Sensor acquisition circuit with fault self-diagnosis function, sensor and instrument

Abstract

The utility model discloses a sensor acquisition circuit with a fault self-diagnosis function, a sensor and an instrument. The sensor acquisition circuit comprises a sensor signal input end, a signal conditioning circuit module and a diagnosis control module, the sensor is an electrochemical sensor with two electrodes, and the signal input end of the sensor comprises a working electrode signal end and a counter electrode signal end; the signal conditioning circuit module is used for carrying out reverse-phase amplification conditioning on the obtained sensor signal; the diagnosis control module comprises a control circuit, a first end of the control circuit is connected with a counter electrode signal end of the sensor, a second end of the control circuit is connected with an in-phase input end of the signal conditioning circuit module, a resistor R14 with a large resistance value is connected in series between the first end and the second end, and the diagnosis control module further comprises a control signal IO1 which is connected with a third end of the control circuit; on-off between the first end and the second end of the control circuit is controlled by controlling high and low levels of a signal IO1, so that the signal conditioning circuit module is switched from a normal working state to a fault self-checking state. And potential safety hazards caused by short-circuit and open-circuit faults of the sensor can be reduced.

Description

Technical Field

[0001] This utility model belongs to the field of sensor technology, specifically relating to a sensor acquisition circuit with fault self-diagnosis function, as well as a sensor and instrument. Background Technology

[0002] Electrochemical sensor-based toxic gas detectors are increasingly widely used. For example, in work environments containing toxic gases such as CO (carbon monoxide), CO sensors are typically used to collect and detect CO gas concentrations in real time to effectively monitor and prevent CO poisoning. However, the reliability of these sensors is not high. Most sensors lack self-diagnostic capabilities for their own operating status, which means that if a sensor malfunctions or fails, it may lead to inaccurate detection results, posing an immeasurable threat to personnel safety.

[0003] Therefore, timely understanding of the sensor's operating status is crucial, as it can significantly reduce the safety risks caused by sensor malfunctions. Research into electrochemical sensors for toxic gases with self-diagnostic capabilities is becoming a technological development trend.

[0004] While the output current range of electrochemical sensors varies depending on their design principles and application scenarios, they generally exhibit micro-current characteristics (typically in the nA to μA range). Conventional gas sensors (such as CO and O2 electrochemical sensors) have an output current range of 10 nA to 100 μA. For sensors with micro-current signals, inverting amplifier circuits are widely used in signal conditioning circuits due to their good noise immunity. This application focuses on online fault diagnosis of electrochemical sensors based on inverting amplifier circuits. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, this utility model proposes a sensor acquisition circuit with fault self-diagnosis function.

[0006] A sensor acquisition circuit with fault self-diagnosis function.

[0007] It includes a sensor signal input terminal, a signal conditioning circuit module, and a diagnostic control module;

[0008] The sensor is a two-electrode electrochemical sensor, and the sensor signal input terminals include a working electrode signal terminal and a counter electrode signal terminal.

[0009] The signal conditioning circuit module uses an inverting amplifier circuit to amplify and condition the acquired sensor signals;

[0010] The diagnostic control module includes a control circuit. The first terminal of the control circuit is connected to the counter electrode signal terminal of the sensor, and the second terminal is connected to the front stage of the non-inverting input resistor of the signal conditioning circuit module. A large-value resistor R14 is connected in series between the first terminal and the second terminal. The module also includes a control signal IO1, which is connected to the third terminal of the control circuit through a series resistor R15.

[0011] The high and low level states of the control signal IO1 are used to control the connection and disconnection between the first and second terminals of the control circuit, so that the signal conditioning circuit switches from the normal working state of the sensor to the sensor fault self-test state.

[0012] It also includes a main controller. The signal output terminal of the signal conditioning circuit is connected to the signal detection terminal of the main controller. The main controller is used to collect the level signal of the signal detection terminal and determine whether the sensor has a short circuit or open circuit fault based on the level signal.

[0013] Furthermore, the signal conditioning circuit module includes an operational amplifier U2A. A resistor R2 is connected in series between the output terminal and the inverting input terminal of the operational amplifier U2A. A capacitor C7 is connected in parallel across the resistor R2. The non-inverting input terminal of the operational amplifier U2A is connected to the counter electrode signal terminal of the sensor through a series resistor R13. The inverting input terminal of the operational amplifier U2A is electrically connected to the working electrode signal terminal of the sensor through an inverting input resistor R1. The output terminal of the operational amplifier U2A outputs a signal SIN after being connected in series with an output resistor R5. The output signal SIN is grounded through a capacitor C9.

[0014] Furthermore, the signal conditioning circuit module also includes a bias anti-interference circuit, including an operational amplifier U2B. The output terminal of the operational amplifier U2B is electrically connected to the inverting input terminal of the operational amplifier U2B, and the non-inverting input terminal of the operational amplifier U2B is connected to a reference voltage, which is slightly higher than the ground level. The output signal XIN of the operational amplifier U2B is electrically connected to the front stage of the non-inverting input resistor in the signal conditioning circuit module. The power supply terminal of the operational amplifier U2B is electrically connected to the appropriate voltage VDD, and the grounding pin of the operational amplifier U2B is grounded.

[0015] The reference voltage is the voltage divided by the power supply VCAP through several resistors.

[0016] Preferredly, the control circuit of the diagnostic control module uses a P-channel JFET.

[0017] The drain of the first terminal of the control circuit is connected to the counter electrode signal terminal of the sensor, and the source of the second terminal of the control circuit is connected to the non-inverting input terminal of the signal conditioning circuit module.

[0018] The source and drain of the control circuit are connected in series through resistor R14;

[0019] A resistor R15 is connected in series between the control signal IO1 and the gate of the third terminal of the control circuit;

[0020] The control signal IO1 is connected to the counter electrode signal terminal of the sensor through a series connection resistor R8;

[0021] When the control signal IO1 is low, the source and drain of the control circuit are turned on; when the control signal IO1 is high, the source and drain of the control circuit Q3 are turned off.

[0022] Preferred, the sensor anti-polarization circuit includes a switching unit, which is a P-channel JFET. The source and drain of the JFET are electrically connected to the counter electrode signal terminal and the working electrode signal terminal of the sensor, respectively. The gate of the switching unit is connected in series with a resistor R7 and then connected to the power supply VDD.

[0023] Furthermore, the main controller determines whether the sensor has malfunctioned based on the level signal, including:

[0024] Determine whether the level signal is within the normal output signal range of the sensor;

[0025] If the level signal is lower than the minimum value of the normal output signal range of the sensor, then the sensor is determined to be internally open-circuited.

[0026] If the voltage level is higher than the maximum value of the normal output signal range of the sensor, then the sensor is determined to be internally short-circuited.

[0027] A sensor that uses a sensor acquisition circuit with fault self-diagnosis function having the above-mentioned features.

[0028] An instrument that uses a sensor acquisition circuit with the above-mentioned features and a fault self-diagnosis function.

[0029] This invention, while acquiring signals from an electrochemical sensor, can switch the signal conditioning circuit module to fault diagnosis mode via a control signal as needed. By comparing the output signal of the signal conditioning circuit module with the normal signal, it can determine short-circuit and open-circuit faults in the electrochemical sensor, and then output a prompt to peripheral devices such as display devices or terminals indicating the sensor's self-operating status. This is of great significance for preventing sensor failures and reducing safety risks. The sampling circuit of this invention is low-cost, simple and reliable in operation, and when using a JFET transistor in the diagnostic control module, the modifications compared to the original sampling circuit are minimal, and the space occupied is very small. Attached Figure Description

[0030] Figure 1 This is a circuit module block diagram of this utility model;

[0031] Figure 2 This is the circuit schematic diagram of this utility model;

[0032] Figure 3 This is a schematic diagram of the bias anti-interference circuit of the signal conditioning circuit module of this utility model. Detailed Implementation

[0033] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; however, any combination of these technical features that does not contradict each other should be considered within the scope of this specification.

[0035] like Figure 1 As shown, a sensor acquisition circuit with fault self-diagnosis function is presented.

[0036] It includes a sensor signal input terminal, a signal conditioning circuit module, and a diagnostic control module;

[0037] The sensor is a two-electrode electrochemical sensor U8, and the sensor signal input terminal includes a working electrode signal terminal pin 1 and a counter electrode signal terminal pin 2.

[0038] The signal conditioning circuit inverts and amplifies the acquired sensor signal;

[0039] The diagnostic control module includes a control circuit Q3. The first terminal of the control circuit Q3 is connected to the counter electrode signal terminal of the sensor, and the second terminal is connected to the front stage of the non-inverting input resistor R13 of the signal conditioning circuit module. A series resistor R14 is connected between the first terminal and the second terminal. The module also includes a control signal IO1. The control signal IO1 is connected to the third terminal of the control circuit Q3 through a series resistor R15. The control signal IO1 is also connected to the counter electrode signal terminal of the sensor through a series resistor R8.

[0040] When the sensor is working normally, the high and low level states of the control signal IO1 control the connection between the first and second terminals of the control circuit Q3, so that the signal conditioning circuit switches from the normal working state to the sensor fault self-test state.

[0041] It also includes a main controller, which is used to acquire the level signal output by the signal conditioning circuit and determine whether the sensor has a short circuit or open circuit fault based on the level signal.

[0042] In one embodiment, the main controller uses a microcontroller to detect the level signal output by the signal conditioning circuit and determine whether the sensor has a short circuit or open circuit fault based on the level signal. Outputting the diagnostic results and prompts to relevant devices is also a common practice. For example, combining a microcontroller with a display unit can output relevant information to the display unit; combining a microcontroller with a wireless communication module can output relevant information to user terminals such as mobile phones and tablets; these details will not be elaborated further here.

[0043] In one embodiment, the signal conditioning circuit uses an inverting operational amplifier to amplify the acquired sensor signal and employs a low-pass filter to filter low-frequency noise in the signal. For example... Figure 2 The signal conditioning circuit includes operational amplifier U2A. A resistor R2 is connected in series between the output and inverting input of operational amplifier U2A. A capacitor C7 is connected in parallel across resistor R2. The non-inverting input of operational amplifier U2A is connected to the counter electrode signal terminal of sensor U8 through a series resistor R13. The inverting input of operational amplifier U2A is electrically connected to the working electrode signal terminal of sensor U8 through an inverting input resistor R1. The output of operational amplifier U2A is connected in series with an output resistor R5 and outputs a signal SIN. The output signal SIN is grounded through capacitor C9. C7 and C9 filter noise from the acquired sensor signal. Adjusting the resistor R13 at the non-inverting input of operational amplifier U2A ensures that operational amplifier U2A performs inverting amplification.

[0044] In one embodiment, such as Figure 3 The bias anti-interference circuit includes operational amplifier U2B. The output terminal of operational amplifier U2B is electrically connected to the inverting input terminal of operational amplifier U2B. The non-inverting input terminal of operational amplifier U2B is connected to a reference voltage, which is slightly higher than ground level. The output signal XIN of operational amplifier U2B is electrically connected to the stage before the non-inverting input resistor R13 of operational amplifier U2A. The power supply terminal of operational amplifier U2B is electrically connected to the appropriate voltage VDD. The grounding pin of operational amplifier U2B is grounded. Operational amplifier U2B achieves voltage following. The output signal XIN of operational amplifier U2B is equal to the voltage signal at the non-inverting input terminal of operational amplifier U2B, that is, the reference voltage at the non-inverting input terminal of operational amplifier U2B.

[0045] Furthermore, the reference voltage at the non-inverting input of op-amp U2B can be obtained by dividing the power supply VCAP through resistors, such as... Figure 3 In the embodiment shown, the power supply VCAP is grounded after being connected in series with resistors R4 and R3. By adjusting the resistance values ​​of resistors R4 and R3, the voltage between resistors R4 and R3 can be made to meet the reference voltage. Figure 3In this embodiment, the power supply VCAP is powered by the microcontroller output of the main controller. Of course, other power supplies can also be used, and there are no restrictions here.

[0046] When sensor U8 is operating normally, control signal IO1 controls Q3 in the diagnostic control module to be in the conducting state; then the signal from sensor U8 is amplified through the signal conditioning circuit, and the input signal of the signal conditioning circuit and the signal output SIN have a certain proportional relationship. The signal output SIN of the signal conditioning circuit is within the normal output signal range of the sensor.

[0047] When it is necessary to detect whether sensor U8 is faulty, Q3 in the diagnostic control module is turned off by controlling IO1; then the counter electrode signal of sensor U8 is connected to the non-inverting input of operational amplifier U2A in the signal conditioning circuit through resistor R14, and the working electrode signal of sensor U8 is connected to the inverting input of operational amplifier U2A in the signal conditioning circuit. Depending on the on / off state of the two electrodes of the sensor, operational amplifier U2A can realize signal amplification or voltage following function.

[0048] If there is a short circuit inside sensor U8, the resistance between the working electrode and the counter electrode of sensor U8 becomes very low, or even directly conductive. In this case, the output voltage of the working electrode of sensor U8 is almost equal to the output voltage of the counter electrode. After the voltage is reduced by resistor R14, the input voltage U0 between the inverting input terminal and the non-inverting input terminal of operational amplifier U2A is much greater than the normal operating input voltage. After being amplified by operational amplifier U2A, the output SIN of the signal conditioning circuit is AU0, and the amplification factor of operational amplifier U2A is A, which is much greater than the maximum value of the normal output signal range of the sensor. Based on this, it can be determined that there is a short circuit inside the sensor.

[0049] If there is an open circuit inside sensor U8, the output current of the working electrode of sensor U8 will be close to 0, and consequently the output voltage of the electrode will be close to 0. At this time, the inverting input of operational amplifier U2A will be close to 0, and the non-inverting input of operational amplifier U2A will be the reference voltage output by the anti-interference circuit (slightly higher than 0). Operational amplifier U2A achieves voltage following, and the output SIN of the signal conditioning circuit is approximately the reference voltage output by the anti-interference circuit, slightly higher than 0, but far lower than the minimum value of the normal output signal range of the sensor. Based on this, it can be determined that there is an open circuit inside the sensor.

[0050] The control circuit Q3 in the diagnostic control module controls the connection between its first and second terminals based on the high and low levels of the control signal IO1. The control circuit Q3 can be composed of a single electronic device or multiple electronic devices and corresponding peripheral circuits; there are no specific limitations, as long as it can ensure the connection between the sensor's counter electrode signal pin 2 and the non-inverting input resistor R13 of the signal conditioning circuit module is maintained according to the high and low levels of the control signal IO1. The control circuit Q3 can be a voltage-controlled switch such as a JFET. In one embodiment, as shown... Figure 2 The control circuit Q3 uses a P-channel JFET. The drain of the first terminal of the control circuit Q3 is connected to the counter electrode signal terminal of the sensor, and the source of the second terminal of the control circuit Q3 is connected to the front stage of the non-inverting input resistor of the signal conditioning circuit module.

[0051] The source and drain of control circuit Q3 are connected in series through resistor R14;

[0052] A resistor R15 is connected in series between the control signal IO1 and the gate of the third terminal of the control circuit Q3;

[0053] The control signal IO1 is connected to the counter electrode signal terminal of the sensor U8 through a series electrical connection resistor R8;

[0054] When control signal IO1 is low, the resistance values ​​of resistors R15 and R8 are adjusted to turn on control circuit Q3, meaning the drain and source of control circuit Q3 are directly connected. The sensor's counter electrode signal is directly connected to the non-inverting input of the signal conditioning circuit module, which amplifies and conditions the sensor signal. When control signal IO1 is high, control circuit Q3 is turned off, meaning the drain and source of control circuit Q3 are disconnected. The sensor's counter electrode signal is connected to the non-inverting input of the signal conditioning circuit module through resistor R14. Resistor R14 has a very high resistance, and the output of the signal conditioning circuit module is in a fault diagnosis state.

[0055] The control signal IO1 controls the on / off state of the control circuit Q3, enabling the sensor to operate in normal working or fault diagnosis state. The on / off state of the control circuit Q3 is related to the specific electronic components or circuit modules of the control circuit Q3 and the corresponding peripheral circuits. By adjusting the resistance values ​​of R15 and R8, as well as the voltage of the control signal IO1, the control circuit Q3 can be turned on or off.

[0056] In one embodiment, the control signal IO1 can be event-triggered or automatically periodically triggered. When not triggered, the control signal IO1 remains high; after triggering, it becomes low. The sensor's online operating status is determined based on the output level signal of the signal conditioning circuit module. The control signal IO1 can be issued by the main controller or other signals. For example, periodic triggering, performing self-checks at regular intervals (six months or quarters), can be implemented by the main controller, such as a microcontroller—a standard function of microcontrollers. Event triggering is generally based on event requirements. For instance, if the detected data suddenly becomes abnormal, it's necessary to first rule out sensor malfunction. A trigger button can be designed on the main controller's peripheral devices, such as touchscreen input or buttons. When self-checking is required, pressing the trigger button or button controls one of the main controller's IO outputs to change from high to low, serving as the control signal IO1. The sensor self-diagnostic signal represented by the high or low level of the control signal IO1 is determined by the on / off state of the first and second terminals of the control circuit Q3, and is not deterministic.

[0057] In one embodiment, such as Figure 2 The sensor anti-polarization circuit in the acquisition circuit includes a switching unit Q1. The first end of the switching unit is connected to the working electrode signal terminal of the sensor, the second end of the switching unit is connected to the counter electrode signal terminal of the sensor, and the power supply terminal of the switching unit is connected to the power supply VDD.

[0058] The function of the anti-polarization circuit is to prevent the sensor's working electrode and counter electrode from accumulating polarization charge when the power is off or not applied. Specifically, when the power supply terminal VDD of the switching unit is 0, the switching unit is in the on state.

[0059] Specifically, the switching unit Q1 is a P-channel JFET. The source and drain terminals of the second terminal of the switching unit Q1 are electrically connected to pin 2 of the counter electrode signal terminal and pin 1 of the working electrode signal terminal of the sensor U8, respectively. The gate terminal is connected to the power supply VDD via a resistor R7. When power is off or de-energized, VDD=0, the drain and source terminals of the switching unit Q1 are conducting, and the counter electrode signal terminal pin 2 and the working electrode signal terminal pin 1 of the sensor U8 are connected, releasing the accumulated charge on both electrodes.

[0060] The power supply VDD can be obtained from the power supply through voltage division, or it can be provided by other power supply outputs.

[0061] After power-on, the sensor begins normal operation, detecting the concentration of toxic gases such as CO. During signal acquisition, the signal conditioning circuit is controlled by the control signal IO1 to initiate a self-test of the sensor's current state. The output signal SIN of the signal conditioning circuit determines whether the sensor is in one of three states: open circuit, short circuit, or normal. If the first two states are detected, the system will prompt the user to replace the sensor before resuming detection. If the sensor is in a normal state, gas concentration acquisition will continue.

[0062] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A sensor acquisition circuit with fault self-diagnosis function, characterized in that: It includes a sensor signal input terminal, a signal conditioning circuit module, and a diagnostic control module; The sensor is a two-electrode electrochemical sensor, and the sensor signal input terminals include a working electrode signal terminal and a counter electrode signal terminal. The signal conditioning circuit module uses an inverting amplifier circuit to amplify and condition the acquired sensor signals; The diagnostic control module includes a control circuit. The first terminal of the control circuit is connected to the counter electrode signal terminal of the sensor, and the second terminal is connected to the front stage of the non-inverting input resistor of the signal conditioning circuit module. A large-value resistor R14 is connected in series between the first terminal and the second terminal. The module also includes a control signal IO1, which is connected to the third terminal of the control circuit through a series resistor R15. The high and low level states of the control signal IO1 are used to control the connection and disconnection between the first and second terminals of the control circuit, so that the signal conditioning circuit switches from the normal working state of the sensor to the sensor fault self-test state. It also includes a main controller. The signal output terminal of the signal conditioning circuit is connected to the signal detection terminal of the main controller. The main controller is used to collect the level signal of the signal detection terminal and determine whether the sensor has a short circuit or open circuit fault based on the level signal.

2. The sensor acquisition circuit with fault self-diagnosis function according to claim 1, characterized in that: The signal conditioning circuit module includes an operational amplifier U2A. A resistor R2 is connected in series between the output terminal and the inverting input terminal of the operational amplifier U2A, and a capacitor C7 is connected in parallel across the resistor R2. The non-inverting input terminal of the operational amplifier U2A is connected to the counter electrode signal terminal of the sensor through a series resistor R13. The inverting input terminal of the operational amplifier U2A is electrically connected to the working electrode signal terminal of the sensor through an inverting input resistor R1. The output terminal of the operational amplifier U2A outputs a signal SIN after being connected in series with an output resistor R5. The output signal SIN is grounded through a capacitor C9.

3. The sensor acquisition circuit with fault self-diagnosis function according to claim 1, characterized in that: The signal conditioning circuit module further includes a bias anti-interference circuit, including an operational amplifier U2B. The output terminal of the operational amplifier U2B is electrically connected to the inverting input terminal of the operational amplifier U2B, and the non-inverting input terminal of the operational amplifier U2B is connected to a reference voltage, which is higher than the ground level. The output signal XIN of the operational amplifier U2B is electrically connected to the front stage of the non-inverting input resistor in the signal conditioning circuit module. The power supply terminal of the operational amplifier U2B is electrically connected to the appropriate voltage VDD, and the grounding pin of the operational amplifier U2B is grounded. The reference voltage is the voltage divided by the power supply VCAP through several resistors.

4. A sensor acquisition circuit with fault self-diagnosis function according to claim 1, characterized in that: The control circuit of the diagnostic control module uses a P-channel JFET. The drain of the first terminal of the control circuit is connected to the counter electrode signal terminal of the sensor, and the source of the second terminal of the control circuit is connected to the non-inverting input terminal of the signal conditioning circuit module. The source and drain of the control circuit are connected in series through resistor R14; A resistor R15 is connected in series between the control signal IO1 and the gate of the third terminal of the control circuit; The control signal IO1 is connected to the counter electrode signal terminal of the sensor through a series connection resistor R8; When the control signal IO1 is low, the source and drain of the control circuit are turned on; when the control signal IO1 is high, the source and drain of the control circuit are turned off.

5. A sensor acquisition circuit with fault self-diagnosis function according to claim 1, characterized in that: The sensor anti-polarization circuit includes a switching unit, which uses a P-channel JFET. The source and drain of the JFET are electrically connected to the counter electrode signal terminal and the working electrode signal terminal of the sensor, respectively. The gate of the switching unit is connected in series with a resistor R7 and then connected to the power supply VDD.

6. A sensor acquisition circuit with fault self-diagnosis function according to claim 1, characterized in that: The main controller determines whether the sensor has malfunctioned based on the level signal, including: Determine whether the level signal is within the normal output signal range of the sensor; If the level signal is lower than the minimum value of the normal output signal range of the sensor, then the sensor is determined to be internally open-circuited. If the voltage level is higher than the maximum value of the normal output signal range of the sensor, then the sensor is determined to be internally short-circuited.

7. A sensor, characterized in that, Use a sensor acquisition circuit with fault self-diagnosis function according to any one of claims 1-6.

8. An instrument, characterized in that, Use a sensor acquisition circuit with fault self-diagnosis function according to any one of claims 1-6.

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