KR101025715B1 - Gas detecting sensor using surface acoustic wave and gas detecting method thereof - Google Patents

Abstract

The present invention provides a gas sensor and a method of detecting the same, which can improve the sensitivity of gas detection and shorten the reaction time by synchronizing the measurement time between the electrical signal measured in the surface acoustic wave (SAW) device and the electrical signal in the conductive member. do.

Gas detection sensor of the present invention,

A piezoelectric plate and an input and output IDT formed on the piezoelectric plate, wherein the electrical signal applied to the input IDT is converted into surface acoustic wave by the piezoelectric plate and transmitted as an electrical signal to the output IDT through the piezoelectric plate. device; A conductive member formed between the input and output IDTs on the SAW element and rapidly and sensitively reacting to gas exposure to cause an electrical change; A first signal detector detecting an electrical signal transmitted to the output IDT; A second signal detector for detecting an electrical signal from the conductive member; And a signal analyzer configured to synchronize the detection time with respect to the electrical signals detected by the first signal detector and the second signal detector, and to analyze the change of the synchronized two electrical signals according to gas exposure. Include.

Surface acoustic wave (SAW) device, IDT, gas, sensor, sensitivity, response time, synchronization

Description

GAS DETECTING SENSOR USING SURFACE ACOUSTIC WAVE AND GAS DETECTING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor and a gas sensing method. In particular, the present invention relates to a gas using a measurement time synchronization between an electrical signal measured in a surface acoustic wave (SAW) device and an electrical signal measured in a conductive member sensing gas. The present invention relates to a gas sensor using a SAW device capable of improving the sensitivity and shortening the reaction time, and a sensing method thereof.

In general, surface acoustic wave (SAW) devices have been widely used in the application of RF components such as filters and duplexers having good band selection characteristics in the RF band by using the characteristics of piezoelectric plates. Such SAW devices typically have an input and output inter-digital transducer (IDT) electrode pattern that filters a specific signal on a piezoelectric plate to create a unique communication signal. It is mainly determined by the shape and configuration of the output IDT electrode pattern and the propagation characteristics of the surface acoustic wave propagating through the piezoelectric plate.

When an AC signal of several MHz to several hundred MHz is applied to the input IDT of the SAW element, a compression wave is formed on the piezoelectric plate to generate sound waves. Is output. At this time, the electrical signal output from the output IDT is very sensitive to the properties (mass) and viscosity (viscosity) of the surface of the piezoelectric plate.

Recently, there have been attempts to apply to various sensors that detect temperature, pressure, gas, etc. using the characteristics of such SAW devices. In particular, in the conventional gas sensor using the SAW device, a gas sensitive sensitive material for gas sensing is formed between the input and output IDT electrodes of the SAW device, and when gas is adsorbed to the sensitive material, the frequency change of the surface acoustic wave occurs. A change occurs in the frequency, phase, amplitude, etc. of the electrical signal output from the output IDT. The change in electrical signal is used to detect the type and concentration of the adsorbed gas.

However, the conventional gas sensor using the SAW element is small in size even if the frequency change of surface acoustic wave does not appear immediately when gas is adsorbed on the gas sensitive material, and thus the sensitivity and response time for gas detection are still present. ) Did not reach a satisfactory level. In particular, such a conventional gas sensor has a problem that the sensitivity and reaction time of the initial gas exposure and low concentration of gas is significantly decreased, and the stability and discrimination against continuous gas concentration change are low.

Therefore, there is a continuous need in the art to develop a technology capable of detecting various gases in a gas sensor using a SAW device and providing excellent sensitivity and fast reaction time for low concentration gas.

The present invention has been proposed to solve the above problems of the prior art, and improves sensitivity to gas detection through synchronization of detection time between the electrical signal detected in the SAW element and the electrical signal detected in the conductive member reacting to the gas. In addition, an object of the present invention is to provide a gas sensor using the SAW device and a method for detecting the same, which can shorten the reaction time.

Gas detection sensor of the present invention for achieving the above object,

A piezoelectric plate and an input and output IDT formed on the piezoelectric plate, wherein the electrical signal applied to the input IDT is converted into surface acoustic wave by the piezoelectric plate and transmitted as an electrical signal to the output IDT through the piezoelectric plate. device;

A conductive member formed between the input and output IDTs on the SAW element and rapidly and sensitively reacting to gas exposure to cause an electrical change;

A first signal detector detecting an electrical signal transmitted to the output IDT;

A second signal detector for detecting an electrical signal from the conductive member; And

A signal analyzer configured to synchronize the detection time with respect to the electric signals detected by the first signal detector and the second signal detector, and to detect the gas exposure by analyzing the change of the two synchronized electric signals according to the gas exposure; It provides a gas sensor using a SAW device comprising a.

In the present invention, it is preferable that the signal analyzer detects the gas exposure by using the electrical signal change of the first signal detector corresponding to the electrical signal change of the second signal detector in the synchronized two electrical signals.

In the present invention, it is preferable that the first signal detector detects at least one of a frequency, a phase, and an amplitude of the electric signal reaching the output IDT.

In the present invention, it is preferable that the second signal detection unit detects at least one signal of voltage, current, resistance, and capacitance with respect to the conductive member.

In the present invention, the conductive member preferably comprises any one selected from carbon nanotubes (CNT), metal oxide (MO) or polymer, wherein the metal oxide is Sn, Zn, Al, Si More preferably, the oxide is any one selected from In, Ti, Cr, Fe, Ni, and Zr.

In the present invention, the signal analyzer pre-stores at least one signal selected from among frequencies, phases, and amplitudes according to a plurality of types of gases, and exposes the signals using the electric signals detected by the SAW signal detector and the pre-stored signals. It is desirable to analyze the type of gas.

In the present invention, the signal analyzer pre-stores at least one signal selected from among voltage, current, resistance, and capacitance for each of a plurality of types of gases, and uses the electrical signal detected by the conductive member signal detector and the pre-stored signal. It is preferable to analyze the type of the exposed gas.

In addition, the gas detection method of the present invention for achieving the above object,

In the gas sensing method using a SAW element comprising a piezoelectric plate and an input and output IDT formed on the piezoelectric plate,

Forming a conductive member on the SAW device that reacts quickly and sensitively to gas exposure to cause an electrical change;

Detecting an electrical signal output to the output IDT;

Detecting an electrical signal at the conductive member; And

Synchronizing the detection time with respect to each of the detected electric signals, and detecting the gas exposure by analyzing changes of the two synchronized electric signals according to gas exposure; It includes.

In the present invention, the step of detecting the gas exposure,

Preferably, the gas exposure is detected by using the electrical signal change of the output IDT corresponding to the electrical signal change in the conductive member in the synchronized two electrical signals.

In the present invention, the step of detecting the electrical signal in the output IDT,

Preferably, the electrical signal is detected by at least one of frequency, phase, and amplitude.

In the present invention, the step of detecting the electrical signal in the conductive member,

The conductive member is preferably detected by at least one of a voltage, a current, a resistance, and a capacitance.

In the present invention, the conductive member preferably includes any one selected from carbon nanotubes (CNT), metal oxide (MO), or polymer.

In the present invention, the metal oxide is preferably an oxide of any one selected from Sn, Zn, Al, Si In, Ti, Cr, Fe, Ni, Zr.

According to the present invention, the electrical signal corresponding to the surface acoustic wave of the SAW element and the change of the electrical signal such as voltage, current, resistance, capacitance, etc. are very fast according to gas adsorption, and the electrical signals are simultaneously measured at the sensitive conductive member. By comparing the measurement time of the gas to detect the gas has the effect of improving the sensitivity to gas detection and shortening the reaction time.

In addition, according to the present invention, it is possible to give selectivity to various gas types in detecting gas.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

1 is a schematic configuration diagram of a gas sensor using a SAW device according to an embodiment of the present invention.

Referring to FIG. 1, the gas sensor 100 using the SAW device according to the present invention includes a SAW device 110, a conductive member 130, a first signal detector 150, a second signal detector 170, and a signal. It is configured to include an analysis unit 190. In the gas sensor 100 of the present invention, the conductive member 130 is preferably formed on the SAW element 110, and the first signal detection unit 150 is connected to the SAW element 110 and the second signal detection unit ( 170 has a structure connected to the conductive member 130.

The SAW element 110 of the present invention includes a piezoelectric plate 111, an input IDT 113, and an output IDT 115. Preferably, power is applied to the SAW element 110 from a power source not shown. In detail, an electrical signal is applied from the power supply unit (not shown) to the input IDT 113 of the SAW element 110. As such, the electrical signal applied to the input IDT 113 of the SAW element 110 is converted into a surface acoustic wave form by the piezoelectric plate 111, which is output through the piezoelectric plate 111 as a medium. 115). The output IDT 115 outputs a mechanical wave as an electric signal by the reverse piezoelectric effect. In this case, when the gas is exposed to the SAW element 110, the transfer speed of the surface acoustic wave is changed by the mass and temperature characteristics of the gas. As a result, a change due to gas exposure occurs in the electrical signal output from the output IDT 115. do. The electrical signal at the output IDT 115 may include, for example, at least one of frequency, phase, and amplitude.

The conductive member 130 is formed substantially in the vicinity of the SAW element 110, and is preferably formed on the piezoelectric plate 111 of the SAW element 110. In particular, it is more preferably formed between the input IDT 113 and the output IDT 115 on the piezoelectric substrate 111. The conductive member 130 is preferably made of a material having a very fast response time and a very sensitive electrical change such as voltage, current, resistance, capacitance, etc. caused by the gas exposed on the surface thereof. Examples preferably include carbon nanotubes (CNTs), metal oxides (MO), or polymers. As such a metal oxide, oxides such as Sn, Zn, Al, Si In, Ti, Cr, Fe, Ni, Zr and the like can be used. However, the present invention is not limited thereto, and the conductive member 130 is sufficient as long as it is a material that has conductivity and can react quickly and sensitively to gas exposure to cause a change in an immediate electrical signal. The conductive member 130 may be implemented as a liquid or a solid material.

The first signal detector 150 detects an electrical signal output from the output IDT 115 of the SAW element 110. Such an electrical signal is preferably detected over time, and more preferably, for example, at least one of frequency, phase, and amplitude according to the detection time. At this time, the electrical signal of the output IDT 115 detected by the first signal detection unit 150 does not change its electrical signal when there is no gas exposure, but when the SAW element 110 is exposed to gas, Changes in the signal occur. By using the change in the electrical signal, it is possible to measure the type and concentration of the gas according to whether the gas is exposed and the characteristics of the exposed gas.

The second signal analyzer 170 detects an electrical change in the conductive member 130 as an electrical signal. For this purpose, it is preferable to apply power to the conductive member 130. The electrical signal is preferably detected over time, and more preferably, for example, at least one signal among voltage, current, resistance, and capacitance according to the detection time. At this time, the electrical signal of the conductive member 130 detected by the second signal analysis unit 170 does not change the electrical signal when there is no gas exposure, but when the conductive member 130 is exposed to gas, A change in the electrical signal occurs. By using the change in the electrical signal, it is possible to measure the type and concentration of the gas according to whether the gas is exposed and the characteristics of the exposed gas.

The signal analyzer 190 synchronizes the detection time with respect to the electrical signals detected by the first signal analyzer 150 and the second signal analyzer 170, respectively. Through this synchronization, when gas exposure occurs, it is possible to confirm that both electric signals simultaneously change at the same detection time. Therefore, the gas exposure can be detected by analyzing a case where a change due to gas exposure occurs at the same time point in two synchronized electric signals. This will be described in detail with reference to FIG. 2.

2 is a diagram illustrating a synchronized electric signal according to an embodiment of the present invention.

FIG. 2A is an electric signal from the output IDT 115 detected by the first signal detector 150, and FIG. 2B is a conductive member 130 detected by the second signal detector 170. The electrical signal at. As an example, FIG. 2A illustrates a frequency f signal over time, and FIG. 2B illustrates a resistance R signal over time. At this time, these two electrical signals are shown synchronized with each other with respect to the detection time. In addition, the drawings show an example in which these two electrical signals change in response to the same gas exposure.

As described above, since the SAW element 110 has a low sensitivity to gas exposure and a slow response time, the electrical signal detected by the first signal detector 150 has a small change in the electrical signal due to the gas exposure. appear. This is a factor that does not detect the gas exposure quickly and accurately, even if there is a change in the electrical signal in response to the gas, it is difficult to distinguish between the electrical signal due to the gas exposure and the electrical signal due to noise.

However, if the change of the electrical signal in the conductive member 130 which reacts very quickly and sensitively to the gas is used, the gas exposure can be detected quickly and accurately, and at the same time the output IDT 115 at the point of time at which the electrical signal changes The type and concentration of gas can be confirmed by analyzing the change of the electrical signal.

In other words, as illustrated in FIG. 2, gas exposure may be detected by using the electrical signal change of the first signal detector 150 corresponding to the electrical signal change of the second signal detector 170 in the two electrical signals synchronized with each other. Can be. That is, if the electrical signal of the first signal detector 150 changes in three parts A, B, and C, and the time points are t1, t2, and t3, respectively, the electrical signals of the second signal detector 170 are t1 and Since it appears to have changed at t3, it means that the conductive member 130 has been exposed to the gas at the time points t1 and t3. At this time points t1 and t3, the electrical signal of the first signal detection unit 150 has a high resolution. By analyzing the gas, the exposed gas can be detected quickly and accurately. At the same time, it is possible to determine the type, concentration, and the like of the gas by using the magnitude of the electrical signal change of the second signal detector 170 at the time points t1 and t3. This determination may use the magnitude of the change when the frequency, phase, amplitude, etc. of the electrical signal changes with gas exposure.

In contrast, in the case of time t2 in FIG. 2, the electrical signal of the first signal detector 150 is changed, but the electrical signal of the second signal detector 170 is not changed. It is desirable to judge not by change, but by change of the electrical signal due to noise, for example.

Meanwhile, in one example of the present invention, the signal analyzer 190 may store the electrical signal output from the output IDT 115 as at least one signal selected from among frequencies, phases, and amplitudes for each type of gas. This is to determine the type of gas according to the electrical signal detected by the first signal detector 150. In addition, in another example of the present invention, the signal analyzer 190 may store the electrical signal from the conductive member 130 in advance as at least one signal selected from among voltage, current, resistance, and capacitance for each type of gas. have. This is to determine the type of gas according to the electrical signal detected by the second signal detector 170.

3 is a flowchart illustrating a gas sensing method using a SAW device according to an embodiment of the present invention.

Referring to FIG. 3, first, an electrical signal is applied to an input IDT 113 by a SAW element 110 including a piezoelectric plate 111 and input and output IDTs 113 and 115 formed on the piezoelectric plate 111 ( S100). At the same time, an electrical signal is also applied to the conductive member 130 formed on the SAW element 110 (S102). Preferably, the electrical signal is either AC voltage or AC current. As such, the electrical signal applied to the input IDT 113 is converted into surface acoustic wave by the piezoelectric plate 111 and transmitted to the output IDT 115 through the piezoelectric substrate 111 which is a medium. Outputs an electric signal.

Subsequently, the first signal detection unit 150 detects an electrical signal output from the output IDT 115 (S104). At this time, the electric signal changes as the piezoelectric plate 111 is exposed to the gas. In addition, the second signal detection unit 170 detects an electrical signal from the conductive member 130 (S106). At this time, as the conductive member 130 that reacts very quickly and sensitively to the gas is exposed to the gas, a change of the electrical signal occurs.

Thereafter, the signal analyzer 190 synchronizes the detection time with respect to the two electrical signals detected as described above (S108). In other words, the reaction time to gas exposure is matched. As a result, the point of time at which the change of the electrical signal occurs in the conductive member 130 is confirmed (S110), and at that time, the change of the electrical signal at the output IDT 115 is analyzed in various ways (S112). The type and the concentration are determined (S114). Here, different electric signal patterns are formed according to the type and concentration of the gas. For example, the frequency, phase, amplitude, etc. of the electrical signal appear differently. To this end, the signal analysis unit 190 previously stores electrical signals for each type of gas, and compares the stored electrical signals with the detected electrical signals to determine the type and concentration of such gases.

As described above, in the gas detection sensor using the SAW device and the gas detection method thereof according to the present invention, the voltage, current caused by the gas adsorbed on the surface such as CNT, metal oxide (MO), polymer, etc. on the SAW device Changes in electrical signals such as resistance, capacitance, etc. are very fast and sensitive conductive members are formed, and then the electrical signals of the SAW elements and the electrical signals of the conductive members are simultaneously measured, resulting in high sensitivity and fast response time for various types of gases. It can be to have. By synchronizing the two electrical signals with respect to the detection time, gas exposure can be detected by using the electrical signal change of the SAW element corresponding to the electrical signal change of the conductive member.

Meanwhile, the above-described embodiments of the present invention are merely preferred embodiments, and are not limited to the description of these embodiments of the present invention. That is, various improvements and modifications are possible within the scope of the technical idea of the present application described above, and it is obvious that any of them fall within the technical scope of the present invention as long as they belong to the appended claims.

Recently, various gases are used in various fields of the industry. For example, oxygen and carbon dioxide gas are used in the medical field, and hydrogen is used as a future fuel in automobiles and power generation fields, and correspondingly, researches on the sensor technology for detecting such various gases are also in progress. In particular, gas flows that can have a fatal effect on the human body or the environment must be supported by a technology that detects trace amounts quickly and accurately for easy and safe use.

In view of this aspect, the gas detection sensor using the SAW device according to the present invention can secure excellent detection capability and stability compared to the conventional, and further has a high sensitivity and a fast reaction time at low concentrations, various gas detection technologies It can be very useful in the field.

1 is a schematic configuration diagram of a gas sensor using a SAW device according to an embodiment of the present invention.

2 is a diagram illustrating a synchronized electric signal according to an embodiment of the present invention.

3 is a flowchart illustrating a gas sensing method using a SAW device according to an embodiment of the present invention.

 Explanation of symbols on the main parts of the drawings

100: gas detection sensor 110: SAW element

111: piezoelectric plate 113: input IDT

115: output IDT 130: conductive member

150: first signal detector 170: second signal detector

190: signal analysis unit

Claims (14)

A piezoelectric plate and an input and output IDT formed on the piezoelectric plate, wherein the electrical signal applied to the input IDT is converted into surface acoustic wave by the piezoelectric plate and transmitted as an electrical signal to the output IDT through the piezoelectric plate. device; A conductive member formed between the input and output IDTs on the SAW element and rapidly and sensitively reacting to gas exposure to cause an electrical change; A first signal detector detecting an electrical signal transmitted to the output IDT; A second signal detector for detecting an electrical signal from the conductive member; A signal analyzer configured to synchronize the detection time with respect to the electric signals detected by the first signal detector and the second signal detector, and to detect the gas exposure by analyzing the change of the two synchronized electric signals according to the gas exposure; Gas detection sensor using a SAW device comprising a. The method according to claim 1, The signal analyzer detects the gas exposure by using the electrical signal change of the first signal detector corresponding to the electrical signal change of the second signal detector in the synchronized two electrical signals. Sensor. The method according to claim 1, The first signal detection unit detects the electrical signal reaching the output IDT by at least one signal of the frequency, phase, amplitude, characterized in that the gas detection sensor using a SAW element. The method according to claim 1, And the second signal detector detects at least one signal of voltage, current, resistance, and capacitance from the conductive member. The method according to claim 1, The conductive member includes a carbon nanotube (CNT), a metal oxide (metal oxide: MO) or a gas sensor using a SAW device, characterized in that it comprises any one selected from a polymer. The method according to claim 5, Wherein the metal oxide is Sn, Zn, Al, Si In, Ti, Cr, Fe, Ni, Zr gas detection sensor using a SAW device, characterized in that any one of the oxide selected from. The method according to claim 1, The signal analyzer pre-stores at least one signal selected from among frequencies, phases, and amplitudes for each type of gas, and the type of the exposed gas using the electric signal detected by the SAW signal detector and the pre-stored signal. Gas detection sensor using a SAW element, characterized in that for analyzing. The method according to claim 1, The signal analyzer pre-stores at least one signal selected from among voltages, currents, resistances, and capacitances according to the types of gases, and the exposure is performed by using the electrical signals detected by the conductive member signal detector and the pre-stored signals. Gas detection sensor using the SAW device, characterized in that for analyzing the type of gas. In the gas sensing method using a SAW element comprising a piezoelectric plate and an input and output IDT formed on the piezoelectric plate, Forming a conductive member on the SAW device that reacts quickly and sensitively to gas exposure to cause an electrical change; Detecting an electrical signal output to the output IDT; Detecting an electrical signal at the conductive member; And Synchronizing the detection time with respect to each of the detected electric signals, and detecting the gas exposure by analyzing changes of the two synchronized electric signals according to gas exposure; Gas detection method using a SAW device comprising a. The method according to claim 9, Detecting the gas exposure, And detecting the gas exposure by using the electric signal change of the output IDT corresponding to the electric signal change in the conductive member in the synchronized two electric signals. The method according to claim 9, Detecting the electrical signal in the output IDT, Gas detection method using a SAW element, characterized in that for detecting the electrical signal with at least one signal of the frequency, phase, amplitude. The method according to claim 9, Detecting the electrical signal in the conductive member, And detecting at least one of a voltage, a current, a resistance, and a capacitance of the conductive member. The method according to claim 9, The conductive member includes a carbon nanotube (CNT), a metal oxide (metal oxide: MO), or a gas detection method using a SAW device, characterized in that it comprises any one selected from a polymer. 14. The method of claim 13, The metal oxide is a gas detection method using a SAW device, characterized in that the oxide of any one selected from Sn, Zn, Al, Si In, Ti, Cr, Fe, Ni, Zr.

Images