H2O2 gas TDLAS analyzer

Abstract

The invention discloses a TDLAS (Tunable Diode Laser Absorption Spectroscopy) analyzer for H2O2 gas, and belongs to the technical field of gas concentration detection. In the H2O2 gas TDLAS analyzer, the inner surface of the gas path system in contact with H2O2 gas is subjected to inert treatment to form a chemical inert layer, so that the gas adsorption loss can be effectively inhibited; the optical path system is arranged in the heat preservation case, a stable physical environment is provided for TDLAS measurement, an instrument is almost not interfered by the field environment, and the long-term drift is extremely small; the laser driving module adopts a composite current source architecture and comprises an operational amplifier serving as an error amplification stage and a push-pull circuit serving as an output stage, so that the stability problem under high-current and high-frequency modulation is fundamentally solved, nearly ideal light source modulation signals are provided for TDLAS detection, and a basis is provided for high-precision harmonic detection. According to the invention, high-performance driving, enhanced protection and precise environment control are deeply coupled, and the precision, stability and reliability of H2O2 gas detection are effectively improved.

Description

Technical Field

[0001] This application relates to the field of gas concentration detection technology, and in particular to a TDLAS analyzer for H2O2 gas. Background Technology

[0002] Hydrogen peroxide (H2O2) is an important industrial oxidant and disinfectant, and accurate monitoring of its gas concentration is crucial in fields such as semiconductor sterilization, medical device disinfection, and food packaging safety. However, H2O2 gas is a strong oxidizing agent and unstable, and it readily adsorbs and catalytically decomposes on surfaces such as sampling pipelines and gas chamber walls, resulting in measured values ​​that are significantly lower than the true concentration. This has long been a problem of "negative measurement bias" in this field.

[0003] While tunable diode laser absorption spectroscopy (TDLAS) technology has been used for the detection of various gases (such as NH3 and CO2), it faces the following unique challenges when applied to H2O2 detection: 1) Gas loss: Ordinary stainless steel or plastic components and optical parts cannot withstand H2O2, resulting in gas loss during transmission due to adsorption and decomposition. 2) Environmental interference: TDLAS measurements are based on Beer-Lambert's law, and the intensity of its absorption signal is directly affected by factors such as gas temperature, pressure, and flow rate. Traditional analyzers lack precise control over the physical state inside the measurement chamber, leading to fluctuations in measured values ​​and poor long-term stability. 3) Thermal management and reliability: High-power lasers and their driving circuits generate a large amount of heat. Uneven heat dissipation from densely packed heat sources can cause laser wavelength drift, performance degradation of driving components, and thermal stress damage to the circuit board, severely restricting the long-term reliability of the equipment. 4) Driving performance issues: Commercially available laser drivers struggle to simultaneously meet the high drive current (>500mA), ultra-high modulation bandwidth (>10MHz), and extremely low noise requirements of quantum cascade lasers (QCLs). Ordinary drive circuits are prone to self-oscillation under high slew rates and high current outputs, leading to modulation waveform distortion and directly affecting the accuracy and stability of harmonic detection. Therefore, existing general-purpose TDLAS analyzers cannot meet the stringent requirements for accuracy, stability, and reliability in H2O2 gas detection. Summary of the Invention

[0004] The purpose of this application is to overcome the shortcomings of the prior art and provide an H2O2 gas TDLAS analyzer to improve the accuracy, stability and reliability of H2O2 gas detection.

[0005] To achieve the above objectives, this application provides the following solution.

[0006] On the one hand, this application provides an H2O2 gas TDLAS analyzer, including a gas path system, an optical path system, and a drive control system; The gas path system includes an inlet, a mass flow controller, a measuring gas chamber, an electronic pressure controller, and a vacuum pump connected sequentially via pipelines; the inner surface of the gas path system in contact with the H2O2 gas is inertized to form a chemically inert layer. The optical path system includes a laser connected in sequence, an optical path containing the measuring gas chamber, and a photodetector; the optical path system is housed inside an insulated enclosure. The drive control system includes a main control unit and a laser drive module electrically connected to the main control unit; the laser drive module adopts a composite current source architecture, including an operational amplifier as an error amplification stage and a push-pull circuit as an output stage.

[0007] Optionally, the inertization treatment is electropolishing and superpassivation treatment; the chemical inert layer is a chromium-rich Cr2O3 oxide layer with a surface roughness Ra≤0.4μm.

[0008] Optionally, the mass flow controller is located at the inlet of the measuring gas chamber to control the gas flow rate entering the measuring gas chamber; the electronic pressure controller is located between the outlet of the measuring gas chamber and the pump; the main control unit is configured to adjust the opening of the electronic pressure controller through a closed-loop PID control algorithm to maintain a constant pressure inside the measuring gas chamber.

[0009] Optionally, the insulation enclosure is further equipped with a wind-bath constant temperature system consisting of a temperature sensor, a heating block, and a fan; the temperature sensor is connected to the main control unit to form a temperature feedback closed loop; the main control unit dynamically adjusts the power of the heating block and the speed of the fan through a PWM signal.

[0010] Optionally, the main control unit is equipped with interlocking protection logic to lock the laser driver module and the air pump when the air bath constant temperature system fails to reach the set temperature.

[0011] Optionally, the laser's housing is coupled with a finned heat sink; a PWM speed-controlled fan is mounted on the finned heat sink.

[0012] Optionally, the push-pull circuit is composed of NPN high-power transistors and PNP high-power transistors; the output of the operational amplifier directly drives the input of the push-pull circuit; a sampling resistor is connected in series with the cathode of the laser, and the voltage signal across the sampling resistor is connected to the inverting input of the operational amplifier as a current feedback signal.

[0013] Optionally, the laser driver module integrates a hardware protection circuit, including a limiting circuit, a precision current limiting circuit, an over-temperature protection switch, a soft-start circuit, and a hardware shutdown circuit; the soft-start circuit and the hardware shutdown circuit are located on the power supply path of the laser.

[0014] Optionally, the laser driving module includes a driving circuit board; the power devices on the driving circuit board are provided with a thermally conductive via array at their bottom; an aluminum alloy heat sink is installed on the back of the driving circuit board; a ventilation window is provided at a corresponding position of the insulated housing, and the ventilation window and the aluminum alloy heat sink are positioned to form an air duct.

[0015] Optionally, the main control unit is equipped with a software protection module; the software protection module is configured to monitor the temperature of the driver circuit board, the temperature of the laser tube housing, the operating current and the output optical power in real time; when the monitored parameters exceed the limits, the software protection module triggers a graded alarm or controls the hardware shutdown circuit to cut off the power supply.

[0016] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application provides an H2O2 gas TDLAS analyzer in which the inner surface of the gas path system in contact with H2O2 gas is inertized to form a chemically inert layer, effectively suppressing gas adsorption loss. The optical path system is housed within an insulated enclosure, providing a stable physical environment for TDLAS measurements, making the instrument virtually unaffected by environmental interference and exhibiting minimal long-term drift. The laser drive module employs a composite current source architecture, including an operational amplifier as an error amplification stage and a push-pull circuit as an output stage, fundamentally solving the stability problem under high current and high-frequency modulation. This provides a near-ideal light source modulation signal for TDLAS detection, laying the foundation for high-precision harmonic detection. This application deeply couples high-performance drive, enhanced protection, and precise environmental control, effectively improving the accuracy, stability, and reliability of H2O2 gas detection. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the overall architecture of the H2O2 gas TDLAS analyzer; Figure 2 This is a three-dimensional structural diagram of some components in a TDLAS analyzer for H2O2 gas. Figure 3This is a schematic diagram of the structure of a wind-bath constant temperature system; Figure 4 This is a schematic diagram of the temperature PID control algorithm. Figure 5 An exploded view of the heat dissipation structure of a laser. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] This application aims to provide a dedicated H2O2 gas TDLAS analyzer that employs TDLAS technology and features high-speed, high-stability drive, multiple safety protections, and precise control of the entire system environment, in order to meet the stringent requirements for accuracy, stability, and reliability in H2O2 gas detection.

[0021] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] In one exemplary embodiment, this application provides an H2O2 gas TDLAS analyzer, including a gas path system, an optical path system, and a drive control system, the overall architecture of which is as follows: Figure 1 As shown, the three-dimensional structure of some of its components is as follows: Figure 2 As shown. The gas path system includes an inlet 1, a mass flow controller (MFC) 2, a measuring gas chamber 3, an electronic pressure controller (EPC) 4, and a vacuum pump 5, all connected sequentially via pipelines. The optical path system includes a laser 6, an optical path containing the measuring gas chamber 3, and a photodetector 7, all connected sequentially. The drive control system includes a main control unit 8 and a laser drive module 9. The main control unit 8 is electrically connected to the MFC 2, EPC 4, vacuum pump 5, and laser drive module 9. The laser drive module 9 is electrically connected to the photodetector 7.

[0023] One innovation of this application lies in the inert surface treatment of the gas path structure. Specifically, the inner surfaces of the gas path system in contact with H2O2 gas undergo inert treatment to form a chemically inert layer. All surfaces in contact with H2O2 gas (including the sampling tube, connectors, MFC flow channel, inner wall of the measuring gas chamber, and EPC flow channel) are made of 316L stainless steel and undergo electropolishing and ultra-passivation treatment to form a chromium-rich, extremely dense, and chemically inert Cr2O3 oxide layer. The surface roughness after treatment is Ra≤0.4μm. This reduces the gas loss rate during transmission to <2%, thereby ensuring that the gas concentration entering the measuring gas chamber 1 is essentially consistent with that at the sampling point.

[0024] Another innovation of this application lies in the system-level precision pressure and flow control structure, including front-end constant current control and back-end constant pressure control.

[0025] Front-end constant flow control: MFC5 is set at the air inlet of the gas path system to precisely control the gas flow rate entering the measuring gas chamber 1 and stabilize it at a set value, such as 1.0 L / min ± 1%.

[0026] Back-end constant pressure control: At the end of the gas path system, the vacuum pump 4 and EPC6 work together. EPC6 is located before the vacuum pump 4 and monitors the pressure in the measuring chamber 1 in real time. The main control unit adopts a closed-loop PID control algorithm to maintain the gas pressure in the measuring chamber 1 at a constant set value, such as 1 standard atmosphere ±0.1%, by adjusting the opening degree of EPC6.

[0027] This application's pre-flow control and post-pressure control scheme ensures a constant number density of gas molecules along the absorption optical path in the measurement chamber 1, directly eliminating the broadening and intensity changes in the absorption spectrum caused by pressure and flow fluctuations, fundamentally improving the accuracy and repeatability of the measurement.

[0028] Another innovation of this application is that the optical path system is housed within the insulated enclosure 10, forming a unified air-bath constant temperature system structure. See [link to relevant documentation]. Figure 1 , Figure 2 and Figure 3The core optical components, including the laser 6, measuring gas chamber 3, and photodetector 7, are integrated and encapsulated within a heat-insulated enclosure 10. The enclosure wall has a double-layer structure with a polyurethane foam insulation layer in between. A PT1000 high-precision temperature sensor 11 is installed inside the enclosure, along with a fan 12 and a heating block 13 driven by a PWM signal from the main control unit 8, forming an "air bath" environment. The heating block 13 is located at the air outlet of the fan 12, which blows the heat generated by the heating block 13 into the interior space of the enclosure, creating a circulating airflow. The main control unit 8 sets an operating temperature point higher than the highest ambient temperature, for example, 40°C. After the system is powered on, the heating block 13 and fan 12 are activated first to heat and circulate the air inside the enclosure, causing the temperature inside the enclosure to rise rapidly and evenly to the set point. Subsequently, the constant temperature maintenance stage begins: temperature sensor 11 provides real-time feedback on the temperature inside the chamber, and main control unit 8 dynamically adjusts the power of heating block 13 and the speed of fan 12 through PWM signal to achieve precise proportional control and keep the temperature fluctuation inside the chamber within ±0.02℃.

[0029] Figure 4 The diagram illustrates the control principle of the temperature PID control algorithm integrated in the main control unit 8. (See also...) Figure 3 and Figure 4 The temperature PID control algorithm is a typical closed-loop negative feedback control system, whose core objective is to maintain a constant air temperature inside the insulation box 10.

[0030] Input and setting: The main control unit 8 presets a target value that is higher than the highest ambient temperature.

[0031] Feedback sensing: The high-precision temperature sensor 11 installed in the chassis 10 monitors the temperature inside the chassis in real time and converts it into an electrical signal to feed back to the main control unit 8.

[0032] Control Calculation: The main control unit 8 compares the target temperature value with the sensor feedback value and calculates the error value. This error value is then fed into the PID control algorithm for further calculation. The algorithm outputs a control signal based on the magnitude, accumulation (integral), and trend (derivative) of the current error. The purpose of the PID control algorithm is to enable the system to quickly and smoothly reach the target temperature without generating large overshoot or oscillations.

[0033] Output: The control signal is divided into two paths. One path controls the heating block 13 by adjusting the voltage or power applied to it to control its heat generation. The other path controls the fan 12 through a PWM channel: it outputs PWM signals with different duty cycles to precisely control the fan speed; high speed is used for rapid temperature equalization, and low speed is used for fine temperature maintenance.

[0034] Dynamic adjustment: The heat generated by the heating block 13 is blown by the fan 12, forming a uniform air bath inside the chassis 10. The system dynamically adjusts the heating power and fan speed by continuously comparing the target temperature with the actual temperature, ultimately keeping the temperature inside the chassis stably controlled within ±0.02℃ of the target value.

[0035] This design places the core optical components in a highly stable thermal environment, effectively avoiding laser wavelength drift, optical element deformation, and thermal expansion and contraction of the air chamber caused by changes in ambient temperature. This is the key to ensuring the instrument's long-term "zero drift".

[0036] Another innovation of this application lies in the high-performance, high-bandwidth laser composite driver circuit structure. The laser driver module employs a negative feedback composite current source architecture consisting of a high-speed operational amplifier and a push-pull transistor pair. Specifically, its circuit topology uses a unity-gain stable high-speed current feedback operational amplifier as the error amplification and pre-drive stage, whose output directly drives the push-pull output stage composed of NPN and PNP high-power transistors. By connecting a low-inductance, non-inductive precision sampling resistor in series with the laser cathode, the voltage signal across the resistor serves as the current feedback signal, connected to the inverting input of the operational amplifier, forming deep voltage-current negative feedback. Furthermore, an RC compensation network (a resistor and capacitor in series) is connected between the output and inverting input of the operational amplifier to adjust the loop phase margin.

[0037] This architecture leverages the high input impedance and precise feedback control of operational amplifiers, combined with the high current output capability of a transistor push-pull pair, to form a deep voltage-current negative feedback. By optimizing the compensation network capacitor in the feedback loop, while ensuring a high bandwidth of 40MHz and a peak drive current output of 900mA, the risk of self-oscillation at high frequencies is completely eliminated, resulting in extremely high slew rate and excellent transient response characteristics. This design is specifically optimized for driving high-current QCL lasers requiring high-speed wavelength modulation.

[0038] Another innovation of this application lies in the three-dimensional hierarchical heat dissipation and thermal optimization structure design, including heat dissipation at the driver circuit board level and heat dissipation at the laser and system level.

[0039] Driver PCB-level heat dissipation: Addressing the heat generation issue in the laser driver circuit, a comprehensive solution combining thermal conductivity structure and layout optimization is employed. In the PCB design, heat-generating components such as power transistors and sampling resistors are placed along the board edge. The bottom of these components is directly connected to a thick-film aluminum alloy heatsink mounted on the back of the PCB via a large copper foil area and multiple thermal via arrays. Furthermore, large ventilation windows are created at corresponding locations on the chassis to form an efficient airflow channel. This design reduces the maximum temperature of the driver PCB under full load from over 120°C to below 45°C, significantly reducing thermal noise and component thermal stress.

[0040] Laser and system-level heat dissipation: See Figure 5 The laser housing 14 is tightly coupled to a finned heat sink 15, with the contact surface coated with thermally conductive silicone grease, and is cooled by forced convection cooling by a PWM speed-controlled fan 16. At the same time, the entire optical path system (including the laser and the measurement gas chamber) is placed in an active air-bath insulated enclosure to achieve secondary temperature stabilization.

[0041] Another innovation of this application lies in the laser's end-to-end hardware and software collaborative protection mechanism, which includes multi-layered hardware protection circuits and software protection and monitoring processes. The multi-layered hardware protection circuits are further divided into driver-level protection and output-level protection.

[0042] Driver-level protection: The composite drive circuit of the laser driver module integrates a limiting circuit (to prevent voltage overshoot), a precision current limiting circuit (to set the absolute maximum current), and an over-temperature protection switch (to monitor the heat sink temperature and is connected in series with the enable terminal).

[0043] Output stage protection: A soft-start circuit (RC delay circuit to prevent power surge), a hardware shutdown circuit (power is cut off in milliseconds via MOSFET after receiving a fault signal) and electrostatic discharge (ESD) protection devices are set up on the laser power supply path.

[0044] Software protection and monitoring process: After the system is powered on, the main control unit first executes the laser soft-start program, controlling the drive voltage to slowly climb and the current to steadily increase to the threshold. Subsequently, all hardware protection functions are enabled in sequence, and the drive current continues to be linearly increased to the target operating point. During operation, the software monitors multiple parameters in real time, such as the driver board temperature, laser housing temperature, operating current, and output optical power. Any parameter exceeding the limit will immediately trigger a graded alarm or safety shutdown (e.g., by controlling the hardware shutdown circuit to cut off the power supply).

[0045] Furthermore, the main control unit can also be equipped with interlocking protection logic. For example, when the air bath temperature control system fails to reach the set temperature, the laser driver and the air pump can be locked to prevent measurement under suboptimal conditions. The main control unit can also be configured with a pressure safety threshold; when the pressure becomes abnormally high, the air intake can be shut off and an alarm triggered to protect the sensors and air chamber.

[0046] The operating process of the H2O2 gas TDLAS analyzer in this application is as follows: Upon power-up of the main control unit 8, the heating block 13 and circulating fan 12 of the air bath constant temperature system are activated, causing the insulation chamber 10 to preheat. Once the temperature of the insulation chamber 10 stabilizes at 40℃, all laser hardware protection circuits are enabled. The main control unit 8 controls the drive circuit of the laser drive module, slowly increasing the laser current from 0 to a preset safety value close to the threshold at a slope of 10mA / ms. After the user initiates the measurement, the vacuum pump 5 starts working, and simultaneously, the main control unit 8 activates MFC2 and EPC4 for gas flow control and pressure stabilization. After the pressure in the measurement chamber 3 stabilizes, the laser drive current is finally increased to the target operating current, and high-frequency sinusoidal modulation is applied to begin formal TDLAS harmonic signal acquisition and concentration calculation. Throughout the process, the software continuously monitors all the temperature, current, and other parameters mentioned above and executes protection logic.

[0047] The beneficial effects of the above-mentioned technical solution of this application are improved driving performance, improved reliability, high precision and high stability, and innovative system integration.

[0048] Improved driving performance: The innovative composite driving circuit fundamentally solves the stability problem under high current and high frequency modulation, providing a near-ideal light source modulation signal for TDLAS detection, which is the basis for achieving high-precision harmonic detection.

[0049] Enhanced reliability: The three-dimensional thermal management from the laser to the circuit board to the system, combined with full-link hardware and software protection, reduces the failure rate of core components to an extremely low level, making it particularly suitable for 24 / 7 uninterrupted industrial operation.

[0050] High precision and high stability: The passivated pipeline throughout ensures the authenticity of the gas, and the system-level environmental control (constant temperature, constant pressure, constant flow) provides a stable physical environment for TDLAS measurement, making the instrument almost unaffected by the field environment and with minimal long-term drift.

[0051] System integration innovation: This application is not a simple stacking of components, but rather a deep coupling of high-performance drive, enhanced protection and precise environmental control, with each subsystem working together to demonstrate the beneficial effect of synergistic efficiency.

[0052] The following provides a specific embodiment of the H2O2 gas TDLAS analyzer of this application.

[0053] This embodiment provides a highly stable H2O2 gas TDLAS analyzer, the overall architecture of which is as follows: Figure 1 As shown, it mainly consists of three parts: (1) Gas path system: The H2O2 gas to be measured enters from the inlet 1, passes through the MFC mass flow meter 2, the measuring gas chamber 3, the EPC electronic pressure controller 4 in sequence, and is finally discharged by the vacuum pump 5; all pipelines and contact parts are made of 316L stainless steel and are electropolished and passivated. (2) Optical path system: The laser emitted by the laser 6 passes through the measuring gas chamber 3 and is received by the photodetector 7; the measuring gas chamber 3 adopts a multi-reflection cell structure to increase the optical path. (3) Drive and control system: The main control unit 8 is the core, connecting the laser drive module 9, the temperature sensor 11, the temperature fan 12 and the heating block 13. The laser drive module 9 is also connected to the photodetector 7; in addition to driving the laser 6, the laser drive module 9 also has the functions of collecting detection signals and performing concentration inversion.

[0054] To address the issue of easy H2O2 adsorption, this embodiment employs special treatment for key components in the gas path. All wetted parts are made of electropolishing-grade 316L stainless steel. After machining, the parts are first mechanically polished to Ra ≤ 0.8 μm, then electropolished in an electrolytic bath containing a mixture of phosphoric acid, sulfuric acid, and chromic acid to remove microscopic protrusions on the surface. Finally, nitric acid passivation is performed to promote the formation of a chromium-rich oxide layer (Cr2O3). The surface roughness of the treated parts must meet Ra ≤ 0.4 μm, and their hydrophobicity and chemical inertness are verified through contact angle testing. Pipeline connections are sealed with VCR metal gaskets, avoiding the use of rubber or plastic sealing rings to prevent the release of organic matter during aging that could interfere with measurements.

[0055] The specific implementation of the composite drive circuit for the laser driver module is as follows: The operational amplifier is a high-speed current-feedback op-amp with a gain-bandwidth product (GBW) ≥ 500MHz; the push-pull transistors are high-frequency, high-power transistors (such as BJTs or MOSFET combinations), with a withstand voltage greater than 1.5 times the laser's operating voltage. In the feedback loop, the sampling resistor is a non-inductive resistor with a low temperature coefficient (±5ppm / ℃), and its resistance value is set according to the maximum drive current (e.g., 1Ω, corresponding to a voltage drop of 0.9V at 900mA). This voltage is fed back to the inverting input of the op-amp, while the non-inverting input receives the modulation waveform signal from the main control unit 8. A small capacitance capacitor (e.g., 10pF-100pF) is connected in parallel across the op-amp feedback resistor to form a low-pass filter compensation, preventing phase lag caused by high-frequency parasitic capacitance from leading to oscillation. The driver circuit board adopts a 4-layer design, with the middle two layers being a single grounded copper plane. Thermal vias (0.3mm diameter, 1mm spacing) are drilled below the power devices to conduct heat to the aluminum alloy heat sink on the back.

[0056] In terms of comprehensive thermal management, the first level of heat dissipation (device level) involves applying thermally conductive silicone grease (thermal conductivity ≥3W / m·K) tightly to a finned heatsink; a PWM fan is installed above the heatsink, with its speed dynamically adjusted according to the laser temperature. The second level of heat dissipation (system level) involves exhausting heat generated by the driver circuit board through chassis ventilation windows, preventing heat accumulation within the optical cavity. Thermal isolation separates the optical module and driver module physically through a heat shield to prevent heat radiation from the driver circuit from affecting optical stability.

[0057] like Figure 3 As shown, the specific implementation of the overall air-bath constant temperature system is as follows: The outer shell of the insulated casing 10 is made of aluminum alloy, and the inner wall is lined with a 10mm thick aerogel insulation felt or polyurethane foam layer. The heating fan 12 is installed on the top of the casing 10, and the heating block 13 is installed below the fan 12. The fan 12 blows air downwards, and after being heated by the heating block 13, the airflow flows downwards along the inner wall of the casing 10, and then flows back from the bottom to the fan inlet, forming a closed loop circulation.

[0058] The control logic of the overall air-bath constant temperature system is as follows: During the preheating stage, the main control unit 8 reads data from the PT1000 sensor 11. If the temperature is <40℃, the heating block 13 outputs full power, and the fan 12 runs at high speed. During the constant temperature stage, when the temperature approaches 40℃, the main control unit 8 switches to PID control mode. Proportional term (P): Adjusts the heating power according to the temperature difference. Integral term (I): Eliminates static error. Derivative term (D): Suppresses temperature overshoot. If the PT1000 detects that the temperature exceeds 45℃ (safety threshold), the main control unit 8 forcibly cuts off the power supply to the heating block and triggers an alarm.

[0059] The workflow and protection logic of the H2O2 gas TDLAS analyzer in this embodiment are as follows.

[0060] Power-on initialization: The main control unit powers on and performs a self-check of the status of each sensor.

[0061] Preheating at a constant temperature: Start the air-bath temperature control system and wait for the temperature of the insulation chamber to stabilize at 40℃±0.02℃. During this process, the laser driver is disabled.

[0062] Protection Enable: Once the temperature reaches the target, enable all hardware protection circuits (current limiting, over-temperature, ESD monitoring).

[0063] Laser soft start: The main control unit controls the drive circuit to slowly increase the laser current from 0 to a preset safe value close to the threshold (such as 80% of the threshold current) at a slope of 10mA / ms.

[0064] Gas path stabilization: After the user starts the measurement, the air pump operates, and the main control unit activates MFC and EPC. Once the gas chamber pressure stabilizes at the set value (e.g., 1 atm ± 0.1%), proceed to the next step.

[0065] Formal Measurement: The laser drive current is finally increased to the target operating current, and a high-frequency sinusoidal modulation (e.g., 10kHz) is applied to begin formal TDLAS harmonic signal acquisition and concentration calculation.

[0066] Real-time monitoring: Throughout the process, the software continuously monitors the driver board temperature, laser housing temperature, operating current, and output optical power. If the current exceeds the set upper limit by 5%, hardware current limiting is triggered. If the temperature exceeds the set upper limit, software power reduction or shutdown is triggered. If the gas chamber pressure is abnormally high, the air intake is shut off and an alarm is triggered.

[0067] In some embodiments, the heating block 13 may use a PTC ceramic heating element instead of a resistance wire heating element to improve safety. The temperature sensor 11 may use a digital temperature sensor (such as DS18B20) instead of PT1000, but it must be ensured that the accuracy meets the ±0.02℃ control requirement. The main control unit 8 may use an MCU, FPGA, or DSP to realize higher frequency modulation signal generation and signal processing.

[0068] This application provides a TDLAS analyzer specifically designed for H2O2 gas, which can effectively suppress gas adsorption loss. Through an innovative high-bandwidth composite current drive circuit, a three-dimensional thermal management architecture, and multiple protection mechanisms that combine hardware and software, along with system-level constant temperature and pressure control, it achieves an integrated design of high precision, strong stability, and long lifespan, effectively improving the accuracy, stability, and reliability of H2O2 gas detection.

[0069] It should be noted that the information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0070] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A TDLAS analyzer for H2O2 gas, characterized in that, This includes the pneumatic system, optical system, and drive control system; The gas path system includes an inlet, a mass flow controller, a measuring gas chamber, an electronic pressure controller, and a vacuum pump connected sequentially via pipelines; the inner surface of the gas path system in contact with the H2O2 gas is inertized to form a chemically inert layer. The optical path system includes lasers connected in sequence, an optical path containing the measuring gas chamber, and a photodetector. The optical path system is housed inside an insulated enclosure; The drive control system includes a main control unit and a laser drive module electrically connected to the main control unit; the laser drive module adopts a composite current source architecture, including an operational amplifier as an error amplification stage and a push-pull circuit as an output stage.

2. The H2O2 gas TDLAS analyzer according to claim 1, characterized in that, The inertization treatment is electropolishing and super passivation; the chemical inert layer is a chromium-rich Cr2O3 oxide layer with a surface roughness Ra≤0.4μm.

3. The H2O2 gas TDLAS analyzer according to claim 1, characterized in that, The mass flow controller is located at the inlet of the measuring gas chamber and is used to control the gas flow rate entering the measuring gas chamber; the electronic pressure controller is located between the outlet of the measuring gas chamber and the pump; the main control unit is configured to adjust the opening of the electronic pressure controller through a closed-loop PID control algorithm to maintain a constant pressure in the measuring gas chamber.

4. The H2O2 gas TDLAS analyzer according to claim 1, characterized in that, The insulated enclosure is also equipped with a constant temperature system consisting of a temperature sensor, a heating block, and a fan; the temperature sensor is connected to the main control unit to form a temperature feedback closed loop; the main control unit dynamically adjusts the power of the heating block and the speed of the fan through PWM signals.

5. The H2O2 gas TDLAS analyzer according to claim 4, characterized in that, The main control unit is equipped with interlocking protection logic. When the air bath constant temperature system fails to reach the set temperature, the laser driver module and the air pump are locked.

6. The H2O2 gas TDLAS analyzer according to claim 1, characterized in that, The laser's housing is coupled with a finned heat sink; a PWM speed-controlled fan is mounted on the finned heat sink.

7. The H2O2 gas TDLAS analyzer according to claim 1, characterized in that, The push-pull circuit is composed of NPN high-power transistors and PNP high-power transistors; the output of the operational amplifier directly drives the input of the push-pull circuit; a sampling resistor is connected in series with the cathode of the laser, and the voltage signal across the sampling resistor is connected to the inverting input of the operational amplifier as a current feedback signal.

8. The H2O2 gas TDLAS analyzer according to claim 1, characterized in that, The laser driver module integrates hardware protection circuitry, including a limiting circuit, a precision current limiting circuit, an over-temperature protection switch, a soft-start circuit, and a hardware shutdown circuit; the soft-start circuit and the hardware shutdown circuit are located on the power supply path of the laser.

9. The H2O2 gas TDLAS analyzer according to claim 8, characterized in that, The laser driving module includes a driving circuit board; the power devices on the driving circuit board are provided with a thermal via array at their bottom; and an aluminum alloy heat sink is mounted on the back of the driving circuit board. The insulation casing has ventilation windows at corresponding positions, and the ventilation windows and the aluminum alloy radiator are positioned to form an air duct.

10. The H2O2 gas TDLAS analyzer according to claim 9, characterized in that, The main control unit is equipped with a software protection module; the software protection module is configured to monitor the temperature of the driver circuit board, the temperature of the laser tube housing, the operating current and the output optical power in real time; when the monitored parameters exceed the limits, the software protection module triggers a graded alarm or controls the hardware shutdown circuit to cut off the power supply.

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