CN102175343B - Carbon nanotube film three-electrode gas temperature sensor and temperature measuring method thereof - Google Patents

Abstract

The invention discloses a carbon nanotube film three-electrode gas temperature sensor and a temperature measuring method thereof. The sensor includes three first, second and third electrodes distributed in sequence, the first electrode is provided with air holes, and its inner surface is glued The substrate is connected with the carbon nanotube thin film; the center of the second electrode is provided with a lead-out hole; the surface of the third electrode is provided with a blind hole; the three electrodes are mutually isolated. The method includes: 1) placing a gas temperature sensor; 2) applying a voltage on the electrode; 3) measuring the output ion current value of the sensor; 4) forming a sample with the measured value and the calibration value of the gas temperature, and constructing a gas temperature measurement database with the interpolated sample ; 5) Build a data fusion instrument and establish a gas temperature measurement model; 6) Input the measured value of the sensor into the measurement model to obtain an accurate measurement value of the gas temperature. The gas temperature sensor has low operating voltage, high sensitivity for measuring gas temperature, good linearity and high accuracy, and can be used for measuring the temperature of flammable, explosive and toxic gases.

Description

Carbon nanotube film three-electrode gas temperature sensor and its temperature measurement method

technical field

The invention relates to the field of gas temperature detection, in particular to a three-electrode gas temperature sensor based on carbon nanotube film and gas discharge principle and a temperature measurement method thereof.

Background technique

With the urgent need of gas detection in all walks of life and the development of nanotechnology, nanosensors have made great progress. Especially with the discovery of carbon nanotubes at the end of the 20th century, carbon nanotubes have shown attractive application prospects in the fields of gas, temperature and humidity detection. The carbon nanotube thin film two-electrode sensor in the carbon nanotube temperature sensor has become a research hotspot in the field of gas temperature detection due to its advantages of high detection sensitivity, wide gas detection range, and fast response. The carbon nanotube film two-electrode gas temperature sensor is based on the principle of gas discharge, and uses carbon nanotubes as the sensitive material. The area of the electrode can be greatly increased; the second is based on the nanoscale tip curvature radius of carbon nanotubes, which greatly reduces the operating voltage of the sensor, and obtains a very strong electric field strength near the tip of the carbon nanotubes, making the measured gas under low voltage ionization; the third is that the size of the sensor is greatly reduced, and the dynamic response is fast. Therefore, it has broad development prospects in biology, chemistry, machinery, aviation, military and other aspects.

The existing carbon nanotube film two-electrode gas temperature sensor was developed by Professors Hui Guohua and Chen Yuquan from the School of Biomedical Engineering and Instrument Science of Zhejiang University under the condition of 120 micron electrode spacing, and the CNT film cathode two-electrode sensor was studied. Temperature-sensitive characteristics (Figure 1), that is, the relationship between breakdown voltage and temperature in air. The two-electrode sensor has a breakdown voltage as high as 360 volts when the temperature is 10 degrees Celsius, and a breakdown voltage of more than 150 volts when the temperature is 60 degrees Celsius. The working voltage is high, and there is no carbon nanotube film two-electrode gas temperature sensor.

Therefore, the current research on the carbon nanotube thin film electrode gas temperature sensor and its temperature measurement method has become a technical problem to be solved urgently.

Contents of the invention

One of the purposes of the present invention is to provide a carbon nanotube film three-electrode gas temperature sensor, which divides the output current of the traditional carbon nanotube film two-electrode sensor into electron flow and ion flow, and establishes the three-electrode gas temperature sensor of the present invention to collect The single-value corresponding relationship between the ion flow collected by the electrode and the gas temperature overcomes the problems of high working voltage and narrow range of temperature-sensitive characteristics of the carbon nanotube film two-electrode sensor. The sensor of the invention has simple structure, low cost and high sensitivity for measuring gas temperature.

Another object of the present invention is to provide a temperature measurement method based on a carbon nanotube film three-electrode gas temperature sensor, which measures the temperature of the gas to be measured by the carbon nanotube film three-electrode gas temperature sensor; the hardware structure required by the temperature measurement method Simple, it can measure the temperature of flammable, explosive and toxic gases, and adopts data fusion algorithm to measure the gas temperature with high accuracy.

The purpose of the present invention is achieved through the following technical solutions.

The carbon nanotube film three-electrode gas temperature sensor is characterized in that it includes three first electrodes, second electrodes, and third electrodes distributed sequentially from top to bottom, and the first electrode is bonded with carbon electrodes distributed on the inner surface. The base of the nanotube film and the electrode with air holes; the second electrode is composed of the lead-out electrode plate with the lead-out hole in the center; the third electrode is composed of the collector with the blind hole on the plate surface; the three electrodes are respectively Separated from each other by insulating struts.

Structural feature of the present invention is also in:

The electrode spacing between two adjacent electrodes among the three electrodes is 30-250 μm; the area of the first electrode and the second electrode plate facing each other is 0.01-17mm ² , and the second electrode and the third electrode plate are facing each other The area is 0.01 to 190 mm ² .

The first electrode has 1 to 4 air holes on the electrode surface, and a carbon nanotube film is attached to the substrate bonded to the inner surface of the electrode;

The center of the second electrode lead-out pole is provided with 1 to 4 lead-out holes;

The collector blind hole of the third electrode corresponds to the lead-out hole of the second electrode, and the number of blind holes is 1-4.

The present invention also provides a method for measuring gas temperature based on a carbon nanotube film three-electrode gas temperature sensor, the method comprising the following steps:

(1) Select a carbon nanotube film three-electrode gas temperature sensor with the electrode spacing between two adjacent electrodes set at 30-250 μm among the three electrodes;

(2) Place the carbon nanotube film three-electrode gas temperature sensor in the gas temperature environment to be measured;

(3) The first electrode of the carbon nanotube film three-electrode gas temperature sensor is loaded with a voltage of 0V, the second electrode is loaded with a voltage of 2-200V, and the third electrode is loaded with a voltage of 1-180V;

(4) Within the temperature measurement range of the gas to be measured, corresponding to different temperature calibration values, measure the gas discharge ion current value output by the sensor;

(5) Combine the sensor output ion current value and the corresponding temperature calibration value measured in step (4) to form different experimental calibration samples, and then use segmental interpolation technology to interpolate the experimental calibration samples to obtain interpolation data and interpolation values samples, and build a gas temperature measurement database based on all samples including experimental calibration samples and interpolation samples;

(6) Using multi-subnetwork data fusion technology, build a data fusion instrument, establish a temperature measurement model for the gas temperature sensor, use the data in the gas temperature measurement database as the input sample and expected output sample of the data fusion instrument, and use the range The different data in the data fusion instrument are respectively used as training samples and inspection samples for training and inspection of the data fusion instrument. When the inspection results meet the actual measurement error requirements, the data fusion instrument outputs the accurate temperature measurement model of the sensor;

(7) Input the ion current value output by the carbon nanotube film three-electrode gas temperature sensor into the gas temperature measurement model obtained in step (6), and the model outputs an accurate measurement value of the gas temperature.

The inventive method is also characterized in that:

In the carbon nanotube film three-electrode gas temperature sensor, the potential of the second electrode is higher than the potential of the first electrode, and the potential of the third electrode is lower than the potential of the second electrode and higher than the potential of the first electrode.

The establishment of the gas temperature measurement database is to form a database with experimental calibration data and interpolation data, using the sensor output ion current value and its interpolation data as input samples, and using the gas temperature calibration value and its interpolation data as expected output samples.

The gas temperature measurement method based on the carbon nanotube film three-electrode gas temperature sensor measures the temperature of the gas to be measured by the carbon nanotube film three-electrode gas temperature sensor; it is powered by the sensor voltage source; the output of the sensor is detected by the pA level current measurement system; the electrodes are adjusted The spacing, adjust the electrode voltage, and perform sensor calibration experiments in the gas to be measured; interpolate the experimental calibration data based on segmental interpolation technology to obtain interpolation data; compose all data including experimental calibration data and interpolation data to form a gas temperature measurement database , to obtain the single-value temperature sensitive characteristics of the sensor; according to the data in the gas temperature measurement database, based on the multi-subnetwork data fusion technology, an accurate temperature measurement model of the gas temperature sensor is established; the output of the sensor during actual measurement is input into the gas temperature measurement model in real time , the measured result of the gas temperature can be obtained. The gas temperature measurement method overcomes the problems of high working voltage and narrow measurement range of the carbon nanotube film two-electrode sensor, requires a simple hardware structure, can measure the temperature of flammable, explosive and toxic gases, and has low cost and high sensitivity of measuring gas temperature. High, high accuracy, suitable for popularization.

Since the present invention adopts the carbon nanotube film three-electrode gas temperature sensor to measure the temperature, the measurement of various gas temperatures can be realized with an accuracy of 1%. The sensor of this structure uses carbon nanotube thin film as electrode, and the tip curvature radius of carbon nanotube nanometer level can realize the safe and practical range of reducing the working voltage of the sensor to below 200 volts. By adjusting the electrode spacing and the inter-electrode voltage of two adjacent electrodes of the three-electrode structure, within the temperature measurement range, the problems of high working voltage and narrow temperature measurement range of the carbon nanotube film two-electrode sensor in the prior art can be solved, and The working voltage is lower than 200 volts, and the temperature measurement range is wider, which can be used for temperature measurement of flammable, explosive and toxic gases. Because the present invention adopts the temperature measurement method based on the carbon nanotube film three-electrode gas temperature sensor, and integrates the pA level current measurement technology, segmental interpolation technology and multi-subnetwork data fusion technology, it can realize the accurate measurement of gas temperature.

Description of drawings

Fig. 1 is the relationship between the breakdown voltage and the ambient air temperature of a carbon nanotube film two-electrode temperature sensor in the prior art.

Fig. 2 is the structural representation of carbon nanotube film three-electrode gas temperature sensor of the present invention;

Fig. 3 is a side view of the three-dimensional structure of the carbon nanotube film three-electrode gas temperature sensor of the present invention;

Fig. 4 is the single-value relationship between the gas discharge ion current output by the carbon nanotube thin film three-electrode gas temperature sensor of the present invention and the ambient air temperature;

Fig. 5 is the single-value relationship between the gas discharge ion current output by the carbon nanotube film three-electrode gas temperature sensor of the present invention and the nitrogen ambient temperature.

In the figure: 1, the first electrode; 2, the second electrode; 3, the third electrode; 4, the electrode provided with air holes; 5, the carbon nanotube film substrate; 6, the carbon nanotube film; 7, the insulating support.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

As shown in Fig. 2 and Fig. 3, the carbon nanotube film three-electrode gas temperature sensor comprises three electrodes superimposed on each other from top to bottom in turn, and the three superimposed electrodes are respectively provided with a first electrode 1, a second electrode Two electrodes 2 and a third electrode 3, the first electrode 1 is made of an inner surface bonded with a substrate 5 that is distributed with a carbon nanotube film and an electrode 4 that is provided with air holes; The third electrode 3 is composed of a collector with blind holes on the surface of the electrode plate; the three electrodes are separated from each other by insulating pillars 7 .

In the embodiment of the carbon nanotube film three-electrode gas temperature sensor shown in Fig. 2, there are 2 vent holes on the electrode surface of the first electrode 1, and the vent holes are circular; one side surface of the vent holes is bonded with carbon The nanotube film substrate 5 is distributed with a carbon nanotube film 6 , and the carbon nanotube tube mouth is downward. A lead-out hole is provided in the center of the second electrode 2, and the lead-out hole is circular. The collector blind hole of the third electrode 3 corresponds to the lead-out hole of the second electrode. Fig. 2 and Fig. 3 show an embodiment in which a blind hole is provided and the blind hole is a cylindrical structure. The insulating pillars 7 are respectively arranged between the carbon nanotube film substrate 5 and the second electrode 2, and between the second electrode 2 and the third electrode 3, that is, the insulating pillars 7 are distributed on the carbon surface of the second electrode 2 facing the first electrode 1. The two sides of the surface of both ends of the nanotube film substrate and the two sides of the inner surface of the third electrode 3 .

The present invention is provided with the plate surface of the electrode 4 with air holes and the carbon nanotube film base 5 all adopts silicon chip material to make; The carbon nanotube film 6 is grown on top of the carbon nanotube film 6, or the carbon nanotube film 6 is screen-printed. Both the second electrode 2 and the third electrode 3 are made of silicon wafers. Metal films are provided on the inner surfaces of the electrode 4 and the third electrode 3 provided with air holes, and on both sides of the second electrode 2 .

There are two air holes on the electrode in the first electrode 1 of the present invention, which is convenient for the gas to be measured to enter the electrode gap; the silicon chip substrate with the carbon nanotube film grown on it has electrical conductivity, and is firmly bonded to the inner surface of the first electrode 1; Through the extraction hole of the second electrode 2, the collector of the third electrode 3 can collect the positive ion flow generated by gas ionization. Between the first electrode 1 and the second electrode 3, between the second electrode 2 and the third electrode 3 are isolated from each other by insulating pillars 7; the gas to be measured enters the gap between two adjacent electrodes of the sensor through the gap between the peripheral electrodes of the sensor .

When the carbon nanotube film three-electrode gas temperature sensor with the above structure measures the gas temperature, the second electrode potential is higher than the first electrode potential, and the third electrode potential is lower than the second electrode potential and higher than the first electrode potential. The second electrode forms an electron flow loop with the first electrode, and the third electrode forms an ion flow loop with the first electrode, so as to separate the electron flow from the ion flow. The relationship between the ion flow output by the carbon nanotube film three-electrode gas temperature sensor and the gas temperature, based on a certain voltage applied to the second electrode, presents a single value relationship (shown in Figure 4 and Figure 5). Through segmental interpolation and multi-subnetwork data fusion, the measurement accuracy of gas temperature is 1%. Carbon nanotube film three-electrode sensor technology, pA level current measurement technology, segment interpolation technology and multi-subnetwork data fusion technology are the characteristics of the temperature measurement method of the present invention.

The method for measuring gas temperature by the carbon nanotube thin film three-electrode gas temperature sensor of the present invention will be further described through a specific example below.

Using a carbon nanotube three-electrode gas temperature sensor with a fixed pole spacing, the single-value temperature characteristics in the air were obtained experimentally (as shown in Figure 4). Temperature measurements in less than 1% of air.

In the embodiment of the carbon nanotube thin film three-electrode gas temperature sensor measuring the ambient air temperature shown in FIG. 4 , the experimental environmental conditions are relative humidity 13.0%RH and atmospheric pressure 94.0KPa. The electrode spacing between the adjacent electrodes of the three electrodes of the gas temperature sensor is 170 μm, the area of the first electrode 1 and the second electrode 2 of the sensor is 17 mm ² , and the area of the second electrode 2 and the third electrode 3 is directly opposite is 190mm ² . The cathode voltage of the first electrode of the sensor is 0V, the lead-out electrode of the second electrode is loaded with a voltage of 70V, and the collector of the third electrode is loaded with a voltage of 10V. As the temperature increases, the ion current collected by the collector increases, and the relationship between the ion current and the temperature shows a single-valued increase. In the temperature range of 35-125°C, 10 sets of experimental calibration data were obtained. The ion current value of the gas temperature sensor is used as the input sample, and the gas temperature calibration value is used as the expected output sample data. The temperature range of 35-125°C was divided into two parts, and data fusion was performed separately. Using piecewise linear interpolation, 4 sets of experimental calibration sample data are interpolated within the temperature range of 35-65 ° C, and interpolation is performed at equal intervals at 0.9 ° C to obtain 34 sets of interpolation data, and form a database with 4 sets of experimental calibration data; 34 sets of data are used as training samples, and 4 sets of experimental calibration data are used as test samples, which are input into the data fusion instrument. After training and testing, the temperature measurement model 1 in the temperature range of 35-65°C in the air is obtained. Interpolate the remaining 6 sets of experimental calibration sample data within the temperature range of 65-125°C, perform equidistant interpolation at intervals of 0.7°C, and perform dense interpolation near the temperature attention value (i.e. gas temperature critical value), and obtain 103 sets of interpolation data, and form a database with 6 sets of experimental calibration data; select 103 sets of interpolation data as training samples, and 6 sets of experimental calibration data as test samples, input data fusion instrument, through training and testing, obtain the temperature range of 65 ~ 125 ℃ in the air Temperature Measurement Model 2. The temperature measurement model in the temperature range of 35 to 125°C is composed of temperature measurement model 1 and temperature measurement model 2. Its linearity is 0.30%, and the maximum quoted error of the test results of 10 groups of test samples is 0.34%, reaching 1%. Accuracy of temperature measurement.

Example 2

The basic structure of the sensor of this embodiment is the same as that of Embodiment 1, the difference is:

Among the three electrodes of the carbon nanotube film three-electrode gas temperature sensor, the electrode spacing between two adjacent electrodes is fixed at 170 μm, the first electrode 1 has two vent holes, the second electrode 2 has one lead-out hole, and the third There is one blind hole for the electrode 3 .

Using the carbon nanotube thin film three-electrode gas temperature sensor with fixed electrode spacing, the single-value temperature characteristics in nitrogen were obtained experimentally (as shown in Figure 5). Temperature measurements in nitrogen with a temperature of less than 1%.

In the embodiment shown in Fig. 5 where the carbon nanotube film three-electrode gas temperature sensor measures the nitrogen ambient temperature, the experimental environmental conditions are relative humidity 12.5%RH and atmospheric pressure 94.0KPa. The electrode spacing between the adjacent electrodes of the three electrodes of the gas temperature sensor is 170 μm, the area of the first electrode 1 and the second electrode 2 of the sensor is 17 mm ² , and the area of the second electrode 2 and the third electrode 3 is directly opposite is 190mm ² . The cathode voltage of the first electrode of the sensor is 0V, the lead-out electrode of the second electrode is loaded with a voltage of 70V, and the collector of the third electrode is loaded with a voltage of 10V. As the temperature increases, the ion current collected by the collector increases, and the relationship between the ion current and the temperature shows a single-valued increase. In the temperature range of 25-80°C, 10 sets of experimental calibration data were obtained. The ion current value of the temperature sensor is used as the input sample, and the temperature calibration value is used as the expected output sample data. Using piecewise linear interpolation, interpolation is performed at equal intervals at 1°C intervals within the temperature range of 25-80°C, and dense interpolation is performed near the temperature attention value (i.e., the critical value of gas temperature), and 202 sets of interpolation data are obtained, and compared with 10 Groups of experimental calibration data form a database; 202 sets of interpolation data are selected as training samples, and 10 sets of experimental calibration data are used as test samples, which are input into the data fusion instrument, and the temperature measurement model in nitrogen is obtained through training and testing. The linearity of the temperature measurement model is 0.565%, and the maximum quoted error of the test results of 10 groups of test samples is 0.568%, reaching a temperature measurement accuracy of 1%.

Example 3

The basic structure of this embodiment is the same as that of Embodiment 1, the difference is that the electrode spacing between two adjacent electrodes in the three electrodes of the carbon nanotube film three-electrode gas temperature sensor is 250 μm and 30 μm respectively, and the first electrode 1 and the second electrode The facing area of the plates of the second electrode 2 is 0.01 mm ² , and the facing area of the plates of the second electrode 2 and the third electrode 3 is 0.01 mm ² .

There is one vent hole on the electrode surface of the first electrode 1, and the vent hole is quadrilateral, pentagonal or hexagonal; the second electrode 2 has 4 center lead-out holes, and the lead-out holes are quadrilateral, pentagonal or hexagonal ; The number of blind holes in the third electrode 3 is 4, and the blind holes are 3-6 prisms or pyramids.

The temperature measuring method of the present embodiment is basically the same as embodiment 1, the difference is:

The cathode voltage of the first electrode of the sensor is 0V, the lead-out pole of the second electrode is loaded with a voltage of 2V, and the collector of the third electrode is loaded with a voltage of 1V.

Example 4

The basic structure of this embodiment is the same as that of Embodiment 1, the difference is that the electrode spacing between two adjacent electrodes in the three electrodes of the carbon nanotube film three-electrode gas temperature sensor is 250 μm and 30 μm respectively, and the first electrode 1 and the second electrode The area facing the plates of the second electrode 2 is 10 mm ² , and the area facing the plates of the second electrode 2 and the third electrode 3 is 100 mm ² .

There are 4 vent holes on the electrode surface of the first electrode 1, and the vent holes are quadrilateral, pentagonal or hexagonal; the second electrode 2 has 2 central lead-out holes, and the lead-out holes are quadrilateral, pentagonal or hexagonal ; The number of blind holes in the third electrode 3 is 2, and the blind holes are 3-6 prisms or pyramids.

The temperature measuring method of the present embodiment is basically the same as embodiment 1, the difference is:

The cathode voltage of the first electrode of the sensor is 0V, the lead-out electrode of the second electrode is loaded with a voltage of 200V, and the collector of the third electrode is loaded with a voltage of 180V.

The present invention forms a new type that can measure the temperature of various gases to be measured and has good linearity through the carbon nanotube film three-electrode gas temperature sensor, the pA level current measurement system to measure the sensor output, the segmental interpolation and the multi-subnetwork data fusion method , Gas temperature measurement method with high accuracy. The sensor directly measures the gas temperature and outputs a weak ion current above the pA level; the pA level current measurement system can measure the pA level ion current output by the gas temperature sensor; the segmental interpolation and multi-subnetwork data fusion method can obtain high accuracy gas temperature Measurements.

Although the present invention has been described in detail with the above preferred embodiments, the above embodiments are not intended to limit the present invention. Without departing from the technical features and structural scope provided by the technical solution of the present invention, any addition, deformation or replacement of the technical features with the same content in the field shall belong to the protection scope of the present invention.

Claims (1)

1. The gas temperature measuring method of the carbon nanotube film three-electrode gas temperature sensor is characterized in that: the carbon nanotube film three-electrode gas temperature sensor comprises three first electrodes, a second electrode and a first electrode distributed sequentially from top to bottom Three electrodes, the first electrode is composed of a substrate with a carbon nanotube film distributed on the inner surface and an electrode with air holes; the second electrode is composed of a lead-out plate with a lead-out hole in the center; the third electrode It is composed of collectors with blind holes on the plate surface; the three electrodes are separated from each other by insulating pillars; among them, the potential of the second electrode is higher than the potential of the first electrode, and the potential of the third electrode is lower than the potential of the second electrode and higher than the potential of the third electrode. One electrode potential; the second electrode and the first electrode form an electron flow loop, and the third electrode and the first electrode form an ion flow loop to separate the electron flow from the ion flow; The method comprises the steps of: (1) Select a carbon nanotube film three-electrode gas temperature sensor with the electrode spacing between two adjacent electrodes set at 30-250 μm among the three electrodes; (2) Place the carbon nanotube film three-electrode gas temperature sensor in the gas temperature environment to be measured; (3) The first electrode of the carbon nanotube film three-electrode gas temperature sensor is loaded with a voltage of 0V, the second electrode is loaded with a voltage of 2-200V, and the third electrode is loaded with a voltage of 1-180V; (4) Within the temperature measurement range of the gas to be measured, corresponding to different temperature calibration values, measure the gas discharge ion current value output by the sensor; (5) Combine the sensor output ion current value and the corresponding temperature calibration value measured in step (4) to form different experimental calibration samples, and then use segmental interpolation technology to interpolate the experimental calibration samples to obtain interpolation data and interpolation values samples, and build a gas temperature measurement database based on all samples including experimental calibration samples and interpolation samples; (6) Using multi-subnetwork data fusion technology, build a data fusion instrument, establish a temperature measurement model for the gas temperature sensor, use the data in the gas temperature measurement database as the input sample and expected output sample of the data fusion instrument, and use the range The different data in the data fusion instrument are respectively used as training samples and inspection samples for training and inspection of the data fusion instrument. When the inspection results meet the actual measurement error requirements, the data fusion instrument outputs the accurate temperature measurement model of the sensor; (7) Input the ion current value output by the carbon nanotube film three-electrode gas temperature sensor into the temperature measurement model of the gas temperature sensor established in step (6), and the model outputs an accurate measurement value of the gas temperature.

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