Charge-to-digital converter for time-domain double lifetime referencing

Abstract

A wearable, miniaturized wireless device detects luminescence response of a carbon dioxide sensitive film to provide accurate measurements of transcutaneous carbon dioxide diffusing through the skin, thereby providing an accurate reflection of a person's blood carbon dioxide level. The device employs a charge-to-digital converter (CDC) architecture operable to implement time-domain double-lifetime referencing calculations to measure transcutaneous carbon dioxide. This potential product enables highly accurate and precise measurements of transcutaneous carbon dioxide while minimizing interference from confounding factors.

Description

[0001] Inventors: Urkuhan Guler, Tuna B. Tufan, and John A. McNeill Statement regarding federally sponsored research and development This invention was developed with the support of the U.S. government under contract number 2143898 granted by the National Science Foundation (NSF). The government holds certain rights to this invention. Background Technology

[0002] Human respiratory parameters (especially blood gas levels) are key indicators of human physiological condition. Real-time dynamics of blood gas measurements of carbon dioxide (CO2) and oxygen (O2) and the quantification of their physiological distribution are crucial for clinicians to understand the mechanisms associated with pathology and normal physiological conditions. Summary of the Invention

[0003] A wearable, miniaturized wireless device provides an accurate measurement of transdermal carbon dioxide diffused through the skin by detecting the luminescence response of a carbon dioxide-sensitive membrane, thus providing an accurate reflection of a person's blood carbon dioxide levels. The device employs a charge-to-digital converter (CDC) architecture, operable to perform time-domain dual lifetime reference calculations to measure transdermal carbon dioxide. This approach enables highly accurate and precise measurements of transdermal carbon dioxide while minimizing interference from confounding factors.

[0004] In the example configuration, the gas measuring device includes a sensing membrane having an emission response based on transdermal carbon dioxide (PtcCO2); and a light source configured to direct pulsed light onto the membrane defined by a sensing planar material suitable for epidermal contact. An adjacent sensor receives the re-emitted light from the sensing membrane, and monitoring circuitry identifies the carbon dioxide-sensitive component of the photocurrent response to the sensed light. A charge-to-digital converter (CDC) is used for a time-domain dual lifetime reference membrane after the luminescence stabilization of the pulsed light. The light source illuminates blue light, and the monitoring circuitry includes a CDC used to derive the carbon dioxide level from the luminescence data using a time-domain dual lifetime reference method.

[0005] The configuration presented in this paper is partly based on the observation that conventional methods for measuring blood gases or transdermal gases suffer from the drawback of inaccessible measuring devices. Conventional methods also suffer from the disadvantages of being thermally based, imposing significant power requirements, and necessitating tethered connections to auxiliary computing and measuring equipment. Therefore, the configuration presented in this paper largely overcomes the size, heating, and power requirements of conventional methods to accurately and precisely measure transdermal carbon dioxide or other sensed gases in the presence of a sensing membrane placed directly on or adhered to the skin. The proposed circuit design is used in a miniaturized wireless device for monitoring transdermal carbon dioxide (referring to carbon dioxide diffused through the skin). This device detects the luminescence response of the carbon dioxide-sensitive membrane, thereby accurately reflecting the blood carbon dioxide level in a person.

[0006] More specifically, the following configuration discloses a circuit and system implemented by a blood gas measuring device using a sensing membrane and a light source. The sensing membrane has an emission response to a sensed gas, wherein the sensing membrane has an emission response to the light source based on the presence of the sensed gas. A photodetector receives the emission response from the sensing membrane, and a sensing circuit responds to the photodetector to calculate: i: a first digital signal indicating the sensed gas; and ii: a second digital signal indicating a reference intensity, such that the concentration of the sensed gas is based on the ratio of the first digital signal to the second digital signal.

[0007] In operation, the method for detecting carbon dioxide includes: configuring a sensing membrane in communication with a gas source (such as the surface of a patient's skin), wherein the sensing membrane has an emission response to the sensed gas; and directing a light source to the sensing membrane. The sensing membrane is selected to generate the emission response in response to the light source being at a certain wavelength. A photodetector receives the emission response from multiple types of light emitters in the sensing membrane. Upon receiving the emission response in response to a pulsed light source, a sensing circuit measures a corresponding digital signal from each of the multiple light emitter types based on the emission response, and calculates the concentration of the sensed gas based on the differences between the multiple digital signals. Attached Figure Description

[0008] The above and other objects, features, and advantages of the invention will become apparent from the following description of specific embodiments of the invention as illustrated in the accompanying drawings, in which the same reference numerals refer to the same parts throughout the different views. These drawings are not necessarily drawn to scale, but are intended to illustrate the principles of the invention.

[0009] Figure 1 This is a system relationship diagram including wearable sensors suitable for use with the configuration described herein.

[0010] Figure 2The light emission response of the sensing film is shown, which exhibits Figure 1 The dual lifetime response of the corresponding luminescent element in the sensing film of the wearable sensor.

[0011] Figures 3A to 3C It shows Figure 2 The excitation and decay emission curves of the corresponding luminescent material in the sensing film.

[0012] Figure 4 The analysis is shown Figures 3A to 3C A schematic diagram of the sensing circuit for the light emission response.

[0013] Figure 5 It shows in Figure 4 A graphical representation of the integral value that changes due to the presence of carbon dioxide gas during the operation of the sensing circuit.

[0014] Figure 6A and Figure 6B The operational trials and verifications of the disclosed methods are described. Detailed Implementation

[0015] The following description presents an example sensing circuit and method for accurately and precisely measuring transdermal carbon dioxide, which refers to carbon dioxide diffused through the skin. The proposed circuit design will be used in miniaturized wireless devices for monitoring transdermal carbon dioxide. Other gas responses can be analyzed based on the sensing membrane. The example circuit and device detect the luminescence response of the carbon dioxide-sensitive membrane, thereby accurately reflecting the carbon dioxide level in a person's blood.

[0016] The example configuration below demonstrates the use of a miniaturized wireless transcutaneous carbon dioxide monitor incorporating the proposed circuit design for remote monitoring of patients' respiratory status outside of clinical settings. In clinical settings, this advancement increases the likelihood of early patient discharge and reduces the risk of undiagnosed medical problems worsening after discharge. This represents a substantial improvement compared to conventional, bulkier bedside blood gas monitors.

[0017] Figure 1 This is a system diagram including wearable sensors suitable for use with the configuration described herein. References Figure 1 In an example use case in a non-bedridden patient environment 100, the gas measuring device 110 includes a sensing membrane 130, a sensing circuit 150, a power supply 112, a transmitter 114, and a light source 118 (such as an LED).

[0018] The gas measuring device 110 has a portable and lightweight shape factor suitable for adhesion or mounting on the arm, wrist, or other skin surface of a patient 102. A sensing membrane 130 is positioned in the presence of a sensed gas 132, whether carbon dioxide or another gas. A transmitter 114 transmits output data 115 from the sensing circuitry 150 to a measurement server 120 via a network 116 using Bluetooth®, WiFi®, or other suitable wireless networks and transmission media. The measurement server 120 includes analysis logic 126 for processing and rendering the output data 115 as described herein via a visual rendering device 122 and a keyboard 124 or other suitable rendering and / or storage media.

[0019] Sensing circuit 150 implements a charge-to-digital converter architecture specifically designed to perform time-domain dual lifetime reference calculations for measuring transdermal carbon dioxide. Transdermal carbon dioxide (defined by the partial pressure of carbon dioxide diffusing through the skin) will be sensed using a commercially available carbon dioxide-sensitive membrane or sensing membrane 130. Sensing membrane 130 emits light with two different peak wavelengths in response to blue light excitation, such as... Figure 2 What is depicted.

[0020] Figure 2 The light emission response 200 of the sensing film 130 is shown, which exhibits the characteristics of light emission response by the sensing film 130. Figure 1 The gas measuring device 110 defines a wearable sensor with a dual-lifetime response in the sensing film 130 of the corresponding light emitter. The sensing film 130 is typically a flexible film encapsulated in a plastic or polymer material for humidity protection and to extend the lifetime of sensing capability. (Reference) Figure 1 and Figure 2 The first emission peak 202 in the sensing film 130 appears at 505 nm, generated by the emission of the carbon dioxide-sensitive luminescent material, while the reference luminescent material reaches its peak emission at 600 nm (204). When carbon dioxide is introduced into the sensing film, the emission intensity from the carbon dioxide-sensitive luminescent material decreases, as shown by the CO2-rich response 210, in contrast to the CO2-poor response 220. However, the emission intensity from the reference luminescent material generally remains unaffected by changes in carbon dioxide. Another difference between the carbon dioxide-sensitive and reference luminescent materials lies in their respective lifetimes. Carbon dioxide-sensitive luminescent materials typically have lifetimes measured in nanoseconds, indicating the average time it takes for them to return to their ground state after excitation. In contrast, reference luminescent materials have lifetimes measured in microseconds, meaning that they take a much longer average time to return to their ground state upon excitation. This duality of lifetimes allows the method for sensing carbon dioxide changes to be modified into a time-domain dual lifetime reference method.

[0021] Figures 3A to 3C It shows Figure 2 The excitation and decay emission curves of the corresponding luminescent material in the sensing film 130. The core concept behind the time-domain dual lifetime reference is to generate measurement results that are immune to external factors affecting the two emission responses. Figures 3A to 3C The luminescence intensity of each component over time is shown when the sensing membrane is excited with blue light pulses under conditions of carbon dioxide deficiency, carbon dioxide depletion, and carbon dioxide enrichment. Figure 3A The polymeric emission A generated by the sensor during excitation is depicted. SEN-ON (301). Figure 3B The polymeric emission A generated by the reference luminescent body during excitation is depicted. REF-ON (303). Total emission A during excitation ON Depending on the luminescence of the two luminescent bodies (A SEN-ON and A REF-ON ), confounding factors and carbon dioxide levels, such as Figure 3B and Figure 3C As shown. Conversely, the total emission after excitation (referred to as A) OFF ) Only the luminescence of the reference luminescent body (A) REF-OFF This is confirmed. This occurs because when the excitation source is deactivated, the emission of the luminescent material decreases at a rate proportional to its corresponding lifetime. Given that the lifetime of a carbon dioxide-sensitive luminescent material is very short, in the nanosecond range, its emission decreases rapidly, causing A... SEN-OFF With A REF-OFF This is negligible in comparison. Furthermore, other confounding factors can also contribute to A. OFF By using a ratio A specified as the luminescence ratio. ON / A OFF The sensing circuit 150 obtains carbon dioxide measurements independent of confounding factors, including excitation source intensity and detector photosensitivity.

[0022] Figure 4 The analysis is shown Figures 3A to 3C A circuit diagram of the sensing circuit 150 that responds to light emission. From Figure 1 Recalling the previous text, the gas measuring device 110 includes a sensing membrane 130 having an emission response to both sensed gas 132 and a light source 118, wherein the sensing membrane 130 has a dual response to the light source 118 based on the gas presence of sensed gas 132. A photodetector 152 receives the emission response from the sensing membrane 130. The sensing circuit 150 responds to the photodetector 152 to calculate: i: A first digital signal 301 indicating the gas 132 sensed during the excitation phase ( Figure 3A ); ii: The second digital signal 303 indicating the reference strength ( Figure 3BThis allows the sensed concentration of gas 132 to be based on the ratio of a first digital signal to a second digital signal. Figure 3C In this context, the response corresponding to the sensed gas varies with the CO2-poor environment 301 and the CO2-rich environment 301'. During the excitation phase, the first and second digital signals are effectively mixed in the total aggregation signal, and during the decay phase, the second digital signal (reference) dominates as the sensed component decays rapidly.

[0023] Figure 4 A sensing circuit 150 is depicted, including a charge-to-digital converter (CDC) 168, which is used to obtain the carbon dioxide level from the emission data using a time-domain dual lifetime reference method. The emission is captured by a photodetector 152, which, in the example configuration, is a photodiode having a spectral range covering the emission wavelengths. The photodiode current (If) is... PD The emission of light by the carbon dioxide-sensitive component (λ) 505 )401 and reference component emission (λ 600 Composed of ) I PD 403, in response to pulse excitation, as follows: Figure 5 As shown.

[0024] In sensor circuit 150, a first digital signal 301 indicates that the emission response from sensing membrane 130 represents both the emission component from sensed gas 132 and the emission component from reference emission. A second digital signal 303 represents only the emission component based on the reference emission and is therefore constant for the presence of carbon dioxide. However, as a reference signal, it normalizes other factors, such as temperature, brightness of light source 110, and others, such that the total difference in emission from the corresponding luminescent type indicates carbon dioxide. A sensing membrane with a luminescent body sensitive to other substances can also be used similarly.

[0025] Therefore, the sensing film 130 is selected to include a sensing emitter 170 that emits a response intensity based on the presence of the sensed gas 132 in response to the light source 118, and a reference emitter 172 that emits a response intensity independent of the presence of the sensed gas 132 in response to the light source 118. In the sensing film 130, the sensing emitter 170 responds to light of a predetermined wavelength to emit an emission response having a sensing wavelength having an intensity indicating the presence of the sensed gas 132. The reference emitter 172 responds to light to emit an emission response of a reference wavelength different from the sensing wavelength, such as... Figure 1 As shown.

[0026] Sensing circuit 150 defines charge-to-digital converter 168, which performs... Figures 3A to 3CThe effective integration of the corresponding areas under curves 301 and 303 is used to determine the presence, concentration, or amount of the sensed gas 132 stimulated by the sensing light source 170 compared to the reference light source 172, thereby allowing accurate measurement of the sensed gas 132 independently of other environmental factors without the need for a heat-generating or bulky power-consuming circuit system.

[0027] Sensing circuit 150 includes a charge-to-digital converter 168, which further includes a photodetector 152 configured to receive sensing emission 401 and reference emission 403 generated by excitation from a light source 118 from sensing membrane 130. Comparator 162 is connected to photodetector 152 to receive a voltage signal indicating sensed gas 132. Digital-to-analog converter 164 is connected to the output of comparator 162 and configured to generate a feedback current 161 in response to the output from comparator 162. The photodetector has an inherent capacitance, commonly referred to as parasitic capacitance or junction capacitance, shown as capacitor 166. Typically, this is not a separate discrete component; however, an external capacitor can be applied. Capacitor 166 is connected in parallel with photodetector 152 such that capacitor 166 receives feedback current 161 to integrate the aggregated signal received from photodetector 152 based on the emission responses (emissions 401, 403).

[0028] Counter 163 is also connected to the output of comparator 162 to generate a count proportional to the emission response from sensing film 130, based on both the sensed gas 132 from emitter 401 and the reference intensity from emitter 403. Sensing emitter 170 has an emission response whose intensity varies with the presence of sensed gas 132 (e.g., carbon dioxide). This characteristic of sensing film 130 causes a first digital signal to indicate the current of photodetector 152 in response to pulsed illumination based on the emission intensities from both sensing emitter 170 and the reference emitter, and a second digital signal to indicate the current of photodetector 152 in response to pulsed illumination based on the emission intensity from reference emitter 172. It is also apparent that photodetector 152 is selected to respond to light at both the sense wavelength and the reference wavelength.

[0029] The basic operation of the charge-to-digital converter 168 is to use a comparator 162 and a digital-to-analog converter 164 (DAC) to charge a photodiode (C). J The charge induced by the photocurrent at the junction capacitance of the junction is integrated, and the voltage (V) at the integration node is also integrated. PD Maintained at an external reference voltage (V) REF Near ) based on V PDThe current feedback to the integrator node is limited by the level of the current. In this sense, the sensing circuit is based on a Δ-Σ modulator CDC. Counter 163 tracks V during the modulation phase. PD More than V REF The number of times is essentially a response to the high output (V) from comparator 162. CMP The counter 153 performs a count. Based on DAC control 165, this count is proportional to the number of active DAC bits involved in the comparison process. CNTR ) provides C J The integral charge is represented digitally. This digital representation is then used to calculate the luminescence ratio, which in turn produces a measurement of the carbon dioxide level.

[0030] Figure 5 It shows in Figure 4 A graphical representation of the integral value changing due to the presence of carbon dioxide gas during the operation of the sensing circuit 150. (Reference) Figure 4 and Figure 5 The operation of CDC 168 can be analyzed in two phases, 501 and 503. Phase 501 occurs when the sensing film 130 is excited by a blue light pulse from the light source 118. The modulation operation begins after the light emission of the sensing film has stabilized (at time t). w1 After that), until the integration node voltage V PD via switch (Φ) RES1 ) Keep in V REF After luminescence stabilization, I PD The area under the curve, A1, is equivalent to the charge Q1 integrated at CJ during the integration period, and can be obtained by the following formula: (1) Among them, I PD(SEN) It is the carbon dioxide sensitive component I of the photocurrent. PD And I PD(REF) This is the photocurrent contribution of the reference luminescent body. T INT This represents the integral duration from the moment when luminescence stabilizes until the excitation ends.

[0031] The second stage 503 begins at the end of excitation. During this stage, the luminescent material decays, and the total emission is dominated by the reference component. The charge Q2 integrated during this stage corresponds to I during the decay period. PD Area under the curve A2: (2) in, τ The lifetime t of the reference luminescent body was described. W2It is configured to approximately correspond to the decay time of the carbon dioxide-sensitive luminescent material, i.e., the lifetime of the reference luminescent material, thereby ensuring that the effect of this component is completely ignored during the integration process. F2 The decay duration of the reference luminescent body is approximately 5. τ Since the lifetime of the carbon dioxide-sensitive luminescent material is much shorter than that of the reference luminescent material, Equation 2 can be simplified to: A2= Q2= τI PD(REF) (3) If we take the ratio of charges Q1 to Q2: (4) Rearrange equation 4: (5) The CDC 168 converts charge Q into a digital N (V at the output of the counter). CNTR This transformation can be mathematically represented as:

[0032] Among them, I DAC,LSB It is the least significant bit of the DAC, and T CLK It is the clock period of the modulator. Using N... 1,2 Replace Q 1,2 :

[0033] Therefore, the emission ratio, expressed as IPD, can be determined by analyzing the CDC 168 output at two different stages: during excitation (501) and after excitation (503). (SEN) / IPD (REF) This ratio provides a quantitative measure of the carbon dioxide level to which the sensing membrane has been exposed. The calculation can be performed in the sensing circuitry 150 on the device, on the server 120, or any combination thereof. In other words, the sensing circuitry 150 can transmit values ​​to the server 120, where analysis logic 126 calculates the measurement of the sensed gas 132. Transmitter 114 allows any suitable internet or other network 116 to connect to and communicate with the server 120 to transmit output data 115, and allows for the calculation of carbon dioxide levels or other sensed gas 132.

[0034] Therefore, the operating logic of the sensing circuit 150 is used to aggregate the intensity of each of the corresponding digital signals during the excitation and decay phases, and to calculate the aggregated intensity difference of the corresponding digital signals to determine the concentration of the sensed gas. This includes aggregating the intensity corresponding to a sense luminescent body of the luminescent body type, and aggregating the intensity corresponding to a reference luminescent body of the luminescent body type. Calculating this difference further includes calculating the luminescence ratio based on the intensity of both the sense luminescent body and the reference luminescent body during the excitation phase and the intensity of the reference luminescent body during the decay phase after excitation by the light source.

[0035] Figure 6A and Figure 6B The operational trials and verifications of the disclosed methods are described. Figure 6A The results of the behavioral simulation were presented, during which IPD was... (SEN) Adjust within the range of 0.1 µA to 3 µA, while adjusting IPD. (REF) Maintain at 1 µA and set the modulator clock rate to 500 MHz. Figure 6B The conversion error between the initial emission ratio and the value obtained from the CDC 168 output is shown to be less than 0.5%. It is worth emphasizing that the error depends on the operating frequency. As the frequency increases, the counter accumulates more counts, which in turn reduces the conversion error.

[0036] Conventional methods demonstrate alternative approaches that typically require heating elements and thus associated circuitry and power requirements, or tethered attachments to fixed processing units.

[0037] US 4,930,506 discloses an integrated sensor equipped with a temperature-controlled heating unit and employing a carbon dioxide measurement component based on pH measurement in an electrolyte. The disclosed method differs from optical methods used for carbon dioxide detection, and the device relies on the electrochemical principle of pH measurement in an electrolyte. Additionally, the '506 device requires the use of a heating element.

[0038] US 2010 / 0130842 discloses a method dependent on local tissue blood flow, which is incorporated into gas measurement. The sensor used in this setup includes an electrochemical measurement device for determining PtcCO2. This electrochemical measurement device includes a micro pH electrode and an Ag / AgCl reference electrode. Changes in carbon dioxide levels at the skin surface cause pH changes in an electrolyte solution in which both the micro pH electrode and the Ag / AgCl reference electrode are located. Unlike the disclosed method, this wired sensor interface for a bulky bedside monitor requires pH measurement.

[0039] US 8,771,184 shows a skin-mounted electrode on a patient for various monitoring functions and employs conventional electrochemical methods to measure PtcCO2, which requires a heating element.

[0040] US 10,307,090 discloses an infrared-based sensor for detecting gases, including carbon dioxide. The sensor has a contact surface that can be pointed towards a measurement site. The sensor includes at least one radiation source, a measurement volume for receiving the gas to be measured, and a detector for emitting radiation. The disclosed method does not incorporate an infrared sensing medium.

[0041] US 6,602,716 relies on fluorescence response to use fluorescence assays to evaluate the biological, chemical, or physical properties of samples of two different luminescent materials.

[0042] Those skilled in the art will readily understand that the programs and methods defined herein can be delivered to user processing and rendering devices in many forms, including but not limited to: a) information permanently stored on non-writable storage media (such as ROM devices); b) information changeably stored on writable non-temporary storage media (such as solid-state drives (SSDs) and media, flash drives, floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media); or c) information transmitted to a computer via communication media (in electronic networks such as the Internet or telephone modem lines). The operations and methods can be implemented in a software executable object or as a set of coded instructions executed by a processor in response to these instructions, including virtual machines and execution environments controlled by a hypervisor. Alternatively, the operations and methods disclosed herein can be embodied, in whole or in part, using hardware components or a combination of hardware, software, and firmware components, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), state machines, controllers, or other hardware components or devices.

[0043] While the systems and methods defined herein have been specifically shown and described with reference to their embodiments, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as covered by the appended claims.

Claims

1. A gas measuring device, comprising: A sensing membrane that has an emission response to the sensed gas; A light source, wherein the sensing film has an emission response to the light source based on the presence of the sensed gas; A photodetector for receiving the emission response from the sensing film; as well as The sensing circuit responds to the photodetector to calculate: i: The first digital signal indicating the sensed gas; as well as ii: A second digital signal indicating the reference intensity, such that the concentration of the sensed gas is based on the ratio of the first digital signal to the second digital signal.

2. The device as claimed in claim 1, wherein: The first digital signal indicates: The emission response from the sensing membrane includes an emission component based on the sensed gas and an emission component based on a reference emission; and The second digital signal is based on the transmitted component transmitted based on the reference transmission.

3. The device as claimed in claim 1, wherein, The sensing membrane includes: Sensors that emit light in response to the light source emit a response intensity based on the sensed presence of the gas; and Reference light emitters, which respond to the light source by emitting a response intensity independent of the presence of the sensed gas.

4. The device as claimed in claim 1, wherein, The sensing circuit includes charge-to-digital converters. A comparator connected to the photodetector to receive a voltage signal indicating the sensed gas; A digital-to-analog converter (DAC) is connected to the output of the comparator and is configured to generate a feedback current in response to the output of the comparator; as well as A capacitor connected in parallel with the photodetector receives the feedback current to integrate the aggregated signal received from the photodetector based on the emission response.

5. The device of claim 4, further comprising: A counter, connected to the output of the comparator, generates a count proportional to the emission response from the sensing membrane based on both the sensed gas and the reference intensity.

6. The device as claimed in claim 1, wherein, The sensing film further includes: Sensors of light-emitting elements, the emission response of which varies in intensity with the presence of the sensed gas; and Reference luminescent body, The first digital signal indicates the photodetector current in response to pulsed illumination based on the emission intensity from both the sensing light emitters and the reference light emitters, and The second digital signal indicates the photodetector current in response to the pulse irradiation based on the emission intensity from these reference luminescent bodies.

7. The device as claimed in claim 6, wherein, These sensing light emitters respond to light of a predetermined wavelength by emitting a sensing wavelength having an intensity indicating the presence of the sensed gas; and These reference luminescent bodies respond to the light by emitting light.

8. The device as claimed in claim 7, wherein, The photodetector responds to light at the sensing wavelength and the reference wavelength.

9. The device as claimed in claim 1, wherein, The sensing membrane has a dual response based on the presence of the sensed gas, which covers the emission spectrum of 500–510 nm and 595–605 nm.

10. The device as claimed in claim 1, wherein, The sensing membrane is a carbon dioxide sensitive membrane.

11. The device as claimed in claim 1, wherein, The light source is configured to emit blue light.

12. The device as claimed in claim 1, wherein, The light source is configured to emit light with a wavelength of 465 nm.

13. A method for detecting carbon dioxide, the method comprising: The sensing membrane is configured to be connected to a gas source, and the sensing membrane has an emission response to the sensed gas; The light source is directed to the sensing film, and the sensing film generates the emission response in response to the light source being at a certain wavelength; The emission response is received at a photodetector from various types of light emitters in the sensing film; Based on this emission response, the corresponding digital signal from each of the multiple luminescent types is measured; The concentration of the sensed gas is calculated based on the differences between these multiple digital signals.

14. The method of claim 13, further comprising: Excitation phase and decay phase; as well as The difference in aggregation intensity of these corresponding digital signals is calculated to determine the concentration of the sensed gas.

15. The method of claim 14, further comprising: The intensity of the aggregated sensor corresponds to the type of luminescent material. The intensity of the polymer corresponding to a reference luminescent body of this luminescent body type. The calculation of this difference further includes calculating the luminescence ratio based on the intensities of both the sensing luminescent bodies and the reference luminescent bodies during the excitation phase and the intensities of the reference luminescent bodies during the decay phase.

16. A gas measuring device, comprising: A sensing membrane having an emission response based on transdermal carbon dioxide (PtcCO2); A light source, configured to direct pulsed light to the sensing planar material; A sensor for receiving light re-emitted from the sensing planar material; as well as A monitoring circuit is used to identify the carbon dioxide-sensitive component of the photocurrent emitted from the sensing membrane after the pulse of light from the pulsed light has stabilized.

17. The device as claimed in claim 16, wherein, The light source emits blue light.

18. The device as claimed in claim 16, wherein, The monitoring circuit includes a charge-to-digital converter (CDC) used to obtain the carbon dioxide level from the luminescence data using a time-domain dual lifetime reference method.

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