Baseline drift suppression system and method and exhalation tester
By using a multi-level constant temperature layer and a closed-loop temperature control system, the baseline drift problem of the breath test instrument under temperature fluctuations has been solved, resulting in improved signal-to-noise ratio and measurement accuracy, while reducing calibration frequency and maintenance costs.
Patent Information
- Application Number
- CN202511792443.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-01
- Publication Date
- 2026-01-02
AI Technical Summary
When there is no target gas or the gas concentration remains constant, the output signal of the breath test instrument changes slowly over time, resulting in large measurement errors, poor repeatability, frequent calibration, and inability to remain stable under temperature fluctuations.
It adopts a multi-level constant temperature layer structure, including the first level for temperature control of optical components, the second level for temperature control of airway structure, and the third level for thermal isolation of the breath test instrument from the external environment. Closed-loop temperature control is achieved through a PID controller to form a uniform temperature environment.
It effectively suppressed baseline drift, improved the signal-to-noise ratio, lowered the detection limit, enhanced measurement repeatability and accuracy, reduced calibration frequency, and lowered maintenance costs.
Smart Images
Figure CN121242545A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of gas detection, and in particular to a baseline drift suppression system and method and a breath test instrument. BACKGROUND
[0002] A breath test instrument detects the concentration of specific marker gases (such as CO2, acetaldehyde, etc.) in human exhaled gas to diagnose diseases. The core detection principle is usually that a broadband infrared light is emitted by an infrared light source, passes through a gas chamber filled with the gas to be detected, the light of a specific wavelength is absorbed by the target gas, and finally the change in light intensity is detected by a detector to calculate the gas concentration.
[0003] However, the primary problem of the breath test instrument at present is that the measurement error is large, the repeatability is poor, and frequent calibration is required, that is, when there is no target gas or the gas concentration is constant, the output signal of the breath test instrument changes slowly and non-directionally over time. Therefore, there is an urgent need for a system and method that can create a highly stable thermal environment for optical detection, suppress baseline drift caused by temperature fluctuations from the root, and improve the accuracy, stability, and reliability of the instrument. SUMMARY
[0004] Therefore, the embodiments of the present application provide a baseline drift suppression system and method and a breath test instrument, which can effectively solve the problem of baseline drift caused by temperature fluctuations.
[0005] In a first aspect, the embodiments of the present application provide a baseline drift suppression system.
[0006] In some embodiments, a baseline drift suppression system is applied to a breath test instrument, and the system comprises a multi-stage constant temperature layer arranged in the breath test instrument and a gas path structure with a preheating function. The multi-stage constant temperature layer comprises: A first-stage constant temperature layer for temperature control of optical components in the breath test instrument. A second-stage constant temperature layer for temperature control of the gas path structure. A third-stage constant temperature layer for thermal isolation of the breath test instrument from the external environment.
[0007] In a second aspect, the embodiments of the present application also provide a baseline drift suppression method.
[0008] In some embodiments, a baseline drift suppression method is applied to a baseline drift suppression system in a breath test instrument, and the system comprises a multi-stage constant temperature layer arranged in the breath test instrument and a gas path structure with a preheating function. The method comprises: Temperature control of optical components in the breath test instrument by the first-stage constant temperature layer. The gas path structure is controlled in temperature by a second constant temperature layer; The exhalation test instrument is thermally insulated from the external environment by a third constant temperature layer.
[0009] In a third aspect, the embodiments of the present application also provide a breath test instrument using the baseline drift suppression system.
[0010] The embodiments of the present application have the following beneficial effects: By controlling the temperature in three stages, the temperature factors causing baseline drift are precisely controlled, effectively solving the baseline drift problem, thereby improving the signal-to-noise ratio of the exhalation test instrument, reducing the lower detection limit, greatly improving the measurement repeatability and accuracy, reducing the calibration frequency, and reducing the maintenance cost.
[0011] The optical assembly, the constant temperature gas chamber wall, and the gas are at the same temperature, avoiding thermal stress (protecting the optical element), thermal convection (interfering with the optical path), and gas density changes (affecting the absorption coefficient) caused by temperature differences.
[0012] The third constant temperature layer can form a thermal barrier, so that the core components in the exhalation test instrument are not affected by the environmental temperature fluctuations and the heat dissipation of the exhalation test instrument itself (such as the main board and the pump), significantly improving the environmental adaptability of the exhalation test instrument. BRIEF DESCRIPTION OF DRAWINGS
[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as limiting the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.
[0014] Figure 1 The overall structure schematic diagram of the baseline drift suppression system of the embodiments of the present application is shown; Figure 2 The structure schematic diagram of the third constant temperature layer of the baseline drift suppression system of the embodiments of the present application is shown; Figure 3 The structure schematic diagram of the second constant temperature layer of the baseline drift suppression system of the embodiments of the present application is shown; Figure 4 The structure schematic diagram of the first constant temperature layer of the baseline drift suppression system of the embodiments of the present application is shown; Figure 5 The gas path structure schematic diagram of the baseline drift suppression system of the embodiments of the present application is shown; Figure 6 The flowchart of the baseline drift suppression method of the embodiments of the present application is shown; Figure 7 The overall structure of the breath test instrument according to the embodiment of the present application is shown. DETAILED DESCRIPTION
[0015] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application.
[0016] The components of the embodiments of the present application generally described and illustrated in the accompanying drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but merely represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.
[0017] Hereinafter, the terms "include", "have", and their conjugates used in the various embodiments of the present application are only intended to denote a certain characteristic, number, step, operation, element, component, or a combination of the foregoing, and should not be construed as excluding the presence or addition of one or more other characteristics, numbers, steps, operations, elements, components, or combinations thereof. In addition, the terms "first", "second", "third", and the like are only used to distinguish descriptions, and cannot be understood as indicating or implying relative importance.
[0018] Unless otherwise defined, all terms used herein (including technical terms and scientific terms) have the same meaning as commonly understood by those skilled in the art to which the various embodiments of the present application belong. The terms (such as those defined in commonly used dictionaries) will be interpreted as having a meaning that is the same as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized or overly formal meaning unless clearly defined in the various embodiments of the present application.
[0019] Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.
[0020] The breath test instrument is a medical or health monitoring device for detecting the concentration of specific marker gases (such as CO2, acetaldehyde, etc.) in human exhaled gas. It measures the degree of absorption of specific wavelength infrared light by the target gas through optical detection methods (such as non-dispersive infrared spectroscopy or photoacoustic spectroscopy), thereby inverting the gas concentration. Among them, the optical assembly used to constitute the optical detection path of the breath test instrument at least includes: an infrared emitter (i.e. an infrared light source): emitting broadband infrared light; a narrowband optical filter: arranged in front of the detector, selectively transmitting light of a wavelength corresponding to the target gas absorption peak; an infrared detector: receiving the light intensity signal after absorption by the gas chamber and converting it into an electrical signal output.
[0021] Figure 1 The overall structure schematic diagram of the baseline drift suppression system of the embodiment of the present application is shown. Exemplarily, the baseline drift suppression system is applied to a breath test instrument, and the system includes a multi-stage constant temperature layer arranged in the breath test instrument and a gas path structure with a preheating function; The multi-stage constant temperature layer includes: The first-stage constant temperature layer is used for temperature control of the optical assembly in the breath test instrument; The second-stage constant temperature layer is used for temperature control of the gas path structure; The third-stage constant temperature layer is used for thermal insulation of the breath test instrument from the external environment.
[0022] Among them, the first-stage constant temperature layer is used for high-precision temperature control of the optical assembly (infrared emitter, detector, narrowband optical filter); the second-stage constant temperature layer is used for temperature control of the key components (constant temperature gas chamber, preheating pipe) in the gas path structure, to realize constant temperature control of the gas; and the third-stage constant temperature layer is used as an external thermal buffer zone to isolate the influence of environmental temperature fluctuations on the internal structure.
[0023] Reference Figure 2 The spatial layout relationship and layered nested structure of the "three-stage temperature control system" in the baseline drift suppression system of the present application are shown, specifically including: the outermost layer, i.e. the third-stage constant temperature layer (system heat insulation and buffer layer), the middle layer, i.e. the second-stage constant temperature layer (constant temperature gas chamber and gas path structure constant temperature layer), and the innermost layer, i.e. the first-stage constant temperature layer (optical assembly constant temperature layer). Each layer pursues uniform temperature, and a reasonable temperature difference is set between layers.
[0024] As an optional solution, each stage includes a heating element, a temperature sensor, and a corresponding PID controller, forming a closed-loop temperature control system. Optionally, the temperatures between the stages are set in a step distribution (for example, 40℃ / 40℃ / 35℃), and the microcontroller is used to coordinate the start sequence and operating parameters.
[0025] The gas path structure is a passage system for guiding the flow of the gas to be tested in the exhalation test instrument. In one embodiment, the gas path structure includes a constant-temperature gas chamber, an air inlet pipe, a preheating pipe, and an air outlet pipe; the preheating pipe is arranged between the connection between the air inlet pipe and the constant-temperature gas chamber, so that the gas to be tested is preheated to the same temperature as the constant-temperature gas chamber before entering the constant-temperature gas chamber.
[0026] In one example, the preheating pipe is spirally arranged in the connection region between the air inlet pipe and the constant-temperature gas chamber and is embedded in or tightly attached to the heat-conducting uniform temperature block of the second constant-temperature layer. This allows the gas before entering the constant-temperature gas chamber to be preheated to the same temperature as the gas chamber body, thereby avoiding the local temperature gradient and density change caused by the impact of cold gas. For example, the preheating pipe can be a spiral preheating pipe arranged at the connection between the air inlet pipe and the constant-temperature gas chamber. In another example, the preheating pipe is coiled or wrapped around the outside of the air inlet pipe and is embedded in or tightly attached to the heat-conducting uniform temperature block of the second constant-temperature layer. This allows the gas before entering the constant-temperature gas chamber to be preheated to the same temperature as the gas chamber body, thereby avoiding the local temperature gradient and density change caused by the impact of cold gas. For example, the preheating pipe can be a coiled or wrapped preheating pipe, which ultimately achieves heating through heat transfer.
[0027] In one embodiment, the inner wall of the constant-temperature gas chamber is provided with a flow guide groove for prolonging the gas residence time; the outer wall of the constant-temperature gas chamber is provided with a groove structure for mounting the second heating element and the second temperature sensor; and the constant-temperature gas chamber is provided with optical windows at both ends.
[0028] The inner wall is a surface area of the constant-temperature gas chamber body directly contacting the gas to be tested, which is processed from a high-thermal-conductivity material (such as aluminum alloy or copper) and constitutes the boundary of the gas flow cavity. The inner wall is not only part of the structural strength of the gas chamber, but also a key interface for achieving uniform heating and stable flow of the gas.
[0029] Further, the inner wall is provided with a flow guide groove or other surface topological structure for regulating the gas flow path, prolonging the residence time of the gas in the gas chamber, and improving the measurement stability; at the same time, the inner wall is coupled with the outer wall and the second heating element through heat conduction, ensuring that the entire gas chamber is in a highly uniform temperature field, avoiding the influence of local cold areas or hot spots on the gas density and infrared absorption characteristics.
[0030] The flow guide groove is a recessed channel structure formed on the surface of the inner wall of the constant-temperature gas chamber, which can be spiral, ring, zigzag, or multi-stage stepped, for changing the direction of the gas flow, increasing the travel length and residence time of the gas in the gas chamber. The flow guide groove does not completely block the airflow, but guides the gas to flow through the detection light path area in a slow and smooth laminar state.
[0031] It can be understood that by prolonging the gas residence time, the flow guide groove helps to: increase the length of time for the gas to interact with infrared light, enhancing signal strength; reduce signal fluctuations caused by transient flow; in conjunction with the preheating function, the gas reaches the set temperature before entering the main detection area.
[0032] The optical window, a transparent sealing component mounted on the end walls of the constant-temperature gas chamber, allows specific band light emitted by the infrared light source to pass through the interior of the gas chamber and be received by the opposite infrared detector. The optical window is usually made of infrared-transmissive materials (such as zinc selenide or calcium fluoride), which have good broadband transmittance and mechanical stability.
[0033] Preferably, the optical window in this application uses materials that match the thermal expansion coefficient of the constant-temperature gas chamber body (for example: aluminum alloy gas chamber with aluminum silicate glass; copper gas chamber with borosilicate glass), and is fixed to the end face of the constant-temperature gas chamber through a low-stress sealing process, to prevent thermal stress cracking, gas leakage or optical deformation caused by temperature changes.
[0034] In one embodiment, the first constant-temperature layer includes: a heat-conducting uniform temperature block, an infrared detector and an infrared emitter are mounted on the heat-conducting uniform temperature block, and a first heating element and a first temperature sensor are embedded in the heat-conducting uniform temperature block, the first heating element and the first temperature sensor are used for temperature control of the narrow-band optical filter, the infrared detector and the infrared emitter in the first constant-temperature layer; The first heating element and the first temperature sensor are tightly mounted on the heat-conducting uniform temperature block through heat-conducting silicone. The uniform temperature block is made of high-thermal-conductivity material, and a high-precision temperature coefficient (NTC) thermistor is embedded in the interior as a temperature sensor, and an insulated film heater is wrapped on the exterior. The heat-conducting uniform temperature block is in the same temperature field, and the narrow-band optical filter is installed in front of the infrared detector.
[0035] The heat-conducting uniform temperature block is a metal structure made of high-thermal-conductivity and high-thermal-capacity material (such as aluminum alloy or copper), which is used for mounting optical components such as infrared emitters (light sources), infrared detectors and narrow-band optical filters, and serves as the core heat-conducting medium of the first constant-temperature layer.
[0036] The uniform temperature block forms a local thermal environment with high temperature uniformity and stability by embedding a heating element and a temperature sensor inside the uniform temperature block, effectively suppressing the temperature difference between the optical components; and constitutes the basic physical platform of the closed-loop temperature control system. The heat-conducting uniform temperature block is in close contact with the optical components through heat-conducting silicone, ensuring the heat coupling efficiency and preventing the formation of local overheating or cold spots.
[0037] The first heating element is an electric heating device embedded in the heat-conducting uniform temperature block, which actively supplies heat to the uniform temperature block to maintain its set target temperature (for example, 40°C).
[0038] Optionally, the flexible thin-film heater (such as a polyimide-based heating film) or resistance wire heating sheet has the characteristics of fast response speed, low power consumption, and good adhesion; after being wrapped with insulation, it is tightly attached or embedded on the surface of the heat-conducting uniform temperature block, ensuring efficient heat transfer to the entire metal block and avoiding local hot spots. The first heating element is controlled by the first PID controller, which adjusts the output power through the control signal to achieve precise temperature control.
[0039] The first temperature sensor is a high-precision temperature detection element embedded on the heat-conducting uniform temperature block, used to monitor the actual temperature of the uniform temperature block in real time and feed back temperature data to the first PID controller in the microcontroller for closed-loop control operation.
[0040] Optionally, it is a negative temperature coefficient thermistor with high sensitivity, small size, fast response, and good long-term stability; its temperature measurement accuracy is not less than ±0.1°C, and it is embedded or bonded in the uniform temperature block body and works cooperatively with the heating element to ensure the accuracy and anti-interference capability of the temperature control system.
[0041] Reference Figure 4 The first-stage constant-temperature layer in the present application includes a heat-conducting uniform temperature block made of aluminum alloy, and the infrared light source, infrared detector, and narrowband filter are fixed on the surface thereof by heat-conducting silicone grease. Optionally, the uniform temperature block is wrapped with a thin-film heater 402 as the first heating element, and a thermistor is bonded as the first temperature sensor. The sensor signal is connected to the signal channel of the microcontroller, and the microcontroller (MCU chip) runs the first PID control algorithm to output a control signal to adjust the heater power, thereby achieving high-precision closed-loop control of the working temperature of the optical assembly.
[0042] Reference Figure 5 The gas path probe 502 is arranged at the front end of the respiratory test instrument and is used to receive the exhaled gas of the user. The probe is connected to the preheating pipe through the gas inlet pipe, and the preheating pipe is in a spiral shape and tightly attached to the heat-conducting uniform temperature block of the second-stage constant-temperature layer, so that the measured gas is preheated to the set temperature before entering the constant-temperature gas chamber.
[0043] It can be understood that the above-mentioned components are integrated and installed on the same heat-conducting uniform temperature block and are in a highly stable temperature field maintained by the first-stage constant-temperature layer to suppress signal drift caused by temperature sensitivity of each element.
[0044] The infrared light source 504 is installed outside the optical window at one end of the constant-temperature gas chamber and is fixed on an independent heat-conducting uniform temperature block by heat-conducting silicone grease.
[0045] Detector 506, a sensor that receives the infrared light signal after passing through the constant temperature gas chamber and converts it into an electrical signal. The detector is tightly attached to the heat-conducting uniform block of the first constant temperature layer through heat-conducting silicone grease, so that its working temperature is stable for a long time, avoiding signal fluctuations caused by temperature changes.
[0046] Narrow-band filter 508, which only allows infrared light of a specific wavelength range (such as 4.3 ± 0.1 μm) to pass through, is used for selective detection of the characteristic absorption peak of the target gas. Optionally, the narrow-band filter is installed in close proximity to the front of the infrared detector and is installed together with the detector on the uniform block of the first constant temperature layer, sharing the same temperature field with the light source and detector, forming a "three same temperature" structure, and completely suppressing the superposition effect of their own temperature drift.
[0047] Gas chamber 510, i.e. constant temperature gas chamber, is a closed optical detection cavity in the breath test instrument for containing the gas to be measured and allowing infrared light to pass through, located at the center of the entire system and wrapped by the second constant temperature layer. It is made of high thermal conductivity materials such as aluminum alloy or copper, and has optical windows at both ends.
[0048] In one embodiment, the second constant temperature layer includes a second heating element wrapped around the outer wall of the constant temperature gas chamber, and a second temperature sensor disposed on the outer wall.
[0049] The outer wall, as the external surface structure of the constant temperature gas chamber body, is made of high thermal conductivity materials such as aluminum alloy or copper, for realizing thermal coupling between the second constant temperature layer. The outer wall is not only the load-bearing part of the gas chamber structure strength, but also the key heat transfer interface for temperature control: it is provided with physical interfaces (such as grooves, channels or fitting planes) for mounting heating elements and temperature sensors, and conducts heat from the second heating element to the entire gas chamber body through close contact, ensuring uniform and stable temperature in the gas chamber cavity.
[0050] Optionally, the outer wall is designed with a specific geometric structure (such as an annular groove or a spiral groove) to fit the wrapping installation of the flexible heating film and prevent displacement; at the same time, it allows the second temperature sensor to be directly attached or embedded, realizing accurate monitoring of the real-time temperature of the gas chamber.
[0051] The second heating element is an electric heating device disposed on the outer wall of the constant temperature gas chamber, which is used to actively heat the constant temperature gas chamber and the preheating pipe area connected thereto, so as to maintain the set target temperature (for example, 40°C).
[0052] Optionally, the flexible thin film heater (such as a polyimide-based heating film), resistance wire heating band or printed thick film heater has good adhesion, corrosion resistance and thermal response characteristics.
[0053] In an example, the second heating element is closely attached to the outer wall of the constant-temperature gas chamber in a wrapped or wound form, ensuring efficient and uniform heat conduction to the entire gas chamber body; its working power is regulated by the microcontroller through a PID algorithm, and is driven by a control signal to achieve precise temperature control.
[0054] The second temperature sensor is a temperature detection element mounted on the outer wall of the constant-temperature gas chamber, used to collect the actual temperature of the gas chamber in real time and transmit the temperature feedback signal to the second PID controller in the microcontroller for closed-loop temperature control operation.
[0055] Optionally, the second temperature sensor is a high-precision negative temperature coefficient thermistor with a temperature measurement accuracy of not less than ±0.1°C, which can be embedded in the reserved hole of the outer wall or fixed at the specified position through heat-conducting glue to ensure good thermal contact with the metal body of the gas chamber.
[0056] In an example, the second temperature sensor works cooperatively with the second heating element to quickly respond to temperature changes in dynamic conditions such as transient cooling caused by gas flow, thereby improving the stability and anti-disturbance capability of the temperature control system.
[0057] Reference Figure 3 The temperature controller, i.e., the microcontroller, periodically collects the signal of the temperature sensor 302 (specifically the second temperature sensor), executes the second-level PID control algorithm, and outputs a control signal to adjust the power of the heating device, i.e., the second heating element, thereby achieving precise temperature control of the constant-temperature gas chamber and the preheating pipe area. This control task runs independently in the microcontroller, and the target temperature is set to 40°C, consistent with the first level, and is started only after the third constant-temperature layer is stable.
[0058] In one of the embodiments, the third constant-temperature layer comprises: a heat-insulating cavity structure located inside the shell of the exhalation test instrument; a third heating element, an air exhaust element, and a third temperature sensor arranged in the heat-insulating cavity structure, and the air exhaust element is used to control the air flow in the cavity formed by the heat-insulating cavity structure to form an air flow loop. The heat-insulating cavity structure is arranged inside the shell of the exhalation test instrument and is used to accommodate the optical detection core component (i.e., the area where the first and second constant-temperature layers are located), and forms a stable internal environment temperature field through active temperature control. The heat-insulating cavity structure is composed of a metal frame and high-thermal-insulation materials (such as high-density polyurethane foam, vacuum insulation board, or aerogel), has a low thermal conductivity, and can effectively block the transmission of external environmental heat or the dissipation of internal heat.
[0059] Optionally, the heat-insulating cavity structure is internally provided with a third heating element, an air exhaust element, and a third temperature sensor, and temperature is uniformly distributed through air flow circulation, thereby constructing a dynamically stable and anti-disturbance environment, and significantly weakening the influence of external temperature fluctuations (such as 15–30°C changes) on the core system.
[0060] The outer shell of the exhalation test instrument is the outermost mechanical structure shell of the exhalation test instrument, which is used to protect the internal air path, optical components and electronic control system (i.e. signal processing unit and temperature control unit), and is made of engineering plastic or metal material. The shell not only provides physical protection and electromagnetic shielding function, but also serves as the installation reference surface and boundary of the heat insulation cavity structure, and the inner space thereof is used for arranging the heat insulation cavity structure.
[0061] Optionally, the shell is designed with a ventilation hole or an air duct interface to cooperate with the exhaust element to realize air circulation in the cavity; at the same time, the material and structure layout thereof should minimize the response speed of the self-thermal inertia to external temperature changes to avoid becoming a heat interference source.
[0062] The third heating element is an electric heating device arranged inside the heat insulation cavity structure, which is used to actively heat the cavity to maintain a stable set temperature (e.g. 35°C) lower than the inner layer.
[0063] Optionally, it can be a resistance wire heater, a heating sheet or an embedded heating film, which is installed on the side wall, the bottom or the support of the cavity and is reasonably distributed to ensure uniform heat diffusion.
[0064] In an example, the third heating element is regulated by a third PID controller, which adjusts the power through a microcontroller output control signal to compensate for heat loss when the ambient temperature drops, thereby maintaining the temperature in the cavity constant, thereby providing a stable "background temperature platform" for the inner layer precision temperature control system.
[0065] The exhaust element is a forced convection device arranged inside the heat insulation cavity structure, which is used to drive the air flow in the cavity (i.e. inside the heat insulation cavity structure) to form a controllable air flow circuit and promote temperature uniformization.
[0066] Optionally, it is a low-speed silent fan or a blower, which is installed on the top or side of the cavity and cooperates with the air inlet and the backflow air duct (such as the vertical air duct on both sides and the backflow port at the bottom) to make the air circulate in the cavity after heat exchange.
[0067] In an example, the working state of the exhaust element can be speed-controlled by the microcontroller according to the feedback of the third temperature sensor, which not only ensures the uniformity of the heat field, but also avoids the vibration of the air flow from being transmitted to the optical system to cause interference.
[0068] The third temperature sensor is a temperature detection element installed inside the heat insulation cavity structure, which is used to monitor the actual temperature of the cavity in real time and feed back the data to the third PID controller in the microcontroller to participate in the closed-loop temperature control operation. Optionally, it is a high-stability thermistor or a digital temperature sensor with a temperature measurement accuracy of not less than ±0.5°C, which is arranged at the center of the cavity or at multiple representative positions to represent the overall temperature level.
[0069] It can be understood that the third sensor does not directly contact the inner optical assembly, but reflects the macro thermal environment state of the peripheral buffer zone, and provides an independent feedback signal for the third level temperature control.
[0070] In one of the embodiments, the first level constant temperature layer further comprises a first PID controller, the second level constant temperature layer further comprises a second PID controller, and the third level constant temperature layer further comprises a third PID controller; wherein the PID parameters of the first PID controller, the second PID controller and the third PID controller are respectively used to determine the target control temperature of the first level constant temperature layer, the second level constant temperature layer and the third level constant temperature layer.
[0071] The first PID controller is used to realize the control module of the closed-loop temperature control of the first level constant temperature layer, and the function thereof is to perform proportional-integral-derivative (PID) operation according to the deviation between the actual temperature signal collected by the first temperature sensor on the heat conduction uniform temperature block and the preset first target control temperature, to generate an adjustment signal to drive the first heating element to work. The first PID controller can be an independent hardware circuit (such as an analog PID circuit).
[0072] Optionally, the first PID controller is integrated into a software task module in the microcontroller, adopts an incremental PID or a position PID algorithm, and has high precision and low overshoot control characteristics. In the present application, the first PID controller is dedicated to the temperature control of the region where the optical assembly is located, and requires high temperature control stability (for example, the fluctuation is ≤±0.05°C).
[0073] The second PID controller is used to realize the control module of the closed-loop temperature control of the second level constant temperature layer, receives the feedback signal from the second temperature sensor on the outer wall of the constant temperature gas chamber, calculates the error between the current temperature and the second target control temperature, and outputs a control signal to adjust the power of the second heating element through the PID algorithm. The second controller can also be realized by an independent control task in the microcontroller, and the PID parameters thereof are specially set, and the response speed is slightly faster than that of the first level, so as to cope with the instantaneous cooling effect caused by the gas flow.
[0074] Optionally, the target temperature of the second PID controller is set to be the same as that of the first level (such as 40°C), so as to suppress the temperature difference between the optical assembly and the gas, and avoid the interference of heat convection and density gradient on the optical path.
[0075] The third PID controller is a control module for realizing the third-stage constant-temperature layer temperature regulation. The third PID controller compares the temperature value detected by the third temperature sensor in the heat-insulating cavity structure with the third target control temperature, performs a PID operation, and then controls the working power of the third heating element. The third controller does not require ultra-high-precision temperature control (allowing fluctuations of ±0.5-1°C), but needs to have good anti-interference ability and thermal inertia compensation ability. Understandably, the main purpose is to establish a dynamically stable "thermal buffer zone" between the instrument shell and the core, to weaken the influence of external environmental temperature changes (such as air flow and room temperature fluctuations) on the internal precision temperature control system.
[0076] PID parameters are a set of key adjustment coefficients for configuring the behavior of each-stage PID controller, including: a proportional coefficient Kp, which reflects the influence intensity of the current error value on the output; an integral time Ti or an integral gain Ki, which is used to suppress steady-state error; a differential time Td or a differential gain Kd, which predicts future trends and suppresses overshoot.
[0077] In the application, the PID parameters are independently set and adjusted for each constant-temperature layer. For example, the first constant-temperature layer uses a smaller Kp and a longer Ti to pursue smoothness without oscillation; the second constant-temperature layer can appropriately increase Kp to speed up the response; and the third constant-temperature layer optimizes the parameters according to the cavity heat capacity characteristics, taking into account energy saving and stability. Optionally, the PID parameters can be stored in the non-volatile memory of the microcontroller.
[0078] Target control temperatures are set temperature values to be reached and maintained by each constant-temperature layer, specifically including: The first target control temperature is the target temperature of the first constant-temperature layer, which is set to a constant value slightly higher than the ambient temperature (such as 40°C), for stabilizing the optical components; The second target control temperature is the target temperature of the second constant-temperature layer, which is the same as the first stage (such as also 40°C), to realize the same temperature of the gas and the optical components; The third target control temperature is the target temperature of the third constant-temperature layer, which is lower than the previous two stages (such as 35°C), as a peripheral buffer temperature platform. The three form a "step distribution" (40-40-35), which avoids the impact of the outside on the core and prevents thermal shock from causing stress damage during startup. Understandably, the setting is determined by the system design and can be pre-set in the firmware or updated through calibration.
[0079] In one embodiment, the system further includes a microcontroller configured to perform a PID operation based on sensor data collected by each temperature sensor in the multi-stage constant-temperature layer, and output a control signal for controlling the power of each heating element in the multi-stage constant-temperature layer. The microcontroller, as a system on chip integrating central processor, memory, multi-channel analog-to-digital converter, pulse width modulation output module and timer / interrupt system, is used to realize the core control function of the baseline drift suppression system in the application. The microcontroller is configured to perform the following operations: First, real-time acquisition of analog or digital temperature signals from the first, second and third temperature sensors; Then, three independent PID control tasks are calculated and processed to calculate the power adjustment amount required by each heating element; Next, the corresponding control signals are output to the driving circuits of the first, second and third heating elements; Finally, the starting timing of each constant temperature layer is coordinated (for example, the third stage is started first, and then the first and second stages are started synchronously after stabilization. Optionally, the working state of the exhaust element is also monitored to optimize the air circulation efficiency.
[0080] The control signal is an electrical signal generated and output by the microcontroller, used to adjust the heating power of each heating element, thereby achieving precise temperature control. The control signal is preferably a pulse width modulation signal, the duty cycle of which is dynamically adjusted according to the calculation results of the PID algorithm. The specific adjustment method is as follows: when the detected temperature is lower than the target value, increase the PWM duty cycle to increase the heating power; when the set temperature is approached, reduce the duty cycle to enter the fine temperature adjustment stage; in the steady state, maintain low-power pulse output to avoid overshoot and oscillation.
[0081] In the application, the control signal acts on the first, second and third heating elements through the driving circuit to form a closed-loop feedback control loop. Each heating element corresponds to an independent control signal channel, ensuring that each level of temperature control is decoupled and operates independently.
[0082] Optionally, the control signal can also include start-stop instructions, fault alarm signals or mode switching commands for system initialization, self-checking or energy-saving sleep state management.
[0083] Figure 6 The flowchart of the baseline drift suppression method of the embodiment of the application is shown. The baseline drift suppression method is applied to a breath test instrument, which includes a multi-stage constant temperature layer and a gas path structure with a preheating function; S602, temperature control of the optical components in the breath test instrument is performed in the first constant temperature layer; S604, temperature control of the gas path structure is performed in the second constant temperature layer; S606, the breath test instrument is thermally insulated from the external environment in the third constant temperature layer.
[0084] In one of the embodiments, in the third constant temperature layer, a heat insulation cavity structure is arranged inside the exhalation test instrument and close to the exhalation test instrument shell; when the exhalation test instrument is powered on, the heat insulation cavity structure is controlled in temperature; when the third constant temperature layer reaches the third target control temperature and is stable, the temperature control of the first constant temperature layer and the second constant temperature layer is simultaneously performed; wherein the target control temperatures of the first constant temperature layer and the second constant temperature layer are set to be the same and higher than the target control temperature of the third constant temperature layer.
[0085] Specifically, first, the third constant temperature layer is started to control temperature, specifically including: after the exhalation test instrument is powered on, the temperature control of the third constant temperature layer is started to make it reach the set third target control temperature (such as 35°C) and keep stable. In this way, a stable peripheral thermal environment is constructed as a "thermal shield" for the internal precision system to weaken the impact of external environmental temperature changes (such as room temperature fluctuations and air flow) on the core.
[0086] Then, the first and second constant temperature layers are simultaneously started, specifically including: the temperature control processes of the first and second constant temperature layers are simultaneously started: the first: the optical components (light source, detector, optical filter) are heated to the target temperature (such as 40°C); the second: the gas path structure (constant temperature gas chamber, preheating pipe) is heated to the same temperature (such as 40°C). Avoiding thermal shock caused by too large temperature difference between inside and outside; ensuring that the optical elements and the gas to be measured are in the same temperature field, and inhibiting thermal convection, thermal stress and gas density changes caused by temperature difference.
[0087] Next, multi-level independent PID closed-loop control is performed, and each constant temperature layer uses an independently operated PID controller: the first PID controller regulates the temperature of the optical components; the second PID controller regulates the temperature of the gas chamber; and the third PID controller regulates the temperature field of the heat insulation cavity. The microcontroller collects data of each temperature sensor in real time, performs PID operation, and outputs a control signal to adjust the heating power.
[0088] In this way, high-precision, no overshoot and fast-response temperature control is achieved: the first level pursues extremely high stability (±0.05°C); the second level considers response speed to cope with air cooling; and the third level focuses on uniformity rather than extreme precision.
[0089] Finally, the gas is preheated and flows through the constant temperature, specifically including: before the gas to be measured enters the constant temperature gas chamber, it flows through the preheating pipe integrated in the second constant temperature layer and preheated to the same temperature (such as 40°C) as the gas chamber, so that the gas completes temperature balance before entering the main detection area. Preventing local temperature disturbance, density mutation or condensation phenomenon caused by sudden entry of cold gas into the high-temperature gas chamber, and avoiding absorption coefficient deviation and optical path disturbance caused thereby.
[0090] Figure 7A structure schematic diagram of the breath test instrument of the embodiment of the present application is shown. The difference from the traditional breath test instrument is that the multi-stage constant temperature layer and the air path structure with preheating function described in the above embodiment. The following will be specifically described with the structure of an actual application breath test instrument as an example.
[0091] Reference Figure 7 The breath test instrument is provided with a heat preservation layer 702, a fan 704, a heat exchanger 706, a heater (i.e. a heating element) 708, a constant temperature gas chamber (i.e. a constant temperature gas chamber) 710, and an air path probe 712.
[0092] The heat preservation layer 702 is arranged inside the breath test instrument, close to the instrument shell, and is used as a physical barrier composed of a layer of high thermal insulation material to wrap the entire optical detection core module (i.e. the region where the first and second constant temperature layers are located).
[0093] The fan 704 is a low-speed silent fan installed inside the heat insulation cavity structure, located at the top or side wall of the cavity, and is used to drive air flow. Its air inlet is connected to external air or internal return air duct, and the air outlet is directed to the core area.
[0094] The heat exchanger 706 is a heat exchange device integrated in the air flow path, used in combination with the third heating element, arranged in the fan outlet or return air channel. Its function is to actively heat or passively dissipate heat to the circulating air, so that it reaches the set temperature before being sent into the heat insulation cavity structure.
[0095] The heater 708, specifically the third heating element, provides a heat source for actively maintaining the target temperature (such as 35°C) of the third constant temperature layer.
[0096] The constant temperature gas chamber 710 is a sealed optical detection cavity in the breath test instrument for containing the gas to be measured and allowing infrared light to pass through, located at the center of the entire system and wrapped by the second constant temperature layer. It is made of high thermal conductivity material (such as aluminum alloy or copper) and has optical windows at both ends.
[0097] The air path probe 712 is located at the front end of the breath test instrument and is used as a sampling interface device for collecting human exhaled gas. It usually includes mouthpieces, filters, one-way valves and other components, and is connected to the subsequent pretreatment unit and constant temperature gas chamber through the air inlet pipe. Its function is to guide the user to exhale into the breath test instrument.
[0098] It can be understood that the optional items in the above embodiments are also applicable to this embodiment, and thus will not be repeatedly described here. In several embodiments provided in the present application, it should be understood that the disclosed apparatus and method can also be implemented in other manners. The above-described apparatus embodiments are merely illustrative. For example, the flowchart and block diagram in the accompanying drawings show the possible implementation architectures, functions and operation of the apparatus, method and computer program product according to the embodiments of the present application. In this regard, each block in the flowchart or block diagram can represent a module, a program segment or a part of code, which contains one or more executable instructions for implementing the specified logical function. It should also be noted that, in alternative implementation manners, the functions noted in the blocks can also occur in different orders from those noted in the accompanying drawings. For example, two consecutive blocks can actually be executed substantially in parallel, and they can also be executed in reverse order, depending on the functions involved. It should also be noted that each block in the structural diagram and / or flowchart, and the combination of blocks in the structural diagram and / or flowchart, can be implemented by a dedicated hardware-based system that performs the specified functions or actions, or can be implemented by a combination of special-purpose hardware and computer instructions.
[0099] In addition, each functional module or unit in the embodiments of the present application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.
[0100] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which can be a smart phone, a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the embodiments of the present application.
[0101] The above describes only the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application.
Claims
1. A baseline drift suppression system, characterized in that, The system is applied to a breath test apparatus and includes a multi-stage constant temperature layer and a gas path structure with preheating function within the breath test apparatus. The multi-level constant temperature layer includes: The first-level constant temperature layer is used to control the temperature of the optical components in the breath test instrument; The second-level constant temperature layer is used for temperature control of the gas path structure; The third-level constant temperature layer is used to thermally insulate the breath test instrument from the external environment.
2. The system according to claim 1, characterized in that, The gas path structure includes a constant temperature gas chamber, an air inlet pipe, a preheating pipe, and an air outlet pipe; The preheating pipe is located between the air inlet pipe and the air inlet of the constant temperature chamber, so that the gas to be tested is preheated to the same temperature as the constant temperature chamber before entering it.
3. The system according to claim 2, characterized in that, The second-level constant temperature layer includes: A second heating element is wrapped around the outer wall of the constant temperature air chamber, and a second temperature sensor is disposed on the outer wall.
4. The system according to claim 1, characterized in that, The optical components include a narrowband filter, an infrared detector, and an infrared emitter, and the first-stage constant temperature layer includes: A heat-conducting and temperature-equalizing block is provided, on which the infrared detector and the infrared emitter are mounted. The heat-conducting and temperature-equalizing block also has a first heating element and a first temperature sensor embedded within it. The first heating element and the first temperature sensor are used to control the temperature of the narrowband filter, the infrared detector, and the infrared emitter in the first-stage constant temperature layer. The first heating element and the first temperature sensor are in the same temperature field along with the heat-conducting and temperature-equalizing block, and the narrow-band filter is installed in front of the infrared detector.
5. The system according to claim 1, characterized in that, The third constant temperature layer includes: A heat-insulating cavity structure is located inside the shell of the breath test instrument; A third heating element, an exhaust element, and a third temperature sensor are installed within the heat-insulating cavity structure. The exhaust element is used to control the airflow within the cavity formed by the heat-insulating cavity structure to form an airflow loop.
6. The system according to claim 1, characterized in that, The first-stage constant temperature layer further includes a first PID controller, the second-stage constant temperature layer further includes a second PID controller, and the third-stage constant temperature layer further includes a third PID controller; The first PID controller, the second PID controller, and the third PID controller are respectively used to control the temperature of the first-stage constant temperature layer, the second-stage constant temperature layer, and the third-stage constant temperature layer to the target temperature.
7. The system according to claim 6, characterized in that, The system also includes a microcontroller, which performs PID calculations based on sensor data collected by each temperature sensor in the multi-level constant temperature layer and outputs a control signal to control the power of each heating element in the multi-level constant temperature layer.
8. The system according to claim 4, characterized in that, The inner wall of the constant temperature gas chamber is provided with a flow guide groove, which is used to extend the gas residence time; The outer wall of the constant temperature chamber is provided with a groove structure for installing the second heating element and the second temperature sensor; optical windows are provided at both ends of the constant temperature chamber.
9. A baseline drift suppression method applied to a breath test apparatus, characterized in that, A baseline drift suppression system applied in a breathalyzer, the system comprising a multi-stage constant temperature layer within the breathalyzer and a gas path structure with preheating function; the method comprising: The temperature of the optical components in the breath test instrument is controlled by the first-level constant temperature layer; The temperature of the gas path structure is controlled by a second-level constant temperature layer. The breath test instrument is thermally isolated from the external environment by a third-level constant temperature layer.
10. A breath test apparatus, characterized in that, The baseline drift suppression system includes any one of claims 1-8.