Two-wire system resistance acquisition circuit capable of realizing self-detection

Abstract

The invention provides a two-wire system resistance acquisition circuit capable of realizing self-detection, which belongs to the technical field of circuit detection, and specifically comprises a power supply, a first resistor, a second resistor, an operational amplifier circuit, a first state change-over switch and a second state change-over switch, the other end of the first resistor is connected with one end of the second resistor through the second state change-over switch, connected with one end of the resistor to be measured through the first state change-over switch and connected with the inverted input end of the operational amplifier circuit, and the other end of the resistor to be measured is connected with the normal phase input end of the operational amplifier circuit. The other end of the second resistor is grounded. Through the processing scheme provided by the invention, the fault can be isolated during fault self-inspection, the fault is prevented from further diffusion, the reliability and safety of the product are greatly improved, and the safety of the electromechanical system is further improved.

Description

Technical Field

[0001] The present application relates to the technical field of self-detection circuits, and in particular to a two-wire resistance acquisition circuit capable of realizing self-detection. Background Art

[0002] In the field of aviation, in order to achieve the reliability and testability of the system, the common method is to add self-test functions to various functional circuits of the airborne computer. It is generally divided into power-on self-test: that is, at the beginning of the product power-on, the various functions of the product are self-tested and the status is reported; periodic self-test: refers to the periodic self-test and status reporting during the operation of the product; maintenance self-test: refers to the period when the airborne equipment is on the ground, through the manual issuance of maintenance instructions, the product performs the corresponding self-test action and reports the status. Through this method, the failure of important functions that affect flight safety is monitored and displayed. The airborne electromechanical control system contains a large number of analog, discrete, bus and other signals. In order to realize the monitoring of the functional status of the airborne electromechanical computer, the self-test function will be considered in the circuit design. For important and critical electromechanical signals, the circuit's own function is tested to ensure that the faults of the airborne computer interfaces can be exposed in time.

[0003] However, the self-detection in the existing airborne mechatronic system interface circuits requires the help of an external excitation source, and is unable to effectively distinguish whether the fault is an external fault or an internal fault in the circuit itself and isolate the fault. Once an interface fails, the fault may spread, endangering the safety of the mechatronic system and, in severe cases, affecting flight safety. Summary of the invention

[0004] In view of this, an embodiment of the present application provides a two-wire resistance acquisition circuit capable of realizing self-detection, which is used to improve the testability and reliability of an onboard computer.

[0005] An embodiment of the present application provides a two-wire resistance acquisition circuit that can realize self-detection. The two-wire resistance acquisition circuit includes a power supply, a first resistor, a second resistor, an operational amplifier circuit, a first state conversion switch and a second state conversion switch. One end of the first resistor is connected to the power supply, and the other end of the first resistor is respectively connected to one end of the second resistor through the second state conversion switch, connected to one end of the resistor to be measured through the first state conversion switch, and connected to the inverting input end of the operational amplifier circuit. The other end of the resistor to be measured is connected to the non-phase input end of the operational amplifier circuit, and the other end of the second resistor is grounded.

[0006] According to a specific implementation method of an embodiment of the present application, the operational amplifier circuit includes a third resistor, a fourth resistor and a comparator, the inverting input terminal of the comparator is connected to the other end of the first resistor through the third resistor, the non-inverting input terminal of the comparator is connected to the other end of the resistor to be measured, the positive power supply terminal of the comparator is connected to the power supply, and the fourth resistor is connected between the output terminal and the inverting input terminal of the comparator.

[0007] According to a specific implementation method of an embodiment of the present application, the two-wire resistance acquisition circuit is provided with a resistance acquisition mode and a self-detection mode. When in the resistance acquisition mode, the first state conversion switch is closed and the second state conversion switch is opened; when in the self-detection mode, by switching the first state conversion switch and the second state conversion switch states, and then comparing the changes in the output voltage of the operational amplifier circuit, it is determined whether the two-wire resistance acquisition circuit has a fault.

[0008] According to a specific implementation of the embodiment of the present application, assuming that the resistance of the first resistor is R1, the resistance of the second resistor is R2, the resistance of the third resistor is R3, the resistance of the fourth resistor is R4, and the power supply voltage is VCC, the voltage at the intersection of the first resistor and the first state conversion switch and the second state conversion switch is V R , then in the resistance acquisition mode, the resistance value of the resistor to be measured is R L The calculation formula is:

[0009]

[0010] According to a specific implementation of the embodiment of the present application, judging whether the two-wire resistance acquisition circuit has a fault by the change of the output voltage of the operational amplifier circuit in the self-detection mode includes:

[0011] Set the circuit voltage state to the first self-test state when the first state conversion switch is closed, set the circuit voltage state to the second self-test state when the first state conversion switch and the second state conversion switch are closed at the same time, and set the output voltage of the operational amplifier circuit to V L ;

[0012] When the operational amplifier circuit passes the first self-test state, the output voltage V L With voltage V R The change of the operational amplifier circuit output voltage V L With voltage V R Based on the changes in , it is comprehensively judged whether the two-wire resistance acquisition circuit has a fault.

[0013] According to a specific implementation of the embodiment of the present application, when the operational amplifier circuit passes the first self-test state, the output voltage V L With voltage V RThe change of the operational amplifier circuit output voltage V L With voltage V R The change of , comprehensively judges whether the two-wire resistance acquisition circuit has a fault, including:

[0014] When the first self-test state V L =-R4 / R3*V R , keep the second state conversion switch unchanged, close the first state conversion switch, at this time if 0<V R <VCC, there is no electrical fault inside or outside the circuit, and the resistance acquisition circuit passes the self-test, then the second state conversion switch is disconnected and the resistance acquisition mode is entered. L The calculation formula is used for resistance acquisition;

[0015] When the first self-test state V L =-R4 / R3*V R , keep the second state conversion switch unchanged, close the first state conversion switch, at this time if V L =0, then the fault mode is an external interface short circuit fault, the first state conversion switch is disconnected, and the fault state is reported;

[0016] When the first self-test state V L =-R4 / R3*V R , keep the second state conversion switch unchanged, close the first state conversion switch, at this time if V L =VCC, then the fault mode is that the impedance of the external interface circuit increases abnormally, the first state conversion switch is disconnected, and the fault state is reported;

[0017] When the first self-test state V L =0, at this time, the circuit failure mode is the failure of the VCC pull-up power supply VCC in the internal interface failure, the first resistor is open circuit, the second resistor is short circuit or the operational amplifier circuit fails, the first state conversion switch is turned off, and the fault state is reported;

[0018] When the first self-test state V L >-R4 / R3*V R And V L = VCC, keep the second state switch unchanged, close the first state switch, at this time if V L ≈-R4 / R3*V R , the circuit fault mode is that the second resistance in the internal interface fault increases abnormally, the first state conversion switch is disconnected, and the fault state is reported;

[0019] When the first self-test state V L>-R4 / R3*V R And V L = VCC, keep the second state switch unchanged, close the first state switch, if the second self-test state is still V L >-R4 / R3*V R , the circuit failure mode is the short circuit failure of the first resistor of the internal interface failure or the operational amplifier circuit failure, the first state conversion switch is disconnected, and the fault state is reported;

[0020] When 0<V L <-R4 / R3*V R , keep the second state conversion switch unchanged, close the first state conversion switch, at this time if the second self-test state is still 0<V L <-R4 / R3*V R , the circuit failure mode is an operational amplifier circuit failure of an internal interface failure, a second resistor drifting smaller or a first resistor drifting larger, the first state conversion switch is disconnected, and the fault state is reported;

[0021] When VCC>V L >-R4 / R3*V R , keep the second state conversion switch unchanged, close the first state conversion switch, at this time if the second self-test state is still VCC>V L >-R4 / R3*V R , the circuit failure mode is an operational amplifier circuit failure of an internal interface failure, the second resistance value drift increases or the first resistance value drift decreases, the first state conversion switch is disconnected, and the fault state is reported.

[0022] Beneficial effects:

[0023] The two-wire resistance acquisition circuit capable of realizing self-detection in the embodiment of the present application uses a state conversion switch to switch the state of the acquisition circuit. When the switch state is switched, the acquisition circuit is disconnected from the external interface. At this time, V R Voltage and V L The voltage is compared, and the interface self-test result is judged and reported through the corresponding software strategy. If the self-test passes, the resistance acquisition mode can be entered. This resistance acquisition circuit and strategy can be used in an airborne environment to isolate the fault when the self-test fails, preventing the fault from spreading further, greatly improving product reliability and safety, and further improving the safety of the electromechanical system. In the ground fault troubleshooting scenario, by measuring V L 、V R The voltage status can quickly identify the fault location, greatly improving product testability and user protection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A schematic diagram of a two-wire resistance acquisition circuit capable of realizing self-detection according to an embodiment of the present invention;

[0026] Figure 2 is an equivalent circuit diagram when the S1 switch is closed and the S2 switch is opened according to an embodiment of the present invention;

[0027] Figure 3 is an equivalent circuit diagram when the S1 switch is opened and the S2 switch is closed according to an embodiment of the present invention;

[0028] Figure 4 is an equivalent circuit diagram when the S1 switch and the S2 switch are both closed according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0030] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0031] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0032] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show the components related to the present application rather than being drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed at will, and the component layout may also be more complicated.

[0033] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0034] The present application embodiment provides a two-wire resistance acquisition circuit capable of realizing self-detection. Figures 1 to 4 Describe in detail.

[0035] In one embodiment, referring to Figure 1 The two-wire resistance acquisition circuit includes a power supply VCC, a first resistor R1, a second resistor R2, an operational amplifier circuit, a first state conversion switch S1 and a second state conversion switch S2. One end of the first resistor R1 is connected to the power supply VCC, and the other end of the first resistor R1 is connected to one end of the second resistor R2 through the second state conversion switch S2, connected to one end of the resistor to be measured RL through the first state conversion switch S1, and connected to the inverting input end of the operational amplifier circuit. The other end of the resistor to be measured RL is connected to the non-inverting input end of the operational amplifier circuit, and the other end of the second resistor R2 is grounded.

[0036] Furthermore, the operational amplifier circuit includes a third resistor R3, a fourth resistor R4 and a comparator, the inverting input terminal of the comparator is connected to the other end of the first resistor R1 through the third resistor R3, the non-inverting input terminal of the comparator is connected to the other end of the resistor to be measured RL, the positive power supply terminal of the comparator is connected to the power supply VCC, and the fourth resistor R4 is connected between the output terminal and the inverting input terminal of the comparator.

[0037] In this embodiment, a power supply (VCC) is used at the front end to pull up and power the operational amplifier; a state conversion switch (S1, S2) is added to realize the switching between the normal acquisition mode and the self-detection mode; an operational amplifier circuit is used for resistance acquisition operation, and this strategy does not require an additional excitation source to be introduced into the circuit to realize self-detection; after the self-detection finds a fault, this strategy can effectively distinguish between internal and external faults, isolate the fault location, ensure the safety of each device, and distinguish different fault states according to different collected electrical signals. Therefore, this embodiment can complete the self-detection of the acquisition circuit by switching its own state switch without the help of an external excitation source of the circuit, and the self-detection strategy can distinguish between external faults or internal faults, and effectively isolate the fault to ensure the safety of airborne equipment. The application of this strategy can not only improve the reliability of airborne electromechanical products, but also report the fault status through the onboard bus through software cooperation; at the same time, this strategy has the effect of making the interface highly testable, greatly improving the efficiency of interface fault troubleshooting, and the troubleshooting personnel only need to measure the VL and VR voltages and compare them to locate the interface fault location.

[0038] In a specific implementation, the two-wire resistance acquisition circuit is provided with a resistance acquisition mode and a self-detection mode. When in the resistance acquisition mode, the first state conversion switch S1 is closed and the second state conversion switch S2 is opened; when in the self-detection mode, by switching the states of the first state conversion switch and the second state conversion switch, and then comparing the changes in the output voltage of the operational amplifier circuit, it is determined whether the two-wire resistance acquisition circuit has a fault.

[0039] Further, assuming that the resistance of the first resistor R1 is R1, the resistance of the second resistor R2 is R2, the resistance of the third resistor R3 is R3, the resistance of the fourth resistor R4 is R4, and the power supply VCC voltage is VCC, the voltage at the intersection of the first resistor R1 and the first state conversion switch S1 and the second state conversion switch S2 is V R , then in the resistance acquisition mode, the resistance value of the resistor to be measured RL is R L The calculation formula is:

[0040]

[0041] When the circuit performs resistance acquisition normally, its first state conversion switch S1 is closed, and the second state conversion switch S2 is open. Its equivalent circuit is shown in the attached figure. Figure 2 As shown, VCC, R1, R3, R4, V L is a known value, and the RL resistance value to be measured can be calculated by the above formula. The control state conversion switches S1 and S2 are activated to perform interface self-test and classified reporting. When the S1 switch is closed, the circuit voltage state is called the first self-test state, and when the S1 and S2 switches are closed at the same time, the circuit voltage state is called the second self-test state.

[0042] In one embodiment, judging whether the two-wire resistance acquisition circuit has a fault by the change of the output voltage of the operational amplifier circuit in the self-detection mode includes the following steps:

[0043] Set the circuit voltage state to the first self-test state when the first state conversion switch S1 is closed, set the circuit voltage state to the second self-test state when the first state conversion switch S1 and the second state conversion switch S2 are closed at the same time, and set the output voltage of the operational amplifier circuit to V L ;

[0044] When the operational amplifier circuit passes the first self-test state, the output voltage V L With voltage V R The change of the operational amplifier circuit output voltage V L With voltage V R Based on the changes in , it is comprehensively judged whether the two-wire resistance acquisition circuit has a fault.

[0045] In the specific implementation, the first state conversion switch S1 is opened and S2 is closed to enter the interface self-detection mode. At this time, the equivalent circuit is as shown in the attached figure. Figure 3 As shown, VCC, R1, R2, R3, R4, V R is a known value, and the output voltage V L Specifically, when the operational amplifier circuit outputs a voltage V L With voltage V R The change of the operational amplifier circuit output voltage V L With voltage V R The change of , comprehensively judges whether the two-wire resistance acquisition circuit has a fault, including:

[0046] When the first self-test state V L =-R4 / R3*V R , keep the second state conversion switch S2 unchanged, close the first state conversion switch S1, at this time if 0<V R <VCC, there is no electrical fault inside or outside the circuit, and the resistance acquisition circuit passes the self-test, then the second state conversion switch S2 is disconnected, and the resistance acquisition mode is entered. L The calculation formula is used for resistance acquisition;

[0047] When the first self-test state V L =-R4 / R3*V R , keep the second state conversion switch S2 unchanged, close the first state conversion switch S1, its equivalent circuit is as shown in the attached figure Figure 4 As shown, if VL =0, then the fault mode is an external interface short circuit fault, the first state conversion switch S1 is disconnected to protect its own internal interface, and the fault state 1 is reported;

[0048] When the first self-test state V L =-R4 / R3*V R , keep the second state conversion switch S2 unchanged, close the first state conversion switch S1, at this time if V L =VCC, then the fault mode is that the impedance of the external interface circuit increases abnormally, the first state conversion switch S1 is disconnected to protect the internal interface of the product itself, and the fault state 2 is reported;

[0049] When the first self-test state V L =0, at this time, the circuit failure mode is the failure of the VCC pull-up power supply VCC in the internal interface failure, the first resistor R1 is open, the second resistor R2 is short-circuited or the operational amplifier circuit fails, the first state conversion switch S1 is turned off to protect the external device, and the fault state 3 is reported;

[0050] When the first self-test state V L >-R4 / R3*V R And V L = VCC, keep the second state conversion switch S2 unchanged, close the first state conversion switch S1, at this time if V L ≈-R4 / R3*V R , the circuit fault mode is that the second resistor R2 in the internal interface fault increases abnormally, the first state conversion switch S1 is disconnected to protect the external device, and the fault state 4 is reported;

[0051] When the first self-test state V L >-R4 / R3*V R And V L = VCC, keep the second state conversion switch S2 unchanged, close the first state conversion switch S1, at this time if the second self-test state is still V L >-R4 / R3*V R , the circuit failure mode is that the first resistor R1 of the internal interface failure is short-circuited or the operational amplifier circuit fails, the first state conversion switch S1 is disconnected to protect the external device to protect the external device, and the fault state 5 is reported;

[0052] When 0<V L <-R4 / R3*V R , keep the second state conversion switch S2 unchanged, close the first state conversion switch S1, at this time if the second self-test state is still 0<V L <-R4 / R3*V R, the circuit failure mode is an operational amplifier circuit failure of an internal interface failure, the second resistor R2 resistance drifts smaller or the first resistor R1 resistance drifts larger, the first state conversion switch S1 is disconnected to protect the external device, and the fault state 6 is reported;

[0053] When VCC>V L >-R4 / R3*V R , keep the second state conversion switch S2 unchanged, close the first state conversion switch S1, at this time if the second self-test state is still VCC>V L >-R4 / R3*V R , the circuit failure mode is an operational amplifier circuit failure of an internal interface failure, the second resistance drift increases or the first resistance drift decreases, the first state conversion switch S1 is disconnected to protect the external device, and the fault state 7 is reported.

[0054] The fault status table is shown in Table 1.

[0055] Table 1 Fault status table

[0056]

[0057]

[0058] The embodiment provided by the present invention adopts the self-detection strategy of the two-wire resistance acquisition circuit proposed in this article, which can complete the self-detection of the acquisition circuit by switching its own state switch without the help of an external excitation source of the circuit, and the self-detection strategy can distinguish between external faults and internal faults, effectively isolating the fault to ensure the safety of airborne equipment. The application of this strategy can not only improve the reliability of airborne electromechanical products, but also report the fault status through the onboard bus through software cooperation; at the same time, this strategy has the effect of making the interface highly testable, greatly improving the efficiency of interface fault troubleshooting, and the troubleshooting personnel only need to measure V L 、V R By measuring and comparing the voltages, the faulty part of the interface can be located.

[0059] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A two-wire resistance acquisition circuit capable of realizing self-detection, characterized in that: The two-wire resistance acquisition circuit includes a power supply, a first resistor, a second resistor, an operational amplifier circuit, a first state conversion switch and a second state conversion switch. One end of the first resistor is connected to the power supply, and the other end of the first resistor is respectively connected to one end of the second resistor through the second state conversion switch, connected to one end of the resistor to be measured through the first state conversion switch, and connected to the inverting input end of the operational amplifier circuit. The other end of the resistor to be measured is connected to the non-phase input end of the operational amplifier circuit, and the other end of the second resistor is grounded.

2. The two-wire resistance acquisition circuit capable of realizing self-detection according to claim 1, characterized in that: The operational amplifier circuit includes a third resistor, a fourth resistor and a comparator, the inverting input terminal of the comparator is connected to the other end of the first resistor through the third resistor, the non-inverting input terminal of the comparator is connected to the other end of the resistor to be measured, the positive power supply terminal of the comparator is connected to the power supply, and the fourth resistor is connected between the output terminal and the inverting input terminal of the comparator.

3. The two-wire resistance acquisition circuit capable of realizing self-detection according to claim 2, characterized in that: The two-wire resistance acquisition circuit is provided with a resistance acquisition mode and a self-detection mode. When in the resistance acquisition mode, the first state conversion switch is closed and the second state conversion switch is opened; when in the self-detection mode, by switching the states of the first state conversion switch and the second state conversion switch, and then comparing the changes in the output voltage of the operational amplifier circuit, it is determined whether the two-wire resistance acquisition circuit has a fault.

4. The two-wire resistance acquisition circuit capable of realizing self-detection according to claim 3 is characterized in that The resistance of the first resistor is R1, the resistance of the second resistor is R2, the resistance of the third resistor is R3, the resistance of the fourth resistor is R4, and the power supply voltage is VCC. The voltage at the intersection of the first resistor, the first state conversion switch, and the second state conversion switch is V R , then in the resistance acquisition mode, the resistance value of the resistor to be measured is R L The calculation formula is:

5. The two-wire resistance acquisition circuit capable of realizing self-detection according to claim 4, characterized in that: The method of judging whether the two-wire resistance acquisition circuit has a fault by the change of the output voltage of the operational amplifier circuit in the self-detection mode includes: Set the circuit voltage state to the first self-test state when the first state conversion switch is closed, set the circuit voltage state to the second self-test state when the first state conversion switch and the second state conversion switch are closed at the same time, and set the output voltage of the operational amplifier circuit to V L ; When the operational amplifier circuit passes the first self-test state, the output voltage V L With voltage V R The change of the operational amplifier circuit output voltage V L With voltage V R Based on the changes in , it is comprehensively judged whether the two-wire resistance acquisition circuit has a fault.

6. The two-wire resistance acquisition circuit capable of realizing self-detection according to claim 5, characterized in that: When the operational amplifier circuit passes the first self-test state, the output voltage V L With voltage V R The change of the operational amplifier circuit output voltage V L With voltage V R The change of , comprehensively judges whether the two-wire resistance acquisition circuit has a fault, including: When the first self-test state V L =-R4 / R3*V R , keep the second state conversion switch unchanged, close the first state conversion switch, at this time if 0<V R <VCC, there is no electrical fault inside or outside the circuit, and the resistance acquisition circuit passes the self-test, then the second state conversion switch is disconnected and the resistance acquisition mode is entered. L The calculation formula is used for resistance acquisition; When the first self-test state V L =-R4 / R3*V R , keep the second state conversion switch unchanged, close the first state conversion switch, at this time if V L =0, then the fault mode is an external interface short circuit fault, the first state conversion switch is disconnected, and the fault state is reported; When the first self-test state V L =-R4 / R3*V R , keep the second state conversion switch unchanged, close the first state conversion switch, at this time if V L =VCC, then the fault mode is that the impedance of the external interface circuit increases abnormally, the first state conversion switch is disconnected, and the fault state is reported; When the first self-test state V L =0, at this time, the circuit failure mode is the failure of the VCC pull-up power supply VCC in the internal interface failure, the first resistor is open, the second resistor is short-circuited, or the operational amplifier circuit fails, the first state conversion switch is turned off, and the fault state is reported; When the first self-test state V L >-R4 / R3*V R And V L = VCC, keep the second state switch unchanged, close the first state switch, at this time if V L ≈-R4 / R3*V R , the circuit fault mode is that the second resistance in the internal interface fault increases abnormally, the first state conversion switch is disconnected, and the fault state is reported; When the first self-test state V L >-R4 / R3*V R And V L = VCC, keep the second state switch unchanged, close the first state switch, if the second self-test state is still V L >-R4 / R3*V R , the circuit failure mode is the short circuit failure of the first resistor of the internal interface failure or the operational amplifier circuit failure, the first state conversion switch is disconnected, and the fault state is reported; When 0<V L <-R4 / R3*V R , keep the second state conversion switch unchanged, close the first state conversion switch, at this time if the second self-test state is still 0<V L <-R4 / R3*V R , the circuit failure mode is an operational amplifier circuit failure of an internal interface failure, a second resistor drifting smaller or a first resistor drifting larger, the first state conversion switch is disconnected, and the fault state is reported; When VCC>V L >-R4 / R3*V R , keep the second state conversion switch unchanged, close the first state conversion switch, at this time if the second self-test state is still VCC>V L >-R4 / R3*V R , the circuit failure mode is an operational amplifier circuit failure of an internal interface failure, the second resistance value drift increases or the first resistance value drift decreases, the first state conversion switch is disconnected, and the fault state is reported.

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