Sensor circuit, sensor and sensor fault detection method

Abstract

The invention discloses a sensor circuit, a sensor and a sensor fault detection method, relates to the technical field of power electronics, and realizes sensor fault detection. The sensor circuit comprises a bridge circuit, an instrument amplifying circuit, a first current-limiting resistor and a control unit, the input end positive electrode of the bridge circuit is electrically connected with a power supply, and the input end negative electrode of the bridge circuit is grounded through the first current-limiting resistor; the output end of the bridge circuit is electrically connected with the input end of the instrument amplification circuit; and the output end of the instrument amplification circuit and the negative electrode of the input end of the bridge circuit are electrically connected with the control unit.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and more specifically, to a sensor circuit, a sensor, and a sensor fault detection method. Background Technology

[0002] Sensor malfunction is a common problem, making fault detection essential before putting sensors into use. Take gas sensors as an example: gas leaks are dangerous safety incidents, and gas sensors can detect leaks and issue alarms promptly. However, if the gas sensor itself malfunctions during a leak, it will be unable to trigger an alarm. Therefore, pre-emptive fault detection of gas sensors is crucial. Summary of the Invention

[0003] In view of this, the present invention provides a sensor circuit, a sensor, and a sensor fault detection method to achieve sensor fault detection.

[0004] A sensor circuit includes: a bridge circuit, an instrumentation amplifier circuit, a current-limiting resistor R8, and a control unit;

[0005] The positive input terminal of the bridge circuit is used to connect to the power supply, the negative input terminal of the bridge circuit is connected to one end of the current limiting resistor R8, and the other end of the current limiting resistor R8 is connected to ground.

[0006] The output terminal of the bridge circuit is electrically connected to the input terminal of the instrumentation amplifier circuit; the output terminal of the instrumentation amplifier circuit and the negative terminal of the input terminal of the bridge circuit are both electrically connected to the control unit.

[0007] The sensor circuit includes a bridge circuit, an instrumentation amplifier circuit, a current-limiting resistor R8, and a control unit. The output terminal of the instrumentation amplifier circuit and the negative terminal of the input terminal of the bridge circuit are both electrically connected to the control unit, enabling the output of data required for sensor fault detection to the control unit, thereby realizing sensor fault detection.

[0008] A sensor, comprising: the sensor circuit disclosed above.

[0009] The sensor has the aforementioned sensor circuit, and at least the aforementioned sensor circuit can be used to detect sensor faults.

[0010] A sensor fault detection method, wherein the sensor includes a sensor circuit, the sensor circuit including a bridge circuit, an instrumentation amplifier circuit, a current-limiting resistor R8, and a control unit; the method is applied to the control unit, and the method includes:

[0011] Acquire the output voltage of the amplifier circuit and / or the negative input voltage of the bridge circuit;

[0012] The instrument determines whether the output voltage of the amplifier circuit exceeds the first preset range, and / or whether the negative voltage at the input terminal of the bridge circuit exceeds the second preset range.

[0013] When it is determined that the output voltage of the instrumentation amplifier circuit exceeds the first preset range or the negative voltage of the input terminal of the bridge circuit exceeds the second preset range, the sensor is deemed to be faulty.

[0014] This sensor fault detection method obtains the output voltage of the instrumentation amplifier circuit and / or the negative input voltage of the bridge circuit in the sensor circuit through the control unit, and makes a judgment. If the voltage value of at least one electrical node exceeds the normal range, it indicates that the sensor is faulty, thereby realizing the sensor fault detection. Attached Figure Description

[0015] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of a sensor circuit principle disclosed in an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of another sensor circuit principle disclosed in an embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of another sensor circuit principle disclosed in an embodiment of the present invention;

[0019] Figure 4 This is a schematic diagram of another sensor circuit principle disclosed in an embodiment of the present invention;

[0020] Figure 5 This is a schematic diagram of another sensor circuit principle disclosed in an embodiment of the present invention;

[0021] Figure 6 This is a flowchart of a sensor fault detection method disclosed in an embodiment of the present invention. Detailed Implementation

[0022] A sensor is a device that can sense a specified measurand and convert it into a usable output signal according to a certain rule. Based on the type of measurand, sensors can be divided into gas sensors, temperature sensors, etc. A gas sensor is a sensor that can detect the presence and concentration of a specific gas and convert it into a usable output signal. A temperature sensor is a sensor that can sense temperature and convert it into a usable output signal.

[0023] With the development of technology, sensors have become an indispensable part of modern industry and technology. However, sensor failure is also a common problem, significantly impacting the normal operation of equipment and / or the personal safety of personnel. Therefore, timely detection and resolution of sensor failures has become an important task for many engineers and technicians.

[0024] Taking gas sensors as an example: Large quantities of gases are generated during industrial production processes such as chemical, pharmaceutical, and petroleum manufacturing, including toxic and harmful gases (such as chlorine and acid mist) and flammable and explosive gases (such as methane, acetylene, and hydrogen). Gas leaks may occur during industrial production, storage, and transportation, such as leaks of toxic and harmful gases or flammable and explosive gases. Gas leaks are dangerous safety accidents. Gas sensors can detect gas leaks in a timely manner and issue alarms. However, in cases where a gas leak has already occurred, if the gas sensor itself malfunctions, it will not be able to issue an alarm. Therefore, it is essential to perform fault detection on the sensor before it is put into use.

[0025] The sensor circuit is the core component of a sensor. To achieve sensor fault detection, this invention discloses a sensor circuit that can not only perform the basic functions of a traditional sensor circuit (i.e., sense the specified measurand and convert it into a usable output signal according to a certain rule), but also provide data support to the control unit for fault detection (i.e., provide the control unit with the data required for sensor fault detection to assist the control unit in completing the sensor fault detection work).

[0026] 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.

[0027] In the embodiments of this invention, the term "and / or" describes the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0028] See Figure 1 The sensor circuit disclosed in this embodiment of the invention includes: a bridge circuit 100, an instrumentation amplifier circuit 200, a first current-limiting resistor R8, and a control unit;

[0029] The positive input terminal of the bridge circuit 100 is used to connect to the power supply VCC, and the negative input terminal of the bridge circuit 100 is grounded to GND through the first current-limiting resistor R8. The bridge circuit 100 has a first bridge arm and a second bridge arm. The upper half of the first bridge arm has a resistor R2 (eighth resistor) and the lower half of the first bridge arm has a resistor R3 (ninth resistor). The upper half of the second bridge arm has a resistor R4 (tenth resistor) and the lower half of the second bridge arm has a resistor R7 (eleventh resistor). The bridge circuit 100 is the probe of the sensor circuit. When the measured quantity changes, the resistance values ​​of the eighth resistor R2 and the ninth resistor R3 inside the bridge circuit 100 will change accordingly.

[0030] The output terminal of the bridge circuit 100 is electrically connected to the input terminal of the instrumentation amplifier circuit 200. The instrumentation amplifier circuit 200 is used to amplify the difference signal and effectively remove the interference of the common-mode signal. The difference signal is the difference between the output voltages of the two arms of the bridge circuit 100. The output terminal of the instrumentation amplifier circuit 200 and the negative terminal of the input terminal of the bridge circuit 100 are both connected to the control unit, and the data required for sensor fault detection is output to the control unit, thereby realizing the sensor fault detection.

[0031] See also Figure 1 In one embodiment, the eighth resistor R2 and the ninth resistor R3 in the bridge circuit 100 are both thermistors, and the tenth resistor R4 and the eleventh resistor R7 are both fixed resistors. Below, using this sensor circuit with thermistors as an example, [the following section discusses...]. Figure 1 The working principle of the sensor circuit shown is described in detail below:

[0032] Figure 1 When the sensor circuit shown is operating normally, it senses the specified measurand and converts it into a usable output signal according to a certain rule. When the measurand changes, the resistance of the thermistor changes, and consequently, the difference signal output by the bridge circuit 100 also changes. The instrumentation amplifier circuit 200 amplifies this difference signal and outputs it to the control unit. The output voltage Vout of the instrumentation amplifier circuit 200 is the usable output signal. The control unit monitors the measurand in real time based on the magnitude of the voltage Vout. This embodiment uses a parallel voltage divider scheme with a thermistor and a fixed resistor, which can accurately capture minute changes caused by environmental changes and facilitates calibration and adjustment. In one embodiment, this gas sensor can be used to detect whether a leak has occurred in a new type of refrigerant (such as environmentally friendly refrigerants like R32 / R290, which are flammable). Therefore, this gas sensor is suitable for refrigeration equipment using new refrigerants.

[0033] Meanwhile, to achieve sensor fault detection, this embodiment of the invention also outputs the voltage VB at the second terminal of the bridge circuit 100 as another output, which, along with the voltage Vout, is sent to the control unit. The control unit is based on an MCU (Microcontroller Unit) and is equipped with an analog-to-digital converter, etc. Since the electrical parameter values ​​of relevant electrical nodes in the sensor circuit will exceed the normal range when the sensor malfunctions, the electrical parameters (including the output of the instrumentation amplifier circuit 200 and the second terminal of the bridge circuit 100) of several electrical nodes are measured and transmitted to the control unit for judgment. Based on the voltages Vout and VB, the control unit can comprehensively judge the fault state of the sensor. As long as the control unit determines that at least one of the voltages Vout and VB exceeds the normal range, it can determine that the sensor is faulty, thereby realizing sensor fault detection. Of course, the state of either the voltage Vout or the voltage VB alone can also determine whether the sensor is faulty to a certain extent.

[0034] The circuit structure of the present invention is simple, which facilitates wiring design and the testing process is simple, making it easy to promote and apply.

[0035] Figure 1 The sensor circuit shown can be applied to a gas sensor. Its working principle is as follows: The thermistor has different sensitivities to different gases. When the thermistor comes into contact with different gases, its resistance will change, which will in turn change the differential signal output by the bridge circuit 100. Consequently, the output voltage Vout of the instrumentation amplifier circuit 200 will change. The control unit can determine whether a target gas leak has occurred based on the change in Vout.

[0036] Figure 1 The sensor circuit shown can also be applied to temperature sensors. Its working principle is as follows: The resistance of the thermistor is related to the ambient temperature. When the temperature of the environment where the sensor is located changes, the resistance of the thermistor will change, which in turn will change the difference signal output by the bridge circuit 100. Consequently, the output voltage Vout of the instrumentation amplifier circuit 200 will change. The control unit can identify the ambient temperature value based on the change of Vout.

[0037] Based on any of the disclosed embodiments above, please refer to... Figure 1The instrumentation amplifier circuit 200 specifically includes: three operational amplifiers IC1~IC3 (first operational amplifier IC1, second operational amplifier IC2, and third operational amplifier IC3) and seven resistors R9~R15 (first resistor R9, second resistor R10, third resistor R11, fourth resistor R12, fifth resistor R13, sixth resistor R14, and seventh resistor R15); the instrumentation amplifier circuit 200 is a two-stage operational amplifier structure, with IC1 and IC2 as the first-stage operational amplifiers. The non-inverting input terminals of IC1 and IC2 are the two input terminals of the instrumentation amplifier circuit 200. The non-inverting input terminal of IC1 is electrically connected to the output terminal of the second bridge arm of the bridge circuit 100, and the non-inverting input terminal of IC2 is electrically connected to the output terminal of the first bridge arm of the bridge circuit 100. The inverting input terminal of IC1 is electrically connected to the connection point of the second resistor R10 and the first resistor R9. The inverting input terminal of IC2 is electrically connected to the connection point of the second resistor R10 and the first resistor R9. The input terminal is electrically connected to the connection point of the first resistor R9 and the third resistor R11. The other end of the second resistor R10 is simultaneously electrically connected to the output terminal of IC1 and one end of the fourth resistor R12. The other end of the third resistor R11 is simultaneously electrically connected to the output terminal of IC2 and one end of the sixth resistor R14. The other end of the fourth resistor R12 is simultaneously electrically connected to the first input terminal of IC3 and one end of the fifth resistor R13. The other end of the fifth resistor R13 is electrically connected to the output terminal of IC3. The other end of the sixth resistor R14 is simultaneously electrically connected to the second input terminal of IC3 and one end of the seventh resistor R15. The other end of R15 is grounded. IC3 is the second-stage operational amplifier. IC3, the fourth resistor R12, the fifth resistor R13, the sixth resistor R14, and the seventh resistor R15 form a differential amplifier circuit (also known as a differential amplifier circuit). The output terminal of IC3 is the output terminal of the instrumentation amplifier circuit 200.

[0038] The first input terminal of IC3 can be either the non-inverting input terminal or the inverting input terminal of IC3. Figure 1 The former is used as an example only.

[0039] When the first input terminal of IC3 is the non-inverting input terminal of IC3, the second input terminal of IC3 is naturally the inverting input terminal of IC3. Usually, R10=R11, R13=R15 and R12=R14. The current circuit structure of the instrumentation amplifier circuit 200 determines that: the inverting input voltage of IC3 is positively correlated with the first bridge arm output voltage V2 of the bridge circuit 100, and the non-inverting input voltage of IC3 is positively correlated with the second bridge arm output voltage V1 of the bridge circuit 100. When V1>V2, the non-inverting input voltage of IC3>the inverting input voltage of IC3, and the lower limit of the output voltage Vout of IC3>0; when V1≤V2, the non-inverting input voltage of IC3≤the inverting input voltage of IC3, and the lower limit of the output voltage Vout of IC3 is 0.

[0040] When the first input terminal of IC3 is the inverting input terminal of IC3, the second input terminal of IC3 is naturally the non-inverting input terminal of IC3. Usually, R10 = R11, R13 = R15 and R12 = R14. The current circuit structure of the instrumentation amplifier circuit 200 determines that: the non-inverting input voltage of IC3 is positively correlated with the output voltage V2 of the first bridge arm of the bridge circuit 100, and the inverting input voltage of IC3 is positively correlated with the output voltage V1 of the second bridge arm of the bridge circuit 100. When V1 < V2, the non-inverting input voltage of IC3 > the inverting input voltage of IC3, and the lower limit value of the output voltage Vout of IC3 > 0; when V1 ≤ V2, the non-inverting input voltage of IC3 ≥ the inverting input voltage of IC3, and the lower limit value of the output voltage Vout of IC3 is 0.

[0041] Based on any of the above-disclosed embodiments, refer to Figure 2 , a second current-limiting resistor R1 may also be connected between the bridge circuit 100 and the power supply VCC. On this basis, in order to enable the sensor circuit to achieve detection within a wider detection range (such as a wider temperature range), the nominal resistance value of the resistor may be set to satisfy R1 = R8; further, the nominal resistance value of the resistor may be set to satisfy R4 = R7 and R2 = R3. In the case of R1 = R8, R4 = R7 and R2 = R3, when the first input terminal of IC3 is the non-inverting input terminal of IC3, the sensor circuit satisfies:

[0042] According to the circuit voltage division principle, it can be obtained that: V1 = VCC / 2 (1) (2) (3) Combining formula (1) and formula (2), the difference signal V1 - V2 output by the bridge circuit can be obtained as: (4) According to the virtual short characteristic of the operational amplifier, it can be obtained that: V4 = V1, V5 = V2 (5) According to the principle that the current is the same everywhere in a series circuit, it can be obtained that (6) Combining formula (5) and formula (6), it can be obtained that: (7) According to the characteristics of the differential amplifier circuit, it can be obtained that: (8) Combining formula (1), formula (2), formula (6) and formula (7), it can be obtained that: (9)

[0043] As can be seen from the above formula, the values of the voltage Vout and the voltage VB are almost related to all the lines in the sensor circuit. Therefore, by monitoring the states of the voltage Vout and the voltage VB, it is possible to relatively comprehensively determine whether there is a fault in the entire sensor.

[0044] Based on any of the above-disclosed embodiments, considering that when V1 ≤ V2, it may cause deviations in the upper and lower limits of the sampled value of the voltage Vout, which may further cause misjudgment of the sensor fault by the control unit. Therefore, as a recommendation, it is best to ensure that V1 > V2 when designing the parameters of the bridge circuit to raise the lower limit value of the voltage Vout in the normal state of the sensor. The specific analysis is as follows: When V1 ≤ V2, the lower limit of the normal range of the voltage Vout in the normal state of the sensor is zero, and the characteristics of the operational amplifier determine that its output voltage cannot be lower than zero. Therefore, even if the sensor fails and causes the voltage Vout to drop, it is impossible for the voltage Vout to be lower than zero. At this time, the control unit believes that the voltage Vout does not exceed the lower limit of the normal range, and thus fails to identify the sensor fault.

[0045] Among them, the bridge circuit parameter design scheme adopted to ensure V1 > V2 can be: the nominal resistance value of the lower half-bridge arm resistor of the first bridge arm of the bridge circuit is less than or equal to the nominal resistance value of the upper half-bridge arm resistor of the first bridge arm, and the nominal resistance value of the upper half-bridge arm resistor of the second bridge arm of the bridge circuit is less than the nominal resistance value of the lower half-bridge arm resistor of the second bridge arm. For example, it can be based on Figure 2 modified to obtain Figure 3 , when the nominal resistance values satisfy R1 = R8, R4 = R7, and R2 = R3, a twelfth resistor R7_1 much smaller than R7 is connected in series to the original lower half-bridge arm resistor R7 of the second bridge arm. At this time, the new lower half-bridge arm resistor of the second bridge arm is R7 + R7_1, and at this time, V1 > V2 is satisfied.

[0046] Similarly, based on any of the above-disclosed embodiments, when the first input terminal of IC3 is the inverting input terminal of IC3, as a recommendation, it is best to ensure that V1 < V2 when designing the parameters of the bridge circuit. For example, it can be based on Figure 2 modified to obtain Figure 4 , when the nominal resistance values satisfy R1 = R8, R4 = R7, and R2 = R3, a thirteenth resistor R4_1 much smaller than R4 is connected in series to the original upper half-bridge arm resistor R4 of the second bridge arm. At this time, the new upper half-bridge arm resistor of the second bridge arm is R4 + R4_1, and at this time, V1 < V2 is satisfied.

[0047] In any of the above - disclosed embodiments for ensuring V1 > V2 or V1 < V2, when the sensor circuit itself has no fault and is operating normally, theoretically the voltage Vout will be between 0 volts and VCC but will not reach 0 volts and VCC (when V1 and V2 are very close, Vout is slightly greater than 0 volts; when there is a large deviation between V1 and V2, Vout is slightly less than VCC). If Vout is less than 0 volts or greater than Vcc, it indicates that the body has a fault. Considering factors such as component parameter design errors and measurement errors, a certain margin needs to be set. For example, if Vout < 0.2V or Vout > VCC - 0.2, it indicates that the sensor circuit has a fault.

[0048] When the sensor circuit itself has no fault and is operating normally, theoretically the voltage will be between V0 and VCC / 2 but will not reach V0 and VCC / 2. Among them, taking the above - mentioned sensor circuit with a thermistor as an example, the thermistor is a negative temperature coefficient thermistor, and V0 represents the VB voltage value detected when the internal temperature of the negative temperature coefficient thermistor is a certain low temperature (such as 0°C); when the temperature is very high, both the thermistor R2 and R3 are very small, and the total resistance of the bridge circuit is slightly greater than zero. At this time, the voltage across the thermistor R2, that is, VB, is very close to but does not reach VCC / 2. When the detected VB voltage is less than V0, it indicates that the internal temperature of the thermistor is less than 0°C, and this situation does not exist. Therefore, when VB < V0, it indicates that the sensor has a fault. When the detected VB voltage is greater than VCC / 2, it indicates that the temperature of the thermistor is very high and exceeds the normal operating range, and at this time, it indicates that the sensor circuit has a fault. Considering factors such as component parameter design errors and measurement errors, a certain margin needs to be set. For example, when VB < V0 - 0.2V, it indicates that the sensor has a fault; when VB > VCC / 2 - 0.2V, it also indicates that the sensor has a fault.

[0049] The above margin of 0.2V is an empirical value, and the size of this margin can be fine - tuned according to the actual situation.

[0050] Based on any of the above - disclosed embodiments, see Figure 5 , the sensor circuit further includes a first filter circuit and / or a second filter circuit; the first filter circuit is connected between the output terminal of the instrumentation amplifier circuit and the control unit, and is used to filter the voltage Vout and then transmit it to the control unit; the second filter circuit is connected between the negative input terminal of the bridge circuit and the control unit, and is used to filter the voltage VB and then transmit it to the control unit.

[0051] The first filter circuit includes, for example, a fourteenth resistor R16 and a first capacitor C1; one end of the fourteenth resistor R16 is electrically connected to the output terminal of the instrumentation amplifier circuit, the other end of the fourteenth resistor R16 is electrically connected to one end of the first capacitor C1, the other end of the first capacitor C1 is grounded, and the connection point of the fourteenth resistor R16 and the first capacitor C1 is electrically connected to the control unit.

[0052] The second filter circuit includes, for example, a second capacitor C2; one end of the second capacitor C2 is electrically connected to the negative input terminal of the bridge circuit and the control unit, and the other end of the second capacitor C2 is grounded.

[0053] In addition, embodiments of the present invention also disclose a sensor, including any of the sensor circuits disclosed above.

[0054] Furthermore, this invention also discloses a sensor fault detection method applied to a control unit in a sensor circuit, wherein the sensor circuit is any of the aforementioned sensor circuits, see [link to relevant documentation]. Figure 6 The method includes:

[0055] Step S01: Obtain the output voltage Vout of the instrumentation amplifier circuit and / or the negative input voltage VB of the bridge circuit;

[0056] Step S02: Determine whether the output voltage Vout of the instrument amplifier circuit exceeds the first preset range, and / or determine whether the negative voltage VB at the input terminal of the bridge circuit exceeds the second preset range;

[0057] Step S03: When it is determined that the output voltage Vout of the instrumentation amplifier circuit exceeds the first preset range or the negative voltage VB at the input terminal of the bridge circuit exceeds the second preset range, the sensor is determined to be faulty.

[0058] In one embodiment, the upper and lower limits of the first preset range are VCC-0.2 and 0.2V, respectively, and the upper and lower limits of the second preset range are VCC / 2-0.2V and V0-0.2V, respectively.

[0059] This invention also discloses an electronic device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement any of the above-described sensor fault detection methods.

[0060] This invention also discloses a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements any of the above-described sensor fault detection methods.

[0061] This invention also discloses a computer program product, including a computer program that, when executed by a processor, implements any of the above-described sensor fault detection methods.

[0062] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the sensors and sensor fault detection methods disclosed in the embodiments, since they correspond to the sensor circuits disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be found in the sensor circuit section.

[0063] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application.

[0064] 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 spirit or scope of the embodiments of the invention. Therefore, the embodiments of the invention are not to be limited to the embodiments shown herein, but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sensor circuit, characterized in that, include: Bridge circuit, instrumentation amplifier circuit, first current limiting resistor (R8) and control unit; The positive input terminal of the bridge circuit is used to connect to the power supply, the negative input terminal of the bridge circuit is connected to one end of the first current limiting resistor (R8), and the other end of the first current limiting resistor (R8) is connected to ground. The output terminal of the bridge circuit is electrically connected to the input terminal of the instrumentation amplifier circuit; the output terminal of the instrumentation amplifier circuit and the negative terminal of the input terminal of the bridge circuit are both electrically connected to the control unit.

2. The sensor circuit according to claim 1, characterized in that, The upper and lower half-arm resistors of the first bridge arm of the bridge circuit are both thermistors. The instrumentation amplifier circuit includes: a first operational amplifier (IC1), a second operational amplifier (IC2), a third operational amplifier (IC3), a first resistor (R9), a second resistor (R10), a third resistor (R11), a fourth resistor (R12), a fifth resistor (R13), a sixth resistor (R14), and a seventh resistor (R15); In this circuit, the non-inverting input of the first operational amplifier (IC1) is electrically connected to the output of the second arm of the bridge circuit; the non-inverting input of the second operational amplifier (IC2) is electrically connected to the output of the first arm of the bridge circuit; the inverting input of the first operational amplifier (IC1) is electrically connected to the junction of the second resistor (R10) and the first resistor (R9); the inverting input of the second operational amplifier (IC2) is electrically connected to the junction of the first resistor (R9) and the third resistor (R11); and the other end of the second resistor (R10) is connected to both the output of the first operational amplifier (IC1) and the fourth resistor (R12). One end of the third resistor (R11) is electrically connected to the output of the second operational amplifier (IC2) and one end of the sixth resistor (R14). The other end of the fourth resistor (R12) is electrically connected to the first input of the third operational amplifier (IC3) and one end of the fifth resistor (R13). The other end of the fifth resistor (R13) is electrically connected to the output of the third operational amplifier (IC3). The other end of the sixth resistor (R14) is electrically connected to the second input of the third operational amplifier (IC3) and one end of the seventh resistor (R15). The other end of the seventh resistor (R15) is grounded.

3. The sensor circuit according to claim 1, characterized in that, The sensor circuit also includes a second current-limiting resistor (R1); the positive input terminal of the bridge circuit is electrically connected to one end of the second current-limiting resistor (R1), and the other end of the second current-limiting resistor (R1) is used to be electrically connected to the power supply; the nominal resistance of the second current-limiting resistor (R1) is equal to the nominal resistance of the first current-limiting resistor (R8).

4. The sensor circuit according to any one of claims 1 to 3, characterized in that, The first input terminal of the third operational amplifier (IC3) is the non-inverting input terminal of the third operational amplifier (IC3), and the second input terminal of the third operational amplifier (IC3) is the inverting input terminal of the third operational amplifier (IC3). Furthermore, the parameters of the bridge circuit are designed to satisfy the following condition: the output voltage (V1) of the second bridge arm is greater than the output voltage (V2) of the first bridge arm. Alternatively, the first input terminal of the third operational amplifier (IC3) is the inverting input terminal of the third operational amplifier (IC3), the second input terminal of the third operational amplifier (IC3) is the non-inverting input terminal of the third operational amplifier (IC3), and the parameters of the bridge circuit are designed to satisfy that the output voltage (V1) of the second bridge arm is less than the output voltage (V2) of the first bridge arm.

5. The sensor circuit according to claim 4, characterized in that, When the parameters of the bridge circuit are designed to satisfy that the output voltage (V1) of the second bridge arm is greater than the output voltage (V2) of the first bridge arm: the upper half-arm resistor of the first bridge arm is the eighth resistor (R2), the lower half-arm resistor of the first bridge arm is the ninth resistor (R3), the upper half-arm resistor of the second bridge arm is the tenth resistor (R4), and the lower half-arm resistor of the second bridge arm is composed of the eleventh resistor (R7) and the twelfth resistor (R7_1) connected in series. The nominal resistance values ​​of each resistor in the bridge circuit satisfy the following: the nominal resistance value of the twelfth resistor (R7_1) is less than the nominal resistance value of the eleventh resistor (R7), the nominal resistance value of the eleventh resistor (R7) is equal to the nominal resistance value of the tenth resistor (R4), and the nominal resistance value of the eighth resistor (R2) is equal to the nominal resistance value of the ninth resistor (R3). When the parameters of the bridge circuit are designed to satisfy that the output voltage (V1) of the second bridge arm is less than the output voltage (V2) of the first bridge arm: the upper half-arm resistor of the first bridge arm is the eighth resistor (R2), the lower half-arm resistor of the first bridge arm is the ninth resistor (R3), the upper half-arm resistor of the second bridge arm is composed of the tenth resistor (R4) and the thirteenth resistor (R4_1) connected in series, and the lower half-arm resistor of the second bridge arm is the eleventh resistor (R7). The nominal resistance values ​​of each resistor in the bridge circuit satisfy the following: the nominal resistance value of the thirteenth resistor (R4_1) is less than the nominal resistance value of the tenth resistor (R4), the nominal resistance value of the tenth resistor (R4) is equal to the nominal resistance value of the eleventh resistor (R7), and the nominal resistance value of the eighth resistor (R2) is equal to the nominal resistance value of the ninth resistor (R3).

6. The sensor circuit according to any one of claims 1 to 3, characterized in that, The sensor circuit includes a first filter circuit and / or a second filter circuit; The first filter circuit is connected between the output of the instrumentation amplifier circuit and the control unit; the second filter circuit is connected between the negative input of the bridge circuit and the control unit.

7. The sensor circuit according to claim 6, characterized in that, The first filter circuit includes a fourteenth resistor (R16) and a first capacitor (C1); one end of the fourteenth resistor (R16) is electrically connected to the output terminal of the instrumentation amplifier circuit, the other end of the fourteenth resistor (R16) is electrically connected to one end of the first capacitor (C1), the other end of the first capacitor (C1) is grounded, and the connection point of the fourteenth resistor (R16) and the first capacitor (C1) is electrically connected to the control unit. The second filter circuit includes a second capacitor (C2); one end of the second capacitor (C2) is electrically connected to the negative input terminal of the bridge circuit and the control unit, and the other end of the second capacitor (C2) is grounded.

8. The sensor circuit according to any one of claims 1 to 3, characterized in that, The control unit is used to acquire the output voltage of the instrumentation amplifier circuit and / or the negative input voltage of the bridge circuit; determine whether the output voltage of the instrumentation amplifier circuit exceeds a first preset range, and / or determine whether the negative input voltage of the bridge circuit exceeds a second preset range; when it is determined that the output voltage of the instrumentation amplifier circuit exceeds the first preset range or the negative input voltage of the bridge circuit exceeds the second preset range, a sensor fault is determined.

9. A sensor, characterized in that, include: The sensor circuit according to any one of claims 1 to 8.

10. A sensor fault detection method, characterized in that, The sensor includes a sensor circuit, which includes a bridge circuit, an instrumentation amplifier circuit, a first current-limiting resistor (R8), and a control unit. The sensor fault detection method is applied to the control unit, and the sensor fault detection method includes: Acquire the output voltage of the amplifier circuit and / or the negative input voltage of the bridge circuit; The instrument determines whether the output voltage of the amplifier circuit exceeds the first preset range, and / or whether the negative voltage at the input terminal of the bridge circuit exceeds the second preset range. When it is determined that the output voltage of the instrumentation amplifier circuit exceeds the first preset range or the negative voltage of the input terminal of the bridge circuit exceeds the second preset range, the sensor is deemed to be faulty.

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