CN110095508B - Method and device for gas identification based on a single sensor - Google Patents

Abstract

The invention discloses a method and a device for identifying gas based on a single sensor, which comprises the following steps: and applying short-period pulse heating voltage to a single sensor, acquiring the test current of unknown gas, and respectively calculating the maximum time and the gas sensitive response value sequence. And determining the position of the gas in a concentration-maximum time relation curve in a pre-established gas characteristic identification library according to the maximum time, and preliminarily prejudging the possible type and concentration of the gas. And matching the closed envelope of the gas-sensitive response value sequence in the radar map with a closed envelope cluster in the radar map in a pre-established gas characteristic identification library, and finally identifying the type and concentration of the gas by combining preliminary prejudgment. The gas identification can be realized by adopting a single sensor, the gas identification device is simple and convenient and easy to operate, the scale of the sensor is greatly reduced, and meanwhile, the single sensor is periodically positioned at a plurality of experimental temperatures by adopting short-period thermal modulation treatment, so that a large amount of experimental data can be quickly acquired, and the working efficiency is further improved.

Description

Method and device for gas identification based on a single sensor

technical field

The invention belongs to the field of nanometer gas sensor detection, in particular to a method and device for gas identification based on a single sensor, and a method and device for establishing a gas feature identification library.

Background technique

Gas detection usually requires large-scale equipment such as gas chromatography mass spectrometers, but this method is expensive and only suitable for gases with non-overlapping characteristic spectral lines. The key is that it is limited to offline detection. Nanomaterial-based gas sensors have the advantages of low cost, miniaturization, easy integration, and high reliability. As the most classic gas detection materials, transition metal oxides (TMOs) have attracted extensive attention due to their good sensitivity to various gases. However, in the existing research, the operating temperature required by TMOs sensors is usually high, and the continuous heating will lead to an increase in the power consumption of the sensor. In addition, a sensor can respond to a variety of gases and has cross-sensitivity characteristics, which is an important reason to limit the application of gas sensors. Traditionally, comparing the response values of sensors for different gases is the most common but very rough method for evaluating selectivity, which is affected by factors such as gas concentration and operating temperature. Another common approach to solving the cross-sensitivity problem is to build an array with multiple sensors of varying performance. However, in order to detect the content of each component in a variety of mixed gases, the required array scale will also be expanded, resulting in a large array and high cost.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention proposes a method and device for gas identification based on a single sensor. The present invention mainly adopts following technical scheme:

A method for gas identification based on a single sensor, comprising:

S1. Apply a short-period pulse heating voltage to the first sensor, so that the first sensor is periodically at N' different temperature points; wherein, the first sensor is placed in the first test gas chamber.

S2, introducing unknown gas into the first test gas chamber.

S3. _Obtain the test current It of the first sensor for sensing the unknown gas at N' different temperature points, where It is the test current at the corresponding _moment in the current heating cycle.

S4. Calculate the current change rate D _t of the test current I _t of the N' group respectively, and then generate a D _t curve cluster; obtain the maximum value of D _t in the D _t curve cluster, and calculate the difference from the introduction of the unknown gas to the maximum value of D _t The time between 1 and N' is recorded as the maximum time τ _m ; calculate the gas-sensing response value sequence of the unknown gas at 1 to N' temperature points, and take the logarithm of the gas-sensing response value sequence, and then according to each temperature point in each cycle The time sequence of , generates a closed envelope in the radar chart.

S5. Determine the position of the maximum time τ _m in the concentration-maximum time relationship curve in the pre-established gas feature identification library, and preliminarily predict the possible types and concentrations of the unknown gas; The line is matched with the closed envelope cluster in the radar chart in the pre-established gas feature identification library, and combined with the above prediction, the type and concentration of the unknown gas are finally identified.

Based on the same inventive concept, the present invention also provides a device for gas identification based on a single sensor, comprising: a first sensor, a first test gas chamber, a first external power supply and a signal generating circuit, a first gas introduction unit, a first test current acquisition unit, a first calculation unit and a gas identification unit; wherein,

The first sensor is placed in the first test gas chamber for sensing the unknown gas introduced into the first test gas chamber.

The first external power supply and the signal generating circuit are used for applying a short-cycle pulse heating voltage to the first sensor, so that the first sensor is periodically at N' different temperature points.

The first gas introducing unit is used for introducing unknown gas into the first test gas chamber.

The first test current acquisition unit is used to acquire the test current I _t of the unknown gas sensed by the first sensor at N′ different temperature points, where It _is the test current at the corresponding moment in the current heating cycle.

The first calculation unit is used to calculate the current change rate D _t of the N' group of test currents I _t respectively, and then generate the D _t curve cluster; obtain the maximum value of D _t in the D _t curve cluster, and calculate from the introduction of the unknown gas to the beginning of the calculation. The time between the maximum values of D _t is recorded as the maximum time τ _m ; calculate the gas-sensing response value sequence of the unknown gas at 1 to N′ temperature points, and take the logarithm of the gas-sensing response value sequence, and then follow each The time sequence of the temperature points in the cycle generates a closed envelope in the radar chart.

The gas identification unit is used to determine the position of the maximum time τ _m in the concentration-maximum time relationship curve in the pre-established gas feature identification library, and preliminarily predict the possible types and concentrations of unknown gases; The envelope is matched with the closed envelope cluster in the radar chart in the pre-established gas feature identification library, and combined with the above prediction, the type and concentration of the unknown gas are finally identified.

Based on the same inventive concept, the present invention also provides a method for establishing a gas feature identification library, including:

A1. Apply a short-cycle pulse heating voltage to the second sensor, so that the second sensor is periodically at N' different temperature points; wherein, the second sensor is placed in the second test gas chamber.

A2. Pass n groups of test gases of the same type and different concentrations into the second test gas chamber in turn, so that the second sensor can sense test gases of different concentrations in sequence; where n is defined by the user according to the actual situation.

A3. Obtain the test current I _t of each group of test gases sensed by the second sensor at N′ different temperature points respectively, where I _t is the test current at the corresponding moment in the current heating cycle.

A4. Calculate the maximum time of N' groups of test currents I _t corresponding to each group of test gases respectively, and then generate the concentration-maximum time relationship curves of the n groups of test gases of the same type and different concentrations.

A5. Calculate the gas-sensing response value sequence of each group of test gases at 1 to N' temperature points respectively, and take the logarithm of each group of gas-sensing response value sequences, and then follow the time sequence of each temperature point in each cycle , to generate the closed envelope clusters of the n groups of test gases of the same type and different concentrations in the radar chart.

A6. Release the gas in the second test gas chamber, introduce another different type of test gas, and repeat A1 to A5 until the concentration-maximum time relationship curve of m groups of different types of gas and the closure in the radar chart are generated Envelope cluster; among them, m is defined by the user according to the actual situation.

A7. Store the concentration-maximum time relationship curves of the m groups of different types of gases and the closed envelope clusters in the radar chart.

Based on the same inventive concept, the present invention also provides a device for establishing a gas feature identification library, comprising a second sensor, a second test gas chamber, a second external power supply and a signal generating circuit, a second gas introduction unit, a second a test current acquisition unit, a second calculation unit and a gas feature identification library; wherein,

The second sensor is placed in the second test gas chamber.

The second external power supply and the signal generating circuit are used for applying a short-cycle pulse heating voltage to the second sensor, so that the second sensor is periodically at N' different temperature points.

The second gas introduction unit is to introduce n groups of test gases of the same type and different concentrations into the second test gas chamber in turn, so that the second sensor can sense the test gases of different concentrations in sequence; where n is defined by the user according to the actual situation.

The second test current acquisition unit is used to acquire the test current I _t of each group of test gases sensed by the second sensor at N′ different temperature points, where It _is the test current at the corresponding moment in the current heating cycle.

The second calculation unit is used to respectively calculate the maximum time of N' groups of test currents I _t corresponding to each group of test gases, and then generate the concentration-maximum time relationship curves of the n groups of test gases of the same type and different concentrations; and respectively calculate The gas-sensing response value sequence of each group of test gases at 1 to N' temperature points, and the logarithm is taken for each group of gas-sensing response value sequences, and then the n is generated according to the time sequence of each temperature point in each cycle. The closed envelope cluster of a group of test gases of the same type with different concentrations in the radar chart; and for another test gas of different types introduced, repeat the above steps until the concentration-maximum time of m groups of different types of gases is generated The relationship curve and the closed envelope cluster in the radar chart; where m is defined by the user according to the actual situation.

The gas feature recognition library is used to store the concentration-maximum time relationship curves of m groups of different types of gases and the closed envelope clusters in the radar chart.

Compared with the prior art, the beneficial technical effects brought by the present invention are:

1. The present invention only needs to use a single sensor to perform gas identification. The method is simple and easy to implement, low in cost, short in time consumption, and convenient for expansion. At the same time, the single sensor used has the advantages of small size, low cost, easy integration, high reliability, and strong anti-interference ability.

2. The present invention performs thermal modulation processing by applying a short-cycle pulse heating voltage to a single sensor, so that the sensor can be rapidly in different temperature ranges, and it is convenient to explore the optimal working temperature of a single sensor in response to a specific gas. In addition, this method can quickly obtain the response curve of a single sensor to the test gas (or unknown gas) at multiple temperature points, which greatly improves the work efficiency.

3. The method for identifying gas types and concentrations based on short-cycle pulse thermal modulation technology proposed by the present invention can achieve the goal of identifying unknown gas types and concentrations based on a single sensor, which is simple and easy to operate, and has low cost, and a single sensor is compared with traditional sensors. The array greatly reduces the overall size of the device. In addition, the method can be extended to online monitoring of various gases.

4. Compared with the traditional constant voltage heating method, the short-cycle pulse thermal modulation technology adopted in the present invention has lower power consumption of the sensor, and the experiments under different conditions can be quickly obtained by simply adjusting various parameters of the applied short-cycle pulse heating voltage. data.

Description of drawings

1 is a schematic flowchart of a method for gas identification based on a single sensor provided by an embodiment of the present invention;

Figure 2(a) is a schematic structural diagram of a single sensor used in an embodiment of the present invention;

Fig. 2(b) is a corresponding diagram of heating current I _heat , heating temperature Temp, and test current I _t passing through the sensor in one heating cycle when a sinusoidal heating voltage is applied to a single sensor in an embodiment of the present invention;

3 is a schematic flowchart of a method for establishing a gas feature identification library provided by an embodiment of the present invention;

Fig. 4 (a) is a current dynamic curve diagram collected by the sensor when 50ppm H ₂ S is fed into the test gas chamber in an embodiment of the present invention;

Fig. ₄ (b) is a current dynamic curve diagram collected by the sensor when 50ppm SO is introduced into the test gas chamber in an embodiment of the present invention;

Fig. 5 (a) is the sampling current curve diagram of 8 groups of temperature separation when passing 50ppm H ₂ S into the test gas chamber in one embodiment of the present invention;

Fig. 5(b) is the sampling current curve diagram of ₈ groups of temperature separation when 50ppm SO is passed into the test gas chamber in an embodiment of the present invention;

Figure 6(a) is a D _t curve cluster diagram corresponding to 50ppm H ₂ S in one embodiment of the present invention;

Figure 6(b) is a D _t curve cluster diagram corresponding to 50ppm SO ₂ in an embodiment of the present invention;

Figure 7(a) is a sequence diagram of gas-sensing response values corresponding to 50 ppm H ₂ S in an embodiment of the present invention;

Figure 7(b) is a sequence diagram of gas-sensing response values corresponding to 50 ppm SO ₂ in an embodiment of the present invention;

Figure 8(a) is a graph of current dynamics corresponding to gases of different concentrations in a test array when a feature identification library for H ₂ S and SO ₂ gas is established in an embodiment of the present invention;

Figure 8(b) is a graph of the concentration-maximum time relationship corresponding to H ₂ S and SO ₂ gas in an embodiment of the present invention;

Figure 8(c) is a closed envelope cluster diagram formed in a radar chart after the logarithm of the sequence of gas-sensing response values of various concentrations of H ₂ S in an embodiment of the present invention;

Fig. 8(d) is a closed envelope cluster diagram formed in a radar chart after taking the logarithm of the sequence of gas-sensing response values of various concentrations of SO ₂ in an embodiment of the present invention;

Fig. 9 (a) is the current dynamic curve diagram of 4 groups of unknown gases collected in order to identify unknown gases in one embodiment of the present invention;

Fig. 9 (b) is the first step of identifying gas in an embodiment of the present invention, namely determining the position schematic diagram of the maximum time of the unknown gas in the concentration-maximum time relationship curve;

Fig. 9(c) and Fig. 9(d) are the second step of gas identification in an embodiment of the present invention, that is, the closed envelope in the radar chart after the logarithm of the gas-sensing response value sequence of the unknown gas is determined, and the Schematic diagram of closed envelope clusters in the gas feature recognition library for matching.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and embodiments, but it is not intended to limit the present invention.

In one embodiment, as shown in FIG. 1 , the present disclosure discloses a method for gas identification based on a single sensor, comprising:

S1. Apply a short-period pulse heating voltage to the first sensor, so that the first sensor is periodically at N' different temperature points; wherein, the first sensor is placed in the first test gas chamber.

S2, introducing unknown gas into the first test gas chamber.

S3. Obtain the test current It of the first sensor for sensing the unknown gas at N' different temperature points, obtain N' groups of test _currents It, and generate a corresponding test current dynamic _curve for each group of test _currents It, I _t is the test current at the corresponding moment in the current heating cycle.

S4. Calculate the current change rate D _t of the test current 1 _t of the N' group respectively, and then generate a D _t curve cluster; obtain the maximum value of D _t in the D _t curve cluster, and calculate the difference from the introduction of the unknown gas to the maximum value of D _t The time between 1 and N' is recorded as the maximum time τ _m ; calculate the gas-sensing response value sequence of the unknown gas at 1 to N' temperature points, and take the logarithm of the gas-sensing response value sequence, and then according to each temperature point in each cycle The time sequence of , generates a closed envelope in the radar chart.

S5. Determine the position of the maximum time τ _m in the concentration-maximum time relationship curve in the pre-established gas feature identification library, and preliminarily predict the possible types and concentrations of the unknown gas; use the closed envelope generated in the radar chart, Match with the closed envelope cluster in the radar chart in the pre-established gas feature recognition library, and combine with the above prediction, and finally identify the type and concentration of the unknown gas.

Applying the technical solutions of the embodiments of the present disclosure has at least the following beneficial effects:

1. The present invention can perform gas identification by using a single sensor. The method is simple and easy to implement, low in cost, short in time consumption, and convenient for expansion.

2. The present invention performs thermal modulation processing by applying a short-cycle pulse heating voltage to a single sensor, so that a single sensor can be rapidly in different temperature ranges, and it is convenient to explore the optimal working temperature of a single sensor in response to a specific gas. In addition, this method can quickly obtain the response curve of a single sensor to an unknown gas at multiple temperature points, which greatly improves the work efficiency.

3. The method for identifying gas types and concentrations based on short-cycle pulse thermal modulation technology proposed by the present invention can achieve the goal of identifying unknown gas types and concentrations based on a single sensor, which is simple and easy to operate, and has low cost, and a single sensor is compared with traditional sensors. The array greatly reduces the overall size of the device. In addition, the method can be extended to online monitoring of various gases.

4. Compared with the traditional constant voltage heating method, the short-cycle pulse thermal modulation technology adopted in the present invention reduces the power consumption of the sensor, and the experimental data under different conditions can be quickly obtained by simply adjusting various parameters of the applied pulse heating voltage.

In another embodiment, in step S4, the current change rates D _t of the N' groups of test currents I _t are respectively calculated by the following formula;

Among them, I _t is the test current at the corresponding moment in the current heating cycle, I _tN′ is the test current at the corresponding moment in the previous heating cycle, and N′ is the number of current sampling points in each heating cycle.

In another embodiment, in step S4, the time from the introduction of the unknown gas to the maximum value of D _t is calculated, denoted as the maximum time τ _m , and the formula is as follows:

Among them, the above formula (2) indicates that the maximum time τ _m takes the average value of the abscissa corresponding to the maximum value of D _τ (1), D _t (2), ..., D _t (N'), and argmaxD _t (N) represents Corresponding to the abscissa when D _t (N) takes the maximum value.

In this embodiment, after the unknown gas is introduced, due to the adsorption of the gas and the nanomaterial coated on the surface of the first sensor, the resistance of the sensor changes, and the test current I _t changes, but the response current changes with the ventilation time. Differently, the time from the introduction of the unknown gas to the maximum value of D _t is the period in which the current variation increases rapidly, and is recorded as the maximum time τ _m . When different types and concentrations of unknown gases are introduced, the corresponding range of τ _m is different, and the maximum time τ _m is used as a characteristic quantity for gas identification.

In another embodiment, in step S4, the sequence of gas-sensing response values of the unknown gas at 1-N' temperature points is calculated, due to the variation of the sampling current I _N corresponding to different temperature points during the process of introducing the unknown gas It is also different, that is, the response at different temperatures is different. Calculate the sequence of gas-sensing response values of unknown gas at 1 to N' temperature points. The gas-sensing response value formula is defined as follows:

S _N =I _gN /I _cN (3)

Wherein, I _gN is the saturation current passing through the first sensor in the test atmosphere, and I _gN is the current passing through the first sensor in the background atmosphere. Calculate the gas-sensing response value sequence S ₁ , S ₂ , ..., S _N' at 1 to N' temperature points according to the above formula, take the logarithm of the gas-sensing response value sequence, and then follow the The time sequence, which constitutes a closed envelope in the radar chart, is another characteristic quantity for gas identification.

In another embodiment, in step S1, the signal waveform of the short-period pulse heating voltage V _heat is one of a rectangular wave, a triangular wave or a sine wave, the period T _heat is 5-10s, and the voltage peak-to-peak value is 0.5-1.75 V.

In this embodiment, the method of applying a short-cycle pulse heating voltage to the first sensor for thermal modulation processing is as follows: applying a short-cycle pulse heating voltage to the heating layer substrate of the first sensor, and setting the pulse heating period and the data sampling period to achieve The effect of 5 to 20 dynamic response curves (ie, 5 to 20 different working temperature points) is obtained in each pulse heating cycle. The heating voltage V _heat is in phase with the heating current I _heat flowing through the heating layer substrate. By changing the amplitude of the applied pulse heating voltage, the first sensor is controlled to be at different working temperatures, and a large amount of experimental data can be obtained in a relatively short time. In this embodiment, the power consumption required for temperature adjustment is between 10 and 200 mW.

The sampling frequency _f of the test current It is 0.5-2 Hz. Under the action of the periodic pulse heating voltage, the test current It also exhibits periodicity, and its cycle is consistent with the applied pulse heating voltage cycle, and the number of data of the test current It contained in each cycle is _f * _{T heat} , denoted as N', represents the current data through a single sensor when N' different temperatures are collected in each cycle.

In order to ensure that the applied heating voltage keeps the first sensor in a suitable working temperature range, the peak-to-peak value of the applied pulsed heating voltage is selected to be 0.5-1.75V.

In order to avoid large test errors caused by too small test current It, set the bias voltage to _100-600mV .

To obtain stable and effective data quickly, set the sampling period to 0.5-1s.

In order to quickly obtain the gas sensor response data of multiple temperature points, it is necessary to set the pulse heating voltage to have a short period, so that the first sensor can be quickly placed at multiple temperature points, and the period of the applied pulse heating voltage is selected to be 5-10s.

In another embodiment, the method identifies at least one type of unknown gas, and the value of N' ranges from 5 to 20.

Based on the same inventive concept, the present disclosure also discloses a device for gas identification based on a single sensor, comprising: a first sensor, a first test gas chamber, a first external power supply and a signal generating circuit, a first gas introduction unit, A first test current acquisition unit, a first calculation unit and a gas identification unit. in,

The first sensor is placed in the first test gas chamber for sensing the unknown gas introduced into the first test gas chamber.

The first external power supply and the signal generating circuit are used for applying a short-cycle pulse heating voltage to the first sensor, so that the first sensor is periodically at N' different temperature points.

The first gas introducing unit is used for introducing unknown gas into the first test gas chamber.

The first test current acquisition unit is used to acquire the test current I _t of the unknown gas sensed by the first sensor at N' different temperature points, obtain N' groups of test currents It _, and generate corresponding test currents It for each group of test currents _It The test current dynamic curve of , I _t is the test current at the corresponding moment in the current heating cycle.

The first calculation unit is used to calculate the current change rates D _t of the N' groups of test currents I _t respectively, and then generate a D _t curve cluster. Obtain the maximum value of D _t in the D _t curve cluster, and calculate the time from the introduction of the unknown gas to the maximum value of D _t , which is recorded as the maximum time τ _m . Calculate the gas-sensing response value sequence of the unknown gas at 1 to N′ temperature points, take the logarithm of the gas-sensing response value sequence, and then generate a closed packet in the radar chart according to the time sequence of each temperature point in each cycle network.

The gas identification unit is used to determine the position of the maximum time τ _m in the concentration-maximum time relationship curve in the pre-established gas feature identification library, and preliminarily predict the possible types and concentrations of the unknown gas. The closed envelope generated in the radar chart is matched with the closed envelope cluster in the radar chart in the pre-established gas feature identification library, and the type and concentration of the unknown gas are finally identified based on the above prediction.

Applying the technical solutions of the embodiments of the present disclosure has at least the following beneficial effects:

1. The present invention can perform gas identification by using a single sensor. The method is simple and easy to implement, low in cost, short in time consumption, and convenient for expansion.

2. The present invention performs thermal modulation processing by applying a short-cycle pulse heating voltage to a single sensor, so that a single sensor can be rapidly in different temperature ranges, and it is convenient to explore the optimal working temperature of a single sensor in response to a specific gas. In addition, this method can quickly obtain the response curve of a single sensor to an unknown gas at multiple temperature points, which greatly improves the work efficiency.

3. The method for identifying gas types and concentrations based on short-cycle pulse thermal modulation technology proposed by the present invention can achieve the goal of identifying unknown gas types and concentrations based on a single sensor, which is simple and easy to operate, and has low cost, and a single sensor is compared with traditional sensors. The array greatly reduces the overall size of the device. In addition, the method can be extended to online monitoring of various gases.

4. Compared with the traditional constant voltage heating method, the short-cycle pulse thermal modulation technology adopted in the present invention reduces the power consumption of the sensor, and the experimental data under different conditions can be quickly obtained by simply adjusting various parameters of the applied pulse heating voltage.

In another embodiment, as shown in FIG. 2( a ), the first sensor includes a test layer 1 , a substrate 2 and a heating layer 3 arranged in sequence from top to bottom. The test layer includes a test electrode, the surface of the test electrode is coated with a nanometer gas-sensitive film, and the heating layer includes a heating electrode and a heating material.

In this embodiment, the first sensor made of nano gas-sensitive material has the advantages of small size, low cost, easy integration, high reliability, and strong anti-interference ability.

In another embodiment, the volume of the substrate is 10.0×5.0×0.2 mm, the heating electrode is a serpentine electrode, the size of the electrode is 3.0×4.0 mm, and the thickness of the electrode is 100 nm. The test electrodes are interdigitated electrodes with a finger spacing of 100 μm and an electrode thickness of 100 nm.

In another embodiment, the preparation method of the first sensor is as follows:

The test electrode is formed on the upper surface of the substrate through the electron beam evaporation coating process and the photolithography process, and the test electrode lead 4 is drawn out at the same time.

The heater electrode and the heater material are formed on the lower surface of the substrate, while the heater electrode lead 5 is drawn out.

The nano gas sensitive material is fully ground and dispersed by ethanol or isopropanol, and then uniformly coated on the center of the upper surface of the test electrode to form a nano gas sensitive film.

In another embodiment, the preparation material of the test electrode is one of gold, platinum or silver-palladium alloy. The nano gas sensitive material is one of cerium oxide, gold-doped cerium oxide, indium oxide, tungsten oxide or zinc oxide, and the coating method is one of spray coating, spin coating or drop coating, and the coating thickness is 50nm-2μm. The preparation material of the heating electrode is gold-nickel alloy or platinum, and the heating material is ruthenium dioxide. The preparation material of the substrate is one of silicon dioxide, silicon nitride or aluminum oxide.

In another embodiment, since the substrate is used to isolate the heating layer and the test layer and support the first sensor at the same time, it is necessary to select an insulating material with good hardness as the preparation material of the substrate. In this embodiment, silicon nitride is selected as the substrate material for base preparation.

In another embodiment, since the heating layer is used to withstand different pulse heating voltages to adjust the temperature of the first sensor, platinum is selected as the preparation material of the heating electrode in this embodiment, and the heating material is selected to have good thermal conductivity and Ruthenium dioxide with high melting point properties.

In another embodiment, in order to obtain good conductivity, gold with excellent conductivity is selected as the test electrode preparation material.

In another embodiment, in order to obtain a stable and more sensitive sensor, preferably, a stable nano gas-sensitive thin film is formed by spin-coating gold-doped cerium oxide (Au-CeO ₂ ) on the surface of the test electrode of the first sensor , the film thickness is 1 μm.

Based on the same inventive concept, as shown in FIG. 3 , the present disclosure also discloses a method for establishing a gas feature identification library, including:

A1. Apply a short-cycle pulse heating voltage to the second sensor, so that the second sensor is periodically at N' different temperature points; wherein, the second sensor is placed in the second test gas chamber.

A2. Pass n groups of test gases of the same type and different concentrations into the second test gas chamber in turn, so that the second sensor can sense test gases of different concentrations in sequence; where n is defined by the user according to the actual situation.

A3. Obtain the test currents I _t of each group of test gases sensed by the second sensor at N' different temperature points respectively, obtain the N' groups of test currents I _t corresponding to each group of test gases, and measure the test currents I of each group of test gases. _t generates a corresponding test current dynamic curve, and I _t is the test current at the corresponding moment in the current heating cycle.

A4. Calculate the maximum time of N' groups of test currents I _t corresponding to each group of test gases respectively, and then generate the concentration-maximum time relationship curves of the n groups of test gases of the same type and different concentrations. Among them, the calculation method of the maximum time of the N' group test current It corresponding to each group of test gases _is as follows: calculate the current change rate D _t of the N' group test current It respectively _{, and then generate the D t curve} cluster; obtain the D _t The maximum value of D _t in the curve cluster, calculate the time from the beginning of the test gas of this group to the maximum value of D _t , and record it as the maximum time τ _m , and obtain the N' group test current I _t corresponding to this group of test gases The maximum time τ _m .

A5. Calculate the gas-sensing response value sequence of each group of test gases at 1 to N' temperature points respectively, and take the logarithm of each group of gas-sensing response value sequences, and then follow the time sequence of each temperature point in each cycle , to generate the closed envelope clusters of the n groups of test gases of the same type and different concentrations in the radar chart.

A6. Release the gas in the second test gas chamber, introduce another different type of test gas, and repeat A1 to A5 until the concentration-maximum time relationship curve of m groups of different types of gas and the closure in the radar chart are generated Envelope cluster; among them, m is defined by the user according to the actual situation.

A7. Store the concentration-maximum time relationship curves of m groups of different types of gases and the closed envelope clusters in the radar chart.

In this embodiment, the formulas for calculating the current change rate D _t of the N' group of test currents I _t , calculating the maximum time τ _m , and calculating the sequence of gas-sensing response values are consistent with the formulas described in the above-mentioned embodiments of the gas identification method. It is not repeated here, and for details, please refer to the relevant description of the above-mentioned embodiment.

Based on the same inventive concept, the present disclosure also discloses a device for establishing a gas feature identification library, comprising a second sensor, a second test gas chamber, a second external power supply and a signal generating circuit, a second gas introduction unit, a second Test the current acquisition unit, the second calculation unit and the gas feature identification library. in,

The second sensor is placed in the second test gas chamber.

The second external power supply and the signal generating circuit are used for applying a short-cycle pulse heating voltage to the second sensor, so that the second sensor is periodically at N' different temperature points.

The second gas introduction unit is to introduce n groups of test gases of the same type and different concentrations into the second test gas chamber in turn, so that the second sensor can sense the test gases of different concentrations in sequence; where n is defined by the user according to the actual situation.

The second test current acquisition unit is used to acquire the test currents I _t of each group of test gases sensed by the second sensor at N' different temperature points respectively, and obtain the N' groups of test currents I _t corresponding to each group of test gases, A _{corresponding} test current dynamic _curve is generated for each group of test currents It, where It is the test current at the corresponding moment in the current heating cycle.

The second calculation unit is used to calculate the maximum time of the N' groups of test currents I _t corresponding to each group of test gases respectively, and then generate the concentration-maximum time relationship curves of the n groups of test gases of the same type and different concentrations (wherein each The calculation method of the maximum time of the N' group test current I _t corresponding to the group of test gases is: calculate the current change rate D _t of the N' group test current I _t respectively _, and then generate the D _t curve cluster; the maximum value of D _t , calculate the time from the start of the test gas in the group to the maximum value of D _t , and record it as the maximum time τ _m to obtain the maximum time of the N' group test current I _t corresponding to this group of test gases τ _m ); and calculate the gas-sensing response value sequence of each group of test gases at 1 to N′ temperature points respectively, and take the logarithm of each group of gas-sensing response value sequences respectively, and then according to each temperature point in each cycle , to generate the closed envelope clusters of the n groups of test gases of the same type and different concentrations in the radar chart; and repeat the above steps for another test gas of different type introduced until m groups of different concentrations are generated. The concentration-maximum time relationship curve of the species gas and the closed envelope cluster in the radar chart; where m is defined by the user according to the actual situation.

The gas feature recognition library is used to store the concentration-maximum time relationship curves of m groups of different types of gases and the closed envelope clusters in the radar chart.

It should be particularly noted that, during specific implementation, the first sensor and the second sensor described in the present disclosure may be the same sensor, or may be different sensors. Meanwhile, the first sensor and the second sensor are of the same type and have the same function. Therefore, the composition structure and preparation method of the second sensor will not be repeated here. For details, please refer to the relevant description of the above-mentioned first sensor embodiment.

Similarly, the second test gas chamber and the first test gas chamber, the second external power supply and the signal generating circuit and the first external power supply and the signal generating circuit, and the second gas passing unit and the first gas communicating The input unit, the second test current acquisition unit and the first test current acquisition unit, and the second calculation unit and the first calculation unit may be the same unit or different units.

In the above-mentioned embodiments of the present disclosure, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

The gas identification using a single sensor in the present disclosure will be described in detail below through some specific embodiments, but it is not intended to limit the present disclosure.

Hydrogen sulfide (H ₂ S) and sulfur dioxide (SO ₂ ) are common gases in industrial production, both of which are colorless, toxic, corrosive, and are atmospheric pollutants. In many industrial scenarios (for example, flue gas from oil refineries, sulfur hexafluoride (SF ₆ ) decomposition products, etc.), the above two gases will exist at the same time, and the detection of the types and concentrations of these two gases is important for the status assessment of equipment Has clear application value. Therefore, this embodiment takes H ₂ S and SO ₂ as examples to illustrate the method for realizing gas identification by using a single sensor.

In this embodiment, the method of applying a short-cycle pulse heating voltage to a single sensor for thermal modulation processing is as follows: applying a short-cycle pulse heating voltage to the heating layer substrate of the single sensor, and setting the pulse heating cycle and data sampling cycle to achieve each The effects of 8 dynamic response curves (ie at different operating temperatures) were obtained during the pulse heating cycle. In this embodiment, the power consumption required for temperature adjustment is between 10 and 200 mW.

In order to ensure that the applied heating voltage keeps a single sensor in a suitable working temperature range, the peak-to-peak value of the applied pulse heating voltage is selected to be 0.5-1.75V.

In order to avoid large test error caused by too small test current, set the bias voltage to 100-600mV.

To obtain stable and effective data quickly, set the sampling period to 0.5-1s.

In order to quickly obtain the gas sensor response data of multiple temperature points, it is necessary to set the pulse heating voltage to have a short period, so that a single sensor can quickly be placed at multiple temperature points, and the pulse heating voltage period to be applied is selected to be 5-10s.

In a specific embodiment, the pulse heating voltage waveform is a sine wave, the peak-to-peak value is 1V, the period is 8s, the DC voltage bias is 600mV, and the power consumption required for temperature adjustment is about 10mW.

The heating current I _heat corresponding to a single pulse heating voltage cycle, the temperature point at which a single sensor is located, and the test current I _t passing through the test electrode of the sensor are shown in Figure 2(b).

In a specific embodiment, SO ₂ and H ₂ S are selected as test gases, and different concentrations of SO ₂ and H ₂ S are sequentially introduced into the test gas chamber to conduct gas-sensing testing.

Figure 4(a) and Figure 4(b) are the test current dynamic curves collected by a single sensor when 50ppm H ₂ S and 50ppm SO ₂ are injected into the test gas chamber, respectively.

The collected test currents I _t are grouped according to 8 temperature points in each heating cycle, and the currents passing through a single sensor at 8 different temperatures, namely the sampling current I _N , are obtained, as shown in Figure 5(a) and Figure 5(b) 8 groups of temperature separation curves corresponding to 50 ppm H ₂ S and 50 ppm SO ₂ were fed in, respectively.

Each group of test currents I _t takes the logarithm of the time t and takes the derivation to obtain the current change rate D _t , and then generates the D _t curve cluster. Obtain the maximum value of D _t in the D _t curve cluster, and calculate the time from the start of the test gas introduction to the maximum value of D _t , which is recorded as the maximum time τ _m , and recorded as the maximum time τ _m , and different types and concentrations are introduced. The range of the corresponding τ _m is different. The maximum time is regarded as a characteristic quantity of gas identification. Figure 6(a) and Figure 6(b) correspond to the D _t curves of 50ppm H ₂ S and 50ppm SO ₂ respectively cluster (with the corresponding maximum time τ _m on the graph).

The variation of the sampling current I _N corresponding to different temperature points during the process of passing the test gas is also different, that is, the responses at different temperatures are different, and the gas-sensing responses of 1 to 8 temperature points are calculated. The gas-sensing response value sequences corresponding to 50 ppm H ₂ S and 50 ppm SO ₂ are shown in Fig. 7(a) and Fig. 7(b), respectively.

The method for establishing the gas feature identification library and the steps for identifying unknown gases are specifically described below with reference to the embodiments.

The method to build the SO ₂ and H ₂ S gas feature recognition library is as follows:

1) A single sensor tests the current changes of various concentrations of SO ₂ and H ₂ S, as shown in Figure 8(a). According to the current change characteristics and the definition of the maximum time τ _m in the figure, the concentration-maximum time relationship curve is drawn As shown in Figure 8(b).

2) Calculate the gas-sensing response value sequence of 1-8 temperature points according to the test current, take the logarithm of the gas-sensing response value sequence, and then draw a closed envelope in the radar chart according to the time sequence of each temperature point in a cycle Line clusters, different concentrations of the same test gas, correspond to similar envelope clusters in the radar chart. Different types of test gases have different shapes and sizes of envelope clusters in the radar chart. Figure 8(c) and Figure 8(d) show the closed envelope cluster in the radar chart after taking the logarithm of the gas-sensing response value series of various concentrations of H ₂ S and SO ₂ .

Above, about the envelope cluster of SO ₂ and H ₂ S gas by the concentration-maximum time relationship curve and the temperature-gas-sensing response value sequence in the radar map of the feature library, the gas feature identification library composed of these two sets of feature quantities built.

In order to test the reliability of the gas identification method proposed in the present invention, the current curves of four groups of single sensors in an unknown atmosphere were measured, as shown in Figure 9(a), and the proposed method was used to identify the gas type and concentration. The method of identifying the type and concentration of gas is divided into two steps:

1) Step 1: Use the position of the obtained maximum time in the concentration-maximum time relationship curve of the gas feature identification library to preliminarily predict the possible gas types and concentrations.

Calculate the current change rate D _t corresponding to the test current curve, generate a D _t curve cluster, and obtain the maximum time τ _m corresponding to the four sets of tests. test-1: 48.1s, referring to its position in the concentration-maximum time relationship curve, as shown in Figure 9(b), it can be seen that the corresponding gas of test-1 may be 22ppmH ₂ S or 67ppm SO ₂ ; test-2: 63.47 s, the corresponding gas is 9ppmH ₂ S; similarly, the corresponding gas in test-3 may be 28ppm H ₂ S or 97ppm SO ₂ , and the corresponding gas in test 4 may be 26ppm H ₂ S or 84ppm SO ₂ .

2) Step 2: In order to further determine the gases in test-1, test-3 and test-4, take the logarithm of the gas-sensing response value sequence of the unknown gas, and use the time sequence of each temperature point in the The closed envelope generated in the figure is matched with the closed envelope cluster in the radar chart of the gas feature recognition library, and combined with the preliminary pre-judgment results of the first step for judgment and identification, and finally the type and concentration of the unknown gas are obtained. .

The position of the closed envelope formed by the sequence of gas-sensing response values of the unknown gas in the radar chart is shown in Fig. 9(c) and Fig. 9(d). For example, the closed envelope of test-2 in Fig. 9(c) lies between the 5 and ₁₀ ppm H2S closed envelope, which does not match the shape of the SO2 closed envelope in Fig. ₉ (d). Combined with the prediction in the first step, the gas in test-2 can be determined to be 9 ppmH ₂ S, which completely matches the actual gas (9 ppmH ₂ S). Likewise, the gases in test-1, test-3, and test-4 can be determined to be _22ppmH2S , _97ppmSO2 , and _84ppmSO2 , respectively.

The results of judging and identifying the four groups of unknown gases and the actual type of gas introduced, and the inspection errors are shown in Table 1 below.

Table 1

Combined with the test results of this embodiment, it is confirmed that the method of realizing gas identification by using a single sensor in the present invention is simple and effective. Potential to scale to multiple applications.

The present disclosure uses specific embodiments to describe the principles and implementations of the present disclosure in detail. The application of the above embodiments is only used to help understand the use method and ideas of the present disclosure, and does not limit the application scenarios of the present disclosure. There will be changes in the specific implementation and application scope of the present disclosure according to the actual situation. Without departing from the technical features given by the technical solutions of the present disclosure, the additions, modifications to the technical features or the same in the art The replacement of the content shall fall within the protection scope of the present disclosure.

Claims (9)

1. A method for gas identification based on a single sensor, comprising: S1. Apply a short-cycle pulse heating voltage to the first sensor, so that the first sensor is periodically at N' different temperature points; wherein, the first sensor is placed in the first test gas chamber; the short-cycle pulse The signal waveform of the heating voltage is one of a rectangular wave, a triangular wave or a sine wave; the period is 5-10s, so that the first sensor can be quickly placed at multiple temperature points, and the gas-sensing response data of multiple temperature points can be quickly obtained; The peak-to-peak value of the pulse heating voltage is 0.5-1.75V, so as to ensure that the applied heating voltage keeps the first sensor in a suitable working temperature range; S2, introducing unknown gas into the first test gas chamber; _S3 , _acquiring the test current It of the first sensor for sensing the unknown gas at N' different temperature points, where It is the test current at the corresponding moment in the current heating cycle; S4. Calculate the current change rate D _t of the test current I _t of the N' group respectively, and then generate a D _t curve cluster; obtain the maximum value of D _t in the D _t curve cluster, and calculate the difference from the introduction of the unknown gas to the maximum value of D _t The time between 1 and 2 is recorded as the maximum time τ _m ; calculate the gas-sensing response value sequence of the unknown gas at 1 to N′ temperature points, and take the logarithm of the gas-sensing response value sequence, and then according to the Time sequence of temperature points, generating closed envelopes in radar charts; S5. Determine the position of the maximum time τ _m in the concentration-maximum time relationship curve in the pre-established gas feature identification library, and preliminarily predict the possible types and concentrations of the unknown gas; The envelope is matched with the closed envelope cluster in the radar chart in the pre-established gas feature identification library, and combined with the above prediction, the type and concentration of the unknown gas are finally identified; Among them, the unknown gases identified include hydrogen sulfide and sulfur dioxide. 2. The method according to claim 1, wherein, in the step S4, the current change rates D _t of the N' groups of test currents I _t are calculated respectively by the following formula;

Among them, I _tN' is the test current at the corresponding moment in the previous heating cycle. 3. The method according to claim 2, wherein, in the step S4, the time from the introduction of the unknown gas to the maximum value of D _t is calculated, denoted as the maximum time τ _m , and the formula is as follows:

Among them, the above formula indicates that the maximum time τ _m takes the average value of the abscissa corresponding to the maximum value of D _t (1), D _t (2), ..., D _t (N'), and argmaxD _t (N) represents the corresponding D _t (N) The abscissa when taking the maximum value. 4. The method according to claim 1, wherein in step S4, the gas-sensing response value sequence of the unknown gas at 1 to N' temperature points is calculated, wherein the gas-sensing response value formula is defined as follows: S _N =I _gN /I _aN Among them, I _gN is the saturation current passing through the first sensor in the test atmosphere, and I _aN is the current passing through the first sensor in the background atmosphere. According to the above formula, the gas-sensing response values at 1 to N' temperature points are calculated respectively, and the gas is obtained. A sequence of sensitive response values. 5 . The method according to claim 1 , wherein the method identifies at least one type of unknown gas, and the value of N′ ranges from 5 to 20. 6 . 6. A device for gas identification based on a single sensor, comprising: a first sensor, a first test gas chamber, a first external power supply and a signal generating circuit, a first gas inlet unit, a first test current acquisition unit, a first calculation unit and gas identification unit; wherein, The first sensor is placed in the first test gas chamber for sensing the unknown gas introduced into the first test gas chamber; The first external power supply and signal generation circuit are used to apply a short-cycle pulse heating voltage to the first sensor, so that the first sensor is periodically at N' different temperature points; the signal waveform of the short-cycle pulse heating voltage It is one of rectangular wave, triangular wave or sine wave; the period is 5-10s, so that the first sensor can be quickly placed in multiple temperature points, and the gas-sensing response data of multiple temperature points can be quickly obtained; the pulse heating voltage The peak-to-peak value is 0.5-1.75V, so as to ensure that the applied heating voltage keeps the first sensor in a suitable working temperature range; The first gas introduction unit is used to introduce unknown gas into the first test gas chamber; The first test current acquisition unit is configured to acquire the test current I _t of the unknown gas sensed by the first sensor at N′ different temperature points, where I _t is the test current at the corresponding moment in the current heating cycle; The first calculation unit is used to calculate the current change rate D _t of the N' group of test currents I _t respectively, and then generate a D _t curve cluster; obtain the maximum value of D _t in the D _t curve cluster, and calculate the unknown gas The time from the start to the maximum value of D _t is denoted as the maximum time τ _m ; calculate the gas-sensing response value sequence of the unknown gas at 1 to N′ temperature points, and take the logarithm of the gas-sensing response value sequence, Then, according to the time sequence of each temperature point in each cycle, a closed envelope is generated in the radar chart; The gas identification unit is used to determine the position of the maximum time τ _m in the concentration-maximum time relationship curve in the pre-established gas feature identification library, and preliminarily predict the possible types and concentrations of the unknown gas; The closed envelope generated in the radar chart is matched with the closed envelope cluster in the radar chart in the pre-established gas feature identification library, and combined with the above prediction, the type and concentration of the unknown gas are finally identified; Among them, the unknown gases identified include hydrogen sulfide and sulfur dioxide. 7. The device according to claim 6, wherein the first sensor comprises a test layer, a substrate and a heating layer arranged in order from top to bottom; the test layer comprises a test electrode, and the surface of the test electrode is coated There is a nanometer gas-sensitive film; the heating layer includes a heating electrode and a heating material. 8. A method for establishing a gas feature identification library, comprising: A1. Apply a short-cycle pulse heating voltage to the second sensor, so that the second sensor is periodically at N' different temperature points; wherein, the second sensor is placed in the second test gas chamber; the short-cycle pulse The signal waveform of the heating voltage is one of a rectangular wave, a triangular wave or a sine wave; the period is 5-10s, so that the second sensor can be quickly placed at multiple temperature points, and the gas-sensing response data of multiple temperature points can be quickly obtained; The peak-to-peak value of the pulse heating voltage is 0.5-1.75V, so as to ensure that the applied heating voltage keeps the second sensor in a suitable working temperature range; A2. Pass n groups of test gases of the same type and different concentrations into the second test gas chamber in turn, so that the second sensor can sense the test gases of different concentrations in turn; wherein, n is defined by the user according to the actual situation; A3. Obtain the test current I _t of each group of test gases sensed by the second sensor at N' different temperature points respectively, where I _t is the test current at the corresponding moment in the current heating cycle; A4. Calculate the maximum time of the N' groups of test currents I _t corresponding to each group of test gases respectively, and then generate the concentration-maximum time relationship curves of the n groups of test gases of the same type and different concentrations; A5. Calculate the gas-sensing response value sequence of each group of test gases at 1 to N' temperature points respectively, and take the logarithm of each group of gas-sensing response value sequences, and then follow the time sequence of each temperature point in each cycle , to generate the closed envelope clusters of the n groups of test gases of the same type and different concentrations in the radar chart; A6. Release the gas in the second test gas chamber, introduce another different type of test gas, and repeat A1 to A5 until the concentration-maximum time relationship curve of m groups of different types of gas and the closure in the radar chart are generated Envelope cluster; among them, m is defined by the user according to the actual situation; A7. Store the concentration-maximum time relationship curves of the m groups of different types of gases and the closed envelope clusters in the radar chart; Among them, the test gases include hydrogen sulfide and sulfur dioxide. 9. A device for establishing a gas feature identification library, comprising a second sensor, a second test gas chamber, a second external power supply and a signal generating circuit, a second gas inlet unit, a second test current acquisition unit, and a second calculation unit and gas feature recognition library; where, the second sensor is placed in the second test gas chamber; The second external power supply and signal generating circuit are used to apply a short-cycle pulse heating voltage to the second sensor, so that the second sensor is periodically at N' different temperature points; the signal waveform of the short-cycle pulse heating voltage It is one of rectangular wave, triangular wave or sine wave; the period is 5-10s, so that the second sensor can be quickly placed in multiple temperature points, and the gas-sensing response data of multiple temperature points can be quickly obtained; the pulse heating voltage The peak-to-peak value is 0.5-1.75V to ensure that the applied heating voltage keeps the second sensor in a suitable working temperature range; The second gas introduction unit is used to sequentially introduce n groups of test gases of the same type and different concentrations into the second test gas chamber, so that the second sensor can sequentially sense the test gases of different concentrations; wherein, n is determined by the user Define it according to the actual situation; The second test current acquisition unit is used to acquire the test current I _t of each group of test gases sensed by the second sensor at N' different temperature points, where I _t is the test current at the corresponding moment in the current heating cycle ; The second calculation unit is used to calculate the maximum time of the N' groups of test currents I _t corresponding to each group of test gases, and then generate the concentration-maximum time relationship curves of the n groups of test gases of the same type and different concentrations; and Calculate the gas-sensing response value sequence of each group of test gases at 1 to N' temperature points respectively, and take the logarithm of each group of gas-sensing response value sequences, and then generate the time sequence of each temperature point in each cycle. The closed envelope cluster of the n groups of test gases of the same kind and different concentrations in the radar chart; and for another test gas of different kind passed in, repeat the above steps until the concentrations of m groups of different kinds of gases are generated- The maximum time relationship curve and the closed envelope cluster in the radar chart; where m is defined by the user according to the actual situation; The gas feature identification library is used to store the concentration-maximum time relationship curves of the m groups of different types of gases and the closed envelope clusters in the radar chart; Among them, the test gases include hydrogen sulfide and sulfur dioxide.

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