CN114994146A - Gas sensor based on catalytic temperature resistance peak signal and gas detection method - Google Patents
Gas sensor based on catalytic temperature resistance peak signal and gas detection method Download PDFInfo
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Abstract
The invention discloses a gas sensor based on catalytic temperature peak-to-peak signals and a gas detection method, belonging to the technical field of gas sensors, wherein the sensor comprises: the device comprises a micro-hotplate unit, a gas-sensitive film, a catalytic film and a processing unit; the micro-hotplate unit comprises an insulating substrate, a heating electrode, a temperature measuring electrode and a measuring electrode, wherein the heating electrode, the temperature measuring electrode and the measuring electrode are arranged on the insulating substrate; the processing unit controls the heating of the heating electrode, so that the temperature of the catalytic film periodically changes within a preset temperature interval at a set speed to correspondingly change the catalytic rate of the catalytic film on the target gas in the gas to be detected, and the resistance value of the gas-sensitive film is related to the catalytic rate; and the processing unit calculates the ratio of the resistors at the same temperature in the temperature increasing and decreasing stages according to the temperature fed back by the temperature measuring electrode and the resistance value fed back by the measuring electrode, and judges that the target gas is detected when the ratio which is greater than a set threshold value is obtained through calculation. The gas selectivity is improved, and therefore the gas detection accuracy is improved.
Description
Technical Field
The invention belongs to the technical field of gas sensors, and particularly relates to a gas sensor based on a catalytic temperature peak resistance signal and a gas detection method.
Background
The gas sensor is integrated in mobile phone, intelligent wearable electronic products and other electronic products to realize a gas detection function, and the gas sensor has important application in numerous application scenes with gas detection requirements. The metal oxide semiconductor gas sensor has the advantages of high sensitivity, small size, low power consumption, high integration degree, low cost and the like, but has the defects of poor selectivity and weak anti-interference capability, and can only be used for alarming generally. The gas-sensitive performance of the gas-sensitive material can be improved by carrying out modification treatment such as doping and modification on the metal oxide semiconductor, so that although the response of target gas is improved, the response amplitude of other impurity gases is also improved, and the interference of other gases is increased. In addition, a laminated device structure is adopted to improve the gas sensitivity selectivity of the metal oxide gas sensor, and the laminated device structure generally comprises a filtering film + a gas sensitive film and a catalytic film + a gas sensitive film.
The "filter membrane + gas sensitive membrane" laminate structure presents two major bottleneck problems: the interference of gas molecules with smaller size than the detection molecules is difficult to eliminate, and the diffusion speed of the gas molecules in the microporous filtering membrane is slow, so that the response recovery time of the gas is long, and the requirement of real-time monitoring cannot be met. The laminated structure of the catalytic film and the gas-sensitive film can be used for eliminating the interference of specific gases or improving the response amplitude of the specific gases. However, the magnitude of the response of the gas molecules that do not react on the catalytic membrane is not substantially changed, and thus high selectivity cannot be completely achieved. Therefore, low selectivity is a major technical bottleneck limiting the wide application of metal oxide gas sensors.
Disclosure of Invention
Aiming at the defects and improvement requirements of the prior art, the invention provides a gas sensor based on a catalytic temperature resistance peak signal and a gas detection method, and aims to construct a gas sensor with high gas selectivity so as to improve the gas detection accuracy.
To achieve the above object, according to one aspect of the present invention, there is provided a gas sensor based on a catalytic temperature peak-to-peak signal, comprising: the device comprises a micro-hotplate unit, a gas-sensitive film, a catalytic film and a processing unit; the micro-hotplate unit comprises an insulating substrate, and a heating electrode, a temperature measuring electrode and a measuring electrode which are arranged on the insulating substrate, wherein the gas-sensitive film is coated on the surface of the measuring electrode, the catalytic film is coated on the gas-sensitive film, and the processing unit is connected with the heating electrode, the temperature measuring electrode and the measuring electrode; the temperature measuring electrode is used for measuring the temperature of the catalytic membrane; the processing unit is used for controlling the heating power of the heating electrode according to the temperature fed back by the temperature measuring electrode, so that the temperature of the catalytic film periodically changes within a preset temperature interval at a set speed, the catalytic rate of the catalytic film on target gas in the measured gas is correspondingly changed, and the resistance value of the gas-sensitive film is related to the catalytic rate; the measuring electrode is used for measuring the resistance value of the gas-sensitive film in real time; the processing unit is further used for calculating the ratio of the resistors at the same temperature in the temperature increasing and decreasing stage according to the temperature fed back by the temperature measuring electrode and the resistance value fed back by the measuring electrode, and judging that the target gas is detected when the ratio which is larger than a set threshold value is obtained through calculation.
Further, the processing unit calculates a ratio of resistances at the same temperature in the temperature increasing and decreasing stages, and when the calculated ratio is greater than a set threshold, it is determined that the target gas is detected, including: the processing unit calculates the ratio of the resistance at the peak temperature in the temperature rising and falling stage, and judges that the target gas is detected when the ratio of the resistance at the peak temperature is greater than a set threshold value; and the peak temperature is a temperature which is stored in the gas sensor in advance, corresponds to the target gas and corresponds to the maximum value of the ratio of the resistance at the same temperature in the temperature increasing and decreasing stage.
Furthermore, the processing unit stores a mapping relation between the ratio and the concentration of the target gas, and is further configured to calculate the concentration of the target gas according to the ratio and the mapping relation.
Furthermore, the temperature measuring electrode is arranged on the insulating substrate and is positioned on the periphery of the heating electrode, and the processing unit controls the electric energy input to the heating electrode according to the temperature fed back by the temperature measuring electrode so as to control the heating power of the heating electrode.
Still further, still include: and the power supply unit is used for supplying electric energy to the heating electrode under the control of the processing unit.
Furthermore, the gas-sensitive film is made of a metal oxide semiconductor material, or a modified material obtained by modifying, doping and compounding the metal oxide semiconductor material.
Furthermore, the material of the catalytic membrane is a metal catalyst, a metal oxide catalyst, a molecular sieve catalyst or a metal organic framework material, or is a modified material obtained by modifying, doping and compounding the metal catalyst, the metal oxide catalyst, the molecular sieve catalyst or the metal organic framework material.
According to another aspect of the present invention, there is provided a gas detection method based on a catalytic temperature peak-to-peak signal, comprising: s1, periodically changing the temperature of a catalytic membrane in a preset temperature interval at a set speed, wherein the catalytic membrane is coated on the surface of a gas-sensitive membrane, the catalytic rate of the catalytic membrane to a target gas in a detected gas is related to the temperature of the catalytic membrane, and the resistance of the gas-sensitive membrane is related to the catalytic rate; and S2, measuring and calculating the ratio of the resistance at the same temperature in the temperature raising and lowering stage, and judging that the target gas is detected when the ratio greater than a set threshold value is obtained through calculation.
Further, the S2 includes: measuring and calculating the ratio of the resistance at the peak temperature in the temperature rising and falling stage, and judging that the target gas is detected when the ratio of the resistance at the peak temperature is greater than a set threshold value; and the peak temperature is a temperature which is stored in the gas sensor in advance, corresponds to the target gas and corresponds to the maximum value of the ratio of the resistance at the same temperature in the temperature increasing and decreasing stage.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) the gas sensor based on the catalytic temperature resistance peak position signal periodically changes the temperature of the catalytic membrane within a preset temperature interval at a set speed, measures and calculates the specific value of the resistance at the same temperature in the temperature raising and lowering stage, and detects the target gas based on whether the specific value is larger than a set threshold value, so that the detection mode has high selectivity, the optimal temperature of the gas sensor does not need to be measured in the early stage, the working time is saved, and the working efficiency is improved;
(2) whether the target gas is detected or not is judged directly on the basis of the relation between the specific value of the resistance at the peak temperature in the temperature rise and drop stage and a set threshold value, and for any gas sensor, the peak temperature can be obtained through experiments in advance, so that the calculated amount and efficiency of target gas detection are reduced, and the working efficiency is further improved;
(3) the gas sensor is simple to prepare, and catalytic temperature peak position signals are obtained by calculating data under a detection atmosphere, so that the interference of other factors such as environment, sensor recovery conditions and the like is reduced; the catalytic membrane only catalyzes and decomposes the target gas, so that the anti-interference performance of a catalytic temperature peak position signal is strong.
Drawings
FIG. 1 is a schematic structural diagram of a gas sensor based on a catalytic temperature peak-to-peak signal according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a gas sensor based on a catalytic temperature peak-to-peak signal according to an embodiment of the present invention;
FIG. 3 shows an example of the present invention in which ZSM-5/SnO is used as the catalytic film/gas-sensitive film 2 A real-time response recovery curve of the time gas sensor to 0.4ppm ethanol under high-speed temperature modulation;
FIG. 4 shows an example of the present invention, wherein ZSM-5/SnO is used as the catalytic film/gas-sensitive film 2 Real-time response curve of the time gas sensor to 0.7ppm ethanol and formaldehyde under high-speed temperature modulation;
FIG. 5A shows an example of the present invention in which ZSM-5/SnO is used as the catalytic film/gas-sensitive film 2 The conductance-temperature reciprocal relation curve of the time gas sensor to ethanol and formaldehyde under high-speed temperature modulation;
FIG. 5B shows an example of the present invention in which ZSM-5/SnO is used as the catalytic film/gas-sensitive film 2 The temperature rising and falling resistance ratio-temperature curve of the ethanol and the formaldehyde is obtained by the gas sensor under high-speed temperature modulation;
FIG. 5C shows an example of the present invention in which ZSM-5/SnO is used as the catalytic film/gas-sensitive film 2 The time gas sensor highly responds to the peak positions of different concentrations of ethanol and formaldehyde under high-speed temperature modulation;
FIG. 6 shows an example of the present invention, wherein ZSM-5/SnO is used as the catalytic film/gas-sensitive film 2 The time gas sensor highly responds to the peak position of different gases such as ethanol and the like under high-speed temperature modulation;
FIG. 7 is the present inventionThe Pt-Pd-Rh/Al provided in the working examples 2 O 3 /Sr@SnO 2 The obtained acetone high-selectivity gas sensor highly responds to the peak positions of different gases such as acetone and the like;
FIG. 8 is a diagram of MCM-48/Sr @ SnO according to an embodiment of the invention 2 The obtained formic acid high-selectivity gas sensor has high response to peak positions of different gases such as formic acid.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
the device comprises a micro-hotplate unit 1, a temperature measuring electrode 11, a heating electrode 12, a measuring electrode 13, an insulating substrate 14, a gas-sensitive film 2 and a catalytic film 3.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
In a conventional metal oxide gas sensor, a metal oxide gas-sensitive film is a sensing element and a conversion element. In the laminated structure of the catalytic film and the gas-sensitive film, the high-selectivity catalytic film can be used as a sensitive element, the high-sensitivity gas-sensitive film can be used as a conversion element, and the gas-sensitive film can convert high-selectivity catalytic reaction information of the catalytic film into a special electric signal by combining a working mode and a signal processing method.
In the embodiment of the invention, by combining the laminated structure of the catalytic film/metal oxide gas-sensitive film, the micro-hotplate and the high-speed temperature modulation technology, the catalytic film has or does not have catalytic activity on different gases at different temperatures, and even if the catalytic films have the catalytic activity, the catalytic activities of the catalytic films are different, so that the following two states can exist: (1) the catalytic film carries out catalytic decomposition on target gas to be detected to form various small molecular gases, and other non-target gases cannot be subjected to catalytic decomposition, so that the concentration of other non-target gases is unchanged, and only the target gas generates a temperature resistance peak signal on the surface of the gas sensitive film under the condition of temperature modulation; (2) the catalytic membrane carries out catalytic decomposition on different gases at different temperatures, so that the concentration of the gas which can only be decomposed becomes high through the catalytic membrane at different temperatures, and the concentration of other gases is unchanged at the temperature, so that different gases can generate temperature resistance peak signals at different temperatures, and a gas high-selectivity gas sensor is constructed. Thus, a highly selective laminated gas sensor can detect the presence or absence of a particular type of gas in a complex gas background and output a gas concentration.
Fig. 1 is a schematic structural diagram of a gas sensor based on a catalytic temperature peak-to-peak signal according to an embodiment of the present invention. Referring to fig. 1, a detailed description will be given of the gas sensor based on the catalytic temperature peak-to-peak signal in the present embodiment with reference to fig. 2 to 8.
Referring to fig. 1, the gas sensor based on the catalytic temperature peak-to-peak signal includes a micro-hotplate unit 1, a gas-sensitive film 2, a catalytic film 3, and a processing unit (not shown in fig. 1). The micro-hotplate unit 1 comprises an insulating substrate 14, and a temperature measuring electrode 11, a heating electrode 12 and a measuring electrode 13 which are arranged on the insulating substrate 14. The gas-sensitive film 2 is coated on the surface of the measuring electrode 13. The catalytic film 3 covers the gas-sensitive film 2. The processing unit is connected with the temperature measuring electrode 11, the heating electrode 12 and the measuring electrode 13.
The temperature measuring electrode is used for measuring the temperature of the catalytic membrane. The processing unit is used for controlling the heating power of the heating electrode according to the temperature fed back by the temperature measuring electrode, so that the temperature of the catalytic membrane periodically changes within a preset temperature interval at a set speed, and the catalytic rate of the catalytic membrane to the target gas in the measured gas is correspondingly changed. The resistance of the gas sensitive film is related to the catalytic rate. The measuring electrode is used for measuring the resistance value of the gas-sensitive film in real time.
The processing unit is used for calculating the ratio of the resistors at the same temperature in the temperature rise and reduction stage according to the temperature fed back by the temperature measuring electrode and the resistance value fed back by the measuring electrode, and judging that the target gas is detected when the ratio larger than a set threshold value is obtained through calculation.
In this embodiment, the gas concentration of the reactant and the product that penetrate through the catalytic film and reach the gas-sensitive film can be changed by changing the catalytic rate of the catalytic film to the target gas in the gas to be detected, so that the resistance value of the gas-sensitive film is changed along with the change of the temperature of the catalytic film.
On one hand, the processing unit changes the heating power of the heating electrode according to the real-time feedback of the temperature measuring electrode, so that the temperature of the catalytic membrane periodically changes in a preset temperature interval at a set speed; on the other hand, the processing unit calculates the ratio of the resistance at the same temperature in the temperature rising and falling stage according to the resistance measured by the measuring electrode and the temperature measured by the temperature measuring electrode, so that a temperature rising and falling resistance ratio-temperature curve can be further generated. And when the ratio of the temperature rise and decrease resistance to the temperature appears in the temperature curve, judging that the target gas is detected. The threshold value is set to a value related to the target gas and can be set according to the detection requirement and the detection scene.
According to the embodiment of the invention, preferably, the processing unit can directly calculate the ratio of the resistance at the peak temperature in the temperature raising and lowering stage, and when the ratio of the resistance at the peak temperature is greater than a set threshold value, the target gas is judged to be detected; the peak temperature is the temperature which is stored in the gas sensor in advance, corresponds to the target gas and corresponds to the maximum value of the ratio of the resistance at the same temperature in the temperature increasing and decreasing stage. For example, when the target gas is ethanol, the peak temperature is 350 ℃, and the temperature rise and decrease resistance ratio at the peak temperature is the temperature resistance peak signal. In this embodiment, only the temperature rise and fall resistance ratio at the peak temperature needs to be calculated to perform target gas detection, and the temperature rise and fall resistance ratio at other temperatures does not need to be calculated, so that target gas detection is realized based on the peak signal of the catalytic temperature rise and fall resistance ratio-temperature curve, the high selectivity of the sensor to the target gas can be improved, and the detection efficiency is improved.
The micro-hotplate unit can set different heating temperatures as required, so that the gas-sensitive film and the catalytic film work in a specific temperature modulation working mode of high-temperature and low-temperature circulation, different catalytic activities of the catalytic film at different temperatures are utilized, target gas is catalytically decomposed into different component gases, the gas atmosphere detected by the gas-sensitive film is changed in real time, and a peak position signal and a peak position height are obtained on a temperature rise and drop resistance ratio-temperature curve calculated by the processing unit to realize the detection of the components and the concentration of the target gas, as shown in fig. 2.
The temperature measuring electrode 11 is arranged on the insulating substrate 14 and is positioned at the periphery of the heating electrode 12, and the processing unit controls external electric energy input to the heating electrode according to the temperature fed back by the temperature measuring electrode so as to control the heating power of the heating electrode. Further, the heating electrode can be arranged at the periphery of the measuring electrode, so that a proper temperature is provided for the work of the gas-sensitive film and the catalytic film.
According to the embodiment of the invention, the processing unit stores the mapping relation between the ratio and the concentration of the target gas, and is further used for calculating the concentration of the target gas according to the ratio and the mapping relation.
According to the embodiment of the invention, the gas-sensitive film is made of a metal oxide semiconductor material, or is a modified material obtained by modifying, doping and compounding the metal oxide semiconductor material, and can also be made of other gas-sensitive materials with excellent performance. Preferably, the metal oxide semiconductor material is SnO 2 、In 2 O 3 Or WO 3 。
The catalytic membrane has high catalytic activity and can catalyze the catalytic decomposition of a certain gas (or certain organic functional group gas molecules), so that the component concentration is reduced, and a new product is generated. According to the embodiment of the present invention, the material of the catalytic membrane is a material having catalytic activity, such as a metal catalyst, a metal oxide catalyst, a molecular sieve catalyst, or a metal organic framework material, or may also be a modified material obtained by modifying, doping, and compounding a metal catalyst, a metal oxide catalyst, a molecular sieve catalyst, or a metal organic framework material.
In this embodiment, the operating mode of the gas sensor adopts a temperature modulation mode with high-low temperature variation. The temperature modulation maximum temperature, minimum temperature, rate of temperature rise and rate of temperature fall, and the holding times at the maximum and minimum temperatures are set according to the test gas and the catalytic membrane material. Preferably, the temperature change rate of the gas sensor is in the range of 100-10000 ℃/s.
The gas-sensitive film is coated on the measuring electrode, and the catalytic film is covered on the gas-sensitive film and completely covers the gas-sensitive film. The printing modes of the gas-sensitive film and the catalytic film can be silk-screen printing, micro-spraying, magnetron sputtering and the like, or the combination of the two printing modes.
Preferably, the material of the insulating substrate is high-temperature-resistant insulating materials such as insulating ceramics and glass; the heating electrode, the measuring electrode and the temperature measuring electrode are circuit electrodes printed on an insulating substrate, are made of metal or alloy with good conductivity, and are manufactured by magnetron sputtering, silk-screen printing and the like.
According to an embodiment of the invention, the gas sensor based on the catalytic temperature peak-to-peak signal further comprises a power supply unit for providing electrical energy to the heating electrode under control of the processing unit. It should be noted that the heating electrode may be supplied with electric power by an external power supply.
Example 1:
the ZSM-5 type molecular sieve has high catalytic selectivity to ethanol molecules and can catalyze ethanol dehydration. ZSM-5 having a pore size of 5.1 to 5.6
The kinetic molecular sizes of methanol, ethanol, propanol and butanol were 3.84 respectively
、4.53
、5.1
、5.6
. In this example, ZSM-5 was selected as the catalytic membrane material, and SnO was selected 2 As a gas sensitive film material. Further, the method can be used for preparing a novel liquid crystal displayAnd secondly, selecting a zirconia ceramic material as the insulating substrate 14, photoetching-magnetron sputtering a measuring electrode, a heating electrode and a temperature measuring electrode on the insulating substrate, and then respectively printing a catalytic film and a gas sensitive film on the zirconia insulating substrate by a screen printing technology to prepare the ZSM-5/SnO2 gas sensor.
During performance testing, the temperature modulation parameters are as follows: the maximum temperature is 400 ℃, the minimum temperature is 100 ℃, the heating rate and the cooling rate are both 500 ℃/s, and the temperature is respectively kept for 1s at the maximum temperature and the minimum temperature.
Referring to fig. 3, in the 1 st temperature change period after the ethanol gas is introduced, the resistance curve in the ethanol atmosphere has a downward "peak" compared with the resistance curve in the air during temperature rise, the "peak" is the reaction of the temperature resistance peak position signal on the resistance-time curve, and the "peak" disappears after 3 temperature change periods after the gas is exhausted, which indicates that the ZSM-5/SnO2 laminated gas sensor has a second-level response recovery speed to ethanol. Referring to fig. 4, the response curve for formaldehyde gas does not have a resistance down "spike".
Referring to fig. 5A, 5B, and 5C, the response curve under the atmosphere of air, formaldehyde, and ethanol is converted into a temperature-rise resistance ratio-temperature curve, and a temperature-rise peak signal under the response of ethanol can be clearly observed. In this embodiment, the magnitude of the temperature-resistant peak signal is defined as R Raising the temperature to 350 DEG C /R Cooling to 350 deg.C The value is the ratio of the resistance corresponding to 350 ℃ in the temperature reduction process to the resistance corresponding to 350 ℃ in the temperature rise process. Further, referring to FIG. 6, ZSM-5/SnO was tested 2 The peak height response value of the gas sensor to the gas in 16 shows that the temperature resistance peak signal has high selectivity to ethanol, which indicates that the ethanol detection accuracy is high.
Example 2:
in this example, Al modified with Pt-Pd-Rh metal ions was selected 2 O 3 The carrier is used as a catalytic film, and the metal Sr is used for modifying SnO 2 The gas-sensitive material is used as a gas-sensitive film, a magnetron sputtering micro hot plate chip (comprising a measuring electrode, a heating electrode and a temperature measuring electrode) is photoetched on a zirconia insulating substrate, then the gas-sensitive material and the catalytic material are sprayed on the micro hot plate chip by utilizing a micro-spraying technology,firing to obtain Pt-Pd-Rh/Al 2 O 3 /Sr@SnO 2 A laminated gas sensor.
Referring to FIG. 7, the use of Pt-Pd-Rh/Al is shown 2 O 3 /Sr@SnO 2 The gas sensor is used for testing the peak position height response of 18 gases including acetone under the high-speed temperature modulation, and the magnitude of a temperature resistance peak position signal is defined as R Raising the temperature to 235 DEG C /R Reducing the temperature to 235 DEG C The measurement results show that the obtained Pt-Pd-Rh/Al 2 O 3 /Sr@SnO 2 The laminated gas sensor has high selectivity to acetone.
Example 3:
in the embodiment, MCM-48 molecular sieve is selected as a catalytic membrane material, and SnO modified by metal Sr 2 The gas-sensitive material is used as a gas-sensitive film, a micro-hotplate chip is photoetched and magnetron sputtered on a zirconia insulating substrate, then the gas-sensitive material and the catalytic material are sprayed on the micro-hotplate chip by utilizing a micro-spraying technology, and the micro-hotplate chip is fired to obtain MCM-48/Sr @ SnO 2 A laminated gas sensor.
Referring to FIG. 8, MCM-48/Sr @ SnO is utilized 2 The gas sensor tests the peak height response of formic acid and other gases under high-speed temperature modulation, and the temperature resistance peak signal is defined as R Heating to 320 deg.C /R Cooling to 320 deg.C The value is obtained. The measurement result shows that the obtained MCM-48/Sr @ SnO2 laminated gas sensor has high selectivity on formic acid.
The embodiment of the invention also provides a gas detection method based on the catalytic temperature peak-to-peak signal, which comprises the steps of operation S1 and operation S2.
Operation S1, periodically changing the temperature of the catalytic film within a preset temperature interval at a predetermined speed, where the catalytic film is coated on the surface of the gas-sensitive film, the catalytic rate of the catalytic film to the target gas in the detected gas is related to the temperature of the target gas, and the resistance of the gas-sensitive film is related to the catalytic rate.
And operation S2, measuring and calculating a ratio of the resistances at the same temperature in the temperature increasing and decreasing stage, and determining that the target gas is detected when the calculated ratio is greater than a set threshold.
According to the embodiment of the present invention, preferably, the ratio of the resistance at the peak temperature during the temperature increase and decrease stage is measured and calculated in operation S2, and when the ratio of the resistance at the peak temperature is greater than a set threshold value, it is determined that the target gas is detected; the peak position temperature is the temperature which is stored in the gas sensor in advance, corresponds to the target gas and corresponds to the maximum value of the ratio of the resistance at the same temperature in the temperature increasing and decreasing stage.
The principle and process of gas detection in this embodiment are the same as those of the gas sensor based on the catalytic temperature peak-to-peak signal in the embodiment shown in fig. 1 to 8, and are not described herein again.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. A gas sensor based on catalytic temperature peak-to-peak signal, comprising: the device comprises a micro-hotplate unit, a gas-sensitive film, a catalytic film and a processing unit;
the micro-hotplate unit comprises an insulating substrate, and a heating electrode, a temperature measuring electrode and a measuring electrode which are arranged on the insulating substrate, wherein the gas-sensitive film is coated on the surface of the measuring electrode, the catalytic film is coated on the gas-sensitive film, and the processing unit is connected with the heating electrode, the temperature measuring electrode and the measuring electrode;
the temperature measuring electrode is used for measuring the temperature of the catalytic membrane; the processing unit is used for controlling the heating power of the heating electrode according to the temperature fed back by the temperature measuring electrode, so that the temperature of the catalytic film periodically changes within a preset temperature interval at a set speed to correspondingly change the catalytic rate of the catalytic film on target gas in the measured gas, and the resistance value of the gas-sensitive film is related to the catalytic rate; the measuring electrode is used for measuring the resistance value of the gas-sensitive film in real time;
the processing unit is further used for calculating the ratio of the resistors at the same temperature in the temperature increasing and decreasing stage according to the temperature fed back by the temperature measuring electrode and the resistance value fed back by the measuring electrode, and judging that the target gas is detected when the ratio which is larger than a set threshold value is obtained through calculation.
2. The catalytic temperature peak-to-peak signal based gas sensor according to claim 1, wherein the processing unit calculates a ratio of resistances at the same temperature in the temperature raising and lowering stages, and when the calculated ratio is larger than a set threshold, the determining that the target gas is detected comprises:
the processing unit calculates the ratio of the resistance at the peak temperature in the temperature rising and falling stage, and judges that the target gas is detected when the ratio of the resistance at the peak temperature is greater than a set threshold value;
and the peak temperature is a temperature which is stored in the gas sensor in advance, corresponds to the target gas and corresponds to the maximum value of the ratio of the resistance at the same temperature in the temperature increasing and decreasing stage.
3. The catalytic temperature spike signal based gas sensor of claim 1 or 2 wherein the processing unit stores a mapping relationship between the ratio and a target gas concentration, and is further configured to calculate the target gas concentration according to the ratio and the mapping relationship.
4. The catalytic temperature peak-to-peak signal-based gas sensor according to claim 1, wherein the temperature measuring electrode is disposed on the insulating substrate and located at the periphery of the heating electrode, and the processing unit controls the electric energy input to the heating electrode according to the temperature fed back by the temperature measuring electrode so as to control the heating power of the heating electrode.
5. The catalytic temperature spike signal based gas sensor of claim 1 or 4 further comprising: and the power supply unit is used for supplying electric energy to the heating electrode under the control of the processing unit.
6. The catalytic thermal peak-to-peak signal-based gas sensor according to claim 1, wherein the gas-sensitive film is made of a metal oxide semiconductor material, or is a modified metal oxide semiconductor material obtained by modifying, doping and compounding the metal oxide semiconductor material.
7. The catalytic temperature peak-to-peak signal-based gas sensor according to claim 1, wherein the material of the catalytic membrane is a metal catalyst, a metal oxide catalyst, a molecular sieve catalyst or a metal organic framework material, or is a modified material obtained by modifying, doping and compounding the metal catalyst, the metal oxide catalyst, the molecular sieve catalyst or the metal organic framework material.
8. A gas detection method based on a catalytic temperature peak-to-peak signal is characterized by comprising the following steps:
s1, periodically changing the temperature of a catalytic membrane in a preset temperature interval at a set speed, wherein the catalytic membrane is coated on the surface of a gas-sensitive membrane, the catalytic rate of the catalytic membrane to a target gas in a detected gas is related to the temperature of the catalytic membrane, and the resistance of the gas-sensitive membrane is related to the catalytic rate;
and S2, measuring and calculating the ratio of the resistance at the same temperature in the temperature raising and lowering stage, and judging that the target gas is detected when the ratio greater than a set threshold value is obtained through calculation.
9. The catalytic temperature peak-to-peak signal-based gas detection method according to claim 8, wherein the S2 includes:
measuring and calculating the ratio of the resistance at the peak temperature in the temperature rising and falling stage, and judging that the target gas is detected when the ratio of the resistance at the peak temperature is greater than a set threshold value;
the peak temperature is a temperature which is stored in the gas sensor in advance, corresponds to the target gas, and corresponds to the maximum value of the ratio of the resistance at the same temperature in the temperature increasing and decreasing stage.
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