Carbon dioxide monitoring protective mask

Abstract

The invention relates to the technical field of carbon dioxide monitoring, and discloses a carbon dioxide monitoring protective mask. The mask comprises a base layer and a flexible composite film layer located on the inner side of the base layer. Wherein the flexible composite film layer sequentially comprises a water vapor absorption layer and a detection layer from inside to outside, and the detection layer comprises a carbon dioxide detection film and a humidity detection film which are located on the same plane; the detection layer is connected with the detection unit; the detection unit obtains the carbon dioxide concentration by monitoring the resistance change of the carbon dioxide detection film and the humidity detection film in real time; the humidity detection film comprises a polyacrylate matrix with a through hole structure and an alkyl chain modified carbon nanomaterial embedded in the hole wall of the polyacrylate matrix. The carbon dioxide monitoring protective mask can monitor the concentration of carbon dioxide in exhaled air in real time, and the response efficiency is high; the detection precision and the adsorption saturation concentration of carbon dioxide are improved through the arrangement of the structure, and the application range is wide.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon dioxide monitoring, and particularly relates to a carbon dioxide monitoring protective mask. BACKGROUND

[0002] The concentration of carbon dioxide exhaled by the human body is about 3-4%. Clinicians use end-tidal carbon dioxide concentration changes to monitor respiratory depression after anesthesia or sedation, quickly identify spontaneous pulse recovery, and monitor lung function in patients with chronic obstructive pulmonary disease. End-tidal carbon dioxide analysis is also used to provide accurate metabolic rate determination to help rehabilitation patients evaluate their physiological metabolic state and physical exercise capacity. For example, in the case of COVID-19, most patients have a long-term decline in exercise capacity after the antigen test result turns negative, and even more serious cases of life-threatening persistent respiratory distress. Providing continuous health monitoring for rehabilitation patients during this process can help doctors develop a reasonable rehabilitation training plan to restore physical exercise as soon as possible. In recent years, the miniaturization of carbon dioxide detection sensors has become a trend, making it possible for end-tidal carbon dioxide monitoring to go from hospitals and clinics to home life, but the shortcomings of large size and high power consumption of carbon dioxide sensors limit its further development. The widely used mask provides a reliable wearable operation platform for carbon dioxide sensing. Integrating a carbon dioxide sensor into a mask can achieve daily out-of-hospital respiratory monitoring, and the flexibility and miniaturization of the carbon dioxide sensor are crucial.

[0003] There are various methods for detecting carbon dioxide gas, among which the nondispersive infrared method is most widely used due to its long life, high sensitivity, and stability. However, the overall structure of the sensor is complex, and the size, volume, and power consumption are too large, making it unsuitable for wearable applications. Therefore, people have tried to use chemical methods for carbon dioxide gas monitoring, using basic substances sensitive to carbon dioxide gas for specific binding, and monitoring the concentration of carbon dioxide gas by changes in the physical quantities such as electrical and optical of the sensor. Certain progress has been made. The sensor structure using chemical methods is simple and light, and can be applied to wearable scenarios, but there are still two problems. First, the sensitive element has adsorption saturation problems and cannot identify high concentrations of carbon dioxide. Second, the water vapor present in the breath can affect the detection of carbon dioxide concentration.

[0004] CN116773514A discloses a carbon dioxide detection device and protective mask. Based on the principle of color change of pH indicator combined with carbon dioxide, an optical detection method is used to react to carbon dioxide concentration. The water vapor present in the breath and the uncontrolled low number of active adsorption sites cannot provide high-precision detection of carbon dioxide gas.

[0005] CN116381041A discloses a quartz crystal microbalance gas-sensitive element based on a covalent organic framework thin film, its preparation method, and its application. The gas concentration is detected by detecting gas concentration through a change in the system's resonant frequency caused by gas adsorption via the covalent organic framework thin film. However, this gas-sensitive element is rigid and easily damaged, and it also exhibits some adsorption capacity for other gases such as water, affecting the detection of carbon dioxide.

[0006] Therefore, there is an urgent need to develop a protective mask that can monitor carbon dioxide concentration in real time, has high detection accuracy, and a high carbon dioxide adsorption saturation concentration. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems existing in the prior art and provide a carbon dioxide monitoring protective mask.

[0008] To achieve the above objectives, the present invention provides a carbon dioxide monitoring protective mask, wherein the mask includes a base layer and a flexible composite membrane layer located inside the base layer;

[0009] The flexible composite membrane layer includes, from the inside out, a water vapor absorption layer and a detection layer, wherein the detection layer includes a carbon dioxide detection membrane and a humidity detection membrane located on the same plane;

[0010] The detection layer is connected to the detection unit; the detection unit obtains the carbon dioxide concentration by real-time monitoring of the resistance changes of the carbon dioxide detection membrane and the humidity detection membrane.

[0011] The humidity detection membrane comprises a polyacrylate matrix with a porous structure and carbon nanomaterials with alkyl chains embedded in the pore walls of the polyacrylate matrix.

[0012] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0013] The carbon dioxide monitoring protective mask provided by this invention can monitor the concentration of carbon dioxide in exhaled breath in real time with high response efficiency; and the structural design improves the detection accuracy and carbon dioxide adsorption saturation concentration, making it widely applicable. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the carbon dioxide monitoring protective mask membrane structure prepared according to the present invention;

[0015] Figure 2 This is a schematic diagram of the detection unit in the carbon dioxide monitoring protective mask prepared according to the present invention;

[0016] Figure 3 This is an overall schematic diagram of the carbon dioxide monitoring protective mask prepared according to the present invention;

[0017] Figure 4 This is a graph showing the change of carbon dioxide concentration over time during actual monitoring in the example.

[0018] Figure 5 This is a graph showing the change of carbon dioxide concentration over time during actual monitoring. Detailed Implementation

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] The first aspect of the present invention provides a carbon dioxide monitoring protective mask, wherein the mask includes a base layer and a flexible composite membrane layer located inside the base layer;

[0021] The flexible composite membrane layer includes, from the inside out, a water vapor absorption layer and a detection layer, wherein the detection layer includes a carbon dioxide detection membrane and a humidity detection membrane located on the same plane;

[0022] The detection layer is connected to the detection unit; the detection unit obtains the carbon dioxide concentration by real-time monitoring of the resistance changes of the carbon dioxide detection membrane and the humidity detection membrane.

[0023] The humidity detection membrane comprises a polyacrylate matrix with a porous structure and carbon nanomaterials with alkyl chains embedded in the pore walls of the polyacrylate matrix.

[0024] Existing technologies suffer from problems such as rigid components being easily damaged and detection accuracy being easily affected by the humidity in exhaled breath.

[0025] This invention uses a water vapor absorption layer to absorb as much water vapor as possible carried in exhaled breath, creating a low-humidity environment for the detection layer. It also desorbs water molecules that were originally adsorbed in the carbon dioxide detection membrane (which is usually hydrophilic). At the same time, the humidity detection membrane corrects the test results of the carbon dioxide detection membrane, which greatly improves the detection accuracy compared to existing technologies and achieves a high adsorption saturation concentration.

[0026] Typically, water vapor desorption recovery time is long (from a few seconds to tens of seconds, especially in high humidity environments). This invention combines a porous membrane with a high saturation concentration carbon dioxide detection threshold with a water vapor absorption layer to form a local low humidity environment (relative humidity less than 30%) in the detection area, making it easier for water molecules in the detection layer to desorb.

[0027] The humidity detection membrane is a hydrophilic, flexible, porous membrane. It exhibits different hydration levels under varying water vapor concentrations, leading to changes in its electrical properties. This allows for real-time feedback of water vapor concentration (current humidity level) to correct the test results of the carbon dioxide detection membrane. The pore wall surface of the humidity detection membrane is composed of modified carbon nanomaterials with a certain degree of hydrophilicity. When water molecules are adsorbed by these modified carbon nanomaterials, the resistance of the porous material changes. Resistance measurement provides feedback on the amount of bound water, thus characterizing the ambient humidity (higher humidity indicates more bound water).

[0028] In this invention, the resistance information of the carbon dioxide detection membrane under different humidity and carbon dioxide concentrations is measured in advance. The humidity detection membrane can reflect the humidity parameter, and the combination of the two information can provide accurate feedback on the carbon dioxide concentration.

[0029] In this invention, the various layers of the flexible composite membrane are bonded together with the base layer to form an integral protective mask through chemical bonding or physical sewing.

[0030] The humidity detection membrane is obtained by emulsifying an emulsion formed by mixing alkyl chain modified carbon nanomaterials, acrylate reaction stock solution and water, and then curing it.

[0031] When modifying carbon nanomaterials (such as conductive carbon black) with alkyl chains, hexadecyltrimethylammonium bromide, bis(tetradecyl)dimethylammonium chloride, etc., can be selected as modifiers.

[0032] In some embodiments of the present invention, the carbon dioxide detection membrane comprises a polyacrylate matrix having a porous structure and carbon nanomaterials with polydopamine and alkyl chains doubly modified and embedded in the pore walls of the polyacrylate matrix.

[0033] In this invention, the preparation method of the carbon dioxide detection membrane is similar to that of the humidity detection membrane, except that the carbon nanomaterial is modified with both polydopamine and alkyl chains. During modification, dopamine is first polymerized on the surface of the carbon nanomaterial to form hydrophilic polydopamine, and then lipophilic alkyl chains are grafted using charge adsorption to obtain a modified carbon nanomaterial with dual functions.

[0034] The carbon dioxide detection membrane provided by this invention has a porous structure, which can increase the effective adsorption area of ​​carbon dioxide and enable high-concentration carbon dioxide adsorption detection.

[0035] In some embodiments of the present invention, the carbon dioxide detection membrane and the humidity detection membrane have the same thickness, which is 0.5-2 mm.

[0036] In some embodiments of the present invention, the base layer includes a spunbond layer and a meltblown layer, for example, a structure of spunbond layer + meltblown layer + spunbond layer.

[0037] In some embodiments of the present invention, the water vapor absorption layer comprises, from the inside out, a first hydrophilic porous membrane, a desiccant layer, and a second hydrophilic porous membrane.

[0038] The combination of the first hydrophilic porous membrane, the desiccant layer, and the second hydrophilic porous membrane absorbs as much water vapor as possible carried in exhaled breath, significantly reducing the humidity in the airflow and ensuring rapid desorption of water molecules from the carbon dioxide detection membrane, thus improving response efficiency. The desiccant is encapsulated within the hydrophilic cellulose membranes on both sides using adhesives or other methods.

[0039] In some embodiments of the present invention, the first hydrophilic porous membrane and the second hydrophilic porous membrane are independently selected from at least one of polyethersulfone membrane, polypropylene membrane, polyamide membrane and cellulose membrane, preferably cellulose membrane.

[0040] In some embodiments of the present invention, a breathable and water-repellent membrane is provided on the inner side of the water vapor absorption layer. This membrane, located on the innermost side, prevents large droplets carried by exhaled breath from entering the carbon dioxide detection membrane, thus providing a water-repellent effect and reducing the influence of the external environment on the detection process.

[0041] In some embodiments of the present invention, the breathable and water-repellent membrane is selected from at least one of porous polyurethane film, porous silicone rubber film and expanded polytetrafluoroethylene film, preferably expanded polytetrafluoroethylene film.

[0042] In some embodiments of the present invention, the average particle size of the desiccant powder in the desiccant layer is greater than 100 μm, preferably 150-500 μm. If the particle size is too small, some powder may leak into the oral cavity.

[0043] In some embodiments of the present invention, the desiccant in the desiccant layer is selected from at least one of silica gel desiccant, montmorillonite desiccant, and superabsorbent polymer.

[0044] In some embodiments of the present invention, the thickness of the desiccant layer is 0.2-0.5 mm, preferably 0.4 mm.

[0045] In some embodiments of the present invention, the thickness of the first hydrophilic porous membrane and the second hydrophilic porous membrane is independently 0.1-0.5 mm, preferably 0.2 mm.

[0046] In some embodiments of the present invention, the thickness of the expanded tetrafluoroethylene film is 0.1-0.5 mm, preferably 0.2 mm; the pore size is greater than 20 μm, preferably 50-200 μm.

[0047] In some embodiments of the present invention, such as Figure 2 As shown, the detection unit includes an impedance testing module, a control module, and an external signal receiving module:

[0048] The impedance testing module is used to acquire the resistance data across the carbon dioxide detection membrane and the humidity detection membrane in real time to obtain the test signal;

[0049] The control module is used to acquire the test signal and send the test signal to the external signal receiving module;

[0050] An external signal receiving module is used to process the test signal to obtain the current carbon dioxide concentration.

[0051] In some embodiments of the present invention, the step of acquiring the resistance data across the carbon dioxide detection membrane and the humidity detection membrane in real time to obtain the test signal includes:

[0052] The resistance on both sides of the humidity detection membrane is tested using a pre-set resistance testing device to obtain a first resistance signal; the resistance on both sides of the carbon dioxide detection membrane is tested using the same testing device to obtain a second resistance signal.

[0053] The test signal is obtained by adjusting the second resistance signal based on the first resistance signal;

[0054] The resistance testing equipment includes an impedance testing chip and a DC bridge circuit. The impedance testing chip has a built-in reference voltage source and an instrumentation amplifier.

[0055] Specifically, such as Figure 2 As shown, the detection unit mainly includes a microcontroller, an impedance testing module, a Bluetooth communication module, and an external signal receiving unit.

[0056] The impedance testing module includes an impedance testing chip and a DC bridge circuit. The impedance testing chip has a built-in reference voltage source and instrumentation amplifier. The entire impedance testing module is used to monitor the resistance across the carbon dioxide detection membrane and the humidity detection membrane in real time.

[0057] The microcontroller controls the impedance testing module and Bluetooth communication module. Using an I / O port to SPI converter, it receives the digital signal of the resistance at both ends of the membrane from the impedance testing chip. This signal is then transmitted via serial port to the Bluetooth chip (Bluetooth communication module) and sent to an external signal receiving unit. The external signal receiving unit processes the resistance signal to determine the current carbon dioxide concentration. A humidity detection membrane measures the humidity at the test site, and a carbon dioxide detection membrane corrects the carbon dioxide detection results based on the humidity level.

[0058] The present invention will be described in detail below through embodiments.

[0059] Unless otherwise specified in the following examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0060] This invention provides a carbon dioxide detection protective mask, the preparation process of which is as follows:

[0061] (1) A silica gel desiccant of 150-500μm is encapsulated in two layers of hydrophilic cellulose membrane with a peripheral hot melt adhesive. The thickness of the cellulose membrane is 0.2mm and the thickness of the silica gel desiccant layer is 0.4mm.

[0062] (2) The carbon dioxide detection membrane is a flexible porous membrane with a polyacrylate matrix having a through-pore structure. The pore wall surface is coated with a large amount of conductive carbon black that is modified with both polydopamine and alkyl chains. The specific preparation process is as follows:

[0063] Modification of conductive carbon black: 100g of bp2000 (Cabot) carbon black was mixed with 50g of modified styrene-maleic anhydride copolymer and 5g of dopamine, and then 845g of water was added. The mixture was ground at 4000rpm for 1h at room temperature to obtain a nano-carbon black dispersion with a D50 of 150nm. Ferrous sulfate (0.0001mol / L concentration in the dispersion) was then added to the dispersion and stirred at room temperature for 1h. Finally, 800g of 1% hexadecyltrimethylammonium bromide solution was added to the above liquid, followed by centrifugation, washing, and separation. The mixture was then dried at 50℃ to obtain the modified conductive carbon black.

[0064] Porous membrane preparation: 1g of modified conductive carbon black was ultrasonically dispersed in 10g of ethyl acrylate containing 1% azobisisobutyronitrile, and then 40g of water was added. The mixture was emulsified at 15000rpm for 5min using a homogenizer to obtain a high internal phase emulsion. The emulsion was coated on a polyethylene plate with a coating thickness of 1mm and cured at 80℃ for 8h to obtain a flexible porous membrane.

[0065] (3) The humidity detection membrane is a flexible porous membrane with a polyacrylate matrix having a through-pore structure. A large amount of alkyl chain modified conductive carbon black is attached to the surface of the pore walls. The preparation process is as follows:

[0066] Modification of conductive carbon black: 100g of bp2000 (Cabot) carbon black was mixed with 50g of modified styrene-maleic anhydride copolymer and 850g of water. The mixture was then ground at 4000rpm for 1h at room temperature to obtain a nano-carbon black dispersion with a D50 of 150nm. Subsequently, 1500g of 2% ditetradecyl dimethyl ammonium chloride solution was added to the above liquid, followed by centrifugation, washing, and separation. The mixture was then dried at 50℃ to obtain the modified conductive carbon black.

[0067] Porous membrane preparation: 1g of modified conductive carbon black was ultrasonically dispersed in 10g of ethyl acrylate containing 1% azobisisobutyronitrile, and then 40g of water was added. The mixture was emulsified at 15000rpm for 5min using a homogenizer to obtain a high internal phase emulsion. The emulsion was coated on a polyethylene plate with a coating thickness of 1mm and cured at 80℃ for 8h to obtain a flexible porous membrane.

[0068] (4) Plasma treatment is performed on one side of the expanded polytetrafluoroethylene membrane with a thickness of 0.2 mm and a pore size of 50-200 μm, and then it is combined with the structure and base layer of steps (1)-(3) according to... Figure 1 The stacking method shown is achieved by bonding the edges with hot melt adhesive.

[0069] (5) The detection unit is based on Figure 2 Assemble the frame shown and then seal and attach it to the inside of the mask.

[0070] (6) The detection unit is connected to the humidity detection membrane and the carbon dioxide detection membrane through two sets of positive and negative leads.

[0071] Figure 3 The diagram shows the overall assembly of the carbon dioxide monitoring protective mask. The hardware part is the detection unit, and the sensing membrane assembly is the flexible composite membrane layer.

[0072] Comparative Example

[0073] The mask is assembled according to the method of the embodiment, except that the water vapor absorption layer and the breathable and water-repellent membrane are omitted.

[0074] Test Example 1

[0075] A carbon dioxide detection membrane and a humidity detection membrane, each cut to 10*10*1mm, are placed in a sealed container. Positive and negative electrodes are led out from the cross-sections of the membranes to the outside of the container. A multimeter is used to test the resistance values ​​when different humidity levels (0-30%) and different carbon dioxide concentrations (2-8%) are introduced, and the ratio of the resistance value to the resistance value when no gas is introduced is calculated.

[0076] The results are shown in Tables 1 and 2.

[0077] Table 1. Resistance change rate of carbon dioxide detection membrane under different humidity and carbon dioxide concentrations

[0078]

[0079] Table 2. Resistance change rate of humidity detection membrane under different humidity conditions

[0080]

[0081] Table 1 shows that humidity affects the resistance of the carbon dioxide detection membrane, and Table 2 establishes the relationship between humidity and the rate of change of resistance of the humidity detection membrane. However, adsorption saturation occurs in high humidity environments (above 50%).

[0082] Test Example 2

[0083] Wearing the masks from the examples and comparative examples, and obtaining the change in carbon dioxide concentration over time, respectively, as shown below. Figure 4 and Figure 5 As shown.

[0084] The humidity detection membrane of the mask in the embodiment detects an exhaled air humidity of approximately 23%, while the humidity detection membrane of the comparative mask detects an exhaled air humidity of approximately 65%.

[0085] The comparative example omits the water vapor absorption layer and the breathable, water-repellent membrane, therefore the humidity level is significantly higher than that of the detection membrane area on the mask in the embodiment. (Comparison) Figure 4 and Figure 5 As can be seen, the high humidity in the comparative environment can affect the adsorption saturation of water molecules, which hinders the adsorption of carbon dioxide molecules, resulting in a delayed signal response and a lower exhaled carbon dioxide value. On the other hand, during inhalation, the desorption of water molecules in the high humidity environment of the detection membrane is hindered, the signal response is delayed, and the inhaled carbon dioxide value is higher.

[0086] Test Example 3

[0087] Similar to Test Example 1, but using a high humidity environment, the test results are shown in Table 3.

[0088] Table 3

[0089]

[0090] As humidity increases, the resistance decreases with increasing carbon dioxide concentration at high carbon dioxide concentrations, approaching adsorption saturation, which adversely affects the detection sensitivity.

[0091] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A carbon dioxide monitoring protective mask, characterized in that, The mask includes a base layer and a flexible composite film layer located inside the base layer; The flexible composite membrane layer includes, from the inside out, a water vapor absorption layer and a detection layer, wherein the detection layer includes a carbon dioxide detection membrane and a humidity detection membrane located on the same plane; The detection layer is connected to the detection unit; the detection unit obtains the carbon dioxide concentration by real-time monitoring of the resistance changes of the carbon dioxide detection membrane and the humidity detection membrane. The humidity detection membrane comprises a polyacrylate matrix with a porous structure and carbon nanomaterials with alkyl chains embedded in the pore walls of the polyacrylate matrix.

2. The carbon dioxide monitoring protective mask according to claim 1, wherein, The carbon dioxide detection membrane comprises a polyacrylate matrix with a porous structure and carbon nanomaterials with dual modification of polydopamine and alkyl chains embedded in the pore walls of the polyacrylate matrix.

3. The carbon dioxide monitoring protective mask according to claim 1 or 2, wherein, The carbon dioxide detection membrane and the humidity detection membrane have the same thickness, which is 0.5-2 mm.

4. The carbon dioxide monitoring protective mask according to any one of claims 1-3, wherein, The base layer includes a spunbond layer and a meltblown layer.

5. The carbon dioxide monitoring protective mask according to any one of claims 1-4, wherein, The water vapor absorption layer comprises, from the inside out, a first hydrophilic porous membrane, a desiccant layer, and a second hydrophilic porous membrane. Preferably, the first hydrophilic porous membrane and the second hydrophilic porous membrane are independently selected from at least one of polyethersulfone membrane, polypropylene membrane, polyamide membrane and cellulose membrane, and preferably cellulose membrane; Preferably, the inner side of the water vapor absorption layer is provided with a breathable and water-repellent membrane; Preferably, the breathable and water-repellent membrane is selected from at least one of porous polyurethane film, porous silicone rubber film and expanded polytetrafluoroethylene film, with expanded polytetrafluoroethylene film being the most preferred.

6. The carbon dioxide monitoring protective mask according to claim 5, wherein, The average particle size of the desiccant powder in the desiccant layer is greater than 100 μm; Preferably, the desiccant in the desiccant layer is selected from at least one of silica gel desiccant, montmorillonite desiccant, and superabsorbent polymer; Preferably, the thickness of the desiccant layer is 0.2-0.5 mm.

7. The carbon dioxide monitoring protective mask according to claim 5 or 6, wherein, The thicknesses of the first and second hydrophilic porous membranes are independently 0.1-0.5 mm.

8. The carbon dioxide monitoring protective mask according to any one of claims 5-7, wherein, The breathable and water-repellent membrane has a thickness of 0.1-0.5 mm and a pore size greater than 20 μm.

9. The carbon dioxide monitoring protective mask according to any one of claims 1-8, wherein, The detection unit includes an impedance testing module, a control module, and an external signal receiving module. The impedance testing module is used to acquire the resistance data across the carbon dioxide detection membrane and the humidity detection membrane in real time to obtain the test signal; The control module is used to acquire the test signal and send the test signal to the external signal receiving module; An external signal receiving module is used to process the test signal to obtain the current carbon dioxide concentration.

10. The carbon dioxide monitoring protective mask according to claim 9, wherein, The real-time acquisition of resistance data across the carbon dioxide detection membrane and humidity detection membrane to obtain a test signal includes: The resistance on both sides of the humidity detection membrane is tested using a pre-set resistance testing device to obtain a first resistance signal; the resistance on both sides of the carbon dioxide detection membrane is tested using the same testing device to obtain a second resistance signal. The test signal is obtained by adjusting the second resistance signal based on the first resistance signal; The resistance testing equipment includes an impedance testing chip and a DC bridge circuit. The impedance testing chip has a built-in reference voltage source and an instrumentation amplifier.

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