CN105388187B - The test method of the semiconductor gas sensor of controlled humidity - Google Patents
The test method of the semiconductor gas sensor of controlled humidity Download PDFInfo
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
- F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
- F24F3/14—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D22/00—Control of humidity
- G05D22/02—Control of humidity characterised by the use of electric means
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Abstract
The test method of the semiconductor gas sensor of controlled humidity belongs to element test field, and the test method for solving the problems, such as existing formaldehyde gas sensor is incomplete, and the problem that humid control precision is low, technical essential are：Have：Semiconductor gas sensor tests the step of system buildup is with test, a kind of humidity control system has been used in the step, including master controller, moisture detection sensor, dehumidifier, ultrasonic humidifier and buzzer, wherein, moisture detection sensor, dehumidifier and ultrasonic humidifier are installed in gas chamber, and master controller is connect with moisture detection sensor, dehumidifier, ultrasonic humidifier, buzzer respectively.The invention enables the test for formaldehyde gas sensor is more perfect, and improve the controllability and control accuracy of humidity.
Description
Technical Field
The invention belongs to the field of element test, and particularly relates to a method for testing a humidity-controllable semiconductor gas-sensitive element.
Background
While the development of semiconductor gas sensor technology is well-established, the development of semiconductor gas sensor testing technology has not kept pace with the development of gas sensor technology. Human awareness and remodeling activities of the objective world are often based on testing efforts. The engineering test technology is an emerging technology which utilizes a modern test means to detect, test and analyze various signals in engineering, particularly dynamic physical signals changing along with time, and extracts useful information from the signals. The measured and analyzed results objectively describe the state, change and characteristics of the research object and provide reliable basis for further modification and control of the research object. Also, advances in sensor technology have not been made without any improvement in the means of testing. At present, an important factor limiting the research progress and the large-scale production of the semiconductor gas sensor is that the detection means is backward, the test environment is complex, the test efficiency and the precision are low, and meanwhile, complete parameters and curves of various characteristics of the gas sensor cannot be obtained due to the lack of perfect test equipment, and the further research and application of the semiconductor gas sensor are also limited, so that a perfect semiconductor gas sensor performance parameter test system is urgently needed for both production and scientific research.
Because of the practical significance of semiconductor gas sensors and the importance of gas sensor testing, researchers at home and abroad carry out a great deal of intensive research work on the testing systems of semiconductor gas sensors, and the researchers build the testing systems of semiconductor gas sensors with different functions in different modes, thereby playing an important role in the development of sensor performance testing and calibration technology. The automatic test system is designed by scholars of foreign L.Harvey, G.s.v., coles, Hildegard D.Jander, Wolfgang Gottler and the like, can test the gas sensor in pure air, single gas and mixed gas, and simultaneously considers the influence of environmental temperature and humidity on performance parameters, but a plurality of operations need to be carried out manually, so that a tester cannot be far away from a toxic test environment, the automation degree of the tester needs to be further improved, the types of parameters capable of being tested are few, and the shape of the tested semiconductor gas sensor is limited; the domestic scholars such as Tuoyu, Pengzhi and Lin Yongbing also develop a set of automatic test system in turn, integrate a test chamber and a detection system into a whole, and provide reliable data for new product development, but the degree of automation is not high enough, the acquired parameters are single, the used hardware is excessive, the reliability is not high, various pure gases are difficult to mix in the high dynamic and low concentration range, and the required concentration and precision requirements are difficult to meet. There are also difficulties in achieving inspection and grading of gas sensors. Many manufacturers mainly use manual testing, have low testing efficiency and low precision, and are far from meeting the requirements of production development, and more importantly, the manual testing cannot realize dynamic measurement, so that some parameters of the gas sensitive element, such as a response time curve, a recovery time curve and the like, cannot be accurately measured. The defect that complete parameters of various characteristics of the gas sensor cannot be obtained limits further research and application of the gas sensor. In order to meet the requirements of enterprise production and research, the development of the gas sensor needs a complete set of complete testing system.
In the process of developing the semiconductor gas sensor, the gas response characteristics of the sensor under different environments and working conditions need to be researched, the quality of the sensor is measured, and the optimal working state is found out in summary, so that good testing equipment cannot be used.
At present, two test modes of static state and gas flow are used for researching the gas response characteristics of a semiconductor gas sensor, the sensor is installed in a gas chamber, certain gas with known concentration is injected into the gas chamber, and the gas-sensitive response characteristics of the sensor to the gas can be obtained by collecting the response signals of the sensor. In general, a system for performing static tests adopts a closed large-capacity gas chamber, and sample gas is injected and uniformly mixed in a container to form test gas with a certain volume. The gas flow mode is that gas flow with constant flow is introduced into a gas chamber with smaller capacity, sample gas with certain concentration is passed through in a time period, and sensor response data in the time period is collected. In the mode, because the gas chamber is small, the time for cleaning residual gas is short, the sensor device can be quickly recovered to the initial state, repeated experiments can be quickly carried out, and the method is particularly favorable for researching the gas-sensitive characteristic of the sensor array.
Disclosure of Invention
In order to solve the technical problems and accurately control the humidity in the testing process, the invention provides a testing method of a humidity-controllable semiconductor gas sensitive element.
The technical scheme adopted by the invention is as follows: a method for testing a humidity-controllable semiconductor gas sensor comprises:
the method comprises the steps of constructing and testing a semiconductor gas sensor testing system, and analyzing the performance of the semiconductor gas sensor testing system and a semiconductor gas sensitive element; wherein,
the step of building and testing the gas sensor testing system is provided with a step of controlling the humidity of the gas chamber, a humidity control system is used in the step, and the humidity control system comprises a main controller, a humidity detection sensor, a dehumidifier, an ultrasonic humidifier and a buzzer, wherein the humidity detection sensor, the dehumidifier and the ultrasonic humidifier are installed in the gas chamber, and the main controller is respectively connected with the humidity detection sensor, the dehumidifier, the ultrasonic humidifier and the buzzer.
Furthermore, in the step of building and testing the semiconductor gas sensor test system, the semiconductor gas sensor test system is used for dynamically distributing different gases under given concentration and enabling the multiple sensor arrays to monitor the change of the surface conductivity of the gas sensitive element in real time when the gases are introduced;
the semiconductor gas sensor test system includes: the system comprises a sample feeding device for automatically carrying out sample gas concentration proportioning, a gas sensor heating and temperature measuring device, a signal measuring and data collecting circuit for coordinating with the sample feeding device and automatically collecting 4-6 paths of gas sensor measuring signals under different gas sample environments, and a data processing circuit for carrying out data processing on the collected measuring signals; and a temperature compensation circuit for compensating for temperature variations caused by changes in the intake process and room temperature;
the gas sensor array is arranged in the gas chamber, the change of the gas concentration measured by the gas sensor is the change of the gas in the gas chamber, and the gas chamber is a dry organic glass chamber with a smooth inner cavity and a square approximate shape;
the gas sensor heating and temperature measuring device heats the gas sensitive element and measures the working temperature of the gas sensor in real time; when the working temperature of the sensor changes due to the influence of the ambient temperature or the airflow, the temperature compensation circuit carries out temperature compensation control in real time so as to keep the working temperature of the sensor unchanged; the signal measurement and data acquisition circuit is used for adjusting and AD sampling signals, the signal adjustment is used for converting the response of the gas sensor to a test gas sample into an electric signal, the AD sampling is used for converting an analog signal into a digital signal through the data processing circuit, and the acquired 4-6 paths of sensor signals are converted into standard signals required by a BP neural network through normalization processing;
the standard gas sample output is divided into two paths or multiple paths, each path is controlled by a mass flow controller and is connected into a testing device, carrier gas and gas to be tested enter a drying tank to be fully mixed under the control of the mass flow controller respectively to prepare a target testing gas sample and enter a testing cavity in the testing device, a gas sensor testing system distributes gas with set target concentration under the control of a computer, one or more target gas samples with standard concentration and standard carrier gas are proportioned according to the proportion and are introduced into a mixing channel to be fully mixed under the control of the mass flow controller, when the mixed testing gas sample is introduced into the testing cavity, 4-6 paths of response signals of a gas sensor array in a gas chamber are collected, and the obtained response information of the gas sensor array to the sample gas is transmitted to the computer for data processing and data analysis, carrying out test gas inlet, response signal acquisition and data processing in sequence; when the temperature monitoring system finds that the working temperature of the semiconductor gas sensitive element changes, the temperature compensation circuit compensates the working temperature of the element in real time, and adjusts the heating voltage of the resistance wire to keep the working temperature of the element unchanged;
the humidity detection sensor detects a humidity signal in the air chamber in real time and transmits the signal to the main controller, the main controller compares the humidity signal with a set value of the controller based on a constant humidity set value or a set humidity range in the air chamber, and the controller outputs a split-range control signal; when the humidity in the air chamber is lower than 10% RH and the humidifier is opened to the maximum, the system can not continue to humidify, or the humidity in the air chamber is higher than 60% RH and the dehumidifier is opened to the maximum, the main controller controls the buzzer to sound, calls the main controller to interrupt, stops signal output to the dehumidifier and the ultrasonic humidifier, and automatically cuts off the power supply and stops testing when the humidity exceeds 60% RH.
Further, the software part of the gas sensor testing system comprises a gas path control module, a voltage sampling module, a temperature compensation module, a data processing module and a display function module, wherein:
the gas circuit control module sets control parameters, wherein the parameters comprise pre-aeration time, post-aeration time, data sampling time interval, mixed gas types, various gas concentrations and carrier gas control voltage;
the voltage sampling module correspondingly controls the start of voltage sampling, the interruption of sampling and the end of sampling;
the data processing module is used for carrying out data acquisition, data storage, image printing and historical data extraction processing.
Further, the data acquisition module finishes data tracking acquisition in a sampling time interval, provided experimental data are automatically stored into six files with two formats after the experiment is finished, the six files are respectively the voltage, the resistance, the response sensitivity digital quantity and the dynamic change curve of a 4-6-path sensor, and simultaneously, the stored image is printed instantly and historical data is extracted according to time; and in the data acquisition process, displaying the dynamic change curves of the standard voltage, the resistance and the response sensitivity of the 4-6 sensors along with time in a display module according to different requirements in real time.
5. The method for testing a humidity-controlled semiconductor gas sensor as recited in claim 4, wherein the step of analyzing the gas sensor test system and the gas sensor performance comprises analyzing various errors of the gas sensor test system, analyzing sensitivity of a measuring resistor, a temperature characteristic of the resistor, a sensitivity-temperature characteristic, a sensitivity-concentration characteristic, and an influence of doping on the element performance.
Further, 4-6 road standard signals adopted by the sensor are subjected to data normalization processing, the data are processed into a BP neural network to obtain a required standard data source, and the BP neural network gas analysis is carried out according to the following steps:
quantitative analysis:
selecting a single formaldehyde gas to detect a sample, carrying out quantitative detection, forming a sensor array by 4-6 sensors to carry out quantitative identification on formaldehyde gas, ammonia gas, benzene and other mixed gases, wherein the number of input neurons of a neural network is 6, the number of output neurons of the neural network is 1, dynamically changing the number of hidden layers, and solving the corresponding training errors of the hidden layers to determine the optimal number of hidden layer neurons;
creating a two-layer network by using a newff function, setting the number of hidden layer neurons of the network as S (i), setting the range of S (i) to be 3-13, setting a training function of the network as Trainbr, setting the weight and the threshold of the network as random variables with special distribution, estimating the weight and the threshold of the network by using a statistical method, taking an input vector P as the input of the trained neural network, training the network by using a train function, and quantitatively detecting 30 groups of formaldehyde gases with different concentrations as the input to obtain the output result of quantitative detection and corresponding experimental errors;
and (3) qualitative analysis:
the method comprises the following steps that a sensor array consisting of 4-6 sensors qualitatively identifies characteristic quantities of formaldehyde, ammonia gas and benzene, the number of input neurons of a network is 6, the number of output neurons of the network is 3, the optimal hidden layer number is determined through error comparison, and the hidden layer number is dynamically changed;
creating a three-layer network by using a newff function, setting the neuron number of a hidden layer of the network as a dynamic variable S (i) with the range of 3-13, obtaining a group of neuron numbers with the minimum training error as the optimal neuron number through 10 times of training, setting the weight and threshold of the network as random variables with special distribution, and estimating the weight and threshold of the network by using a statistical method; training is stopped until experimental errors meet requirements; the odd group is used as the input of the trained neural network.
Further, humidity control system, still include the host computer, the host computer has man-machine interaction interface to human-machine interaction operation shows humidity set value and humidity measurement value in real time, main control unit is PLC, and uses PLC's PID adjusting module to carry out closed-loop control to the humidity in the air chamber.
Further, the method for controlling humidity by using the STEP 7 software comprises the following STEPs:
creating items and hardware configuration: firstly, entering a STEP 7 software interface, clicking a menu, creating a new item, clicking an item name on the left menu of a right button, clicking and inserting an S7-300 site, double clicking to open the inserted S7-300 site, double clicking to hardware of a right window, and performing hardware configuration on a popped hardware window;
configuration:
and finding the rack in the right frame, clicking the slot 2 after double-clicking the set rack, finding the CPU with the corresponding model in the right frame, and inserting the CPU into the slot 2 after double-clicking. Then double clicking the CPU, setting a corresponding subnet MPI in a pop-up window, and inserting the analog input module into the No. 4 slot in the same operation as inserting the CPU;
after all the hardware is inserted into the corresponding slots, clicking a shortcut key of 'save and compile' of the upper menu bar to complete the hardware configuration, and returning to the STEP 7 main interface to perform the next programming;
an OB1 organization block appears on a main interface after hardware configuration is completed, other needed organization blocks and logic blocks are added in a blank position, the insertion of an upper menu bar is clicked, an S7 module is clicked in a popped pull-down menu, and the module needed to be added is selected;
the programming method needed by each part control is as follows: the automatic control system comprises a manual automatic switch, a manual dehumidification start-stop, a manual humidification start-stop and a manual operation output, wherein an intermediate relay is used for simulating the opening and closing of a normally open and normally closed contact so as to achieve the purposes of control and self-locking, when the humidity is lower than 20% RH and higher than 40% RH, an alarm is given, an output coil is arranged with 1, a buzzer is enabled to whistle, a main program is interrupted, and all pulses sent to an external solid-state relay are stopped, namely, the dehumidification or humidification of a dehumidifier and an ultrasonic humidifier are realized;
the PID regulating module is used for carrying out closed-loop regulation on the humidity, and the closed-loop regulation is FB58 'TCONT _ CP', and is used for controlling a continuous humidity processing process or a humidity processing process with a pulse signal; calling the module can generate a background data block DB58, double-clicking a DB58 background data block of a main interface, clicking a viewing parameter, and observing data on a popped interface;
the method for setting the parameters of the FB58 module is as follows:
(1) PV _ IN is a set value of a controlled variable;
(2) SP _ INT is the actual value of the controlled variable and needs to input a humidity measured value;
(3) QPULSE is output pulse and is connected with an external solid-state relay;
the internal variable setting method comprises the following steps:
(1) the GAIN of the dehumidification calling module is set to be negative, the GAIN is set to be-4.0, and the GAIN value is positive in the humidifying part and the GAIN initial value is 2;
(2) PULSE _ ON turns ON the PULSE generator, which is activated when this value is changed from FALSE to true;
(3) TI integral action reset time, the initial value is 4.0S;
(4) the reset time of TD differential action is 1.0S as the initial value;
(5) TUN _ ON self-adjusts open, here changing the initial value FALSE to TURE;
(6) TUN _ ST initiates self-adjustment, where the initial value FALSE is changed to TURE.
Has the advantages that:
1. the invention can realize the distribution of common test gas in the conventional test concentration range with high precision; multiple sensors or gas sensor arrays can be tested simultaneously.
2. The invention can realize multi-parameter measurement: because the test system is modularized, a plurality of measurement modules can be connected at the same time, and each measurement module can realize multi-channel measurement, the simultaneous test of a plurality of kinds of parameters is easy to realize.
3. The invention prepares and tests the sensitive elements of various doping technologies, and makes the semiconductor gas sensitive element have progress in detecting volatile organic gases.
4. The invention realizes qualitative identification of various gases and quantitative identification of single gas by combining the gas sensor array with the artificial neural network technology and based on the BP algorithm.
5. The humidity control system provided by the invention can effectively perform control such as humidity sensing, dehumidification, humidification, humidity display, humidity alarm and the like on a humidity environment. The humidity can be effectively monitored and controlled, the test process is smoothly carried out, the humidity control in a closed environment within the humidity range of 10-60% RH is realized, the dehumidification effect is obvious, and the requirement on the humidity control during the test of the gas sensitive element is effectively met. And the invention sets the system to be powered off when the humidity of the air chamber exceeds 60% RH, aiming at ensuring that the test is carried out in a safe environment, and when the humidity exceeds 60% RH, the test system is in a dangerous state and is not suitable for the test experiment.
Drawings
FIG. 1 is a flowchart of a method of example 1 of the present invention;
FIG. 2 is a schematic diagram of a closed loop process of a semiconductor gas sensor test system according to embodiment 2 of the present invention;
fig. 3 is a block diagram showing the structure of a semiconductor gas sensor test system according to embodiment 2 of the present invention; (humidity control system has been added)
FIG. 4 is a software functional block diagram of embodiment 3 of the present invention;
FIG. 5 is a measurement circuit of a semiconductor gas sensor test system in embodiment 5 of the present invention;
FIG. 6.1 is a schematic diagram of the structure of the quantitatively identified BP neural network in embodiment 6 of the present invention;
FIG. 6.2 is a schematic diagram of the training process of the quantitative gas detection in example 6 of the present invention;
FIG. 6.3 is a diagram showing the structure of a qualitatively identified BP neural network in embodiment 6 of the present invention;
FIG. 6.4 is a diagram showing the result of the qualitative analysis training in example 6 of the present invention;
FIG. 7 is a schematic block diagram of a humidity control system according to the present invention;
FIG. 8 is a block diagram of a closed loop control system for the humidity control system of the present invention.
Detailed Description
Example 1:
a method for testing a humidity-controllable semiconductor gas sensor comprises: SnO2The method comprises the steps of preparing a gas sensitive material, manufacturing a gas sensitive element, building and testing a semiconductor gas sensor testing system, and analyzing the performance of the semiconductor gas sensor testing system and the semiconductor gas sensitive element.
The step of building and testing the gas sensor testing system is provided with a step of controlling the humidity of the gas chamber, a humidity control system is used in the step, and the humidity control system comprises a main controller, a humidity detection sensor, a dehumidifier, an ultrasonic humidifier and a buzzer, wherein the humidity detection sensor, the dehumidifier and the ultrasonic humidifier are installed in the gas chamber, and the main controller is respectively connected with the humidity detection sensor, the dehumidifier, the ultrasonic humidifier and the buzzer.
Example 2:
the technical scheme is the same as that of the embodiment 1, and more specifically comprises the following steps: SnO2The preparation method of the gas sensitive material comprises the following steps: with SnCl4·5H2Taking O as raw material and dilute ammonia water as precipitator, weighing a certain amount of SnCl4·5H2Dissolving O raw material in a proper amount of deionized water, adding a small amount of citric acid, stirring to completely dissolve the O raw material, and heating to boil for reaction; slowly dripping prepared diluted ammonia water into SnCl4Stirring in water solution, and heating until precipitation is completeWashing with water, centrifugally cleaning for many times to remove Cl & lt- & gt in the precipitate, drying the precipitate at 60-100 ℃, grinding the precipitate, and firing the ground precipitate in a muffle furnace at about 700 ℃ for 2-4 hours to obtain SnO2A gas sensitive material.
Example 3:
the technical scheme is the same as that of the embodiment 1 or 2, and more specifically comprises the following steps: in the manufacturing step of the gas sensor, the tube core of the sensor is provided with a capillary ceramic tube, a heating wire penetrates into the ceramic tube, a metal electrode is coated outside the ceramic tube to be used as a signal electrode for measuring the resistance of the sensor, and a gas-sensitive material SnO is coated outside the metal electrode2And firing to obtain the product;
the manufacturing steps are as follows: the ceramic tube substrate coated with metal electrodes at two ends is sequentially cleaned by toluene, alcohol and deionized water in an ultrasonic mode, ground slurry is coated on the surface of the ceramic tube after being dried under an infrared lamp, the ceramic tube substrate is dried under the infrared lamp and then sintered in a tubular resistance furnace, finally a heating wire with a proper resistance value penetrates into a burnt tube core, an electrode lead and a heating wire lead are welded on a tube seat of an element, a gas sensor is manufactured, and the gas sensor is manufactured by using the gas sensor.
The structure overcomes the defects of a direct heating element, avoids mutual interference between a measuring loop and a heating loop because the heating wire is not contacted with the gas sensitive material, greatly improves the consistency of the element performance and greatly improves the mechanical strength.
Example 4:
the technical scheme is the same as that of the embodiment 1, 2 or 3, and more specifically is as follows: in the step of building and testing the semiconductor gas sensor testing system, the semiconductor gas sensor testing system is used for dynamically distributing different gases under given concentration and enabling a plurality of sensor arrays to monitor the change of the surface conductivity of the gas sensitive element in real time when the gases are introduced;
the semiconductor gas sensor test system includes: the system comprises a sample feeding device for automatically carrying out sample gas concentration proportioning, a gas sensor heating and temperature measuring device, a signal measuring and data collecting circuit for coordinating with the sample feeding device and automatically collecting 4-6 paths of gas sensor measuring signals under different gas sample environments, and a data processing circuit for carrying out data processing on the collected measuring signals; and a temperature compensation circuit for compensating for temperature variations caused by changes in the intake process and room temperature; the coordination action with the sample injection device means that the signal acquisition and the sample injection are synchronous or corresponding, so that the coordination of the sample injection and the acquisition in time sequence can be realized.
The gas sensor array is arranged in the gas chamber, the change of the gas concentration measured by the gas sensor is the change of the gas in the gas chamber, and the gas chamber is a dry organic glass chamber with a smooth inner cavity and a square approximate shape;
the gas sensor heating and temperature measuring device heats the gas sensitive element and measures the working temperature of the gas sensor in real time; when the working temperature of the sensor changes due to the influence of the ambient temperature or the airflow, the temperature compensation circuit carries out temperature compensation control in real time so as to keep the working temperature of the sensor unchanged; the signal measurement and data acquisition circuit is used for adjusting and AD sampling signals, the signal adjustment is used for converting the response of the gas sensor to a test gas sample into an electric signal, the AD sampling is used for converting an analog signal into a digital signal through the data processing circuit, and the acquired 4-6 paths of sensor signals are converted into standard signals required by a BP neural network through normalization processing;
the humidity detection sensor detects a humidity signal in the air chamber in real time and transmits the signal to the main controller, the main controller compares the humidity signal with a set value of the controller based on a constant humidity set value or a set humidity range in the air chamber, and the controller outputs a split-range control signal; when the humidity in the air chamber is lower than 10% RH and the humidifier is opened to the maximum, the system can not continue to humidify, or the humidity in the air chamber is higher than 60% RH and the dehumidifier is opened to the maximum, the main controller controls the buzzer to sound, calls the main controller to interrupt, stops signal output to the dehumidifier and the ultrasonic humidifier, and automatically cuts off the power supply and stops testing when the humidity exceeds 60% RH.
Humidity control system, still include the host computer, the host computer has man-machine interaction interface to human-machine interaction operation shows humidity set value and humidity measurement value in real time, main control unit is PLC, and uses PLC's PID regulating module to carry out closed-loop control to the humidity in the air chamber.
Wherein: a Programmable Controller (Programmable Controller) is a member of the computer family, and is manufactured for industrial control applications, and an early Programmable Controller is called a Programmable Logic Controller (PLC), which is called PLC for short, and is mainly used to replace a relay to realize logic control. Although today's PLCs have long been able to perform more than just the task of logic control, they are still called PLCs by their habit, but they are called programmable controllers (PLC) by the name of Chinese. The embodiment uses the S7-300 PLC manufactured by Siemens company, belongs to a medium PLC, adopts a modular structure and has wide application range.
The humidity sensitive element is the simplest humidity sensor, the humidity sensitive element mainly comprises a resistance type humidity sensor and a capacitance type humidity sensor, the embodiment adopts an HM1500 humidity sensor, which belongs to the capacitance type humidity sensor, and particularly, the humidity sensitive element is a linear voltage output type integrated humidity sensor.
The methods of dehumidification are quite abundant, the most common being through-air drying. The more effective way of indoor dehumidification is to select different types of dehumidifiers, which are classified into a freezing dehumidifier, a rotary dehumidifier and an electro-osmotic dehumidifier due to different working principles. Most of household dehumidifiers are refrigeration type dehumidifiers, and the dehumidification method adopted by the embodiment belongs to the refrigeration type dehumidifier category.
The humidification mode is very abundant, and traditional humidification is sprayed water on the ground, utilizes the natural evaporation of moisture in order to reach the purpose that increases air humidity. Modern times mainly utilize humidifiers for humidification. The humidifier can be classified into an industrial use, a commercial use and a household use through different use ranges. Heat evaporation type humidifiers are commonly used in industry, and ultrasonic humidifiers are generally used commercially. Many home humidifiers choose pure type humidifiers. The embodiment adopts an ultrasonic humidifier, and the humidifying module mainly comprises a power supply unit (the same as the humidifying unit), an ultrasonic transducer, a water pool and a fan.
The method for controlling humidity by using STEP 7 software in this embodiment is as follows:
creating items and hardware configuration: firstly, entering a STEP 7 software interface, clicking a menu, creating a new item, clicking an item name on the left menu of a right button, clicking and inserting an S7-300 site, double clicking to open the inserted S7-300 site, double clicking to hardware of a right window, and performing hardware configuration on a popped hardware window;
configuration:
and finding the rack in the right frame, clicking the slot 2 after double-clicking the set rack, finding the CPU with the corresponding model in the right frame, and inserting the CPU into the slot 2 after double-clicking. Then double clicking the CPU, setting a corresponding subnet MPI in a pop-up window, and inserting the analog input module into the No. 4 slot in the same operation as inserting the CPU;
after all the hardware is inserted into the corresponding slots, clicking a shortcut key of 'save and compile' of the upper menu bar to complete the hardware configuration, and returning to the STEP 7 main interface to perform the next programming;
an OB1 organization block appears on a main interface after hardware configuration is completed, other needed organization blocks and logic blocks are added in a blank position, the insertion of an upper menu bar is clicked, an S7 module is clicked in a popped pull-down menu, and the module needed to be added is selected;
the programming method needed by each part control is as follows: the automatic control system comprises a manual automatic switch, a manual dehumidification start-stop, a manual humidification start-stop and a manual operation output, wherein an intermediate relay is used for simulating the opening and closing of a normally open and normally closed contact so as to achieve the purposes of control and self-locking, when the humidity is lower than 20% RH and higher than 40% RH, an alarm is given, an output coil is arranged with 1, a buzzer is enabled to whistle, a main program is interrupted, and all pulses sent to an external solid-state relay are stopped, namely, the dehumidification or humidification of a dehumidifier and an ultrasonic humidifier are realized;
the PID regulating module is used for carrying out closed-loop regulation on the humidity, and the closed-loop regulation is FB58 'TCONT _ CP', and is used for controlling a continuous humidity processing process or a humidity processing process with a pulse signal; calling the module can generate a background data block DB58, double-clicking a DB58 background data block of a main interface, clicking a viewing parameter, and observing data on a popped interface;
the method for setting the parameters of the FB58 module is as follows:
(1) PV _ IN is a set value of a controlled variable;
(2) SP _ INT is the actual value of the controlled variable and needs to input a humidity measured value;
(3) QPULSE is output pulse and is connected with an external solid-state relay;
the internal variable setting method comprises the following steps:
(7) the GAIN of the dehumidification calling module is set to be negative, the GAIN is set to be-4.0, and the GAIN value is positive in the humidifying part and the GAIN initial value is 2;
(8) PULSE _ ON turns ON the PULSE generator, which is activated when this value is changed from FALSE to true;
(9) TI integral action reset time, the initial value is 4.0S;
(10) the reset time of TD differential action is 1.0S as the initial value;
(11) TUN _ ON self-adjusts open, here changing the initial value FALSE to TURE;
(12) TUN _ ST initiates self-adjustment, where the initial value FALSE is changed to TURE.
During the testing process of the semiconductor gas sensitive element: the standard gas sample output is divided into two paths or multiple paths, each path is controlled by a mass flow controller and is connected into a testing device, carrier gas and gas to be tested enter a drying tank to be fully mixed under the control of the mass flow controller respectively to prepare a target testing gas sample and enter a testing cavity in the testing device, a gas sensor testing system distributes gas with set target concentration under the control of a computer, one or more target gas samples with standard concentration and standard carrier gas are proportioned according to the proportion and are introduced into a mixing channel to be fully mixed under the control of the mass flow controller, when the mixed testing gas sample is introduced into the testing cavity, 4-6 paths of response signals of a gas sensor array in a gas chamber are collected, and the obtained response information of the gas sensor array to the sample gas is transmitted to the computer for data processing and data analysis, carrying out test gas inlet, response signal acquisition and data processing in sequence; when the temperature monitoring system finds that the working temperature of the semiconductor gas sensitive element changes, the temperature compensation circuit compensates the working temperature of the element in real time, and the heating voltage of the resistance wire is adjusted to keep the working temperature of the element unchanged.
Wherein: because the working characteristics of the semiconductor gas sensitive element are related to the temperature, the semiconductor gas sensitive element needs to be heated, the working temperature of the gas sensitive element directly influences the sensitivity of the sensor, and meanwhile, the temperature sensor is needed to measure the working temperature of the gas sensor in real time, so that the testing system in the embodiment is provided with a gas sensor heating and temperature measuring device and a working temperature compensation circuit.
In the test, the heating resistance wire is selected to be nickel-chromium alloy, the resistance is 30 ohms, and the heating voltage is controlled by adopting a direct current power supply, so that the working temperature of the gas sensitive element is controlled. The thermocouple temperature sensor for measuring temperature detects the temperature of the surface of the ceramic tube, but the temperature is obtained by directly detecting the surface of the element through the thermocouple, the surface of the contact element has small surface area, the surface material is extremely easy to damage after being contacted, and the surface temperature of the element is reduced during temperature measurement, so that certain deviation is brought to measurement.
| Heating voltage | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
| Temperature (. degree.C.) | 26 | 55 | 89 | 137 | 179 | 225 | 268 | 302 | 343 | 377 | 416 |
The output of the standard gas sample is divided into two paths or multiple paths, each path is controlled by a mass flow controller and is connected into a testing device, carrier gas and gas to be tested (such as formaldehyde, ammonia, benzene, carbon monoxide, oxygen and the like) respectively enter a drying tank to be fully mixed under the control of the mass flow controller to be prepared into a testing gas sample and enter a testing cavity in the testing device, a gas sensor testing system distributes gas with set target concentration under the control of a computer, the target gas sample with one or more standard concentrations and the standard carrier gas are proportioned according to the proportion and are introduced into a mixing channel to be fully mixed under the control of the mass flow controller, when the mixed testing gas sample is introduced into a gas chamber, response signals of a gas sensor array in the gas chamber are collected, and the obtained response information of the gas sensor array to the sample gas is transmitted to the computer for data analysis, carrying out test gas inlet, response signal acquisition and data processing in sequence; when the temperature monitoring system finds that the working temperature of the semiconductor gas sensitive element changes, the temperature compensation circuit compensates the working temperature of the element in real time, and the heating voltage of the resistance wire is adjusted to keep the working temperature of the element unchanged. The method overcomes the defects that the traditional test method not only consumes excessive manpower, but also has a plurality of unstable factors due to manual operation, so that a large deviation value is added to the measurement.
In order to observe the response process visually, the corresponding application software on the computer is provided with a graphical interface and can display the response curve of the sensor array in real time.
Example 5:
the method has the same technical scheme as that of the embodiment 1, 2, 3 or 4, and more specifically comprises the following steps: the software part of the gas sensor testing system comprises a gas path control module, a voltage sampling module, a temperature compensation module, a data processing module and a display function module, wherein:
the gas circuit control module sets control parameters, wherein the parameters comprise pre-aeration time, post-aeration time, data sampling time interval, mixed gas types, various gas concentrations and carrier gas control voltage;
the voltage sampling module correspondingly controls the start of voltage sampling, the interruption of sampling and the end of sampling;
the data processing module is used for carrying out data acquisition, data storage, image printing and historical data extraction processing.
Example 6:
the method has the same technical scheme as that of the embodiment 1, 2, 3, 4 or 5, and more specifically comprises the following steps: the data acquisition module finishes data tracking acquisition in a sampling time interval, provided experimental data are automatically stored into six files with two formats after the experiment is finished, the six files are respectively the voltage, the resistance, the response sensitivity digital quantity and the dynamic change curve of a 4-6-path sensor, and simultaneously, the stored image is printed immediately and historical data is extracted in time; and in the data acquisition process, displaying the dynamic change curves of the standard voltage, the resistance and the response sensitivity of the 4-6 sensors along with time in a display module according to different requirements in real time.
Example 7:
the method has the same technical scheme as that of the embodiment 1, 2, 3, 4, 5 or 6, and more specifically comprises the following steps: the step of analyzing the performance of the gas sensor testing system and the gas sensitive element comprises the steps of analyzing various errors of the gas sensor testing system, analyzing the sensitivity, the resistance temperature characteristic, the sensitivity-temperature characteristic and the sensitivity-concentration characteristic of the measuring resistor and analyzing the influence of doping on the element performance.
Example 8:
the method has the same technical scheme as that of the embodiment 1, 2, 3, 4, 5, 6 or 7, and more specifically comprises the following steps: carrying out data normalization processing on 4-6 road standard signals adopted by the sensor, processing the data into a BP neural network to obtain a required standard data source, and carrying out BP neural network gas analysis according to the following steps:
quantitative analysis:
selecting a single formaldehyde gas to detect a sample, carrying out quantitative detection, forming a sensor array by 4-6 sensors to carry out quantitative identification on formaldehyde gas, ammonia gas, benzene and other mixed gases, wherein the number of input neurons of a neural network is 6, the number of output neurons of the neural network is 1, dynamically changing the number of hidden layers, and solving the corresponding training errors of the hidden layers to determine the optimal number of hidden layer neurons;
creating a two-layer network by using a newff function, setting the number of hidden layer neurons of the network as S (i), setting the range of S (i) to be 3-13, setting a training function of the network as Trainbr, setting the weight and the threshold of the network as random variables with special distribution, estimating the weight and the threshold of the network by using a statistical method, taking an input vector P as the input of the trained neural network, training the network by using a train function, and quantitatively detecting 30 groups of formaldehyde gases with different concentrations as the input to obtain the output result of quantitative detection and corresponding experimental errors;
and (3) qualitative analysis:
the method comprises the following steps that a sensor array consisting of 4-6 sensors qualitatively identifies characteristic quantities of formaldehyde, ammonia gas and benzene, the number of input neurons of a network is 6, the number of output neurons of the network is 3, the optimal hidden layer number is determined through error comparison, and the hidden layer number is dynamically changed;
creating a three-layer network by using a newff function, setting the neuron number of a hidden layer of the network as a dynamic variable S (i) with the range of 3-13, obtaining a group of neuron numbers with the minimum training error as the optimal neuron number through 10 times of training, setting the weight and threshold of the network as random variables with special distribution, and estimating the weight and threshold of the network by using a statistical method; training is stopped until experimental errors meet requirements; the odd group is used as the input of the trained neural network.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.
Claims (1)
1. A method for testing a humidity-controllable semiconductor gas sensor, comprising:
the method comprises the steps of constructing and testing a semiconductor gas sensor testing system, and analyzing the performance of the semiconductor gas sensor testing system and a semiconductor gas sensitive element; wherein,
the step of building and testing the gas sensor testing system is provided with a step of controlling the humidity of the gas chamber, and a humidity control system is used in the step and comprises a main controller, a humidity detection sensor, a dehumidifier, an ultrasonic humidifier and a buzzer, wherein the humidity detection sensor, the dehumidifier and the ultrasonic humidifier are arranged in the gas chamber, and the main controller is respectively connected with the humidity detection sensor, the dehumidifier, the ultrasonic humidifier and the buzzer;
in the step of building and testing the semiconductor gas sensor testing system, the semiconductor gas sensor testing system is used for dynamically distributing different gases under given concentration and enabling a plurality of sensor arrays to monitor the change of the surface conductivity of the gas sensitive element in real time when the gases are introduced;
the semiconductor gas sensor test system includes: the system comprises a sample feeding device for automatically carrying out sample gas concentration proportioning, a gas sensor heating and temperature measuring device, a signal measuring and data collecting circuit for coordinating with the sample feeding device and automatically collecting 4-6 paths of gas sensor measuring signals under different gas sample environments, and a data processing circuit for carrying out data processing on the collected measuring signals; and a temperature compensation circuit for compensating for temperature variations caused by changes in the intake process and room temperature;
the gas sensor array is arranged in the gas chamber, the change of the gas concentration measured by the gas sensor is the change of the gas in the gas chamber, and the gas chamber is a dry organic glass chamber with a smooth inner cavity and a square approximate shape;
the gas sensor heating and temperature measuring device heats the gas sensitive element and measures the working temperature of the gas sensor in real time; when the working temperature of the sensor changes due to the influence of the ambient temperature or the airflow, the temperature compensation circuit carries out temperature compensation control in real time so as to keep the working temperature of the sensor unchanged; the signal measurement and data acquisition circuit is used for adjusting and AD sampling signals, the signal adjustment is used for converting the response of the gas sensor to a test gas sample into an electric signal, the AD sampling is used for converting an analog signal into a digital signal through the data processing circuit, and the acquired 4-6 paths of sensor signals are converted into standard signals required by a BP neural network through normalization processing;
the standard gas sample output is divided into two paths or multiple paths, each path is controlled by a mass flow controller and is connected into a testing device, carrier gas and gas to be tested enter a drying tank to be fully mixed under the control of the mass flow controller respectively to prepare a target testing gas sample and enter a testing cavity in the testing device, a gas sensor testing system distributes gas with set target concentration under the control of a computer, one or more target gas samples with standard concentration and standard carrier gas are proportioned according to the proportion and are introduced into a mixing channel to be fully mixed under the control of the mass flow controller, when the mixed testing gas sample is introduced into the testing cavity, 4-6 paths of response signals of a gas sensor array in a gas chamber are collected, and the obtained response information of the gas sensor array to the sample gas is transmitted to the computer for data processing and data analysis, carrying out test gas inlet, response signal acquisition and data processing in sequence; when the temperature monitoring system finds that the working temperature of the semiconductor gas sensitive element changes, the temperature compensation circuit compensates the working temperature of the element in real time, and adjusts the heating voltage of the resistance wire to keep the working temperature of the element unchanged;
the humidity detection sensor detects a humidity signal in the air chamber in real time and transmits the signal to the main controller, the main controller compares the humidity signal with a set value of the controller based on a constant humidity set value or a set humidity range in the air chamber, and the controller outputs a split-range control signal; when the humidity in the air chamber is lower than 10% RH, the humidifier is opened to the maximum, the system cannot continue humidifying, or the humidity in the air chamber is higher than 60% RH, and the dehumidifier is opened to the maximum, the main controller controls the buzzer to sound, calls the main controller to interrupt, stops signal output to the dehumidifier and the ultrasonic humidifier, and automatically cuts off the power of the system and stops testing when the humidity exceeds 60% RH;
carrying out data normalization processing on 4-6 road standard signals adopted by the sensor, processing the data into a BP neural network to obtain a required standard data source, and carrying out BP neural network gas analysis according to the following steps:
quantitative analysis:
selecting a single formaldehyde gas to detect a sample, carrying out quantitative detection, forming a sensor array by 4-6 sensors to carry out quantitative identification on formaldehyde gas, ammonia gas, benzene and other mixed gases, wherein the number of input neurons of a neural network is 6, the number of output neurons of the neural network is 1, dynamically changing the number of hidden layers, and solving the corresponding training errors of the hidden layers to determine the optimal number of hidden layer neurons;
creating a two-layer network by using a newff function, setting the number of hidden layer neurons of the network as S (i), setting the range of S (i) to be 3-13, setting a training function of the network as Trainbr, setting the weight and the threshold of the network as random variables with special distribution, estimating the weight and the threshold of the network by using a statistical method, taking an input vector P as the input of the trained neural network, training the network by using a train function, and quantitatively detecting 30 groups of formaldehyde gases with different concentrations as the input to obtain the output result of quantitative detection and corresponding experimental errors;
and (3) qualitative analysis:
the method comprises the following steps that a sensor array consisting of 4-6 sensors qualitatively identifies characteristic quantities of formaldehyde, ammonia gas and benzene, the number of input neurons of a network is 6, the number of output neurons of the network is 3, the optimal hidden layer number is determined through error comparison, and the hidden layer number is dynamically changed;
creating a three-layer network by using a newff function, setting the neuron number of a hidden layer of the network as a dynamic variable S (i) with the range of 3-13, obtaining a group of neuron numbers with the minimum training error as the optimal neuron number through 10 times of training, setting the weight and threshold of the network as random variables with special distribution, and estimating the weight and threshold of the network by using a statistical method; training is stopped until experimental errors meet requirements; the odd group is used as the input of the trained neural network.
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| CN201710890876.1A CN107677710A (en) | 2015-11-13 | 2015-11-13 | The test system of the semiconductor gas sensor of controlled humidity |
| CN201710890245.XA CN107807152A (en) | 2015-11-13 | 2015-11-13 | SnO2The method of testing of gas sensitive preparation method and semiconductor gas sensor |
| CN201710890870.4A CN107807154A (en) | 2015-11-13 | 2015-11-13 | The method of testing of the semiconductor gas sensor of controlled humidity with gas sensor making step |
| CN201710890627.2A CN107807153A (en) | 2015-11-13 | 2015-11-13 | Humidity control method in the semiconductor gas sensor test of controlled humidity |
| CN201710890877.6A CN107817270A (en) | 2015-11-13 | 2015-11-13 | The method of testing of gas sensor preparation method and semiconductor gas sensor |
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Also Published As
| Publication number | Publication date |
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| CN107677710A (en) | 2018-02-09 |
| CN107677709B (en) | 2020-07-21 |
| CN107807153A (en) | 2018-03-16 |
| CN107807152A (en) | 2018-03-16 |
| CN107677709A (en) | 2018-02-09 |
| CN107817270A (en) | 2018-03-20 |
| CN105388187A (en) | 2016-03-09 |
| CN107807154A (en) | 2018-03-16 |
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