CO2 sensor calibration system

Abstract

The utility model relates to the technical field of infrared gas sensors, and discloses a CO2 sensor calibration system which comprises an infrared light source, an optical gas chamber, an infrared detector and a main circuit system which are sequentially connected, and the main circuit system comprises an amplifying circuit, a single chip microcomputer, an A / D converter and a microprocessor which are sequentially connected. Wherein the infrared detector is internally provided with an NTC temperature sensor, the NDIR technology is adopted, interference of other gases can be avoided, high-precision CO2 concentration measurement is achieved, when the CO2 concentration is measured, the NTC temperature sensor is arranged in the module, a temperature compensation algorithm is used for correcting the CO2 concentration, and the measurement precision is improved.

Description

Technical Field

[0001] The present application relates to the technical field of infrared gas sensors, and in particular to a CO2 sensor calibration system. Background Art

[0002] The increasing concentration of CO2 in the atmosphere is negatively impacting the global ecosystem, climate, and people's lives. Therefore, accurate and real-time monitoring of CO2 concentrations is imperative. This paper proposes a miniaturized, non-dispersive infrared CO2 sensor based on the infrared pyroelectric effect. Using a calibration method, a temperature compensation method is explored. The detector output values at different concentrations and temperatures are measured, and a relationship model between temperature, CO2 concentration, and detector output values is established. This achieves temperature compensation for the sensor, enabling accurate measurements at varying temperatures and concentrations.

[0003] In view of the above-mentioned related technologies, the inventors believe that the sensor has the following defects during the measurement process:

[0004] 1. The preheating time is long. When the product is just powered on, the waveform of the op amp circuit is unstable, resulting in the concentration output of the product not being a stable value when it is just powered on.

[0005] 2. The product recovery time is long. When the product is placed in high-concentration CO2 gas and the gas is taken to normal concentration after entering the product, the concentration value output by the sensor recovers slowly;

[0006] 3. There is some light leakage in the air chamber breathable membrane, which will cause a slight difference in concentration output during the day and night;

[0007] Therefore, a CO2 sensor calibration system is proposed to solve the above problems.

[0008] The above information disclosed in this background technology is only used to increase the understanding of the background technology of this application. Therefore, it may contain information that does not constitute the prior art known to ordinary technicians in this field. Utility Model Content

[0009] In order to solve the problem in the prior art that the product preheating time is long and the operational amplifier circuit waveform is unstable when the product is just powered on, resulting in the product concentration output not being a stable value when just powered on, the present application provides a CO2 sensor calibration system.

[0010] The CO2 sensor calibration system provided in this application adopts the following technical solutions:

[0011] A CO2 sensor calibration system includes an infrared light source, an optical air chamber, an infrared detector, and a main circuit system connected in sequence. The main circuit system includes an amplifier circuit, a single-chip microcomputer, an A / D converter, and a microprocessor connected in sequence. The infrared detector has a built-in NTC temperature sensor. The optical air chamber is provided with an air inlet. A filter is provided at the end of the air inlet, and a breathable membrane is provided on the inner wall of the air inlet. The single-chip microcomputer outputs a 1HZ PWM drive signal to control the on and off of the infrared light source. Infrared light passes through the optical air chamber and is emitted through the infrared detector. The infrared detector converts the optical signal into an electrical signal and sequentially passes through the amplifier circuit and the A / D converter to obtain a detection signal. The detection signal is sent to the microprocessor for processing and the data is transmitted to an external system via a data line.

[0012] Preferably, the optical air chamber is a reflective air chamber structure with a dual-channel design.

[0013] Preferably, the breathable membrane is made of frosted material, which is used to increase ventilation and also has a light-shielding effect.

[0014] Preferably, two infrared detectors are provided, and a 4.26um filter and a 3.91um filter are placed above the two infrared detectors respectively.

[0015] Preferably, the data line adopts the LIN center line.

[0016] In summary, this application has the following beneficial technical effects:

[0017] 1. The use of NDIR technology can avoid interference from other gases and achieve high-precision CO2 concentration measurement. When measuring CO2 concentration, the module has a built-in NTC temperature sensor and uses a temperature compensation algorithm to correct the CO2 concentration, thereby improving measurement accuracy.

[0018] 2. The system can detect changes in CO2 concentration in real time, helping to promptly detect problems such as gas leaks and pollutant emissions;

[0019] 3. When the product is taking in air, the breathable membrane is made of frosted material, which increases the ventilation volume and plays a role of light shielding. It can detect the change of gas concentration in time and achieve the purpose of rapid response;

[0020] 4. The dual-channel design of the optical gas chamber can eliminate the impact of factors such as light source aging and gas chamber pollution on the sensor, thereby improving long-term stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the embodiment of the application;

[0022] Figure 2This is a data graph showing the relationship between peak value difference and concentration at different temperatures in the application examples;

[0023] Figure 3 This is a data graph showing the relationship between the peak value difference and temperature at different concentrations in the application examples. DETAILED DESCRIPTION

[0024] The following is combined with Figure 1-3 This application is described in further detail.

[0025] The present application embodiment discloses a CO2 sensor calibration system. Figure 1-3 A CO2 sensor calibration system includes an infrared light source, an optical air chamber, an infrared detector and a main circuit system connected in sequence. The main circuit system includes an amplifier circuit, a single-chip microcomputer, an A / D converter and a microprocessor connected in sequence. The infrared detector has a built-in NTC temperature sensor, the optical air chamber is provided with an air inlet, a filter is provided at the end of the air inlet, and a breathable membrane is provided on the inner wall. The single-chip microcomputer outputs a 1HZ PWM drive signal to control the on and off of the infrared light source. The infrared light passes through the optical air chamber and is emitted through the infrared detector. The infrared detector converts the optical signal into an electrical signal and obtains a detection signal through the amplifier circuit and the A / D converter in sequence. The detection signal is sent to the microprocessor for processing and the data is transmitted to the external system through a data line.

[0026] The infrared detector adopts an Indium Gallium Arsenide (InGaAs) infrared detector, which is sensitive to infrared radiation and has high linearity and stability.

[0027] The optical air chamber is a reflective air chamber structure with a dual-channel design, which is used to achieve a longer optical path in a smaller volume. In addition, the reflective air chamber can limit the dispersion of light intensity, which is beneficial to improving the air chamber's light focusing ability and improving the system sensitivity.

[0028] The breathable membrane is made of frosted material, which is used to increase the ventilation volume and also plays a light-shielding role, and can detect changes in gas concentration in a timely manner.

[0029] There are two infrared detectors, and a 4.26um filter and a 3.91um filter are placed above the two infrared detectors respectively.

[0030] The data line adopts a LIN center line, and transmits data to an external system via the LIN center line.

[0031] The implementation principle of a CO2 sensor calibration system in this embodiment of the application is as follows:

[0032] Step 1: Place a filter at the air inlet of the sensor to remove moisture and impurities in the gas to prevent moisture and impurities from affecting infrared radiation;

[0033] Step 2: Due to the dual-channel reflective structure of the optical gas chamber, the infrared light source can pass through a CO2 absorption unit with a longer optical path and then be received by two infrared detectors;

[0034] Step 3: The microcontroller outputs a 1HZ PWM drive signal to control the on and off of the infrared light to increase the service life of the infrared light source;

[0035] Step 4: Select an Indium Gallium Arsenide (InGaAs) infrared detector. Indium Gallium Arsenide is sensitive to infrared radiation and has high linearity and stability. Place a 4.26um filter and a 3.91um filter on the two detectors respectively. The peak of CO2's infrared light absorption is around 4.26um, while it basically does not absorb infrared light at 3.91um. CO2's absorption of infrared light increases with increasing concentration. The absorbed infrared light passes through the filter and irradiates the detector. At the same time, when the infrared detector measures CO2 concentration, the temperature affects the accuracy and stability of the sensor. The infrared detector module has a built-in NTC temperature sensor, and a temperature compensation algorithm is used to correct the CO2 concentration to improve measurement accuracy.

[0036] Step 5: Connect the outputs of the two infrared detectors to the main circuit system, where the amplifier circuit is used to amplify the detected signal. The amplifier circuit is implemented using an operational amplifier to condition and filter the amplifier circuit.

[0037] Step 7: The compensated CO2 concentration signal is sent from the amplifier circuit to the A / D converter to be converted into a digital signal, and the data is transmitted to the external system through the LIN line.

[0038] Finally, a few points should be explained: First, in the description of this application, it should be noted that, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense, and may refer to mechanical or electrical connections, internal communication between two components, or direct connection. "Up," "down," "left," and "right" are only used to indicate relative positional relationships. When the absolute positions of the objects being described change, the relative positional relationships may also change.

[0039] Secondly: The drawings of the embodiments disclosed in this utility model only involve structures related to the embodiments disclosed in this utility model. Other structures can refer to common designs. In the absence of conflicts, the same embodiment and different embodiments of the utility model can be combined with each other.

[0040] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0041] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A CO2 sensor calibration system, characterized by: The invention comprises an infrared light source, an optical air chamber, an infrared detector and a main circuit system connected in sequence. The main circuit system comprises an amplifier circuit, a single-chip computer, an A / D converter and a microprocessor connected in sequence. The infrared detector has a built-in NTC temperature sensor. The optical air chamber is provided with an air inlet. A filter is provided at the end of the air inlet, and a breathable membrane is provided on the inner wall. The single-chip computer outputs a 1HZ PWM drive signal to control the on and off of the infrared light source. The infrared light passes through the optical air chamber and is emitted through the infrared detector. The infrared detector converts the optical signal into an electrical signal and obtains a detection signal through the amplifier circuit and the A / D converter in sequence. The detection signal is sent to the microprocessor for processing and the data is transmitted to the external system through a data line.

2. A CO2 sensor calibration system according to claim 1, characterized in that: The optical air chamber is a reflective air chamber structure and has a dual-channel design.

3. A CO2 sensor calibration system according to claim 1, characterized in that: The breathable membrane is made of frosted material, which is used to increase ventilation and also has a light-shielding effect.

4. A CO2 sensor calibration system according to claim 1, characterized in that: There are two infrared detectors, and a 4.26um filter and a 3.91um filter are placed above the two infrared detectors respectively.

5. A CO2 sensor calibration system according to claim 1, characterized in that: The data line adopts the LIN center line.

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