CN100399015C - A method and device for detecting gas with a single sensor - Google Patents

Abstract

A method and device for identifying and detecting multiple gases with a single sensor, because the molecules of various gases have different chemical properties, and the output variation mode is different when the sensor acts, thereby realizing the detection of multiple gases; the device of the present invention, It mainly consists of at least one sensor probe, a microprocessor and an output device; wherein: the sensor probe is provided with a heating module and a sensor sensitive film; the heating module and the sensor sensitive film are respectively connected to a computer or other data acquisition equipment; by the above device, the micro The processor controls the temperature of the sensor head while acquiring and processing the output voltage of the sensor head.

Description

A method and device for detecting gas with a single sensor

technical field

The present invention relates to a method for identifying and detecting various organic or inorganic molecules by using the dynamic response signal of a single sensor, and especially relates to the identification and concentration of organic volatiles, flammable gases and environmental pollution gases such as CO and nitrogen oxides detection.

The present invention also relates to an electronic nose device for implementing the above method.

Background technique

Electronic nose (also known as electronic tongue working in liquid medium) is an environmental monitoring instrument that can detect and identify many organic and inorganic molecules. At present, the electronic nose is generally defined as an instrument composed of an array of sensors with different sensitive characteristics and a pattern recognition system, which is used to identify and detect various organic and inorganic molecules. The current identification of sensitive molecules by electronic noses is realized by pattern recognition of the output value of the sensor array when it is balanced, and the use of dynamic corresponding signals of a single sensor to realize the identification of detected objects has not been reported.

Contents of the invention

The object of the present invention is to provide a method for identifying and detecting multiple organic or inorganic molecules by utilizing the dynamic response signal of a single sensor.

Another object of the present invention is to provide an electronic nose (tongue) for realizing the above method.

The recognition and detection method and the electronic nose (tongue) provided by the present invention can use a simple recognition algorithm to replace the pattern recognition algorithm, while reducing the number of sensors, reducing hardware complexity and computational complexity, thereby reducing hardware cost and having the advantages of Very high recognition rate is conducive to large-scale commercialization.

In order to achieve the above object, the method for using the dynamic response signal of a single sensor to identify and detect multiple organic or inorganic molecules provided by the present invention is based on the principle that, due to the different chemical properties of various detected molecules, the molecules and sensors are sensitive The role of the material is different. Although the output of the sensor (such as conductivity, temperature, mass, pressure, color change, etc.) The change mode of the sensor output in the process is different. The present invention realizes the identification and detection of the detected molecule just based on the difference of these modes.

Specifically, the present invention uses a computer to control the temperature of the sensor probe within a certain range and make the temperature range change periodically, and the temperature range depends on the properties of the sensitive material of the sensor and the molecules to be detected. Various measured molecules react to a certain extent at different temperatures. At this time, the measured molecules with different concentrations and different components will display a series of response signals through the sensor probe. Use the computer to record the response signal of the sensor probe and get a response. Curve, calculate the differential calculation of this series of curves, and compare with the pre-established standard curve to identify and detect the composition and concentration of each molecule.

According to the sequence of operations, the steps of the present invention are:

a) Program temperature control, precise control of temperature changes within a cycle;

b) record the output voltage of at least one sensor in real time;

d) identify the output voltage curve of the sensor, and calculate the differential calculation of the series of curves;

e) Use the standard curve of the gas to calculate its concentration.

The method, wherein the plurality of gases are various organic or inorganic molecules.

The method, wherein the range of temperature variation in step a includes the most sensitive temperature range of the detected gas.

Said method, wherein the series of curves in step d are the voltage curves output by the same sensor for multiple gases.

The device for realizing the above-mentioned method provided by the present invention mainly consists of at least one sensor probe, microprocessor and recording equipment; wherein:

The sensor probe is equipped with a heating module and a sensor sensitive film;

The heating module and the sensitive film of the sensor are respectively connected with the computer;

By the above device, the microprocessor controls the temperature of the sensor probe, and at the same time collects and processes the output voltage of the sensor probe.

Said device, wherein the heating module is connected to the computer through the D/A interface, and the sensor sensitive film is connected to the computer through the A/D interface.

Said device, wherein a thermistor is pasted on the sensitive film of the sensor, and the thermistor is connected with the computer through the A/D interface.

Said device, wherein the display device is a computer monitor, a nixie tube, a liquid crystal module, a loudspeaker or other output devices.

The present invention adopts computer to control temperature, and technologies such as computer recording and data processing are all known technologies, and those skilled in the art are easy to understand and implement.

Description of drawings

Fig. 1 is a schematic diagram of the testing device of the present invention. Among them, Figure 1a is the structure of the sensor probe, and Figure 1b is the structure diagram of the entire test system;

Figure 2 is the probe temperature curve. The 7 curves in the figure are the change curves of the temperature of the sensor probe in 7 different measurements when the total amount of methanol injected is 0.1uL, 0.2uL, 0.5uL, 1.0uL, 2.0uL, 5.0uL and 10.0uL. is overlapping;

Fig. 3 is the output voltage curve of sensor to ethanol;

Fig. 4 is the output voltage curve of sensor to methanol;

Fig. 5 is the differential signal comparison of methanol and ethanol sensor output voltage curves;

Figure 6 is a comparison of the differential signals of the four gases of methanol, ethanol, benzene and water vapor through the output voltage curve of the same sensor;

Fig. 7 is a standard curve of methanol output by the sensor, where the abscissa is proportional to the logarithm of its concentration, and the ordinate is proportional to the logarithm of the resistance value of the sensitive membrane of the sensor.

Detailed ways

The method of using the dynamic response signal of a single sensor to identify and detect various organic or inorganic molecules according to the present invention will be described in detail below with reference to the accompanying drawings.

According to the present invention, in order to realize a single-sensor electronic nose, it is first required to select a sensor that responds to the measured gas, and determine the most sensitive temperature of the sensor to these measured gases, and the range of sensor heating temperature will include the most sensitive temperature .

In this embodiment, the identification and concentration detection of methanol, ethanol, benzene and water vapor performed by the commercially available QM-NG1 combustible gas sensor is taken as an example to describe the present invention in detail.

Please refer to FIG. 1 , which is a schematic diagram of an electronic nose device for implementing a detection method provided by the present invention, which mainly includes a sensor probe 1 , an analog-to-digital conversion chip 2 , a digital-to-analog conversion chip 3 , a microprocessor 4 and a display device 5 . The device can be realized with a computer and a data acquisition card, or can be realized with a dedicated ADC and DAC chip and various other micro-processing chips such as a single-chip microcomputer and a DSP chip. The structure of the sensor probe in the electronic nose device is shown in Figure 1a. Its heating module 9, thermistor 10 and sensor sensitive film 11 are integrated on a _SnO2 sensor probe 12, and only the sensitive film of the thermistor 10 needs to be installed during installation. One side is close to the sensor sensitive film. Wherein the thermistor 10 is only used during debugging, and can be omitted in actual products. During measurement, the sensor sensitive film 11 and a sampling resistor R _load are connected in series to the test circuit, and the voltage drop on R _load is the output voltage of the sensor (since the sampling resistor is a well-known common circuit, no specific description is given, and no accompanying drawings are recommended) . Figure 1b is a structural diagram of the entire testing system. The temperature signal and voltage output signal of the sensor probe 1 are respectively connected to the microprocessor 4 through an A/D interface, and the heating voltage control of the sensor probe 1 is realized by a D/A interface. The collected data is processed by the microprocessor to obtain identification and quantification results, and the results are output through the terminal display device 5 (such as a display or recorder, etc.) to output the detection results.

The QM-NG1 combustible gas sensor has a good response to water vapor and various organic volatiles. It is a general-purpose gas sensor. Its temperature curve is shown in Figure 2. Place the sensor probe in a closed container with a volume of 1500mL, which is filled with clean and dry air. There is an injection hole in the upper part of the container, through which the detected substance is injected into the test container.

The most sensitive temperature of the QM-NG1 sensor to the four gases of methanol, ethanol, benzene and water vapor is between 200-250°C, so the heating temperature range is selected to be 100-400°C.

The temperature is detected by the thermistor. When the heating voltage is 2V, the corresponding temperature of the sensor probe is about 100°C, and when the heating voltage is 8V, the corresponding temperature is about 400°C. Therefore, the heating voltage can be controlled to change periodically between 3-8V (such as sine wave, triangle wave, sawtooth wave and other arbitrary waveforms), and the temperature of the sensor can be changed periodically between 100-400°C. The heating waveform used in this example is

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; the\; heat</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 5.0</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3.0</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; *</span>\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="400"\; label="t"\; filenames="C20051001210700082.png,C20051001210700091.png"\; state="\{\{state\}\}">t</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 400</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span>$

Place the sensor probes in standard measured gases of different concentrations, start the program temperature control, and record the waveform output by the sensor. The results are shown in Figure 3 and Figure 4.

The sensor output voltage curve is differentially calculated to obtain the mode information of different measured gases, as shown in Figure 5 and Figure 6. According to the different mode information of various measured gases, these measured objects can be identified.

Take the logarithm of the concentration of the gas to be measured as the horizontal axis, and take the logarithm of the minimum resistance value of the sensor during the heating process (this resistance value corresponds to the peak value of the output voltage during the heating process) as the vertical axis to draw a graph to obtain a standard curve. As shown in Figure 7.

For the measured gas, use the same heating waveform to control its temperature change to obtain the output voltage waveform. After differentiation, compare it with the model of the standard candidate, and judge that the measured object is the closest candidate to its model. According to the standard working curve of the candidate, the concentration of the analyte can be obtained.

For increasing the accuracy of detection results, the present invention can also be made up of a detection system by a plurality of above-mentioned sensor probes, each sensor probe in this system detects independently, and microprocessor can be processed according to the identification result of each sensor to get a more reliable output.

Compared with the traditional multi-sensor electronic nose system, the invention can greatly reduce the number of sensors while maintaining high identification accuracy.

Claims (7)

1. one kind is detected the method for multiple gases with single-sensor, because the molecule of all gases has different chemical character, to make time spent output quantity changing pattern different with sensor, thereby realizes the detection of multiple gases; The steps include:

A) temperature programmed control is in one-period inner control temperature variation;

B) output voltage of real time record sensor;

D) the different tested gases of identification are at the serial output voltage curve of this sensor, to the calculating of differentiating of this series output voltage curve;

E) typical curve that obtains under the same terms with this gas calculates its concentration.

2. the multiple gases that the process of claim 1 wherein is by multiple organic or inorganic molecular composition.

3. the process of claim 1 wherein that range of temperature comprises the sensitive temperature interval of detected gas among the step a.

4. device that is used for the described method of claim 1, it mainly is made up of at least one sensor probe, microprocessor and recording unit; Wherein:

Sensor probe is provided with heating module and sensor sensing film;

Heating module is connected with computing machine respectively with sensor sensing film;

By said apparatus, microprocessor control sensor probe temperature, the output voltage of collection and processes sensor probe simultaneously.

5. the device of claim 4, wherein heating module is connected with computing machine by the D-A converter interface, and sensor sensing film passes through the analog-digital converter interface and is connected with computing machine.

6. the device of claim 4 wherein is pasted with thermistor on the sensor sensing film, and this thermistor is connected with computing machine by the analog-digital converter interface.

7. the device of claim 4, display device wherein is graphoscope, charactron, Liquid Crystal Module or loudspeaker.

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