Sensor sensitivity test circuit, device and method

Abstract

The sensor sensitivity test circuit comprises a sensor sampling resistor reading circuit, a four-channel selector, a sampling resistor reading circuit and a sampling resistor reading circuit, one end of the first resistor is electrically connected to a pin I of the four-channel selector, one end of the second resistor is electrically connected to a pin II of the four-channel selector, one end of the third resistor is electrically connected to a pin III of the four-channel selector, and a common end of the first resistor, the second resistor and the third resistor is connected with a power supply; one end of the sensor working resistor is electrically connected to the pin 8 of the four-channel selector, and the other end is connected with a power supply; one end of the variable sampling resistor is electrically connected to the pin 9 of the four-channel selector, and the other end is electrically grounded; calculating the resistance value of the variable sampling resistor; calculating the resistance value of the sensor working resistor as the initial resistance value of the sensor working resistor; after testing the gas concentration, calculating the current resistance value of the working resistor of the sensor; the ratio of the current resistance value of the sensor working resistor to the initial resistance value of the sensor working resistor is the sensor sensitivity.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more specifically to sensor sensitivity testing circuits, equipment, and methods. Background Technology

[0002] Gas sensors incorporate a working resistor and a compensation resistor, with a catalytic material coated on the surface of the working resistor. Gas detection is achieved through the adsorption, activation, and chemical reaction of the gas by the catalytic material on the working resistor surface. The sensitivity of a gas sensor affects the test results for gas concentration. For example, a low-sensitivity sensor may not be able to distinguish gas samples with similar concentrations. The sensitivity of most gas sensors changes after prolonged use, typically decreasing gradually (sensitivity decay). Therefore, the sensitivity of gas sensors needs to be tested after a period of use. Summary of the Invention

[0003] The purpose of this invention is to provide a sensor sensitivity testing circuit, device, and method for testing the sensitivity of gas sensors.

[0004] On the one hand, a sensor sensitivity test circuit is provided, including a sensor sampling resistor reading circuit, wherein the sensor sampling resistor reading circuit includes: a four-channel selector; The first resistor has one end electrically connected to a pin of the four-channel selector and the other end connected to the power supply. The second resistor has one end electrically connected to pin 2 of the four-channel selector and the other end connected to the power supply. The third resistor has one end electrically connected to pin 3 of the four-channel selector and the other end connected to the power supply. The sensor's operating resistor is electrically connected at one end to pin 8 of the four-channel selector and at the other end to the power supply. A variable sampling resistor, one end of which is electrically connected to pin nine of the four-channel selector, and the other end is connected to ground; The power supply voltages of the first resistor, the second resistor, and the third resistor are denoted as the first power supply voltage value; the power supply voltage of the sensor's working resistor is denoted as the second power supply voltage value. Calculating the sensitivity of the sensor includes: Before testing gas concentration: The resistance value of the variable sampling resistor is calculated using the method of calculating the resistance value of the variable sampling resistor. The resistance value of the sensor's working resistance is calculated using the method of calculating the resistance value of the sensor's working resistance, and the initial resistance value of the sensor's working resistance is obtained. After starting to test gas concentration: By controlling the levels of pins six and seven of the four-channel selector, pins nine and eight are connected. The variable sampling resistor and the sensor working resistor form a series circuit. After testing the gas concentration, the voltage drop value of the variable sampling resistor is tested. Based on whether the voltage drop value of the variable sampling resistor is within the range of 0.5V to 4.5V, the current resistance value of the sensor working resistor is calculated using the method of calculating the current resistance value of the sensor working resistor. The ratio of the current resistance value of the sensor's operating resistor to its initial resistance value is the sensor sensitivity.

[0005] On the other hand, a sensor sensitivity testing device is provided, including a main control chip and the sensor sensitivity testing circuit. The sensor sensitivity testing circuit is electrically connected to the main control chip, and the main control chip is connected to the display screen via a USB communication module. The main control chip is connected to a smart terminal via a Bluetooth module.

[0006] On the other hand, a sensor sensitivity testing method is provided, applied to the sensor sensitivity testing circuit and the sensor sensitivity testing equipment, including the following steps: Step 1, calculate the resistance value of the variable sampling resistor: By controlling the levels of pins six and seven of the four-channel selector, pin nine is connected to one of pins one, two, or three to form a series circuit with the variable sampling resistor, and the voltage division of the variable sampling resistor is measured and recorded as the first voltage division value; combining the resistance values ​​of the selected first, second, and third resistors used to form the series circuit, the first power supply voltage value, and the first voltage division value, the resistance value of the variable sampling resistor is calculated according to the voltage divider law; Step 2, calculate the resistance value of the sensor working resistor: By controlling the level of pins six and seven of the four-channel selector, pins nine and eight are connected, and the variable sampling resistor and the sensor working resistor form a series circuit. The voltage division value of the variable sampling resistor is recorded as the second voltage division value. Combining the second power supply voltage value, the second voltage division value, and the resistance value of the variable sampling resistor, the resistance value of the sensor working resistor is calculated according to the voltage divider law. Step 3, calculate the sensor sensitivity, including: Step 3.1, before testing gas concentration: The resistance value of the variable sampling resistor is calculated using the method described above. Using the method described above for calculating the resistance value of the sensor's working resistance, the resistance value of the sensor's working resistance is calculated as the initial resistance value of the sensor's working resistance. Step 3.2, after starting the gas concentration test: By controlling the levels of pins six and seven of the four-channel selector, pins nine and eight are connected. The variable sampling resistor and the sensor operating resistor form a series circuit. After testing the gas concentration, the voltage drop across the variable sampling resistor is measured to determine if it falls within the range of 0.5V to 4.5V. If the voltage division value of the variable sampling resistor is in the range of 0.5V to 4.5V, the voltage division value of the variable sampling resistor shall be recorded as the second voltage division value; At this point, the current resistance value of the sensor's working resistance is calculated according to the method for calculating the resistance value of the sensor's working resistance. The wall ratio of the current resistance value of the sensor's operating resistor to the initial resistance value of the sensor's operating resistor is the sensor sensitivity. If the voltage division value of the variable sampling resistor is not within the range of 0.5V to 4.5V, adjust the variable sampling resistor to make the voltage division value of the variable sampling resistor within the range of 0.5V to 4.5V, and then record the voltage division value of the variable sampling resistor that is re-acquired as the second voltage division value; The resistance value of the variable sampling resistor is recalculated using the method described above for calculating the resistance value of the variable sampling resistor; At this point, the current resistance value of the sensor's working resistance is calculated according to the method for calculating the resistance value of the sensor's working resistance. The ratio of the current resistance value of the sensor's operating resistor to its initial resistance value is the sensor sensitivity.

[0007] The advantages of this invention are as follows: Before the gas sensor tests the gas concentration: First, connect the variable sampling resistor in series with any one of the first, second, and third resistors. Then, based on the voltage of the current series circuit, the measured voltage drop across the variable sampling resistor, and the resistance value of the resistor connected in series with the variable sampling resistor, calculate the resistance value of the variable sampling resistor using the voltage divider law.

[0008] Next, the variable sampling resistor and the sensor operating resistor are connected in series. Based on the current power supply voltage of the series circuit, the current voltage division of the variable sampling resistor, and the resistance value of the variable sampling resistor, the initial resistance value of the sensor operating resistor is calculated according to the voltage divider law.

[0009] After the gas sensor measures the gas concentration: The resistance value of the gas sensor changes as the test proceeds. In the series circuit consisting of the variable sampling resistor and the sensor's operating resistance, the current resistance value of the gas sensor is calculated according to the voltage divider law based on the current power supply voltage of the circuit, the detected voltage drop across the variable sampling resistor, and the resistance value of the variable sampling resistor.

[0010] Calculate the ratio of the current resistance value of the gas sensor to its initial resistance value. The larger the ratio, the more sensitive the gas sensor. Conversely, the smaller the ratio, the less sensitive the gas sensor. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the functional modules of the sensor sensitivity testing device in this embodiment.

[0012] Figure 2 This is the circuit in this embodiment used to read the voltage divider of the variable sampling resistor.

[0013] Figure 3 This is a circuit diagram of the sensor sampling resistor reading circuit in this embodiment.

[0014] Figure 4 This is the sensor sampling and processing circuit in this embodiment.

[0015] Figure 5 This is the analog-to-digital converter circuit in this embodiment.

[0016] Figure 6 This is the circuit of the second follower section in the catalytic processing circuit of the sensor material in this embodiment.

[0017] Figure 7 This is the circuit of the digital-to-analog converter section in the catalytic processing circuit of the sensor material in this embodiment. Detailed Implementation

[0018] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0019] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" used to indicate orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0020] To test gas sensitivity, this embodiment provides a sensor sensitivity testing circuit, including a sensor sampling resistor reading circuit, as shown in the reference... Figure 3 The sensor sampling resistor reading circuit includes: The four-channel selector is model RS2255XN.

[0021] One end of the first resistor R1 is electrically connected to pin 1 of the four-channel selector (corresponding to the attached pin). Figure 3 The other end of the first resistor R1 is connected to the power supply (pin X2 of RS2255XN in this embodiment). In this embodiment, a 3.3V power supply is selected.

[0022] One end of the second resistor R2 is electrically connected to pin two of the four-channel selector (corresponding to the attached pin). Figure 3 The RS2255XN has pin X3), and the other end of the second resistor R2 is connected to the power supply. In this embodiment, a 3.3V power supply is selected.

[0023] One end of the third resistor R3 is electrically connected to pin three of the four-channel selector (corresponding to the attached pin). Figure 3 The RS2255XN has pin X1), and the other end of the third resistor R3 is connected to the power supply. In this embodiment, a 3.3V power supply is selected.

[0024] One end of the sensor working resistor R4 is electrically connected to pin 8 of the four-channel selector, and the other end of the sensor working resistor R4 is connected to the power supply. In this embodiment, a 5V power supply is selected.

[0025] One end of the variable sampling resistor R5 is electrically connected to pin nine of the four-channel selector, and the other end of the variable sampling resistor R5 is grounded.

[0026] The power supply voltages of the first resistor, the second resistor, and the third resistor are denoted as the first power supply voltage value, and the power supply voltage of the sensor's working resistor is denoted as the second power supply voltage value.

[0027] The specific method for calculating the resistance value of the variable sampling resistor R5 is as follows: by controlling the levels of pins six and seven of the four-channel selector, pin nine (corresponding to the attached pin) is selected. Figure 3 The variable sampling resistor R5 is connected to one of the following pins: pin X and pin 1, pin 2, or pin 3. A series circuit is formed by selecting one of the following resistors: first resistor R1, second resistor R2, third resistor R3, and variable sampling resistor R5. The voltage division of the variable sampling resistor is then measured and recorded as the first voltage division value. Combining the resistance values ​​of the selected first, second, and third resistors used to form the series circuit, the first power supply voltage, and the first voltage division value, the resistance value of the variable sampling resistor is calculated according to the voltage divider law.

[0028] For example, if pins nine and three are connected, and the third resistor R3 and the variable sampling resistor R5 are connected in series, with a power supply of 3.3V, the voltage detected at the common terminal of the variable sampling resistor and pin nine is the first voltage divider value. Based on the power supply being 3.3V, the resistance value of the third resistor R3 (known), and the first voltage divider value, the resistance value of the variable sampling resistor R5 can be calculated according to the voltage divider law.

[0029] The specific method for calculating the resistance value of the sensor's operating resistance R4 is as follows: By controlling the levels of pins six and seven of the four-channel selector, pin nine (attached) is selected. Figure 3 Pin X and pin 8 (attached) Figure 3 Pin X0 is connected, and the variable sampling resistor R5 and the sensor operating resistor R4 form a series circuit. The voltage division value of the variable sampling resistor is recorded as the second voltage division value. Combining the second power supply voltage value, the second voltage division value, and the resistance value of the variable sampling resistor, the resistance value of the sensor operating resistor is calculated according to the voltage divider law.

[0030] For example, if the second power supply voltage provided to the sensor operating resistor R4 is 5V, the voltage detected at the common terminal of the variable sampling resistor and pin nine is the second voltage divider value. Based on the second power supply voltage value, the second voltage divider value, and the previously calculated resistance value of the variable sampling resistor R5, the resistance value of the sensor operating resistor R4 can be calculated according to the voltage divider law.

[0031] The change in the resistance value of the sensor's operating resistor R4 after the gas concentration test relative to the resistance value before the gas concentration test reflects the sensor's sensitivity. Therefore, calculating the sensor's sensitivity requires determining the resistance value of the sensor's operating resistor before and after the gas concentration test.

[0032] Calculating the sensitivity of the sensor includes: Before testing gas concentration: The resistance value of the variable sampling resistor R5 is calculated using the method of calculating the resistance value of the variable sampling resistor. The resistance value of the sensor working resistance R4 is calculated using the method of calculating the resistance value of the sensor working resistance, and is taken as the initial resistance value of the sensor working resistance. After starting to test gas concentration: By controlling the levels of pins six and seven of the four-channel selector, pins nine and eight are connected. The variable sampling resistor and the sensor operating resistor form a series circuit. After testing the gas concentration, the voltage drop across the variable sampling resistor is measured. Based on whether the voltage drop across the variable sampling resistor is within the range of 0.5V to 4.5V, the current resistance value of the sensor operating resistor is calculated using the method for calculating the current resistance value of the sensor. Specifically: If the voltage division value of the variable sampling resistor is in the range of 0.5V to 4.5V, the voltage division value of the variable sampling resistor shall be recorded as the second voltage division value; At this point, the current resistance value of the sensor's working resistance is calculated using the method for calculating the resistance value of the sensor's working resistance. If the voltage division value of the variable sampling resistor is not within the range of 0.5V to 4.5V, adjust the variable sampling resistor to make the voltage division value within the range of 0.5V to 4.5V, and record the voltage division value of the variable sampling resistor as the second voltage division value; recalculate the resistance value of the variable sampling resistor using the same method. At this point, the current resistance value of the sensor's operating resistance is calculated using the method for calculating the sensor's operating resistance.

[0033] The ratio of the current resistance value of the sensor's operating resistor to its initial resistance value is the sensor sensitivity.

[0034] In this embodiment, the power supply provided to the working resistor of the sensor is 5V.

[0035] The ratio of the current resistance value of the sensor's working resistor R4 to its initial resistance value is the sensor sensitivity. The larger the ratio, the greater the relative change in resistance, and the more sensitive the sensor is to the gas being measured, i.e., the higher the sensitivity.

[0036] Case: The first step is to calculate the resistance value of the variable sampling resistor R5 and the initial resistance value of the sensor's operating resistance before gas concentration detection.

[0037] A third resistor R3 and a variable sampling resistor R5 are connected in series. The resistance of the third resistor R3 is 10 kΩ, and the power supply is 3.3V. The detected voltage drop across the variable sampling resistor R5 is 2V. Calculate the voltage drop using the voltage divider rule: Pressure division formula: in, It's 3.3V. The voltage is 2V, R3 is 10 kΩ, and the calculated value of R5 is 15.38462 kΩ.

[0038] The variable sampling resistor R5 and the sensor's operating resistor R4 are connected in series. The current voltage drop across the variable sampling resistor R5 is 3V, while the power supply to the sensor's operating resistor is 5V. Calculations based on the voltage divider law are as follows: Pressure division formula:

[0039] in, It's 5V. The voltage is 3V, R5 is 15.38462 kΩ, and the calculated initial resistance value of the sensor's operating resistance R4 is 10.25641 kΩ.

[0040] The second step is to calculate the current resistance value of the sensor's operating resistance after gas concentration detection.

[0041] Three sensors were used for comparison, and the initial resistance value of the operating resistors of the three sensors was 10.25641 kiloohms.

[0042] (1) Connect the variable sampling resistor R5 and the working resistor R4 of the first sensor in series to perform a gas concentration test. The current voltage of the variable sampling resistor R5 is 2.8V and the initial resistance of the sensor's working resistor is 10.25641 kΩ.

[0043] (2) Connect the variable sampling resistor R5 and the working resistor R4 of the second sensor in series to perform a gas concentration test. The current voltage of the variable sampling resistor R5 is 2.3V and the initial resistance of the sensor's working resistor is 10.25641 kΩ.

[0044] (3) Connect the variable sampling resistor R5 and the working resistor R4 of the third sensor in series to perform a gas concentration test. The current voltage of the variable sampling resistor R5 is 2V and the initial resistance of the sensor's working resistor is 10.25641 kΩ.

[0045] In this embodiment, the power supply voltage provided to the series circuit of the variable sampling resistor R5 and the sensor's operating resistor R4 is 5V, and the resistance value of the variable sampling resistor R5 is 15.38462 kΩ. The current resistance value of the sensor's operating resistor is calculated according to the voltage divider law.

[0046] Pressure division formula:

[0047] By comparing the operating resistance of the three sensors before and after testing the gas concentration, the ratio of the resistance values ​​reflects the sensitivity of the gas sensor. The larger the ratio, the higher the sensitivity of the corresponding gas sensor. Among them, 2.25 is the largest, indicating that the resistor has the highest sensitivity. This completes the sensitivity test of the sensor's operating resistance.

[0048] By controlling the levels of pins six and seven of the four-channel selector, pin nine can be connected to one of pins one, two, or three. Specifically, when pins six and seven are both set to high level, pin nine is connected to pin two; when pins six and seven are set to high level and low level respectively, pin nine is connected to pin one; and when pins six and seven are set to low level and high level respectively, pin nine is connected to pin three.

[0049] By controlling the levels of pins six and seven of the four-channel selector, pins nine and eight are selected to be connected. Specifically, when pins six and seven are set to low levels, pins nine and eight are connected.

[0050] The first, second, and third resistors are 1000 kΩ, 100 kΩ, and 10 kΩ, respectively. The variable sampling resistor R5 is connected in series with any one of the first, second, and third resistors R1, R2, and R3, respectively, to calculate the corresponding three candidate resistor values. The three candidate resistor values ​​are compared with the corresponding first, second, and third resistors to obtain three differences. The candidate resistor value with the smaller difference is taken as the resistance value of the variable sampling resistor. The resistor with the smaller difference is then connected in series with the variable sampling resistor R5.

[0051] Specifically: Connect the first resistor R1 and the variable sampling resistor R5 in series. Then, calculate the resistance value of the variable sampling resistor R5 according to the method described above, and use it as the first candidate resistor value. Compare the first candidate resistor value with the resistance value of the first resistor R1, and determine the difference as the first difference value.

[0052] Connect the second resistor R2 and the variable sampling resistor R5 in series. Then, calculate the resistance value of the variable sampling resistor R5 according to the method described above, and use it as the second candidate resistor value. Compare the second candidate resistor value with the resistance value of the second resistor R2, and determine the difference as the second difference value.

[0053] Connect the third resistor R3 and the variable sampling resistor R5 in series. Then, calculate the resistance value of the variable sampling resistor R5 using the method described above, and use it as the third candidate resistor value. Compare the third candidate resistor value with the resistance value of the third resistor R3 to determine the difference as the third difference value.

[0054] The absolute values ​​of the first, second, and third differences are used to select the resistor corresponding to the smallest of the three values. For example, since the absolute value of the third difference is the smallest, the third resistor R3 and the variable sampling resistor R5 are connected in series.

[0055] Reference Figure 2 The sensor sensitivity test circuit also includes a sixteen-channel selector. In this embodiment, the sixteen-channel selector is a CD74HC4067SM96 model. Pin nine of the four-channel selector and the common terminal of the variable sampling resistor R5 are electrically connected to the sixteen-channel selector to test the voltage division value of the variable sampling resistor.

[0056] In this embodiment, the sensor sampling resistor reading circuit includes 16 four-channel selectors, each of which is electrically connected in sequence to pins I0 to I7 and pins I8 to I15 of the sixteen-channel selector.

[0057] In this embodiment, 16 four-channel selectors are used, with each four-channel selector corresponding to one sensor. The common terminal of pin 9 and the variable sampling resistor R5 on each of the four-channel selectors is sequentially connected to pins 2 to 9 and pins 16 to 23 of the sixteen-channel selector, for simultaneously detecting the voltage drop across multiple variable sampling resistors R5.

[0058] Reference Figure 4 The sensor sensitivity testing circuit also includes a sensor sampling and processing circuit, which includes multiple first followers. The non-inverting input of the first follower is electrically connected to pin 8 of the four-channel selector and the common terminal of the sensor working resistor R4. The output of the first follower is electrically connected to the analog input channel of the analog-to-digital converter chip AD7616BSTZ. The first follower performs voltage regulation and transmits the analog signal of the voltage of the sensor working resistor collected to the analog-to-digital converter chip to convert it into digital information.

[0059] Reference Figure 5 The circuit of the analog-to-digital converter chip AD7616BSTZ is existing technology and will not be described in detail.

[0060] In this embodiment, 16 first followers are configured, each corresponding to one of the sensors, to collect the sensor's operating resistance voltage and display it digitally. The output terminals of the 16 first followers are electrically connected to pins 2, 4, 7, 9, 12, 14, 17, 19, 22, 24, 26, 28, 73, 75, 77, and 79 of the AD7616BSTZ chip, respectively.

[0061] Reference Figure 6 The sensor sensitivity testing circuit also includes a sensor material catalytic treatment circuit, which includes multiple second followers.

[0062] The input terminal of the second follower is electrically connected to the analog signal output pin of the digital-to-analog converter chip, and the output terminal of the second follower is electrically connected to the compensation resistor of the sensor. The digital-to-analog converter chip outputs a voltage signal to the second follower, and the voltage at the output terminal and input terminal of the second follower are kept consistent. The second follower amplifies the current, and its output terminal supplies a large current to the compensation resistor of the sensor. The compensation resistor heats up, meeting the temperature requirements of the sensor's operating resistance when testing the gas. The digital-to-analog converter chip used is the DAC8568IAPWR model. The DAC8568IAPWR is existing technology and will not be described in detail further.

[0063] Reference Figure 6 and Figure 7 In this embodiment, two digital-to-analog converter chips, DAC8568IAPWR, are used. The pins VOUTA, VOUTB, VOUTC, VOUTD, VOUTE, VOUTF, VOUTG, and VOUTH of the digital-to-analog converter chips are electrically connected to the input terminal of a second follower, and the two digital-to-analog converter chips are electrically connected to a total of 16 second followers.

[0064] By individually adjusting the input voltage of each of the second followers, the output voltage of the second follower changes with the input voltage. The voltage in the series circuit between the output terminal of the second follower and the compensation resistor of the sensor changes, and the current supplied by the second follower to the compensation resistor of the sensor changes accordingly. The heating of the compensation resistor of the sensor changes with the change of current, thereby realizing individual control of the temperature rise of each sensor.

[0065] In another embodiment, a sensor sensitivity testing device is provided, including a main control chip, specifically an STM32H750VBT6 model. The sensor sensitivity testing device uses a sensor sensitivity testing circuit electrically connected to the main control chip. The main control chip is connected to a display screen via a USB communication module and to a smart terminal via a Bluetooth module. The STM32H750VBT6 main control chip is prior art and will not be described in detail.

[0066] Another embodiment provides a sensor sensitivity testing method, applied to the sensor sensitivity testing circuit and the sensor sensitivity testing equipment, comprising the following steps: Step 1, calculate the resistance value of the variable sampling resistor: By controlling the levels of pins six and seven of the four-channel selector, pin nine is connected to one of pins one, two, or three to form a series circuit with the variable sampling resistor, and the voltage division of the variable sampling resistor is measured and recorded as the first voltage division value; combined with the resistance value of the selected resistor used to form the series circuit, the first power supply voltage value, and the first voltage division value, the resistance value of the variable sampling resistor is calculated according to the voltage divider law; Step 2, calculate the resistance value of the sensor working resistor: By controlling the level of pins six and seven of the four-channel selector, pins nine and eight are connected, and the variable sampling resistor and the sensor working resistor form a series circuit. The voltage division value of the variable sampling resistor is recorded as the second voltage division value. Combining the second power supply voltage value, the second voltage division value, and the resistance value of the variable sampling resistor, the resistance value of the sensor working resistor is calculated according to the voltage divider law. Step 3, calculate the sensor sensitivity, including: Step 3.1, before testing gas concentration: The resistance value of the variable sampling resistor is calculated using the method described above. Using the method described above for calculating the resistance value of the sensor's working resistance, the resistance value of the sensor's working resistance is calculated as the initial resistance value of the sensor's working resistance. Step 3.2, after starting the gas concentration test: By controlling the levels of pins six and seven of the four-channel selector, pins nine and eight are connected. The variable sampling resistor and the sensor operating resistor form a series circuit. After testing the gas concentration, the voltage drop across the variable sampling resistor is measured to determine if it falls within the range of 0.5V to 4.5V. If the voltage division value of the variable sampling resistor is in the range of 0.5V to 4.5V, the voltage division value of the variable sampling resistor shall be recorded as the second voltage division value; At this point, the current resistance value of the sensor's working resistance is calculated according to the method for calculating the resistance value of the sensor's working resistance. The wall ratio of the current resistance value of the sensor's operating resistor to the initial resistance value of the sensor's operating resistor is the sensor sensitivity. If the voltage division value of the variable sampling resistor is not within the range of 0.5V to 4.5V, adjust the variable sampling resistor to make the voltage division value of the variable sampling resistor within the range of 0.5V to 4.5V, and then record the voltage division value of the variable sampling resistor that is re-acquired as the second voltage division value; The resistance value of the variable sampling resistor is recalculated using the method described above for calculating the resistance value of the variable sampling resistor; At this point, the current resistance value of the sensor's working resistance is calculated according to the method for calculating the resistance value of the sensor's working resistance. The ratio of the current resistance value of the sensor's operating resistor to its initial resistance value is the sensor sensitivity.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A sensor sensitivity testing circuit, including a sensor sampling resistor reading circuit, characterized in that the sensor sampling resistor reading circuit includes: a four-channel selector; The first resistor has one end electrically connected to pin 1 of the four-channel selector and the other end connected to the power supply. The second resistor has one end electrically connected to pin 2 of the four-channel selector and the other end connected to the power supply. The third resistor has one end electrically connected to pin 3 of the four-channel selector and the other end connected to the power supply. The sensor's operating resistor is electrically connected at one end to pin 8 of the four-channel selector and at the other end to the power supply. A variable sampling resistor, one end of which is electrically connected to pin nine of the four-channel selector, and the other end is connected to ground; The power supply voltages of the first resistor, the second resistor, and the third resistor are denoted as the first power supply voltage value; the power supply voltage of the sensor's working resistor is denoted as the second power supply voltage value. Calculating the sensitivity of the sensor includes: Before testing gas concentration: The resistance value of the variable sampling resistor is calculated using the method of calculating the resistance value of the variable sampling resistor. The resistance value of the sensor's working resistance is calculated using the method of calculating the resistance value of the sensor's working resistance, and the initial resistance value of the sensor's working resistance is obtained. After starting to test gas concentration: By controlling the levels of pins six and seven of the four-channel selector, pins nine and eight are connected. The variable sampling resistor and the sensor working resistor form a series circuit. After testing the gas concentration, the voltage drop value of the variable sampling resistor is tested. Based on whether the voltage drop value of the variable sampling resistor is within the range of 0.5V to 4.5V, the current resistance value of the sensor working resistor is calculated using the method of calculating the current resistance value of the sensor working resistor. The ratio of the current resistance value of the sensor's operating resistor to its initial resistance value is the sensor sensitivity.

2. The sensor sensitivity testing circuit according to claim 1, characterized in that... , The specific method for calculating the resistance value of the variable sampling resistor is as follows: By controlling the levels of pins six and seven of the four-channel selector, one of pins nine and pins one, two, or three is connected to form a series circuit with one of the first resistor, second resistor, or third resistor, and the variable sampling resistor is tested and recorded as the first voltage divider value; combining the resistance values ​​of the selected first, second, and third resistors used to form the series circuit, the first power supply voltage value, and the first voltage divider value, the resistance value of the variable sampling resistor is calculated according to the voltage divider law; The specific method for calculating the resistance value of the sensor's working resistance is as follows: By controlling the levels of pins six and seven of the four-channel selector, pins nine and eight are connected, forming a series circuit with the variable sampling resistor and the sensor's working resistance. The voltage division value of the variable sampling resistor is recorded as the second voltage division value. Combining the second power supply voltage value, the second voltage division value, and the resistance value of the variable sampling resistor, the resistance value of the sensor's working resistance is calculated according to the voltage divider law.

3. The sensor sensitivity testing circuit according to claim 2, characterized in that... Based on whether the voltage division value of the variable sampling resistor is within the range of 0.5V to 4.5V, the current resistance value of the sensor's operating resistance is calculated using a method for calculating the current resistance value of the sensor's operating resistance. Specifically: If the voltage division value of the variable sampling resistor is in the range of 0.5V to 4.5V, the voltage division value of the variable sampling resistor shall be recorded as the second voltage division value; At this point, the current resistance value of the sensor's working resistance is calculated using the method for calculating the resistance value of the sensor's working resistance. If the voltage division value of the variable sampling resistor is not within the range of 0.5V to 4.5V, adjust the variable sampling resistor to make the voltage division value within the range of 0.5V to 4.5V, and record the voltage division value of the variable sampling resistor as the second voltage division value; recalculate the resistance value of the variable sampling resistor using the same method. At this point, the current resistance value of the sensor's operating resistance is calculated using the method for calculating the sensor's operating resistance.

4. The sensor sensitivity testing circuit according to claim 2, characterized in that... By controlling the levels of pins six and seven of the four-channel selector, pin nine can be connected to one of pins one, two, or three. Specifically, when pins six and seven are both set to high level, pin nine and pin two are connected; when they are set to high level and low level respectively, pin nine and pin one are connected; when they are set to low level and high level respectively, pin nine and pin three are connected. By controlling the levels of pins six and seven of the four-channel selector, pins nine and eight are selected to be connected. Specifically, when pins six and seven are set to low levels, pins nine and eight are connected.

5. The sensor sensitivity testing circuit according to claim 1, characterized in that... The first, second, and third resistors are 1000 kΩ, 100 kΩ, and 10 kΩ, respectively. The variable sampling resistor is connected in series with any one of the first, second, and third resistors. The three candidate resistor values ​​for the variable sampling resistor are calculated in turn. The three candidate resistor values ​​are compared with the corresponding first, second, and third resistors to obtain three differences. The candidate resistor value with the smaller difference is taken as the resistance value of the variable sampling resistor.

6. The sensor sensitivity testing circuit according to claim 1, characterized in that... It also includes a sixteen-channel selector, with pin nine of the four-channel selector and the common terminal of the variable sampling resistor electrically connected to the sixteen-channel selector for testing the voltage division value of the variable sampling resistor.

7. The sensor sensitivity testing circuit according to claim 6, characterized in that... It also includes a sensor sampling and processing circuit, which includes multiple first followers. The non-inverting input of the first follower is electrically connected to pin 8 of the four-channel selector and the common terminal of the sensor working resistor. The output of the first follower is electrically connected to the analog-to-digital converter chip. The first follower performs voltage regulation and transmits the analog signal of the sensor working resistor voltage collected to the analog-to-digital converter chip to convert it into digital information.

8. The sensor sensitivity testing circuit according to claim 1, characterized in that... It also includes a sensor material catalytic processing circuit, which includes multiple second followers; the input terminal of the second follower is electrically connected to the digital-to-analog converter chip, and the output terminal of the second follower is electrically connected to the compensation resistor of the sensor; the output terminal of the second follower supplies a large current to the compensation resistor of the sensor, causing the compensation resistor to heat up and meet the temperature requirements of the sensor's working resistance when testing the gas; by individually adjusting the input voltage of each second follower, the current supplied by the second follower to the compensation resistor of the sensor is adjusted, thereby achieving individual control of the temperature rise of each sensor.

9. A sensor sensitivity testing device, characterized in that... The device includes a main control chip and a sensor sensitivity testing circuit as described in any one of claims 1 to 8, wherein the sensor sensitivity testing circuit is electrically connected to the main control chip, and the main control chip is connected to a display screen via a USB communication module; the main control chip is connected to a smart terminal via a Bluetooth module.

10. A sensor sensitivity testing method, applied to the sensor sensitivity testing circuit according to any one of claims 1 to 8 and the sensor sensitivity testing device according to claim 9, characterized in that... The steps include: Step 1, calculate the resistance value of the variable sampling resistor: By controlling the levels of pins six and seven of the four-channel selector, pin nine is connected to one of pins one, two, or three to form a series circuit with the variable sampling resistor, and the voltage division of the variable sampling resistor is measured and recorded as the first voltage division value; combining the resistance values ​​of the selected first, second, and third resistors used to form the series circuit, the first power supply voltage value, and the first voltage division value, the resistance value of the variable sampling resistor is calculated according to the voltage divider law; Step 2, calculate the resistance value of the sensor working resistor: By controlling the level of pins six and seven of the four-channel selector, pins nine and eight are connected, and the variable sampling resistor and the sensor working resistor form a series circuit. The voltage division value of the variable sampling resistor is recorded as the second voltage division value. Combining the second power supply voltage value, the second voltage division value, and the resistance value of the variable sampling resistor, the resistance value of the sensor working resistor is calculated according to the voltage divider law. Step 3, calculate the sensor sensitivity, including: Step 3.1, before testing gas concentration: The resistance value of the variable sampling resistor is calculated using the method described above. Using the method described above for calculating the resistance value of the sensor's working resistance, the resistance value of the sensor's working resistance is calculated as the initial resistance value of the sensor's working resistance. Step 3.2, after starting the gas concentration test: By controlling the levels of pins six and seven of the four-channel selector, pins nine and eight are connected. The variable sampling resistor and the sensor operating resistor form a series circuit. After testing the gas concentration, the voltage drop across the variable sampling resistor is measured to determine if it falls within the range of 0.5V to 4.5V. If the voltage division value of the variable sampling resistor is in the range of 0.5V to 4.5V, the voltage division value of the variable sampling resistor shall be recorded as the second voltage division value; At this point, the current resistance value of the sensor's working resistance is calculated according to the method for calculating the resistance value of the sensor's working resistance. The wall ratio of the current resistance value of the sensor's operating resistor to the initial resistance value of the sensor's operating resistor is the sensor sensitivity. If the voltage division value of the variable sampling resistor is not within the range of 0.5V to 4.5V, adjust the variable sampling resistor to make the voltage division value of the variable sampling resistor within the range of 0.5V to 4.5V, and then record the voltage division value of the variable sampling resistor that is re-acquired as the second voltage division value; The resistance value of the variable sampling resistor is recalculated using the method described above for calculating the resistance value of the variable sampling resistor; At this point, the current resistance value of the sensor's working resistance is calculated according to the method for calculating the resistance value of the sensor's working resistance. The ratio of the current resistance value of the sensor's operating resistor to its initial resistance value is the sensor sensitivity.

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