JP2004093550A - Intelligent gas identifying system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intelligent gas identifying system for identifying gas or volatile chemical substances under a specific environment and a method of the same. <P>SOLUTION: The intelligent gas identifying system comprises a sensor, a pulsed power supply module, and a processor. The sensor, which comprises a voltage input terminal, an output terminal, and a detecting element, conducts gas identification with being exposed to a specific environment. The pulsed power supply module is connected to the voltage input terminal, and sends amplitude modulate pulse voltage to the sensor by the voltage input terminal. The sensor sends an output signal by the output terminal. The processor stores a plurality of chemical substance characteristic signals, receives the output signal from the output terminal of the sensor, and then compares the output signal with the chemical substances characteristic signals to determine a result of the identification of the gas. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an intelligent gas identification system and method for identifying gas or volatile chemicals in a specific environment.
[0002]
[Prior art]
Generally, a gas concentration sensor is used to obtain the concentration of a specific gas. An example of a known gas concentration sensor 500 will be described in detail with reference to FIGS.
[0003]
As shown in FIG. 5, a known gas concentration sensor 500 includes a main body 510, a voltage input terminal 520, and an output terminal 530. The main body 510 shown in FIG. 6 includes a substrate 512, an electrode 514, a detection element 516, and a heater 518. In general, the detection element 516 is a thin film of a metal oxide such as a thin film of tin dioxide (SnO ₂ ) and reacts with a specific gas near the gas concentration sensor 500. When the known gas concentration sensor 500 is applied to a specific environment to perform gas concentration measurement, a fixed voltage is input to the sensor 500 through the voltage input terminal 520, and the heater 518 is operated to activate the detection element 516. The thin film is heated to a predetermined temperature, such as 400C. Therefore, the thin film of the detection element 516 reacts to a specific gas measured in a specific environment, and this reaction changes the resistance of the detection element 516. Thereafter, the output voltage determined by the resistance of the detection element 516 is obtained as an output signal by the output terminal 530.
[0004]
It is clear that the concentration of a particular gas in a particular environment affects the reaction, and the relationship between the concentration of the particular gas and the resistance of the detection element 516 is experimentally determined based on the gas concentration sensor 500. You can decide.
[0005]
FIG. 7 is a diagram showing an example of gas concentration measurement by a known gas concentration sensor 500, and curves L1 and L2 represent different concentrations of a specific gas. When a voltage is input to the sensor 500 via the voltage input terminal 520 to activate the heater 518, the thin film of the detection element 516 is heated to a predetermined temperature, for example, 400 ° C. Due to this reaction, the resistance of the detection element 516 changes, and an output voltage is generated as indicated by a point A at the density L1 and a point B at the density L2. It should be noted that the predetermined temperature of the known gas concentration sensor 500 is set such that the response of the gas concentration sensor becomes clear and the output voltage thereof increases. For example, as shown in FIG. 7, the optimum temperature at which the output of the gas concentration sensor increases is about 400 ° C.
[0006]
The known gas concentration sensor 500 has a thin film structure and is relatively inexpensive. Further, the known gas concentration sensor 500 measures in a short time in response to a gas and is used effectively for a long time. As a result, gas concentration sensors are widely used in various locations. For example, in the gas concentration measurement device disclosed in Patent Document 1, a gas concentration sensor is applied, and a heating control circuit is used to repeatedly apply a voltage to a heater of the sensor by a pulse-width-modulation (PWM) signal. Supply. In this case, the device corrects the error contained in the gas concentration signal, the signal is adjusted, and the output signal of the gas concentration sensor is increased.
[0007]
[Patent Document 1]
US Pat. No. 6,336,354
[Problems to be solved by the invention]
However, the known gas concentration sensor 500 is mainly used to measure the concentration of a specific gas. Obviously, when a particular gas is present in a particular environment, the known gas concentration sensor 500 is used in the particular environment. However, the thin film of the known gas concentration sensor 500 reacts to multiple gases. Therefore, in a specific environment, when two or more types of gases are present, the known gas concentration sensor 500 does not make a distinction in each gas, and the output signal of the sensor 500 is output between a plurality of gases and the specific gas. Does not correspond exactly. Further, when the composition of the gas in a particular environment is completely unknown, the known gas concentration sensor 500 does not identify the composition of the gas.
[0009]
[Means for Solving the Problems]
In view of these, the present invention provides an intelligent gas identification system and method, wherein the input to a conventional gas concentration sensor is such that the output signals corresponding to various gas types are different. An amplitude modulation voltage signal is used as the signal. Thereby, a chemical feature database is established experimentally, and the chemical feature data can be used as a so-called “reference fingerprint” of the composition and / or gas concentration.
[0010]
The present invention provides an intelligent gas identification system. The intelligent gas identification system consists of a sensor, a pulse power module and a processing device. The sensor includes a voltage input terminal, an output terminal, and a detection element, and is exposed to a specific environment to perform gas identification. The pulse power supply module is connected to the voltage input terminal, and sends the amplitude modulated pulse voltage to the sensor through the voltage input terminal, and the sensor sends out the output signal through the output terminal. The processing device stores the plurality of chemical characteristic signals, receives the output signal from the output terminal of the sensor, and then compares the output signal with the chemical characteristic signal to determine a gas identification result.
[0011]
Further, the present invention provides a gas identification method. First, the sensor is exposed to a particular environment. The sensor is supplied with an Amplitude Modulated Pulse (AMP) voltage, and the sensor outputs an output signal corresponding to the gas in a particular environment. The output signal is then compared to a plurality of chemical feature signals to determine the outcome of identifying a gas in a particular environment.
[0012]
In the gas identification method, a chemical feature signal is obtained by exposing the sensor to a plurality of predetermined chemicals and sending a variable amplitude modulated pulse voltage to the sensor, wherein the sensor is configured to provide each chemical corresponding to each predetermined chemical. Output the characteristic signal. Thereafter, the chemical feature signal is stored in a database.
[0013]
In the system and method of the present invention, the output signal is an amplitude modulated pulse voltage signal. Further, the detecting element is a metal oxide such as a thin film of tin dioxide (SnO ₂ ). Furthermore, the result of the gas identification is the composition of the gas and / or the concentration of the respective constituent substances.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to further clarify the objects, features, and advantages of the present invention, preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
[0015]
In conventional gas concentration measurement, a fixed voltage is input to a sensor to activate a heater. The thin film of the sensing element is heated, causing a reaction to a particular gas measured in a particular environment, and the resistance of the sensing element is changed by the reaction. Thus, an output signal is obtained. The fixed voltage is set such that the thin film of the sensing element is heated until it reaches an optimum temperature that indicates a maximum output signal. However, in the present invention, the voltage input to the sensor is changed in a range including the optimum temperature, thereby changing the output signal.
[0016]
FIG. 8 is a diagram showing output signals corresponding to a plurality of gases measured by the sensors. The gas contains hydrogen (H ₂ ), carbon monoxide (CO), ethanol (C ₂ H ₅ OH), methane (CH ₄ ) and (iso) butane (C ₄ H ₁₀ ), and the concentration of each gas is 0. .1% to obtain the output signal. The sensor provided is the widely used gas concentration sensor described above. Note that the curves in FIG. 8 show that the output signal of the gas corresponding to the film temperature (ie, the voltage input to the sensor) changes, each output signal being recognized as an individually identifiable pattern. You. Therefore, the output signal of each gas is used as a chemical substance characteristic signal of the gas in the gas identification. This is the concept introduced in the present invention.
[0017]
Further, the gas identification concept of the present invention shown in FIG. 8 will be described in comparison with the conventional gas concentration measurement shown in FIG. In the prior art shown in FIG. 7, the output signal of the gas concentration sensor 500 is one point of data corresponding to the selected specific thin film temperature (because a fixed voltage is input to the sensor 500). However, in the present invention shown in FIG. 8, the output signal of the sensor is a curve related to a specific range of the thin film temperature, and is used as a chemical characteristic signal of the gas and used for gas identification.
[0018]
An embodiment of the intelligent gas identification system of the present invention will be described in detail with reference to FIG. The intelligent gas identification system of the present invention is used to perform gas identification (or volatile chemical identification) in specific environments. The intelligent gas identification system includes a sensor 10, a pulse power supply module 20, and a processing device 30.
[0019]
The sensor 10 is a known gas concentration sensor 500 shown in FIG. 5, and includes at least one voltage input terminal 520, at least one output terminal 530, and a detection element (that is, the main body 510). The detection element is a metal oxide such as a thin film of tin dioxide (SnO ₂ ), and reacts with a specific gas near the sensor 10.
[0020]
The pulse power supply module 20 is connected to a voltage input terminal of the sensor 10 and sends a variable amplitude modulated pulse voltage to the sensor 10, and the sensor sends an output signal through an output terminal.
[0021]
The processing device 30 is a computer including a pattern recognition module for storing a plurality of chemical substance characteristic signals and a database. The pattern recognition module is, for example, graphic recognition software. Further, the processing device 30 receives an output signal from an output terminal of the sensor 10.
[0022]
When the intelligent gas identification system of the present embodiment is used for gas identification, the sensor 10 is exposed to a specific environment. The pulse power supply module 20 sends the variable amplitude modulation pulse voltage to the sensor 10 through the voltage input terminal, and the thin film of the detection element is repeatedly heated. In each heating step, the thin film temperature changes with the variable amplitude modulation pulse voltage. Thus, the thin film reacts to the gas in a specific environment at different temperatures, and the sensor 10 outputs an output signal such as a variable amplitude modulation pulse signal to the processing device 30. Thereafter, the processing device 30 compares the output signal with the chemical substance characteristic signal to determine a gas identification result such as a gas composition and / or a concentration of a constituent material of each gas.
[0023]
A further embodiment of the gas identification method of the present invention is shown in the flow chart of FIG. The example assumes that gas G is present in the particular environment to be identified, and two given chemicals X and Y are applied to compare with gas G to be identified. That is, if the gas G exactly matches X or Y, gas identification can be performed.
[0024]
When gas identification is performed, the sensor 10 described above is prepared (S10) and exposed to the provided chemicals X and Y (S20). Thereafter, the variable amplitude modulation pulse voltage is supplied to the sensor 10, and the sensor 10 outputs chemical substance characteristic signals SX and SY for the given chemical substances X and Y (S30). These chemical feature signals SX, SY are stored in a database for further gas identification of gas G (S40).
[0025]
Thereafter, the sensor is exposed to a specific environment including the gas G (S50). The sensor supplies a variable amplitude modulation pulse voltage, and the sensor outputs an output signal SG corresponding to the gas G in a specific environment (S60). Therefore, the processing device 30 receives the output signal SG, compares the output signal SG with the chemical substance characteristic signals SX and SY, and determines the identification result of the gas G (S70).
[0026]
The identification result is a value indicating “the gas G exactly matches X or Y” or “the gas G does not match either X or Y”. It should be noted that when the X and Y patterns (chemical substance characteristic signals) do not match as shown in the identification curves L1 and L2 in FIG. 8, gas identification is performed and the gas G is mixed with X and Y. Whether the substance is a substance and the respective concentrations of X and / or Y contained in the gas G are determined.
[0027]
An example of a variable amplitude modulated pulse voltage signal input to the sensor 10 of the intelligent gas identification system of the present invention is shown in FIG. The variable amplitude modulated pulse voltage signal in the present invention is a series of pulse trains in which the voltage amplitude increases or decreases sequentially. Further, two examples of the output signal of the sensor 10 are shown in FIGS. 4A and 4B.
[0028]
It should be noted that the chemical feature signal (pattern) obtained in the present invention is used as a so-called "fingerprint" of a given gas. With graphic recognition technology, the present invention can simulate "smell" in qualitative analysis.
[0029]
In the intelligent gas identification system of the present invention, a variable amplitude modulated pulse voltage is used as an input voltage to be sent to the sensor 10, and for each pulse of the AMP voltage, the input voltage returns to 0 and the thin film temperature returns to room temperature. Since the sensor responds to the gas to be measured, reacts in a short time, and can be effectively used for a long period of time, the present invention provides an output signal corresponding to each pulse of the AMP voltage to the sensor corresponding to each pulse. Ensure accurate correspondence to one-to-one and increase the accuracy of gas identification.
[0030]
Also, it should be noted that the variable amplitude modulation pulse voltage input to the sensor 10 by the pulse power supply module 20 has a predetermined pattern such as the pattern shown in FIG. The pulse of the variable amplitude modulation pulse voltage is maintained for a specific period of 3-5 seconds to ensure that the thin film temperature of the detector reaches a certain temperature. However, even a short time such as one second to several hundred milliseconds is acceptable.
[0031]
Further, the variable amplitude modulation pulse voltage input to the sensor 10 must be set so that the maximum voltage thereof becomes a thin film temperature exceeding an appropriate temperature (maximum output temperature) of the detection element. For example, a suitable temperature for carbon monoxide is 300 ° C. or less, and a suitable temperature for hydrogen exceeds 300 ° C. As a result, when the embodiment of the present invention is applied to the gas discrimination of carbon monoxide and hydrogen, the pulse power module 20 is adjusted so that the maximum voltage pulse of the variable AMP signal increases the thin film temperature of the sensor 10 by 300 ° C. or more. Need to be
[0032]
The present invention applies to identify a variety of gases or volatile chemicals. For example, the present invention is used for identification of toxic gas in chemical laboratories, and is applied as a so-called “electric nose” in wine identification or perfume manufacturing processes. Other possible uses of the invention include identification of odor or industrial toxic gases around toilets.
[0033]
Although preferred embodiments of the present invention have been disclosed as described above, they are not intended to limit the present invention in any way, and any person skilled in the art may make various modifications without departing from the spirit and scope of the present invention. Changes and modifications can be made, and the protection scope of the present invention is based on the contents specified in the claims.
[0034]
【The invention's effect】
The type and concentration of various specific gases can be identified.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an intelligent gas identification system of the present invention.
FIG. 2 is a flowchart of the intelligent gas identification method of the present invention.
FIG. 3 is a diagram illustrating a variable amplitude modulation pulse voltage according to an embodiment of the present invention.
FIG. 4 is a diagram showing an embodiment of an output signal obtained by the present invention.
FIG. 5 is a perspective view showing a known gas concentration sensor.
FIG. 6 is a sectional view showing a main body of a known gas concentration sensor.
FIG. 7 is a diagram showing an example of gas concentration measurement by a known gas concentration sensor 500.
FIG. 8 is a diagram showing output signals corresponding to a plurality of gases measured by sensors.
[Explanation of symbols]
Reference Signs List 10 sensor 20 pulse power supply module 30 processing device 500 gas concentration sensor 510 main body 520 voltage input terminal 530 output terminal 512 substrate 514 electrode 516 detection element 518 heater

Claims (13)

An intelligent gas identification system,
A sensor that is exposed to a specific environment and includes a voltage input terminal, an output terminal, and a detection element;
A pulse power supply module connected to the voltage input terminal, wherein the voltage input terminal sends a variable amplitude modulation pulse voltage to the sensor, and the sensor outputs an output signal through the output terminal;
A processing device that stores a plurality of chemical substance characteristic signals and receives the output signal from the output terminal of the sensor;
Consisting of
The system of claim 1, wherein the processor receives the output signal and compares the output signal with the chemical feature signal to determine a result of the gas identification. The system of claim 1, wherein the output signal is an amplitude modulated pulse signal. The system of claim 1, wherein the sensing element is a metal oxide thin film. The oxide The system of claim 3, wherein the tin dioxide (SnO _2). The system of claim 1, wherein the identification of the gas is a composition of the gas. The system according to claim 5, wherein the identification result of the gas is a concentration of a constituent material of the gas. A gas identification method,
Providing a sensor for a particular environment;
Sending a variable amplitude modulated pulse voltage to the sensor, the sensor outputting an output signal corresponding to the gas in the particular environment;
Comparing the output signal with a plurality of chemical feature signals to determine a result of identifying the gas in the particular environment;
A method characterized by comprising: The chemical feature signal is:
Exposing the sensor to a plurality of predetermined chemicals, sending a variable amplitude modulated pulse voltage to the sensor, and the sensor outputting the chemical characteristic signal corresponding to each of the predetermined chemicals;
Storing the chemical substance characteristic signal in a database;
8. The method according to claim 7, wherein the method is obtained by: The method of claim 7, wherein the output signal is an amplitude modulated pulse voltage signal. The method according to claim 7, wherein the detection element is a thin film of a metal oxide. The metal oxide The method of claim 10, wherein the tin dioxide (SnO _2). The method of claim 7, wherein the identification of the gas is a composition of the gas. 13. The method according to claim 12, wherein the identification result of the gas is a concentration of a constituent of the gas.

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