A high-performance gas sensor detection method

Abstract

The application provides a high-performance gas sensor detection method, which comprises the following steps: setting up a detection circuit; connecting a low-temperature drift resistor in series with a compensation element of a Wheatstone bridge circuit; collecting the voltage across the low-temperature drift resistor at 25 DEG C, collecting the voltage of the compensation element at 25 DEG C, and calculating the equivalent resistance of the compensation element at 25 DEG C as a calibration value; collecting the voltage of the compensation element and the input voltage in real time, and calculating the equivalent resistance of the compensation element; and adjusting the input voltage across the sensitive element and the compensation element so that the equivalent resistance of the compensation element is the same as the calibration value in step two. The application can accurately calculate the voltage value that needs to be compensated on the bridge arm, completely eliminates the measurement error caused by temperature drift, completely compensates the excessive temperature drift of the sensor caused by the change of the ambient temperature, completely eliminates the measurement error caused by temperature drift, improves the detection accuracy, and solves the problem of unsatisfactory high and low temperature detection effect.

Description

Technical Field

[0001] This invention relates to the technical field of sensor detection, and more particularly to a high-performance gas sensor detection method. Background Technology

[0002] Sensors serve as a bridge between the physical and digital worlds, sensing a specified measurand and converting it into a usable signal according to a certain rule. The catalytic combustion sensor principle is one of the most widely used principles for detecting combustible gases, characterized by good linearity of the output signal, fast response speed, and low cost. Currently, catalytic combustion gas sensors have broad application prospects, finding wide application in industrial energy conservation, environmental monitoring, smart homes, and healthcare, among other areas.

[0003] With the advancement of technology, the performance requirements for catalytic combustion gas sensors are becoming increasingly stringent. Catalytic combustion gas sensors utilize the thermal effect of catalytic combustion, and the detection circuit typically employs a Wheatstone bridge, such as... Figure 1 As shown, a bridge circuit consists of a sensitive element 1 and a compensation resistor R0 forming one arm, and resistors R1 and R2 forming the other arm. The sensitive element 1 and the compensation resistor R0 have the same resistance value at 25°C. Here, Vi is the input voltage, VO is the output voltage, and resistor R3 is the equivalent resistance of the sensitive element 1. When combustible gas undergoes flameless combustion on the surface of the sensitive element 1 carrier under the action of a catalyst, the temperature of the sensitive element 1 carrier increases, and the resistance of its internal platinum wire also increases accordingly. This leads to a larger bridge output voltage, and the voltage change increases proportionally with the increase in gas concentration, causing the balanced bridge to become unbalanced and output an electrical signal proportional to the combustible gas concentration.

[0004] In actual measurements, the bridge balance is affected by environmental factors. In high or low temperature environments, the resistance value of the sensitive element 1 will change significantly with temperature. However, the compensation resistor R0 cannot change with temperature in the same way as the equivalent resistance R3 of the sensitive element 1, resulting in a large measurement error of the catalytic combustion gas sensor.

[0005] To eliminate interference and ensure that the components in both arms remain consistent, actual Wheatstone bridges require some corrections or compensations to guarantee the accuracy of measurement results. Typically, this involves... Figure 1 Replace the compensation resistor R0 in the middle with Figure 2The compensation element 2 in the circuit consists of a bridge arm formed by the pairing of the sensing element 1 and the compensation element 2. Both sensing element 1 and compensation element 2 are made of the same platinum alloy, ensuring that they have the same resistance change and that the bridge remains balanced when no combustible gas is detected. Resistor R4 is the equivalent resistance of compensation element 2. Therefore, compensation element 2 is used to compensate for synchronous changes in sensing element 1 caused by environmental changes. Platinum wires are installed inside the casings of sensing element 1 and compensation element 2, with a sensing element mounted on the wires. The two ends of the platinum wires are led out through lead posts. The sensing element and compensation element are manufactured using the same process, both containing platinum wires. However, the surface of the sensing element contains a catalyst, which reacts upon contact with combustible gas in the air; while the compensation element is sealed and cannot come into contact with air, thus not reacting with the gas being measured.

[0006] When combustible gas undergoes flameless combustion on the surface of the carrier of sensing element 1 under the action of the catalyst, the temperature of sensing element 1 rises, and the resistance of the platinum wire inside it also increases accordingly. That is, the equivalent resistance R3 of sensing element 1 increases. At this time, the bridge circuit becomes unbalanced, and the bridge output voltage increases. The voltage change increases proportionally with the increase of gas concentration, outputting an electrical signal proportional to the concentration of combustible gas. The compensation element 2 is used to compensate for the synchronous change of sensing element 1 caused by environmental changes. Because platinum is a temperature-sensitive element, its resistance changes when the temperature rises. The purpose of using the compensation element is to ensure that the resistance of the compensation element and the sensing element changes synchronously when the temperature of the environment changes. Because a bridge circuit is used, i.e., R1 / R2 = sensing element R3 / compensation element R4 = 1, even with environmental changes, the changes in the resistance of the sensing element and the compensation element are consistent. At this time, the bridge circuit is still in a balanced state, and R1 / R2 = sensing element R3 / compensation element R4 = 1, so no voltage is output.

[0007] Compared to a fixed resistor, when the environment changes, R1 / R2 = (sensitive element R3 + ΔR) / R0 ≠ 1. In this case, even if no combustible gas is detected, a voltage will still be output. The compensation element is used to eliminate this voltage. ΔR refers to the change in resistance of the sensitive element during this environmental change, and resistance R0 is... Figure 1 R0 in the middle.

[0008] However, the operating environment of catalytic combustible gas sensors varies greatly, generally ranging from -40°C to 70°C. Temperatures that are too low or too high can significantly affect the sensitive element 1 and the compensation element 2. The sensitivity coefficients of both elements change with temperature, increasing the temperature-related error and resulting in a significant difference in resistance values ​​compared to those measured at 25°C. Specifically, at the same gas concentration, the output voltage VO at high or low temperatures differs considerably from the output voltage VO measured at 25°C. Compensation element 2 can only partially compensate for these synchronous changes, leading to suboptimal performance of the catalytic combustible gas sensor in high or low temperature environments. For instance, while temperature changes can alter the resistance of sensitive element 1, this compensation circuit ensures that both elements maintain the same resistance at the same temperature, mitigating the synchronous changes caused by temperature and preventing bridge imbalance caused by a change in the resistance of sensitive element 1 while compensation element 2 retains its original resistance. However, it cannot fully compensate for the temperature drift caused by temperature changes, and cannot fully compensate for the temperature drift error of the sensor. This often limits the application of catalytic combustible gas sensors in precision instruments.

[0009] The output value of a typical resistive sensor is usually a function of the ambient temperature. For instruments with high performance requirements, it is particularly important to perform reasonable temperature compensation on the sensor without affecting measurement performance. Summary of the Invention

[0010] To address the technical problem of excessive temperature drift in the detection circuit of a synchronously compensated catalytic combustible gas sensor under high and low temperature conditions, resulting in unsatisfactory measurement accuracy, this invention proposes a high-performance gas sensor detection method. This method performs voltage compensation on the sensitive element 1 and the compensation element 2 to compensate for the effects of high and low temperatures on them, making their measurement curves more ideal and improving the measurement accuracy and environmental adaptability of the catalytic combustible gas sensor under high and low temperature environments.

[0011] To achieve the above objectives, the technical solution of the present invention is implemented as follows: a high-performance gas sensor detection method, comprising the following steps:

[0012] Step 1: Build the detection circuit: Connect a low-temperature drift resistor in series with the power supply circuit of the compensation element in the Wheatstone bridge circuit;

[0013] Step 2: Collect the voltage across the low-temperature drift resistor when operating at 25℃, and simultaneously collect the voltage across the compensation element when operating at 25℃. Calculate the equivalent resistance of the compensation element when operating at 25℃ as the calibration value.

[0014] Step 3: Real-time acquisition of the voltage of the compensation element and the input voltage, and calculation of the equivalent resistance of the compensation element; adjust the input voltage across the sensitive element and the compensation element so that the equivalent resistance of the compensation element is the same as the calibration value in Step 2.

[0015] Preferably, in high-temperature or low-temperature applications, to compensate for excessive temperature drift and zero-point drift caused by temperature, the equivalent resistance of the sensitive element and the compensation element is kept consistent with the resistance value when operating at 25°C.

[0016] Preferably, the function of the low-temperature drift resistor is to maintain a stable resistance value at different temperatures.

[0017] Preferably, the Wheatstone bridge circuit has a differential output mode, and when operating at a constant temperature of 25°C, Output voltage V O When the output is 0, the Wheatstone bridge is balanced; where R1 and R2 are the resistors on the other arm, R3 is the equivalent resistance of the sensitive element, R4 is the equivalent resistance of the compensation element, and R5 is the resistance value of the low temperature drift resistor.

[0018] Preferably, the method for calculating the equivalent resistance of the compensation element at 25°C in step two is as follows: the voltage V3 across the low-temperature drift resistor is acquired by the first voltage acquisition module. t0 Calculate the current through the low-temperature drift resistor. The current of the compensation element is equal to the current of the low-temperature drift resistor; the voltage V2 of the compensation element is acquired through the second voltage acquisition module. t0 At this point, the equivalent resistance value of the compensation element is:

[0019]

[0020] Preferably, the resistance value R5 of the low-temperature drift resistor is less than half the resistance value of R4 and is not 0Ω; the equivalent resistance R4 of the compensation element when operating at 25°C t0 The calibration values ​​are stored in memory.

[0021] Preferably, when the sensitive element comes into contact with combustible gas, heat is released due to the intense oxidation, causing the temperature of the sensitive element to rise and the equivalent resistance R3 of the sensitive element to increase accordingly. At this time, the Wheatstone bridge is no longer balanced, and the output potential difference is the output voltage Vo.

[0022] Preferably, when the bridge is unbalanced, the relationship between the output voltage Vo and the input voltage Vi is as follows:

[0023]

[0024] Right now

[0025] Preferably, the first voltage acquisition module acquires the voltage V3 across the low-temperature drift resistor. t And calculate the current A2 through the compensation element. t The second voltage acquisition module acquires the voltage V2 of the compensation element in real time. t When the ambient temperature changes, calculate the equivalent resistance of the compensation element:

[0026]

[0027] To compensate for zero-point drift in the circuit, the supply voltage of the bridge circuit, i.e., the input voltage Vi, is adjusted so that the equivalent resistance of the compensation element is adjusted to R4. t0 At this time, the voltage of the supply voltage V2 is: V2 t =A2 t R4 t0 ,Right now

[0028]

[0029] Among them, V2 t0 This indicates the voltage value of the supply voltage measured at 25℃.

[0030] Preferably, by It can be seen that R4 t0 Consider it as a constant, voltage V2 t and current A2 t It is a direct proportional function; retrieve the calibration value from memory and calculate the voltage V2. t The value is obtained through the voltage V3 across the low-temperature drift resistor. t The value of voltage V2 t The value is finely adjusted, and the input voltage Vi is monitored in real time by the third voltage acquisition module. The third voltage acquisition module acquires the input voltage Vi, and the voltage across the equivalent resistance of the sensitive element is Vi-V2. t Based on the obtained voltage V3 value, adjust the input voltage value according to the collected input voltage Vi.

[0031] When the equivalent resistance Rt is greater than the rated value R4 t0 At that time, reduce the input voltage Vi;

[0032] When the equivalent resistance Rt is less than the rated value R4 t0 At that time, increase the input voltage Vi.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: voltage compensation is performed on the sensitive element and the compensation element to compensate for the effects of high temperature and low temperature on the sensitive element and the compensation element, and the equivalent resistance of the sensitive element and the compensation element is compensated to the resistance value when operating in an ideal environment of 25°C, thereby improving the measurement accuracy and environmental adaptability of the catalytic combustible gas sensor under high temperature and low temperature environments.

[0034] Compared to catalytic combustion sensors with synchronous compensation, the significant feature of this invention is that it can accurately calculate the voltage value that needs to be compensated on the bridge arm through multiple voltage acquisition modules, data storage, data calculation, and voltage output control, completely eliminating measurement errors caused by temperature drift. This invention can completely compensate for excessive sensor temperature drift caused by changes in ambient temperature during use through voltage detection and adjustment, completely eliminating measurement errors caused by temperature drift, improving detection accuracy, and solving the problem of unsatisfactory high and low temperature detection results. Attached Figure Description

[0035] 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.

[0036] Figure 1 This is a schematic diagram of a traditional catalytic combustion sensor.

[0037] Figure 2 This is a schematic diagram of a catalytic combustion sensor with synchronous compensation.

[0038] Figure 3 This is a flowchart of the present invention.

[0039] Figure 4 This is a schematic diagram of the catalytic combustible gas sensor of the present invention.

[0040] In the diagram, 1 is the sensitive element and 2 is the compensation element. Detailed Implementation

[0041] 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.

[0042] like Figure 3 As shown, a high-performance gas sensor detection method comprises the following steps:

[0043] Step 1: Set up the detection circuit: Connect the low temperature drift resistor R5 in series with the compensation element 2.

[0044] The purpose of this invention is to compensate for the influence of ambient temperature on the detection value, improve detection accuracy, and enhance the temperature drift and environmental stability of the catalytic combustible gas sensor under high and low temperature environments.

[0045] In practical applications, when the temperature changes, the resistance characteristics of the sensing element 1 and the compensation element 2 will change compared to their resistance when operating at the standard temperature of 25°C. In particular, when the temperature change is too large, the change in sensitivity characteristics is more obvious, and the temperature drift is greater, resulting in a larger error of the catalytic combustion gas sensor in high or low temperature environments.

[0046] like Figure 4 As shown, in high-temperature or low-temperature applications, to compensate for excessive temperature drift, zero-point drift, and large measurement deviations caused by temperature, the equivalent resistance of the sensing element 1 and the compensation element 2 can be kept consistent with the resistance value at 25℃. By adjusting the input voltage Vi, the current increases as the voltage increases, and the sensor temperature also rises to a certain level when measuring at 25℃ (because gas sensors typically operate at relatively high temperatures). However, when the ambient temperature is significantly lower than 25℃, the sensor's operating temperature will not reach the 25℃ operating temperature, and the platinum resistance will also be inconsistent. The same principle applies to excessively high temperatures; by adjusting the voltage and current to increase or decrease the power, the sensor temperature is controlled, maintaining the sensor's resistance at 25℃. The low-temperature drift resistor R5 maintains a stable resistance value at different temperatures.

[0047] In this invention, the Wheatstone bridge circuit uses differential output, and when operating at a constant temperature of 25°C, At this time, the output voltage V O The output is 0, indicating that the bridge is balanced.

[0048] Step 2: Collect the voltage across the low-temperature drift resistor R5 when operating at 25℃, and simultaneously collect the voltage of compensation element 2 when operating at 25℃. Calculate the equivalent resistance of compensation element 2 when operating at 25℃ as the calibration value.

[0049] The voltage V3 across the cryogenic resistor R5 is acquired via the voltage acquisition module V3. t0 The resistance of the low-temperature drift resistor R5 is less than half the resistance of R4 and is not 0Ω. Therefore, the current through compensation element 2 can be calculated. The current in compensation element 2 is equal to the current in low-temperature drift resistor R5. At this time, the voltage V2 of compensation element 2 is acquired by voltage acquisition module V2. t0 The equivalent resistance value of compensation element 2 at this time can be calculated using the following:

[0050]

[0051] The equivalent resistance R4 of compensation element 2 when it operates at 25℃ t0 The calculated calibration value is stored in memory as the calibration value. Equivalent resistance R4 t0 Including the low-temperature drift resistor R5, it is necessary to ensure that the resistance value of the low-temperature drift resistor R5 remains unchanged, because the characteristic of the low-temperature drift resistor is that its resistance does not change with temperature. It is usually used in precision instruments.

[0052] Step 3: Real-time acquisition of the voltage and input voltage of compensation element 2, calculation of the equivalent resistance of compensation element, and adjustment of the input voltage across sensitive element 1 and compensation element 2 to make the equivalent resistance of compensation element 2 the same as the calibration value.

[0053] When the sensing element 1 comes into contact with the combustible gas, it releases heat due to the intense oxidation, causing the temperature of the sensing element 1 to rise. The equivalent resistance R3 of the sensing element 1 also increases accordingly. At this time, the bridge is no longer balanced, and the output potential difference is the output voltage Vo.

[0054] When the bridge circuit is unbalanced, the relationship between the output voltage Vo and the input voltage Vi is as follows:

[0055]

[0056] Right now

[0057] Note: By convention, when the voltage output Vo detects combustible gas, it is represented by Vs.

[0058] During use, the reference bridge voltage acquisition module V2 acquires the voltage of compensation element 2 and the voltage of the equivalent resistance R3 of sensitive element 1 in real time (V1-V2-V3); when the ambient temperature changes, the equivalent resistance of compensation element 2 is calculated at this time:

[0059]

[0060] To compensate for zero-point drift in the circuit, the supply voltage V2 of the bridge circuit can be adjusted so that the equivalent resistance of the compensation element 2 is adjusted to R4. t0 At this time, the voltage of the supply voltage V2 is:

[0061] V2 t =A2 t R4 t0

[0062]

[0063] Among them, V2 t0 This indicates that the voltage value of V2 measured at 25℃ has been stored in the storage module.

[0064] By V2 t =A2t R4 t0 It can be seen that R4 t0 It can be regarded as a constant, namely voltage V2 t and current A2 t It is a directly proportional function. The calibration value from memory can be retrieved, and the voltage V2 can be calculated in advance using this formula. t Value, and through feedback voltage V3 t The value of voltage V2 t The value of V3 is fine-tuned, and the input voltage Vi is monitored in real time by the power supply voltage acquisition module. Based on the acquired voltage value of V3, it is then used as an input parameter to the microcontroller. The microcontroller adjusts the value of the input voltage Vi according to the acquired voltage. The input voltage Vi serves as a feedback voltage, allowing for a direct understanding of the magnitude of the input voltage.

[0065] When the equivalent resistance Rt is greater than the rated value R4 t0 At this time, reduce the input voltage Vi;

[0066] When the equivalent resistance Rt is less than the rated value R4 t0 When the gas is not detected, increase the input voltage Vi. The output voltage VO should remain at 0V when no gas is detected; when detected, the output voltage is proportional to the concentration of the gas.

[0067] After data calculation, the power supply voltage of the entire circuit is adjusted by voltage control to adjust the compensation voltage of compensation element 1, so that the equivalent resistance value of compensation element 2 is consistent with that when it is working at 25℃. This is to offset the influence of ambient temperature on the detection value, compensate for the temperature drift of the environment, improve the detection accuracy, greatly improve the reliability and stability of the catalytic combustion gas sensor, and completely eliminate the measurement error caused by temperature drift.

[0068] Each voltage acquisition module and memory is connected to the data calculation module, which in turn is connected to the voltage output control module. The data calculation module calculates the equivalent resistance value of the compensation element, compares it with the calibration value in the memory, and issues control commands. The voltage output control module adjusts the input voltage according to the control commands.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-performance gas sensor detection method, characterized in that, The steps are as follows: Step 1: Build the detection circuit: Connect a low-temperature drift resistor in series with the power supply circuit of the compensation element in the Wheatstone bridge circuit; Step 2: Collect the voltage across the low-temperature drift resistor when operating at 25℃, and simultaneously collect the voltage across the compensation element when operating at 25℃. Calculate the equivalent resistance of the compensation element when operating at 25℃ as the calibration value. Step 3: Real-time acquisition of the voltage of the compensation element and the input voltage, and calculation of the equivalent resistance of the compensation element; adjust the input voltage to adjust the voltage across the sensitive element and the compensation element so that the equivalent resistance of the compensation element is the same as the calibration value in Step 2. The method for calculating the equivalent resistance of the compensation element at 25℃ in step two is as follows: the voltage V3 across the low-temperature drift resistor is acquired through the first voltage acquisition module. t0 Calculate the current through the low-temperature drift resistor. The current of the compensation element is equal to the current of the low-temperature drift resistor; the voltage V2 across the compensation element is acquired by the second voltage acquisition module. t0 At this point, the equivalent resistance value of the compensation element is: 。 2. The high-performance gas sensor detection method according to claim 1, characterized in that, The Wheatstone bridge circuit has a differential output mode and operates at a constant temperature of 25°C. When the output voltage V0 is 0, the Wheatstone bridge reaches balance; where R1 and R2 are resistors on the other arm, R3 is the equivalent resistance of the sensitive element, R4 is the equivalent resistance of the compensation element, and R5 is the resistance value of the low temperature drift resistor.

3. The high-performance gas sensor detection method according to claim 2, characterized in that, The resistance value R5 of the low-temperature drift resistor is less than half the resistance value of R4 and is not 0Ω; the equivalent resistance R4 of the compensation element when operating at 25℃ t0 The calibration values ​​are stored in memory.

4. The high-performance gas sensor detection method according to any one of claims 1-3, characterized in that, When the sensitive element comes into contact with combustible gas, it releases heat due to intense oxidation, causing the temperature of the sensitive element to rise. The equivalent resistance R3 of the sensitive element increases accordingly. At this time, the Wheatstone bridge is no longer balanced, and the output potential difference is the output voltage V0.

5. The high-performance gas sensor detection method according to claim 4, characterized in that, When the bridge is unbalanced, the output voltage V0 and the input voltage V i The relationship is: Right now .

6. The high-performance gas sensor detection method according to claim 5, characterized in that, The first voltage acquisition module acquires the real-time voltage V3 across the cryogenic resistor. t And calculate the current A2 through the compensation element. t The second voltage acquisition module acquires the real-time voltage V2 across the compensation element. t When the ambient temperature changes, calculate the equivalent resistance of the compensation element in real time: ； To compensate for zero-point drift in the circuit, the supply voltage of the bridge circuit, i.e., the input voltage V, is adjusted. i This adjusts the equivalent resistance of the compensation element to R4. t0 At this time, the real-time voltage of the compensation element is: ,Right now Among them, V2 t0 This indicates the voltage of the compensation element measured at 25℃.

7. The high-performance gas sensor detection method according to claim 6, characterized in that, When the equivalent resistance R4 of the real-time compensation element t Greater than the calibration value R4 t0 When, reduce the input voltage V i The voltage; When the equivalent resistance R4 of the real-time compensation element t Less than the calibration value R4 t0 When the input voltage V is increased i The voltage.

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