CN101776596B - Gas density intelligent test system and method - Google Patents

Abstract

The invention relates to a gas concentration intelligent testing system and method, which mainly includes an optical interference gas sensor, a signal conditioning circuit, a temperature sensor, an air pressure sensor, an A/D converter, a data acquisition and processing module, a clock signal generator for setting an alarm, and a host computer; Its characteristics are: three kinds of data of gas concentration, temperature and air pressure at the measured point are measured by optical interference gas sensor, temperature sensor and air pressure sensor; the upper computer reads the data of gas concentration, temperature and air pressure in the data acquisition and processing module, and Set the year, month, day and hour data generated by the alarm clock signal generator, and calculate and display the real gas concentration value of the measured point on the monitor by the host computer, or display the real gas concentration value with the whole point time change curve. The invention has the advantages of simple operation, high measurement accuracy, improved real-time processing and data correction capabilities, and opens up a new way for automatic detection and remote measurement of underground gas in coal mines.

Description

Gas Concentration Intelligent Testing System and Method

technical field

The invention belongs to the technical field of gas concentration measurement, and in particular relates to an intelligent gas concentration testing system and method based on microprocessors, computers and double-beam interference technology.

Background technique

The safety hazards of underground coal mine work mainly come from the high concentration of gas content. The main component of gas is methane, which is a colorless and odorless gas. It is difficult for people to feel its existence from their own physiological functions. The detection mainly depends on the instrument and equipment. At present, the measurement of gas mainly includes thermal catalytic element detection method, gas-sensitive semiconductor element sensor, optical interference gas detection method and infrared absorption detection method. In these methods, thermal catalytic elements and gas-sensitive semiconductor elements are used as sensors. The temperature, humidity, and oxygen content of the measurement points, as well as the inherent defects of the components themselves, will cause the stability of the sensor to deteriorate and the measurement accuracy to decrease; The infrared absorption method has the disadvantages of complex structure and high price, which are not conducive to mass promotion; the optical interference gas detection method has the advantages of high measurement accuracy, durability, and can measure high and low concentrations. For example, in terms of gas detection based on optical interference, Chinese patent 91205283.X "Intelligent optical interference gas detector" uses a microprocessor for data processing; patent 200520033421.0 "Portable intelligent optical interference methane detector" uses light sources The optical path and other improvements have been made; the patent 200810195648.3 "Optical Interference Methane Detector" has also improved the optical path used and the contact method between the gas chamber and the outside world, but it is worth observing the optical interference fringes with the human eye to obtain the gas concentration value. , the operation process is relatively complicated, the detection speed is slow, and even inaccurate situations may occur. In short, when detecting the gas concentration in the prior art or method, the temperature and air pressure of the measured point cannot be measured in real time at the same time, therefore, the real gas concentration value cannot be given, and the law of gas change cannot be displayed in the form of a graph. In addition, the measurement data has no correlation with time, which is not conducive to the automatic detection and telemetry of underground gas, and is not conducive to the establishment of an underground gas network measurement system.

Contents of the invention

The purpose of the present invention is to overcome the defects of the above-mentioned optical interference gas concentration detection method in the prior art, and provide a gas sensor based on optical interference with simple operation, fast detection speed and high measurement accuracy, which can not only detect the gas concentration of the measured point, At the same time, the temperature and air pressure of the measured point are also detected, and it is also beneficial to the automatic detection and remote measurement of underground gas, and is also beneficial to the establishment of an intelligent gas concentration testing system and method of an underground gas network measurement system.

The present invention is achieved through the following technical solutions:

An intelligent gas concentration test system, comprising an optical interference gas sensor, a signal conditioning circuit, an analog switch, an A/D converter, a data acquisition and processing module, a data transmission module and a system power supply; the data acquisition and processing module includes micro Processor, data memory, program memory, 3-8 line decoder, address latch, fixed alarm clock signal generator and microprocessor monitoring circuit; it is characterized in that:

●It also includes a temperature sensor, an air pressure sensor and a host computer; the system, data acquisition and processing software are installed in the host computer;

●The alarm-fixed clock signal generator is an hourly alarm-fixed mode, and the alarm-fixed clock signal generator generates an alarm-fixed interrupt signal at the hour;

●The interference fringe signal of the optical interference gas sensor is converted and calculated by the signal conditioning circuit, analog switch and A/D converter, and the temperature information collected by the temperature sensor is converted by the analog switch and A/D converter Data, and the air pressure data collected by the air pressure sensor are stored in the data storage;

●The program memory also includes a data acquisition and processing program for controlling the acquisition of data and calculating and storing the acquired data.

The air pressure sensor U11 adopts a digital air pressure sensor, and the main clock signal of the digital air pressure sensor is generated by an external oscillating circuit; the oscillating circuit consists of two ceramic capacitors C1 and C2, a crystal CRY1, The metal film resistor R4 is composed of two inverters U17 and U18. One end of the two ceramic capacitors C1 and C2 is grounded and the other end is respectively connected to both ends of the crystal CRY1. At the same time, after the two ends of the crystal CRY1 are connected to the two ends of the resistor R4, one end is connected to the input end of the inverter U17, and the other end is connected to the The output terminal of the inverter U17 is connected to the input terminal of the inverter U18, and the output terminal of the inverter U18 is connected to the main clock signal input terminal of the air pressure sensor U11.

The optical interference gas sensor of the gas concentration intelligent test system includes a light source, a condenser, an air chamber, a plane mirror coated with a reflective film on the back, a refracting prism, a reflective prism, a negative lens, a large reflective prism and a photoelectric conversion device, and is characterized in that A filter chamber is added between the end of the air outlet pipe of the light interference gas sensor gas sample chamber and the plug installed on the outer casing.

An intelligent test method for gas concentration, using the above-mentioned optical interference gas sensor, signal conditioning circuit, analog switch, A/D converter, data acquisition and processing module, data transmission module and system power supply; temperature sensor, air pressure sensor and host computer The gas concentration intelligent testing system that forms; It is characterized in that: the gas concentration intelligent testing method is:

●Measuring the three data of gas concentration, temperature and air pressure at the measured point by optical interference gas sensor, temperature sensor and air pressure sensor;

●The fixed alarm mode of the fixed alarm clock signal generator is hourly fixed alarm;

After the microprocessor receives the off signal from the alarm clock signal generator, the data acquisition and processing module converts the interference fringe signal of the optical interference gas sensor to the gas concentration data converted by the signal conditioning circuit, analog switch and A/D converter , the temperature information collected by the temperature sensor is converted by the analog switch and the A/D converter, the temperature data and the air pressure data collected by the air pressure sensor, and the data storage of the year, month, day, and hour generated by the alarm clock signal generator into data storage;

●The data acquisition and processing software is installed in the host computer, which is used to read the data of gas concentration, temperature and air pressure in the data storage, and the data of year, month, day and hour generated by the alarm clock signal generator, and Calculated by the host computer and display the real gas concentration value of the measured point on the display, or display the change curve of the real gas concentration value with the whole point time;

The upper computer calculates the real gas concentration value of the measured point, and its calculation mathematical model is:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; 101325</span>}}{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; 293</span>}}$

Among them: the real gas concentration of the measured point is X _A , the directly measured gas concentration is X _m , the temperature of the measuring point is T, and the atmospheric pressure of the measuring point is p.

The outstanding substantive features of the gas concentration intelligent testing system and method of the present invention are:

It uses the method of double-beam interference to measure the gas concentration. It can not only detect the gas concentration of the measured point, but also detect the temperature and air pressure of the measured point, and use the three data fusion to improve the accuracy of the gas concentration calculation; At the same time, the above data also records the data of year, month, day and whole point, which ensures the correlation between gas concentration and time, and can accurately calculate and display the gas content in real time. These have improved the ability to use the computer platform to process data in real time, and can further enable the automation and telemetry of gas detection in coal mines, which is conducive to the establishment of a network detection system for gas concentration.

Its remarkable beneficial effect is:

1. Using the powerful software and hardware resources of the computer, better data preprocessing can be performed, and the resolution and accuracy of the measurement can also be improved;

2. Not only can the data be collected in real time, but also the collected data can be saved, played back, processed and displayed;

3. Due to the adoption of multi-sensor fusion technology, the calculation of gas concentration is more accurate and reliable;

4. It can display the change curve of the real gas concentration with the whole point time, which is beneficial to analyze the change law of gas concentration;

5. It can further realize the network measurement and monitoring of coal mine gas, and grasp the distribution of gas content at different measurement points from a macro perspective.

Description of drawings

Fig. 1 is the general principle block diagram of gas concentration intelligent testing system and method of the present invention;

Fig. 2 is a structural schematic diagram of the filter chamber connected in series between the air outlet pipe of the gas sample chamber and the outside world in the optical interference gas sensor;

Fig. 3 is a schematic diagram of the circuit principle in which the data acquisition and processing module is connected with the photoelectric conversion device, signal conditioning, A/D converter, analog switch, air pressure sensor and temperature sensor;

Fig. 4 is a schematic diagram of the principle of the data transmission module and the system power supply circuit;

Fig. 5 is the flow chart of data acquisition and processing program in the program memory;

Fig. 6 is a flow chart of the serial port interrupt subroutine among Fig. 5;

Fig. 7 is the external interrupt 0 subroutine flowchart among Fig. 5 and Fig. 6;

Fig. 8 is the main functional diagram of the data acquisition and processing software in the host computer;

Fig. 9 is a flow chart of host computer reading data;

Fig. 10 is the date and time flow chart of upper computer correction fixed alarm clock signal generator;

Fig. 11 is a flow chart of the host computer collecting and displaying the current value;

Fig. 12 is a flow chart showing the change curve of the real gas concentration with the whole point time displayed by the host computer.

Detailed ways

The following describes specific embodiments in conjunction with the accompanying drawings, and further describes the present invention in detail.

As shown in Figure 1, the gas concentration intelligent testing system of the present invention. The system includes optical interference gas sensor, signal conditioning circuit, analog switch, A/D converter, data acquisition and processing module, data transmission module and system power supply; it also includes temperature sensor, air pressure sensor and host computer; the data The acquisition and processing module includes microprocessor, data memory, program memory, 3-8 line decoder, address latch, fixed alarm clock signal generator and microprocessor monitoring circuit; the microprocessor sets the alarm clock signal to generate The alarm-setting mode of the device is hour-setting alarm, and the alarm-setting clock signal generator generates an alarm-setting interrupt signal at the hour. After the microprocessor receives the interrupt signal, the interference fringe signal of the optical interference gas sensor passes through the signal conditioning circuit, the analog The data converted and calculated by the switch and A/D converter, the temperature information collected by the temperature sensor converted by the analog switch and the A/D converter, and the air pressure data collected by the air pressure sensor are stored in the data storage at the same time .

The program memory of the data acquisition and processing module also includes a data acquisition and processing program, which is mainly used to control the collected data and calculate and store the collected data.

As shown in FIG. 2 , it is a schematic structural diagram of the filter chamber connected in series between the air outlet pipe of the gas sample chamber and the outside world in the optical interference gas sensor of the present invention. The optical interference gas sensor is an optical interference gas sensor based on the prior technology "Patent No. 200520033421.0 "Portable Intelligent Optical Interference Methane Detector", including a light source, a condenser mirror, a gas chamber, a plane mirror coated with a reflective film on the back, and a refractive prism , reflective prism, negative lens, large reflective prism and photoelectric conversion device, on this basis, an improvement of its gas chamber, the improved structure is that the end of the gas sample chamber of the light interference gas sensor is connected to the outer shell A filter chamber is passed between the plugs. The advantage of this is that when the plug is opened to deflate, the water vapor, CO ₂ and other gases in the external gas will not enter the gas pattern, thereby affecting the accuracy of the measurement.

The light source of the light interference gas sensor in the prior art is a white light bulb, so its interference fringes are a group of central white stripes (called white baselines), two identical zero-order black fringes and several colored fringes on both sides. These interference fringes have the following characteristics: the white baseline is thinner and brighter than the secondary bright fringes; the zero-order black fringes are thinner and darker than the secondary black fringes. That is to say, the brightness of the white baseline is the highest, and the brightness of the zero-level black streak is the lowest. In this way, we can use the difference in brightness and width information between the zero-order fringe and the secondary fringe to distinguish between the white baseline and the zero-order black fringe. For this reason, the zero-order fringe is used as the identification mark of the interference pattern. For example, assume that when the gas sample chamber is not filled with gas, the pixel point corresponding to the white baseline is A, and after the gas sample chamber is filled with gas, the interference fringe will move, and the pixels corresponding to the two zero-level black stripes are B and C , then C-B is a fringe spacing. At this time, as long as you know the position of the pixel corresponding to the white baseline after the fringe moves, you can know the distance of the interference fringe movement. If the pixel point corresponding to the white baseline after the fringe moves is D, then the interference fringe The moving distance N is:

$\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; B</span>}}$

Assuming that the refractive index of air is n ₀ , the refractive index of pure gas is n ₁ , the wavelength of the light source is λ, and the length of the gas chamber is L. According to the principle of light interference, the directly measured gas concentration X _m can be calculated as:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}\frac{\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; B</span>}}$

The program for completing the above calculations is written in MCS-51 assembly language or C51 language.

As shown in FIG. 3 , a schematic diagram of the circuit principle of the connection between the data acquisition and processing module of the present invention and the photoelectric conversion device, signal conditioning, A/D converter, analog switch, air pressure sensor and temperature sensor. Described photoelectric conversion device U16 adopts TCD1251UD, and TCD1251UD is a kind of high sensitivity, low dark current that Toshiba Company produces, has the two-phase linear array charge coupler (CCD) of 2700 pixels, and operating voltage is 12V, has two output Signal terminal: one is the signal output terminal OS, which contains the effective photoelectric signal after optical integration; the other is the compensation output terminal DOS, which reflects the dark current characteristics of the two-phase linear array charge coupler. The two-phase linear array charge coupler driving circuit is composed of transfer pulse SH, the first phase T1A and the second phase T1B of the driving clock, the first phase T2A and the second phase T2 of the polar clock, and the reset pulse RS four-way pulse. Drive pulses are generated by a microprocessor.

The connection method of the microprocessor U1 and the photoelectric conversion device U16 is: the transfer pulse SH of the photoelectric conversion device U16, the reset pulse RS, the first phase T1A and T1B of the drive clock and the second phase T2A and T2B of the last pole clock and The pins P1.1, P1.2, P1.3 and P1.4 of the microprocessor U1 are connected.

Signal conditioning circuit U13 adopts instrumentation amplifier AD623, AD623 is an integrated instrumentation amplifier with a single power supply (+3~+12V) output swing that can reach the power supply voltage introduced by American Analog Devices. The purpose of signal conditioning is to eliminate all kinds of noise and interference as much as possible, improve and amplify the image quality, so as to ensure that the image signal changes linearly with the brightness of the measured target within the dynamic range of the two-phase linear array charge-coupled device. The phases of the signal output terminal OS and the compensation output terminal DOS of the two-phase linear array charge coupler model TCD1251UD are the same when they are capacitively interfered by the reset pulse RS, so the differential amplifier can be used to amplify the signal and suppress common-mode interference. The specific connections are as follows: the effective output terminal OS and the compensation output terminal DOS are respectively connected to pins 2 and 3 of the signal conditioning circuit U13, and pin 6 of the signal conditioning circuit U13 is connected to pins 12 and 14 of the analog switch U10.

Described analog switch U10 selects CD4051 for use, and the logic control end of CD4051 is pin 6, 9, 10, 11, when pin 6 is low level, makes common terminal pin by controlling the potential change of pin 9, 10 and 11 3 Connect with pins 1, 2, 4, 5, 12, 13, 14 and 15 respectively to achieve the purpose of signal gating. When pin 6 is high level, no matter how the potential of pins 9, 10 and 11 changes , pin 3 is not connected to other pins.

The wiring method of the analog switch U10 is: the pin 6 of the analog switch U10 is grounded; the pins 3, 13, 12 and 14 of the analog switch U10 are respectively connected to the pin 13 of the A/D converter U4, the output terminal of the temperature sensor and the signal The pin 6 of the conditioning circuit U13 is connected; the pins 9, 10 and 11 of the analog switch U10 are respectively connected with the pins 5, 19 and 2 of the address latch U3.

Described A/D converter U4 adopts A/D1674, and A/D1674 is a kind of complete 12-bit parallel analog/digital conversion monolithic integrated circuit produced by American AD Company, and its basic characteristics are as follows: the conversion time is 10 ns, Linearity error: ±1/2LSB; full-scale calibration error is 0.125%; unipolar or bipolar voltage input ranges are 0-10V, 0-20V, ±5V, ±10V, respectively. A/D1674 has 5 control lines, among which CE, /CS and R/C are general control lines, which complete the timing, addressing, start-up and readout operations of the device, 12/8 and A0 determine the conversion cycle and data output of the chip format, the effective order of CE, /CS and R/C can come first.

The connection between the A/D converter U4 and the microprocessor U1, the pin 2 of the A/D converter U4 is grounded; the pins 20 to 27 of the A/D converter U4 are respectively connected to the pins 39 to 27 of the microprocessor U1 32 is correspondingly connected, and at the same time, the pins 16 to 19 of the A/D converter U4 are respectively connected to the pins 35 to 32 of the microprocessor U1; the pins 16 and 17 of the microprocessor U1 are connected to A through the NAND gate U15 The pin 6 of the /D converter U4 is connected; the pin 3 of the A/D converter U4 is connected with the pin 12 of the 3-8 line decoder U8; the pins 4 and 5 of the A/D converter U4 are respectively connected with The pin 19 and 2 of the address latch U3 are connected; the pin 28 of the A/D converter U4 is connected to the pin 13 of the microprocessor U1, and STS is the conversion end flag, which can provide the microprocessor to query the A/D Whether the conversion is complete. Combining the above hardware connection method, it can be seen that the programming address of the A/D converter U4 is 0x7FFF, the programming address of the upper 8 bits of reading temperature is 0x7FFD, the programming address of the lower 8 bits of reading temperature is 0x7FFF; the programming address of the upper 8 bits of reading gas It is 0x7FF9, and the low 8-bit programming address of reading gas is 0x7FFB.

Described microprocessor supervisory circuit U9 selects MAX690 for use, and MAX690 can produce a low-level reset signal output when power-on, power-off or power supply is unstable, and CMOSRAM can be switched to backup battery when power-off, if watchdog timer is in When it is not activated within the specified time (such as 1.6 seconds), a reset pulse signal will be generated.

The connection method of the microprocessor U1 and the microprocessor monitoring circuit U9 is: the pin 6 of the microprocessor monitoring circuit U9 is connected with the pin 15 of the microprocessor U1; the pin 7 of the microprocessor monitoring circuit U9 is connected with the triode The base of T1 is connected through a resistor R1, the emitter of the transistor T1 is grounded, the collector of the transistor T1 is connected to the power supply VCC (+5V) through a resistor R2, and at the same time, the collector of the transistor T1 is connected to the pin of the microprocessor U1 9 is connected; the pin 1 of the microprocessor monitoring circuit U9 is connected with the pins 26 and 28 of the data memory U7; the pins 4 and 5 of the microprocessor monitoring circuit U9 are unused; the pin 8 of the microprocessor monitoring circuit U9 It is connected to the positive pole of the spare battery B through a resistor R12, and at the same time, connected to the power supply VCC through a diode D1, and the negative pole of the spare battery B is grounded.

The alarm clock signal generator U6 adopts DS12887. DS12887 is a real-time calendar clock chip produced by DALLAS Company in the United States. It is made of CMOS technology and has the advantages of low power consumption, simple peripheral interface, high precision, stable and reliable operation, etc. . Its main functions include nonvolatile calendar clock, alarm, 100-year calendar, programmable interrupt, square wave generator and 114 bytes of nonvolatile SRAM.

The connection method between the microprocessor U1 and the alarm clock signal generator U6 is: the address/data line pins AD0-AD7 of the alarm clock signal generator U6 and the pins P0.0-P0.7 of the microprocessor U1 Corresponding connection; the pin 1 of the fixed alarm clock signal generator U6 is grounded; the pins 14, 15 and 17 of the fixed alarm clock signal generator U6 are respectively connected with the pins 30, 16 and 17 of the microprocessor U1; the fixed alarm clock The pin 13 of the signal generator U6 is connected with the pin 14 of the 3-8 line decoder U8; the pin 19 of the alarm clock signal generator U6 is connected with the pin 12 of the microprocessor U1 after being connected with the pull-up resistor R3 ; The pin 9 of the microprocessor U1 is connected with the pin 18 of the alarm clock signal generator U6 through the inverter U14. Combining the above hardware connection method, it can be seen that the programming address of the alarm clock signal generator U6 is 0x3FFF, the programming address of the year unit is 0x3F09, the programming address of the month unit is 0x3F08, the programming address of the day unit is 0x3F07, the programming address of the hour unit is 0x3F04, and the programming address of the hour unit is 0x3F04. The unit programming address is 0x3F02. In order to collect data at the whole hour, the hour alarm clock of the alarm clock signal generator U6 can be set as a certain number in 0xc0-0xff.

The microprocessor U1 uses AT89S52, AT89S52 is a high-performance COMS 8-bit machine, produced by Atmel's high-density, non-volatile storage technology, compatible with standard 8051 instruction system and pins, and contains 8k system The programmed Flash read-only program memory is used to store data acquisition, calculation, storage and transmission programs; the data memory U7 adopts 6264, 6264 is an 8kB SRAM, the power supply is a single +5V power supply, and all input terminals and outputs are compatible with TTL circuits.

The data line of the data memory U7 is connected to the data line of the microprocessor U1, the low 8-bit address line of the data memory U7 is connected to the address latch U3, and the high 5-bit address line of the data memory U7 is connected to the pin of the microprocessor U1 21 to 25 are connected correspondingly; it should be noted that the pins 26 and 28 of the data memory U7 are connected to the pin 1 of the microprocessor monitoring circuit U9; the pin 20 of the data memory U7 is connected with the pins of the 3-8 line decoder U8 15 connections. Combining the above hardware connection method, it can be seen that the programming address of the data memory U7 is 0x5FFF.

Microprocessor U1 collects data at the hour (such as 1, 12, 23, etc.), or collects data after receiving a command from the upper computer to collect the current value, and the data collected at the hour is stored in the data memory. The realization of the above functions of data collection, calculation, storage and transmission is mainly accomplished by executing the data collection and processing program in the program memory by the microprocessor U1.

The AD590 chip is selected for the temperature sensor, and the influence of temperature should be eliminated when measuring the gas content. Therefore, it is an important link to measure the ambient temperature of the gas point. Since the AD590 is a current-type temperature sensor, its output varies linearly with the absolute temperature, that is, 1μA/K. Therefore, as long as the temperature of two points and the corresponding current value are known, the mathematical model of the system about the temperature can be determined, which gives the calculation Temperature brings great convenience. According to the experiment, when the temperature is in the range of 0℃～40℃, the output current of AD590 is 0.2mA～0.3mA, so a 10kΩ resistor can be connected in series to AD590 to get an output voltage of 2~3V. However, the input voltage range of the A/D converter is 0~5V, so the output voltage of AD590 can be extended to 0~5V. The advantage of this is that the sensitivity of measuring temperature is improved, and the amplified signal passes through the two-pin socket P1 is connected to pin 13 of analog switch U10.

The air pressure sensor U11 adopts MS5534BM, which is a digital air pressure sensor. The digital air pressure sensor integrates an instrument amplifier and an analog-to-digital converter, which can directly output the measured atmospheric pressure in the form of a digital signal. The air pressure sensor also integrates a digital temperature sensor inside, and the digital air pressure signal output by the air pressure sensor It is temperature compensated, and the air pressure sensor U11 and the microprocessor U1 can communicate through a 3-wire serial interface (serial data clock terminal SCLK, data input terminal DIN and data output terminal DOUT). The main clock signal MCLK needs to be connected to an external 32.768 kHz clock signal. The main clock signal of the air pressure sensor U11 is generated by an external oscillating circuit. The oscillating circuit consists of two ceramic capacitors C1 and C2, a crystal CRY1, a metal film resistor R4 and two inverters U17 and U18 composition. One end of the two ceramic capacitors C1 and C2 is grounded and the other end is respectively connected to both ends of the crystal CRY1. At the same time, after the two ends of the crystal CRY1 are connected to the two ends of the resistor R4, one end is connected to the input end of the inverter U17, and the other end is connected to the The output terminal of the inverter U17 is connected to the input terminal of the inverter U18, and the output terminal of the inverter U18 is connected to the main clock signal input terminal of the air pressure sensor U11.

The connection method between the microprocessor U1 and the air pressure sensor U11 is: the serial data clock terminal SCLK, the data output terminal DOUT and the data input terminal DIN of the air pressure sensor U11 are respectively connected to the pins P1.5 and P1.6 of the microprocessor U1. Connect with P1.7.

As shown in FIG. 4 , a schematic diagram of the principle of the data transmission module and the system power supply circuit of the present invention. The data transmission module is composed of communication interface circuits U5, U12 and AND gate U19, and the communication interface circuits U5 and U12 use MAX232 and MAX485 respectively. The connection method between the microprocessor U1 and the communication interface circuits U5 and U12 is: the pin 1 of the communication interface circuit U12 and the pin 9 of the communication interface circuit U5 are respectively connected to the two input ends of the AND gate U19, and the output of the AND gate U19 The terminal is connected with the pin 10 of the microprocessor U1; the pin 11 of the microprocessor U1 is connected with the pin 4 of the communication interface circuit U12 and the pin 11 of the communication interface circuit U5, and the pin 1 of the microprocessor U1 is connected with the communication The pins 2 and 3 of the interface circuit U12 are connected. In addition, an electrolytic capacitor E3 is connected between pins 1 and 3 of the communication interface circuit U5, and an electrolytic capacitor E4 is connected between pins 4 and 5, wherein pins 1 and 4 are connected to the positive polarity end of the electrolytic capacitor; An electrolytic capacitor E5 is connected between pin 6 and the power ground, and an electrolytic capacitor E2 is connected between pin 2 and the power supply VCC, where pin 6 is connected to the negative terminal of the electrolytic capacitor, and pin 2 is connected to the positive terminal of the electrolytic capacitor; communication Pins 7, 10, 12 and 13 of the interface circuit U5 are not used; the communication interface circuit U5 transmits data with the host computer through the three-pin socket P2, and the communication interface circuit U12 transmits data with the host computer through the two-pin socket P3.

The system power supply is composed of transformer BY, two rectifier bridges B1, B2 and four voltage regulator modules V1, V2, V3 and V4. The voltage regulator module V1 uses a three-terminal voltage regulator tube 78M12, and the voltage regulator module V2 uses a three-terminal voltage regulator tube 79M12, the voltage regulator module V3 uses a three-terminal voltage regulator tube 78M05, and the voltage regulator module V4 uses a voltage regulator chip NCP500SN30T1. The system power input 220V AC is stepped down by transformer BY and full-wave rectified by two rectifier bridges B1 and B2, and then becomes a stable power supply voltage of ±12V through three-terminal voltage stabilizing modules V1 and V2, and the power supply voltage of ±12V is supplied to A/D The converter U4 supplies power, the power supply voltage +12V supplies power to the signal conditioning circuit U13 and the photoelectric conversion device U16; the power supply voltage +12V becomes the power supply voltage VCC (+5V) through the voltage stabilizing module V3 to supply the analog switch, temperature sensor, and data transmission module and the data acquisition and processing module; the power supply voltage VCC (+5V) is further changed to the power supply voltage +3V through the voltage stabilizing module V4 to supply power to the air pressure sensor U11. The use of three-stage step-down and voltage regulation effectively improves the anti-interference ability of the system power supply.

Intelligent test method for gas concentration of the present invention

An intelligent test method for gas concentration, using the above-mentioned optical interference gas sensor, signal conditioning circuit, analog switch, A/D converter, data acquisition and processing module, data transmission module and system power supply; temperature sensor, air pressure sensor and host computer Composed of gas concentration intelligent test system; its data acquisition and processing module includes microprocessor, data memory, program memory, 3-8 line decoder, address latch, alarm clock signal generator and microprocessor monitoring circuit ; It is characterized in that: the gas concentration intelligent test method is:

●Measuring the three data of gas concentration, temperature and air pressure at the measured point by optical interference gas sensor, temperature sensor and air pressure sensor;

●The fixed alarm mode of the fixed alarm clock signal generator is hourly fixed alarm;

After the microprocessor receives the off signal from the alarm clock signal generator, the data acquisition and processing module converts the interference fringe signal of the optical interference gas sensor to the gas concentration data converted by the signal conditioning circuit, analog switch and A/D converter , the temperature information collected by the temperature sensor is converted by the analog switch and the A/D converter, the temperature data and the air pressure data collected by the air pressure sensor, and the data storage of the year, month, day, and hour generated by the alarm clock signal generator into data storage;

●The data acquisition and processing software is installed in the host computer, which is used to read the data of gas concentration, temperature and air pressure in the data storage, and the data of year, month, day and hour generated by the alarm clock signal generator, and Calculated by the host computer and display the real gas concentration value of the measured point on the display, or display the change curve of the real gas concentration value with the whole point time;

●The upper computer is connected externally, and the data acquisition and processing software is installed in the upper computer. Since the refractive index of gas gas is related to the ambient temperature and air pressure, when the ambient temperature and air pressure change, it will affect the measurement results of the gas concentration. Therefore, a mathematical model that can reflect the real gas concentration of the measured point is required. Assuming that the real gas concentration of the measured point is X _A , the directly measured gas concentration is X _m , the temperature of the measuring point is T (absolute temperature K), and the atmospheric pressure of the measuring point is p(p _a ), then the real gas concentration The calculation formula between the directly measured gas concentration is:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; 101325</span>}}{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; 293</span>}}$

The software for completing the above calculations is written in Delphi language or VC++ language.

As shown in Figure 5, the main flow of the data acquisition and processing program in the program memory is:

After power-on, initialize the system, including opening the serial port communication interrupt, setting INT0 and INT1 as external interrupts, setting the communication baud rate, and the transmission data format is eight data bits, no parity bit, and one stop bit; Set the clock chip to prohibit cycle and update interruption, allow alarm clock interruption, allow update to proceed normally, adopt 24h system, do not use daylight saving time function, time, calendar, and alarm clock adopt BCD data format, no need to output square wave signal, set the alarm clock unit It is a certain number in 0xc0~0xff, and the unit of second, minute, hour, week, date, month and year is set as the corresponding actual data.

Determine whether there is a serial port interrupt signal? If yes, execute the serial port interrupt subroutine, and then judge whether there is a serial port interrupt signal; otherwise, judge whether there is an hour interrupt signal;

Determine whether there is an hourly interrupt signal? If yes, execute the external interrupt 0 subroutine, and then judge whether there is a serial port interrupt signal; otherwise, return to judge whether there is a serial port interrupt signal.

As shown in Figure 6, the serial port interrupt subroutine flow is:

Perform a push operation on registers A, DPH, and DPL,

Determine whether there is an hourly interrupt signal? If yes, execute the external interrupt 0 subroutine, and then judge whether it is the command to read the current value; if not, then judge whether it is the command to read the current value;

Determine whether it is the command to read the current value? Yes, when the alarm clock interrupt flag AF=0 of the alarm clock signal generator, measure and send the temperature, air pressure and gas concentration data to the host computer; when the alarm clock interrupt flag AF=1 of the alarm clock signal generator, Only send the last stored temperature, air pressure and gas concentration data to the host computer, and clear the interrupt request flag bit IRQF and alarm clock interrupt flag bit AF of the alarm clock signal generator. Afterwards, register DPL, DPH, A are carried out stack operation, interrupt and return; No, then judge whether to correct and set alarm clock signal generator command;

Determine whether it is a correction date and time command? If yes, correct the date and time, and then perform pop-out operations on registers DPL, DPH, and A, and return from the interrupt; if not, start to judge whether it is a read data command;

Determine whether it is a read data command? Yes, send all the data in the data memory to the host computer through the data transmission module, and then perform a pop-up operation on the registers DPL, DPH, A and interrupt the return; no, perform a pop-up operation on the registers DPL, DPH, A, Interrupt returns.

As shown in Figure 7, the external interrupt 0 subroutine flow is:

Push the registers A, DPH, and DPL into the stack, read the starting address of the stored data from the storage address register, and read the data of the year, month, day, and hour. These data occupy one byte each and are stored in the initial address, start address+1, start address+2 and start address+3 in units corresponding to;

The microprocessor generates the driving pulse required by the photoelectric conversion device, starts the A/D conversion, and collects the gas concentration data;

Determine whether the A/D conversion is over? No, wait for the A/D conversion to end; if yes, calculate the directly measured gas concentration X _m , X _m occupies 2 bytes, and the high 8 bits and low 8 bits are stored in the start address + 4 and the start address respectively In the unit corresponding to address +5, after that, start A/D conversion and collect temperature data;

Determine whether the A/D conversion is over? No, wait for the end of the A/D conversion; yes, calculate the temperature data, the data occupies 2 bytes, the high 8-bit and low 8-bit bytes are stored in the corresponding start address +6 and start address +7 respectively In the unit, after that, the air pressure data is collected and calculated. The data occupies 2 bytes, and the high 8-bit and low 8-bit bytes are stored in the units corresponding to the start address +8 and start address +9 respectively;

Send the starting address + 10 (decimal) to the storage address register;

Is it equal to 8191 after judging the starting address +10? No, perform stack operation on registers DPL, DPH, A, interrupt return; if yes, set the start address to the initial value, send it to the storage address register, and then perform stack operation on registers DPL, DPH, A, interrupt return.

As shown in Figure 8, the main functions of the data acquisition and processing software installed in the host computer are:

Read data: the upper computer reads all the year, month, day, hour, directly measured gas concentration, temperature and air pressure data in the data memory through the data transmission module, and the upper computer sends them to the database after receiving these data Save and back up to keep and query history records. After closing the display, return to the main interface of the software running;

Calibrate the date and time of the alarm clock signal generator: that is, send the year, month, day, hour and minute of the upper computer to the microprocessor through the data transmission module, and the microprocessor will only correct the alarm clock signal after receiving the order. The year, month, day, hour and minute of the generator are corrected, but no data is returned, and the software returns to the main interface;

Collect and display the current value: the microprocessor sends the real-time directly measured gas concentration, temperature and air pressure data to the upper computer through the data transmission module. After these data are calculated and processed in real time by the upper computer, the upper computer displays the current value. Real gas concentration, temperature and air pressure values, but do not store these data, after closing the display, return to the main interface of the software running;

Display the change curve of the real gas concentration with the whole time: it can display the change curve of the real gas concentration with the whole time in one day, one week or one month, which is used to analyze the change law of the gas concentration. After closing the display, return to the main software running interface.

As shown in Figure 9, the process of reading data by the upper computer is as follows:

Set the communication baud rate, the transmission data format is eight data bits, no parity bit, one stop bit;

Send read data command: BB(HEX)+31313131;

Receive 8190 bytes of data + 2 bytes of checksum (the checksum is the sum of 8190 bytes of data);

Is it judged that the data reception is completed? No, continue to receive the data; yes, store the received data in the database, and then judge whether to query the historical records?

Judging query history? No, finish and return to the main interface; Yes, display historical record data, and return to the main interface after closing the display.

As shown in Figure 10, the process of correcting the date and time of the alarm clock signal generator by the host computer is as follows:

Set the communication baud rate, the transmission data format is eight data bits, no parity bit, one stop bit;

Read the year (YEAR) month (MONTH) day (DATE) hour (HOUR) minute (MINUTE) of the host computer;

Send the command to correct date and time: BB(HEX)+32323232+YEAR:MONTH:DATE:HOUR:MINUTE;

Is it judged that the sending command is over? No, continue to send commands; Yes, end and return to the main world.

As shown in Figure 11, the process of collecting and displaying the current value by the host computer is as follows:

Send command to collect and display current value: BB(HEX)+33333333;

Receive 6 bytes of data + 1 byte of checksum (the checksum is the sum of 6 bytes of data);

Is it judged that the data reception is completed? No, continue with received data; Yes, calculate real gas concentration X _A ;

Display the real gas concentration X _A , temperature and air pressure, and return to the main interface after closing the display.

As shown in Figure 12, the process of displaying the change curve of the real gas concentration with the whole point time is:

Determine whether to display a day's change curve? Yes, call out the gas concentration, temperature, air pressure data and the corresponding hourly time in the library for one day, calculate the real gas concentration X _A , and then display the change curve of the real gas concentration X _A with the hourly time, after closing the display Return to the main interface; No, determine whether to display a week's change curve;

Determine whether to display a week's change curve? Yes, call out the gas concentration, temperature, air pressure data and the corresponding hourly time in the library for a week, calculate the real gas concentration X _A , and then display the change curve of the real gas concentration X _A with the hourly time, after closing the display Return to the main interface; No, determine whether to display the change curve in January;

Determine whether to display the change curve in January? Yes, call out the data of gas concentration, temperature, air pressure and the corresponding hourly time in the library in January, calculate the real gas concentration X _A according to the mathematical model, and then display the change curve of the real gas concentration X _A with the hourly time , turn off the display and return to the main interface; No, return to the main interface.

Claims (4)

1. a gas density intelligent test system comprises interference of light firedamp sensor, signal conditioning circuit, analog switch, A/D converter, data acquisition and processing (DAP) module, data transmission module and system power supply; Described data acquisition and processing (DAP) module comprises microprocessor, data-carrier store, program storage, 3-8 line code translator, address latch, locking clock-signal generator and microprocessor monitors circuit; It is characterized in that:

● it also comprises temperature sensor, baroceptor and host computer; Installation system, data acquisition and processing (DAP) software in the described host computer;

● described locking clock-signal generator is a hour locking pattern, and in integral point locking clock-signal generator generation constantly locking look-at-me;

● the data of the interferometric fringe signal of described interference of light firedamp sensor after signal conditioning circuit, analog switch and A/D converter conversion and calculating, the data of the temperature information that temperature sensor collects after analog switch and A/D converter conversion, and the barometric information that baroceptor collects stores in the data storage;

● also comprise the data acquisition and processing (DAP) program that is used for controlling image data and the data of gathering are calculated and stored in the described program storage.

2. gas density intelligent test system according to claim 1 is characterized in that described baroceptor U11 adopts digital baroceptor, and the master clock signal of this digital baroceptor is to be produced by external oscillatory circuit; Described oscillatory circuit is made up of two ceramic disc capacitor C1 and C2, crystal CRY1, metalfilmresistor R4 and two phase inverter U17 and U18; The end ground connection other end of two ceramic disc capacitor C1 and C2 is connected with crystal CRY1 two ends respectively, simultaneously, the two ends of crystal CRY1 are with after the two ends of resistance R 4 are connected, the input end of one termination phase inverter U17, the output terminal of another termination phase inverter U17, the output terminal of phase inverter U17 is connected with the input end of phase inverter U18, the master clock signal input end of the output termination baroceptor U11 of phase inverter U18.

3. gas density intelligent test system according to claim 1, described interference of light firedamp sensor, comprise that light source, condenser, air chamber, the back side are coated with the level crossing of reflectance coating, refractive prism, reflecting prism, negative lens, big reflecting prism and photoelectric conversion device, is characterized in that: terminal and be contained between the plug on the shell body and have additional a filter chamber at the escape pipe of interference of light firedamp sensor gas specimen chamber.

4. the gas density intelligent test method of gas density intelligent test system according to claim 1 is characterized in that this gas density intelligent test method is:

● measure gas density, temperature and three kinds of data of air pressure of measured point by interference of light firedamp sensor, temperature sensor and baroceptor;

● the locking pattern of locking clock-signal generator is a hour locking;

● after microprocessor is received the break signal that the locking clock-signal generator sends, the data acquisition and processing (DAP) module is changed the interferometric fringe signal of interference of light firedamp sensor through signal conditioning circuit, analog switch and A/D converter gas density data, temperature data and the baroceptor barometric information that collect of the temperature information that temperature sensor collects after the conversion of analog switch and A/D converter, and the year, month, day that produces of locking clock-signal generator, the time data storage in data storage;

● installation data collection and process software in the host computer, this software is used for the data of reading of data reservoir gas density, temperature and air pressure, and the year, month, day that produces of locking clock-signal generator, the time data, and calculate and on display, show the true gas concentration in measured point, or show that true gas concentration is with the integral point time changing curve by host computer;

● described host computer calculates the true gas concentration in measured point, and its computational mathematics model is:

$x_A=x_m\&CenterDot;\frac{101325}{p}\&CenterDot;\frac{T}{293}$

Wherein: the real gas density in measured point is x _A, directly the gas density of measuring is x _m, measurement point temperature be T, the atmospheric pressure of measurement point is p.

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