to shut down the corresponding transmission channel according to the fault command.

[0023] Optionally, in the above-described safety instrumented system, the safety circuit includes: a conversion unit, a second power supply unit, and a central processing unit of the safety circuit;

[0024] The second power supply unit is used to supply power to the central processing unit of the conversion unit and the safety circuit.

[0025] Optionally, in the above-described safety instrumented system, the safety circuit further includes a diagnostic unit for diagnosing whether the safety circuit meets safety requirements;

[0026] The second power supply unit is also used to supply power to the diagnostic unit.

[0027] The safety instrumented system provided by the above embodiments of the present invention includes: a controller, a primary working module, and a backup working module; both the primary and backup working modules include a safety circuit and a HART circuit. The channel selection switch unit in the HART circuit is provided with a signal transmission channel corresponding to the number of transmission paths required by the safety circuit, and the on / off state of each signal transmission channel is controlled by the selection switch; the primary working module and the backup working module exchange data through the central processing unit in their respective safety circuits, and the safety circuit and HART circuit are powered independently; the controller is communicatively connected to the primary working module and the backup working module respectively, and switches to the backup working module to operate when the primary working module fails. Through the redundant configuration of the working modules and the independent power supply of the safety circuit and HART circuit in each working module, the system solves the problem that the failure of the HART circuit in the safety instrumented system can easily affect the operating safety functions and cause a shutdown. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0029] Figure 1 A schematic diagram of a safety instrumented system provided in this application;

[0030] Figure 2A schematic diagram illustrating the switching between a primary working module and a backup working module, provided for an embodiment of this application;

[0031] Figure 3 A schematic diagram of the structure of the HART circuit and the security circuit in a working module provided in this application embodiment;

[0032] Figure 4 This is a schematic diagram of the structure of a signal coupling unit provided in an embodiment of this application;

[0033] Figure 5 This application provides a schematic diagram of the structure of a channel selection switch unit according to an embodiment of the present application.

[0034] Figure 6 This is a schematic diagram of the structure of an EMC protection unit circuit provided in an embodiment of this application. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 are within the scope of protection of the present invention.

[0036] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0037] This invention provides a safety instrumented system to address the problem that failure of the HART circuit in a safety instrumented system can easily affect the operation of safety functions, leading to a shutdown.

[0038] Please see Figure 1 The safety instrumented system mainly includes: controller 101, main working module 102 and backup working module 103.

[0039] The main working module 102 and the backup working module 103 both include a safety circuit and a HART circuit. The channel selection switch unit in the HART circuit is equipped with a signal transmission channel corresponding to the number of transmission paths required by the safety circuit. The on / off state of each signal transmission channel is controlled by the selection switch.

[0040] The main working module 102 and the backup working module 103 exchange data through the central processing unit in their respective safety circuits. The safety circuits and HART circuits are powered independently.

[0041] The controller 101 is communicatively connected to the main working module 102 and the backup working module 102 respectively, and switches to the backup working module 103 to operate when the main working module 102 fails.

[0042] In practical applications, setting up a primary working module 102 and a backup working module 103 in a safety instrumented system can form a redundant configuration. When the primary working module 102 experiences a fault that affects safety performance, the system can switch to the backup working module 103 to operate, thereby ensuring the control accuracy of the safety instrumented system. A switching diagram can be seen as follows: Figure 2 As shown.

[0043] The HART circuit in each working module works in sync with the working module and synchronizes with the real-time operating conditions, enabling high-precision control of the process.

[0044] In some embodiments, such as Figure 3 As shown, the HART circuit may include: a signal coupling unit, a channel selection switch unit, a modulation and demodulation unit, a first power supply unit, and a central processing unit of the HART circuit;

[0045] The first power supply unit is used to supply power to the signal coupling unit, the channel selection switch unit, the modulation and demodulation unit, and the central processing unit of the HART circuit.

[0046] In practical applications, the HART circuit can be independently powered through the first power supply unit.

[0047] To ensure that device-level faults in HART circuits do not disrupt safety and improve system security, redundant design can be implemented for signal coupling units in the HART circuit. Specifically, for example... Figure 4 As shown, the signal coupling unit may include: a second capacitor (capacitor 2 in the figure), a third capacitor (capacitor 1 in the figure), a second resistor (resistor 3 in the figure), a third resistor (resistor 1 in the figure), and a fourth resistor (resistor 2 in the figure).

[0048] One end of the second capacitor serves as the input terminal of the signal coupling unit, connected to the signal input / output port of the HART circuit (output / input in the figure); the other end of the second capacitor is connected to one end of the second resistor through the third capacitor, and the other end of the second resistor is connected to one end of the third resistor and one end of the fourth resistor respectively. The connection point serves as the output terminal of the signal coupling unit (input / output in the figure).

[0049] In practical applications, the second, third, and fourth resistors can be voltage divider resistors. The second and third capacitors can be coupling capacitors, which have the function of blocking DC and passing AC, providing a high-frequency signal path, isolating DC signals, and ensuring safe signal transmission.

[0050] It should be noted that the second capacitor, the third capacitor, the second resistor, the third resistor, and the fourth resistor together form a voltage divider network to ensure that the output signal amplitude range is within the requirements of the HART physical layer protocol.

[0051] It should also be noted that the second and third capacitors are redundant designs for fault avoidance. The failure models of the capacitors are capacitance change, short circuit, and open circuit. If there is only one coupling capacitor, when a short circuit failure occurs, the safety circuit signal voltage will be pulled to the voltage division of the third and fourth resistors, which will cause a safety failure. However, by using two coupling capacitors, the operation of the safety function can be ensured without affecting the occurrence of a single fault.

[0052] In some embodiments, the central processing unit in the HART circuit is used to receive control commands sent by the central processing unit in the security circuit, control the gating switch in its own channel gating unit to operate according to the control commands, and report the current state of the HART circuit to the central processing unit in the security circuit.

[0053] The controller 101 is used to determine whether the working module of the safety circuit and the HART circuit in the working module are faulty based on the data of the central processing unit in the safety circuit, and to generate a fault alarm when the determination result is a fault.

[0054] The control commands can include signal transmission commands and fault commands. The central processing unit (CPU) in the HART circuit controls the gating switch to enable the corresponding transmission channel based on the signal transmission command; the CPU controls the gating switch to disable the corresponding transmission channel based on the fault command.

[0055] In practical applications, the specific structure of the channel selection switch unit can be as follows: Figure 5 As shown, it mainly includes a selection switch and has multiple HART signal transmission channels. It is used to switch the transmission channels at high speed according to the control instructions issued by the central processing unit of the HART circuit (that is, the signal control in the figure), so that each channel can work independently and without interference.

[0056] It should be noted that each safety loop in this application has a corresponding separate HART channel. When a certain HART channel fails, the channel can be shut down by controlling the gating switch, thereby avoiding affecting other channels.

[0057] It should also be noted that the HART circuit can obtain its current state through the HART communication protocol via its own central processing unit, and report the current state to the central processing unit in the security circuit.

[0058] In practical applications, the central processing unit (CPU) of the HART circuit and the CPU of the security circuit can both be programmed through the CPU to achieve their respective functions.

[0059] In some embodiments, the modulation and demodulation unit is mainly used for digital signal modulation, analog signal demodulation, master check and calibration, anti-interference, and communication rate and distance adaptation.

[0060] Specifically, taking the error-free transmission of 1200Hz and 2200Hz at 4-20mA as an example, the signal modulation process of this HART circuit can be as follows: after the signal input and output are filtered by the signal coupling unit, they are transmitted to the channel selection switch unit to open the corresponding channel signal. The demodulation unit converts the 1200Hz and 2200Hz signals superimposed on the 0.5mA low-level digital signals of 4-20mA into "1" and "0" and sends them to the central processing unit of the HART circuit. The central processing unit of the HART circuit then sends the converted signals to the central processing unit of the security circuit for unified processing. The HART signal modulation process is the reverse.

[0061] In practical applications, the controller 101 can generate a fault alarm to alert relevant personnel in case of a fault in the working module where the safety circuit is located, or in the HART circuit of the working module, so that relevant personnel can handle the situation in a timely manner.

[0062] In some embodiments, such as Figure 3 As shown, the safety circuit may include: a conversion unit, a second power supply unit, and a central processing unit for the safety circuit.

[0063] The second power supply unit is used to supply power to the central processing unit of the conversion unit and the safety circuit.

[0064] In practical applications, a second power supply unit can be used to achieve independent power supply for the safety circuit.

[0065] It should be noted that the HART circuit is powered by the first power supply unit, and the safety circuit is powered by the second power supply unit. The first and second power supply units are relatively independent. A power failure in the HART circuit will not cause the safety circuit to malfunction, ensuring that the fault is controllable and reducing the risk.

[0066] In practical applications, when the central processing unit in the HART circuit identifies a fault in the hardware or communication link, it can report it to the central processing unit of the security circuit. At this time, the controller 101 can determine whether there is a fault in the working module based on the data received by the central processing unit of the security circuit and its own data. If so, it will perform a master-slave switch and perform security isolation.

[0067] When the safety circuit receives a safety analog signal, the safety analog signal can be converted into a digital signal by the conversion unit and sent to the central processing unit of the safety circuit. The central processing unit of the safety circuit then sends the signal to other modules.

[0068] The conversion unit can include a digital-to-analog (D / A) conversion unit and an analog-to-digital (A / D) conversion unit. Specifically, the D / A conversion unit is mainly used to convert the output digital quantity into an analog quantity; the A / D conversion unit converts the input analog quantity into a digital quantity.

[0069] Alternatively, in some embodiments, the same applies. Figure 3 As shown, the safety circuit also includes a diagnostic unit for diagnosing whether the safety circuit meets safety requirements.

[0070] The second power supply unit is also used to power the diagnostic unit.

[0071] In practical applications, the central processing unit in the safety circuit also periodically outputs a sequence. This sequence is then sampled by the diagnostic unit to check if it matches the expected sequence, thereby determining whether a fault has occurred and diagnosing whether the safety circuit meets safety requirements. If a fault is found, the safety requirements are not met; otherwise, they are met.

[0072] In addition, the diagnostic unit is also used to perform other conventional safety requirement determination functions in the safety instrumented system to ensure that the safety instrumented system can be used while meeting safety requirements.

[0073] It should be noted that the diagnostic unit can enhance the safety performance of the safety instrumented system and make the system operation more reliable.

[0074] It is understandable that the central processing unit of the safety circuit and the central processing unit of the HART circuit communicate non-safety data only through SPI; the power domains are different and the signals are isolated, so there is no potential risk that directly affects the safety function; the safety circuit can take cutting-off and isolation measures based on the fault transmission information of the HART circuit to prevent the fault from spreading and protect the integrity and safety of the system; and use its own central processing unit to determine the cause of the fault, thereby improving the reliability of the system.

[0075] It should also be noted that the controller 101 in this application may be the upper-level processor of the central processing unit of the safety circuit, the host computer, etc.; this application does not limit it, and all of them are within the protection scope of this application.

[0076] Based on the above principles, the safety instrumented system provided in this embodiment includes: a controller 101, a primary working module 102, and a backup working module 103. Both the primary working module 102 and the backup working module 103 include a safety circuit and a HART circuit. The channel selection switch unit in the HART circuit has signal transmission channels corresponding to the number of transmission paths required by the safety circuit. The on / off state of each signal transmission channel is controlled by the selection switch. The primary working module 102 and the backup working module 103 exchange data through the central processing unit in their respective safety circuits. The safety circuits and HART circuits are independently powered. The controller 101 is communicatively connected to both the primary working module 102 and the backup working module 103. When the primary working module 102 fails, the controller switches to the backup working module 103 for operation. Through redundant configuration of the working modules and independent power supply to the safety circuits and HART circuits in each working module, the system solves the problem that the failure of the HART circuit in the safety instrumented system can easily affect the operating safety functions, leading to a shutdown.

[0077] Optionally, please see Figure 3 In another safety instrumented system provided in this application, the signal input / output ports of the safety circuit and / or the signal input / output ports of the HART circuit are further provided with EMC (Electromagnetic Compatibility) protection unit circuits. In the figure, the signal input / output represents the signal input / output ports of the safety circuit and the signal input / output ports of the HART circuit.

[0078] like Figure 6 As shown, the EMC protection unit circuit mainly includes: a diode (diode 1 in the figure), a first capacitor (capacitor 3 in the figure), and a first resistor (resistor 4 in the figure).

[0079] One end of the diode is connected to the signal input / output port, and the other end of the diode is connected to one end of the first capacitor and one end of the first resistor, respectively, with the connection point connected to the signal ground; the other end of the first capacitor and the other end of the first resistor are connected, with the connection point connected to the protective ground.

[0080] In practical applications, in order to enable the safety instrumented system to meet EMC requirements and achieve error-free transmission at 1200Hz and 2200Hz under 4-20mA, EMC protection unit circuits can be set at the signal input / output ports of the safety circuit of the safety instrumented system and / or the signal input / output ports of the HART circuit.

[0081] It should be noted that the diode can be a TVS diode (transient voltage suppressor), connected in parallel with the protected circuit to suppress transient pulses; the first capacitor and the first resistor can form a discharge circuit, which can quickly discharge during EMC impacts to protect HART signals and safety signals.

[0082] It should also be noted that the selection of diodes, the first capacitor, and the first resistor parameters must meet the requirements of the safety level for electrostatic discharge, burst pulses, and surges, thereby reducing the risk to the safety circuit caused by EMC issues of HART signals.

[0083] In this embodiment, by setting EMC protection unit circuits at the signal input / output ports of the safety circuit of the safety instrumented system and / or the signal input / output ports of the HART circuit, electromagnetic compatibility protection functions can be realized, meeting the EMC level for safety applications. It can still ensure error-free transmission at 1200Hz and 2200Hz under 4-20mA, with strong anti-interference capabilities, further improving the reliability and safety of the safety instrumented system.

[0084] In summary, the safety instrumented system provided in this application can be improved through HART circuits and safety circuits, thus filling the gaps in fault avoidance in existing safety applications of safety instrumented systems. Specifically, this can be manifested in the following aspects:

[0085] 1. It meets the EMC level for safe applications and can still guarantee error-free transmission at 1200Hz and 2200Hz under 4-20mA, with strong anti-interference capability.

[0086] 2. The failure of a single component in a HART circuit has no impact on safety functions.

[0087] 3. Channels are separated and processed in parallel to ensure that the modulation and demodulation processes do not interfere with each other.

[0088] 4. The HART signal follows the primary / backup switching of the safety circuit to ensure data reliability.

[0089] 5. The power supplies for the HART circuit and the safety circuit are independent to prevent the spread of faults.

[0090] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0091] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0092] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0093] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A safety instrumented system, characterized in that, include: Controller, main working module and backup working module; Both the primary working module and the backup working module include a safety circuit and a HART circuit. The channel selection switch unit in the HART circuit is provided with a signal transmission channel corresponding to the number of transmission paths required by the safety circuit. The on / off state of each signal transmission channel is controlled by a selection switch. The primary working module and the backup working module exchange data through the central processing unit in their respective security circuits. The security circuits and the HART circuits are powered independently. The controller is communicatively connected to both the primary working module and the backup working module, and switches to the backup working module to operate when the primary working module fails.

2. The safety instrumented system according to claim 1, characterized in that, The signal input / output ports of the safety circuit and / or the signal input / output ports of the HART circuit are further provided with EMC protection unit circuits.

3. The safety instrumented system according to claim 2, characterized in that, The EMC protection unit circuit includes: a diode, a first capacitor, and a first resistor; One end of the diode is connected to the signal input / output port, and the other end of the diode is connected to one end of the first capacitor and one end of the first resistor, respectively, with the connection point connected to signal ground; The other end of the first capacitor is connected to the other end of the first resistor, and the connection point is connected to the protective ground.

4. The safety instrumented system according to claim 1, characterized in that, The HART circuit includes: a signal coupling unit, a channel selection switch unit, a modulation and demodulation unit, a first power supply unit, and a central processing unit of the HART circuit; The first power supply unit is used to supply power to the signal coupling unit, the channel selection switch unit, the modulation and demodulation unit, and the central processing unit of the HART circuit.

5. The safety instrumented system according to claim 4, characterized in that, The signal coupling unit includes: a second capacitor, a third capacitor, a second resistor, a third resistor, and a fourth resistor; One end of the second capacitor serves as the input terminal of the signal coupling unit and is connected to the signal input / output port of the HART circuit; the other end of the second capacitor is connected to one end of the second resistor through the third capacitor, and the other end of the second resistor is connected to one end of the third resistor and one end of the fourth resistor respectively, with the connection point serving as the output terminal of the signal coupling unit.

6. The safety instrumented system according to claim 4, characterized in that, The central processing unit of the HART circuit is used to receive control commands sent by the central processing unit in the security circuit, control the operation of the selection switch in its own channel selection switch unit according to the control commands, and report the current status of the HART circuit to the central processing unit in the security circuit. The controller is used to determine whether the working module of the safety circuit and the HART circuit in the working module are faulty based on the data of the central processing unit in the safety circuit, and to generate a fault alarm when the determination result is that a fault has occurred.

7. The safety instrumented system according to claim 6, characterized in that, The control commands include signal transmission commands and fault commands; The central processing unit in the HART circuit is used to control the gating switch to enable the corresponding transmission channel according to the signal transmission command. The central processing unit in the HART circuit is used to control the gating switch to shut down the corresponding transmission channel according to the fault command.

8. The safety instrumented system according to claim 1, characterized in that, The safety circuit includes: a conversion unit, a second power supply unit, and a central processing unit of the safety circuit; The second power supply unit is used to supply power to the central processing unit of the conversion unit and the safety circuit.

9. The safety instrumented system according to claim 8, characterized in that, The safety circuit further includes a diagnostic unit for diagnosing whether the safety circuit meets safety requirements. The second power supply unit is also used to supply power to the diagnostic unit.

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