CN104297297A - Measuring system and method of gas response sensitivity in oxygen-free environment - Google Patents

Measuring system and method of gas response sensitivity in oxygen-free environment Download PDF

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CN104297297A
CN104297297A CN201410578622.2A CN201410578622A CN104297297A CN 104297297 A CN104297297 A CN 104297297A CN 201410578622 A CN201410578622 A CN 201410578622A CN 104297297 A CN104297297 A CN 104297297A
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gas
air
voc
air chamber
response sensitivity
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CN104297297B (en
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孙炎辉
杜海英
宋鹏
钱瑞
陈诗尧
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Dalian Minzu University
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Dalian Nationalities University
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Abstract

The invention relates to a measuring system and a measuring method of the gas response sensitivity in an oxygen-free environment. The measuring system comprises the oxygen-free environment, a gas chamber, a VOC (Volatile Organic Compound) gas sensor, a signal acquisition and transmission system and an upper computer, wherein the gas chamber is in the oxygen-free environment. The measuring method comprises the steps of (S1) obtaining a gas chamber in a vacuum environment; (S2) connecting the VOC gas sensor with a voltage dividing resistor in series, so as to form a voltage dividing circuit; (S3) distributing gas; (S4) measuring output voltage of the voltage dividing resistor, calculating to obtain voltage in measured gas when the VOC gas sensor is adsorbed, and selecting an appropriate voltage dividing resistor; (S5) desorbing the VOC gas sensor, measuring the output voltage of the voltage dividing resistor, and calculating to obtain voltage in air after the VOC gas sensor is desorbed; and (S6) calculating to obtain the gas response sensitivity S. By using the measuring system and the measuring method, the response characteristic of the VOC gas sensor in to-be-measured gas in the oxygen-free environment can be obtained.

Description

A kind of calculating system of gas response sensitivity under non-oxygen environment and method
Technical field
The present invention relates to a kind of calculating system and method for gas sensitivity, particularly relate to a kind of calculating system and method for gas response sensitivity under non-oxygen environment.
Background technology
At present, in the development process of gas sensor, need the gas response characteristic of research sensor under varying environment and condition of work, weigh the quality of sensor, sum up the optimum Working finding out sensor, this be unable to do without good testing apparatus.Usually, when the gas that can detect exists, the concentration of this gas is higher, and the conductivity of sensor is higher.The change of this conductivity is converted to the output signal corresponding with gas concentration.The characteristic of VOC gas sensor under aerobic environment is widely studied, but, in industrial practical application, gas detect needs to carry out under some comparatively rugged environment often, more particularly as in the anaerobic environments such as mine, larger difference is there is in the response characteristic of sensor and aerobic environment in these environment, its accuracy of detection must be affected, in order to obtain the support to gas detect data under oxygen-free environment of VOC gas sensor, the response characteristic under testing sensor oxygen-free environment in gas to be measured is particularly important.
Summary of the invention
In order to solve the problem, the present invention proposes a kind of calculating system and method for gas response sensitivity under non-oxygen environment, to obtain the response characteristic of VOC gas sensor in gas to be measured under oxygen-free environment.
The present invention adopts following technical scheme: a kind of calculating system of gas response sensitivity under non-oxygen environment, comprising: non-oxygen environment, air chamber, VOC gas sensor, signals collecting and transmission system and host computer;
Be non-oxygen environment in described air chamber;
Described signals collecting and transmission system, comprise
Bleeder circuit, described bleeder circuit is VOC gas sensor and divider resistance R lcompose in series, for aerial output voltage V after exporting VOC sensor desorption airoutput voltage V when adsorbing with VOC sensor in tested gas gas;
A/D modular converter, is connected with bleeder circuit, for the V exported by bleeder circuit airand V gasvoltage analog signal be converted to voltage digital signal;
Microprocessor, is connected with A/D modular converter, for A/D conversion, and V after changing airand V gasvoltage signal carry out pre-service, export V airand V gascan for display and the digital signal transmitted;
Data transmission module, is connected with microprocessor, the V exported for making microprocessor airand V gasdigital data transmission to host computer;
Described host computer, is connected with data transmission module, receives the V of data transmission module transmission airand V gasdigital signal, computing obtains the air-sensitive response sensitivity under non-oxygen environment in the tested gas of VOC gas sensor in air chamber.
Further, native system also comprises heating arrangement, and making liquid charging stock gas sample heat vaporized is gaseous feed gas, and it is arranged in air chamber, for the injection port of alignment liquid unstripped gas sample is placed.
Further, native system also comprises display module, is connected with microprocessor, for showing the V that microprocessor exports airand V gasnumerical value
Under non-oxygen environment, a measuring method for gas response sensitivity, comprises the steps:
The air chamber of S1, acquisition vacuum environment;
S2, by VOC gas sensor and divider resistance R lcompose in series bleeder circuit;
S3, distribution;
S4, measurement divider resistance R loutput voltage, output voltage V in tested gas when calculating the absorption of VOC gas sensor gas;
S5, make VOC gas sensor desorption, measure divider resistance R loutput voltage, aerial output voltage V after calculating VOC gas sensor desorption air;
S6, computing obtain gas response sensitivity S;
S7, change and pass into the concentration of unstripped gas in air chamber, repeat step S2-S6;
S8, change the kind passing into unstripped gas in air chamber, repeat step S1-S7.
Further, the method for computing gas response sensitivity is:
For P type VOC gas sensor, gas response sensitivity S is the element ratio of resistance after resistance and element adsorbed gas in atmosphere:
S = R g R a
For N-type VOC gas sensor, gas response sensitivity S is defined as the element ratio of resistance after resistance and element adsorbed gas in atmosphere:
S = R a R g
Wherein, R a = V - V air V air R L , R g = V - V gas V gas R L ; V airand V gasoutput voltage when aerial output voltage and VOC gas sensor adsorb after being respectively VOC gas sensor desorption in tested gas, V is the supply voltage of bleeder circuit, R lfor divider resistance.
Further, obtain vacuum environment air chamber adopt method be following in one:
(1) use aspiration pump by the air extracting method in air chamber: the injection port of aspiration pump seal, from the bleeding point of air chamber, the air in air chamber extracted out, the rubber tube of bleeding point shrink become flat after, air chamber is interior is vacuum environment or close to vacuum;
(2) inert gas degassing method: pass into inert gas in air chamber, wherein, helium and neon use downward degassing method to be filled with air chamber, and argon gas, Krypton and xenon use upwards degassing method to be filled with air chamber;
Further, the step of described distribution is: the unstripped gas of a certain amount of gaseous state or steam-like is added in the air chamber of known volume, and after being filled with carrier gas, tested gas is made in mixing, and described unstripped gas is the mixed gas of pure gas or concentration known, wherein, the method obtaining the concentration of unstripped gas is:
(1) when passing into unstripped gas directly to air chamber, the amount of the unstripped gas that service property (quality) flowmeter survey passes into;
(2) when the unstripped gas used is for liquid state, extract in the heating arrangement of a certain amount of liquid material gas injected gas indoor, making liquid state heat vaporized is gaseous state, is learnt the concentration value of the unstripped gas after gasification by following formulae discovery;
ρ×v×ω％/M＝c×V L/(22.4×(273+T)/273)
v＝(273/(273+T))×V L×c×M/(22.4×ρ×ω％)
In formula, ρ is the density of organic liquid, and ω % is the massfraction of tested composition in organic liquid, and M is the molal weight of tested gas, the Celsius temperature in T air chamber, V lfor the volume of air chamber.
Further, the method obtaining gas response sensitivity is:
The V that bleeder circuit in step S4 and step S5 exports by A/D modular converter airand V gasvoltage analog signal be converted to voltage digital signal;
Microprocessor receives the V after the conversion of A/D modular converter airand V gasvoltage digital signal;
The V that data transmission module makes microprocessor export airand V gasdigital data transmission to host computer;
Display module shows the V that microprocessor exports in real time airand V gasnumerical value;
Host computer receives the V of data transmission module transmission airand V gasdigital signal, obtain the air-sensitive responsiveness of VOC gas sensor in tested gas under non-oxygen environment according to the formula operation in claim 5.
Further, host computer also draws out V airand V gasreal-time change curve, the resistance signal Rg of display VOC sensor, and draw out resistance change curves; Also draw out the air-sensitive response sensitivity change curve of VOC gas sensor, demonstrate the real time value of air-sensitive response sensitivity.
Beneficial effect: the calculating system and the method that the invention provides a kind of gas response sensitivity under non-oxygen environment, wherein, calculating system achieves the gas response sensitivity Autonomous test of VOC gas sensor in the gas of concentration known to be measured, from display, bring great convenience to data monitoring process, the realization of the automation process of data acquisition and display makes the gas sensitivity detection level of VOC gas sensor all be improved in precision or timeliness.Measuring method provides a kind of method obtaining the gas response sensitivity of VOC sensor in the gas of concentration known under oxygen-free environment, due under aerobic environment and oxygen-free environment, VOC gas response sensitivity there are differences, therefore present method solves the response data support owing to lacking VOC gas sensor under oxygen-free environment, under the anoxic caused or oxygen-free environment there is problem compared with big error to gas detect in existing VOC gas sensor, compensate for the defect of VOC gas sensor response characteristic disappearance under oxygen-free environment.
Accompanying drawing explanation
Fig. 1 is the structural frames schematic diagram of the calculating system in embodiments of the invention;
Fig. 2 is the process flow diagram of measuring method of the present invention;
Fig. 3 is in embodiment, the curve map of ethanol VOC sensor response characteristic under aerobic environment and oxygen-free environment of variable concentrations.
Embodiment
Below in conjunction with drawings and the specific embodiments, the present invention is further described.
Embodiment:
A calculating system for gas response sensitivity under non-oxygen environment, comprising: non-oxygen environment, air chamber, VOC gas sensor, signals collecting and transmission system and host computer;
Be non-oxygen environment in described air chamber;
Described signals collecting and transmission system, comprise
Bleeder circuit, described bleeder circuit is VOC gas sensor and divider resistance R lcompose in series, for aerial output voltage V after exporting VOC sensor desorption airoutput voltage V when adsorbing with VOC sensor in tested gas gas;
A/D modular converter, is connected with bleeder circuit, for the V exported by bleeder circuit airand V gasvoltage analog signal be converted to voltage digital signal;
Microprocessor, is connected with A/D modular converter, for A/D conversion, and V after changing airand V gasvoltage signal carry out pre-service, export V airand V gascan for display and the digital signal transmitted;
Data transmission module, is connected with microprocessor, the V exported for making microprocessor airand V gasdigital data transmission to host computer;
Described host computer, is connected with data transmission module, receives the V of data transmission module transmission airand V gasdigital signal, computing obtains the air-sensitive response sensitivity under non-oxygen environment in the tested gas of VOC gas sensor in air chamber.
VOC gas sensor is comparatively responsive to ethanol, ammonia, carbon monoxide, sulfide, formaldehyde, benzene and cigarette smell, is described below below to the formula that sensitivity definition and the present invention of VOC gas sensor use:
For P type VOC gas sensor, gas response sensitivity S is the element ratio of resistance after resistance and element adsorbed gas in atmosphere:
S = R g R a (formula one)
And for N-type VOC gas sensor, gas response sensitivity S is defined as the element ratio of resistance after resistance and element adsorbed gas in atmosphere:
S = R a R g (formula two)
Wherein, R a = V - V air V air R L (formula three)
R g = V - V gas V gas R L (formula four)
V airand V gasoutput voltage when aerial output voltage and VOC gas sensor adsorb after being respectively VOC gas sensor desorption in tested gas, V is the supply voltage of bleeder circuit, R lfor divider resistance.
VOC gas sensor is a kind of Gas Sensors of Electric Resistance Semiconductors, adopt the impedance device that tin ash semiconductor material is made, itself and gas molecule interacts time material film surface there is reduction reaction, cause with carrier moving the change of the conductivity being feature, therefore, the resistance of VOC gas sensor can change along with the change detecting gas concentration, and the present invention according to this principle system devises following method, in order to measuring and calculating, obtains gas response sensitivity under non-oxygen environment.
Under non-oxygen environment, a measuring method for gas response sensitivity, comprises the steps:
The air chamber of S1, acquisition vacuum environment;
Obtain vacuum environment air chamber adopt method be following in one:
(1) use aspiration pump by the air extracting method in air chamber: the injection port of aspiration pump seal, from the bleeding point of air chamber, the air in air chamber extracted out, the rubber tube of bleeding point shrink become flat after, air chamber is interior is vacuum environment or close to vacuum;
(2) inert gas degassing method: pass into inert gas in air chamber, wherein, helium and neon use downward degassing method to be filled with air chamber, and argon gas, Krypton and xenon use upwards degassing method to be filled with air chamber;
S2, by VOC gas sensor and divider resistance R lcomposing in series bleeder circuit is placed in air chamber;
S3, distribution;
The step of described distribution is: the unstripped gas of a certain amount of gaseous state or steam-like is added in the air chamber of known volume, after being filled with carrier gas, tested gas is made in mixing, described unstripped gas is the mixed gas of pure gas or concentration known, and wherein, the method obtaining the concentration of unstripped gas is:
(1) when passing into unstripped gas directly to air chamber, the amount of the unstripped gas that service property (quality) flowmeter survey passes into;
(2) when the unstripped gas used is for liquid state, extract in the heating arrangement of a certain amount of liquid material gas injected gas indoor, making liquid state heat vaporized is gaseous state;
When the unstripped gas used is for liquid state, extract in the heating arrangement of a certain amount of liquid material gas injected gas indoor, make liquid heating
Be vaporizated into gaseous state, learnt the concentration value of the unstripped gas after gasification by following formulae discovery;
ρ×v×ω％/M＝c×V L/(22.4×(273+T)/273)
v＝(273/(273+T))×V L×c×M/(22.4×ρ×ω％)
In formula, ρ is the density of organic liquid, and ω % is the massfraction of tested composition in organic liquid, and M is the molal weight of tested gas, and T is the Celsius temperature of plenum interior, V lfor the volume of air chamber.
Heating arrangement can direct boiling be gas after will making fluid sample injection air chamber, wherein the efficiency of heating surface of heater block is most important, because the fluid sample amount injecting air chamber is very little, it is generally micro updating, so do not allowed fluid loss in the process of fluid sample vaporization, that is, the fluid sample of injected gas indoor will all volatilize for gas, in the present embodiment, heating arrangement we select nichrome wire gas evaporation stove, gas evaporation stove is placed in air chamber, fire door alignment liquid sample feeding mouth is placed, generate heat after the internal heating wire two ends making alive of vapourizing furnace, along with the rising of both end voltage, the temperature of heating wire raises, the condition that the heating-up temperature of heating wire meets all can be vaporized into gaseous state after touching heating wire after fluid sample is injected into air chamber, the two ends of the present embodiment to gas evaporation stove pass to 4.4V voltage, meet the condition that all can be vaporized into gaseous state after touching heating wire after fluid sample is injected into air chamber.Gas evaporation stove selected by heating arrangement, the heater strip of gas evaporation stove selects nickel chromium to make, and compared with the longer service life of ferrum-chromium-aluminum heating wire, nichrome wire, ductility is better, more due to not yielding under its high temperature, the test of long-term test can be stood.
Above-mentioned distribution mode is static distribution, static test system adopts airtight Large Copacity air chamber under normal circumstances, is also uniformly mixed into the test gas of certain volume in a reservoir, container closure by injecting sample gas, be not vulnerable to environment temperature, humidity, electric field, the impact of the factor such as temperature, flow velocity of magnetic field gas flow, especially test that is a small amount of, micro-concentrations gas is applicable to, test accuracy rate is high, and method of testing, equipment are comparatively simple, convenient test.
In distribution process, just can learn the concentration information passing into tested gas in air chamber, namely in air chamber, pass into concentration known gaseous feed gas or in air chamber, add the liquid material gas of known volume, by above-mentioned formula operation, the volume of tested gas in air chamber can be known.
S4, measurement divider resistance R loutput voltage, output voltage V in tested gas when calculating the absorption of VOC gas sensor gas;
S5, make VOC gas sensor desorption, measure divider resistance R loutput voltage, aerial output voltage V after calculating VOC gas sensor desorption air; During desorption, the tested gas aspiration pump in air chamber is extracted out, to the gas in air chamber is taken out to the greatest extent, in air chamber, pass into air, after a period of time, can be considered that desorption completes.
S6, computing obtain gas response sensitivity S;
The method obtaining gas response sensitivity S is:
The V that bleeder circuit in above-mentioned steps S4 and step S5 exports by A/D modular converter airand V gasvoltage analog signal be converted to voltage digital signal;
Microprocessor receives the V after the conversion of A/D modular converter airand V gasvoltage digital signal;
The V that data transmission module makes microprocessor export airand V gasdigital data transmission to host computer;
Display module shows the V that microprocessor exports in real time airand V gasnumerical value;
Host computer receives the V of data transmission module transmission airand V gasdigital signal, obtain the air-sensitive responsiveness of VOC gas sensor in tested gas under non-oxygen environment according to the computing of formula 1-formula 4; Namely host computer is according to the V obtained airand V gasnumerical value, apply preset formula and carry out computing, air-sensitive responsiveness can be calculated fast, output display, utilize the powerful calculating ability calculated, make air-sensitive responsiveness calculate more succinct, to those skilled in the art, to gather data carry out in a computer mathematical computations obtain output data are conventional technological means.
Host computer draws out V airand V gasreal-time change curve, the resistance signal Rg of display VOC sensor, and draw out resistance change curves; Also draw out the air-sensitive response sensitivity change curve of VOC gas sensor, demonstrate the real time value of air-sensitive response sensitivity, host computer shows current tested gas gas and concentration simultaneously.
S7, change and pass into the concentration of unstripped gas in air chamber, repeat step S1-S6; As shown in Figure 3 and Table 1, for adding the liquid ethanol of different volumes in the air chamber of 50L, the response sensitivity curve of the alcohol gas obtained under aerobic environment and oxygen-free environment.
Table 1 concentration-response numerical value relation table
S8, change the kind passing into unstripped gas in air chamber, repeat step S1-S7.
The calculating system of gas response sensitivity under non-oxygen environment in embodiment is used to obtain gas response sensitivity, wherein relate to various electronic devices and components, its power pack is described below: power supply needs for VOC gas sensor provides adjustable dc voltage, galvanic current pressure is provided to heating-device modules, galvanic current pressure is provided to bleeder circuit module, the present embodiment uses DC power supply, DC power supply is two-way adjustable power supply, the adjustable extent of voltage is 0V-30V, the adjustable extent of electric current is 0A-3A, the degree of regulation of electric current and voltage is 0.1.
AVR single chip selected by microprocessor, and turning Power supply mode for single-chip minimum system by USB provides 5V DC voltage, and in addition, A/D modular converter, display module and data transmission module also can use this 5V DC-voltage supply.
In the present embodiment, select PCF8591 integrated device to extend out A/D modular converter as single-chip minimum system, make the analog voltage signal at VOC gas sensor two ends change into the accessible digital signal of single-chip microcomputer and carry out liquid crystal display and data transmission.Display module uses LCD1602 to show the VOC gas sensor both end voltage of single-chip microcomputer collection.Data transmission uses CP2102 module, and its inside is that a USB turns UART data converting circuit, and it can make the digital data transmission of single-chip microcomputer process carry out associative operation to host computer.
The present invention adopts host computer graphical interfaces to carry out graph curve display, to reach the direct vision to data.
The present embodiment selects LabVIEW to write master system display interface, LabVIEW uses graphical author language G coding, program is block diagram format, write comparatively simple, its data acquisition realized and graphical interfaces show and are those skilled in the art's conventional techniques means, briefly introduce as follows:
In host computer interface, the change of the change in voltage of VOC gas sensor, resistance variations and response is observed, need draw voltage change curve, resistance change curves and response change curve and curve can be preserved, and the magnitude of voltage in system acquisition process, resistance value and response are recorded and preserves.
Process is as follows:
1, initialization: initialization is carried out to data, curve, form, path etc., during initialization, is built the general frame of a front panel by tab control, allow the front panel of program seem more directly perceived.Again by calling the attribute node of chart for its initialization assignment, make calling program front panel more attractive in appearance.Carry out the path initialization of squiggle figure, formulate an operable path to preserve curve waveform figure.
2, host computer communicates with slave computer: host computer is wanted to communicate with between slave computer, process in the data upload of slave computer collection to host computer, in order to the process communicated is simple and easy to use, the present embodiment have selected asynchronous serial communication, LabVIEW serial port function uses two kinds of modes, one is call the serial ports control commen32 that Microsoft carries, another is the LabVIEW VI control visa using NI company to provide, in order to the succinct ease for use of program, the present embodiment choice for use second method.First initialization is carried out to serial port function, the serial ports number of serial ports, baud rate, check bit, verification mode are set; Secondly read vi by VISA and carry out digital independent, optimum configurations is as follows: COM1 serial ports, and baud rate is 9600, verification mode is no parity check.When the communication of data in order to avoid there is unnecessary interference, data can be carried out packing operation, the data sent each time are a frame, and the frame head of setting data is 0xAA, 0xBB, 0xFA, and postamble is 0xFB.Frame head and postamble are removed when data arrive, all the other are the data needed, if mistake appears in frame head or postamble, then abandon this frame data.
3, curve display: the local variable that calling data receives makes data be transferred to program area, converts data character to value data, then calculates response curve, resistance curve, the curve values calculated is composed in respective waveform chart respectively.
4, data are preserved:
(1) time converse routine
Because the collection of data needs clear and definite time representation, so we are by calculating time with time .Vi, then convert the form that we want to squeeze in form by calculating.
(2) data save routine
First temporal information, data message, in addition format information are packaged in together, are driven in attribute node, then by attribute node, data are all preserved.
5, curve observation is preserved with data: by handoff options card " voltage curve ", " resistance curve " and " response curve ", can the change of real-time monitored VOC gas sensor voltage, the change of resistance and response curve, by clicking " preserving data to electrical form " and " preservation curve map ", the related data that curve shows can be saved in EXCEL electrical form, give full play to the data-handling capacity that EXCEL is powerful, and curve is saved as the picture of bmp form.Switch " concentration and volume computing " tab, the required amount injecting liquid of known gas concentration can be calculated, and the gauge of known injection liquid calculates gas concentration in air chamber, for gas sensor of different nature, also can switch the metering system of N-type, P type VOC gas sensor, gas sensor be carried out to the measurement of correlation properties.

Claims (9)

1. the calculating system of gas response sensitivity under non-oxygen environment, is characterized in that, comprising: non-oxygen environment, air chamber, VOC gas sensor, signals collecting and transmission system and host computer;
Be non-oxygen environment in described air chamber;
Described signals collecting and transmission system, comprise
Bleeder circuit, described bleeder circuit is VOC gas sensor and divider resistance R lcompose in series, for aerial output voltage V after exporting VOC sensor desorption airoutput voltage V when adsorbing with VOC sensor in tested gas gas;
A/D modular converter, is connected with bleeder circuit, for the V exported by bleeder circuit airand V gasvoltage analog signal be converted to voltage digital signal;
Microprocessor, is connected with A/D modular converter, for A/D conversion, and V after changing airand V gasvoltage signal carry out pre-service, export V airand V gascan for display and the digital signal transmitted;
Data transmission module, is connected with microprocessor, the V exported for making microprocessor airand V gasdigital data transmission to host computer;
Described host computer, is connected with data transmission module, receives the V of data transmission module transmission airand V gasdigital signal, computing obtains the air-sensitive response sensitivity under non-oxygen environment in the tested gas of VOC gas sensor in air chamber.
2. the calculating system of gas response sensitivity under non-oxygen environment as claimed in claim 1, it is characterized in that: also comprise heating arrangement, making liquid charging stock gas sample heat vaporized is gaseous feed gas, and it is arranged in air chamber, for the injection port of alignment liquid unstripped gas sample is placed.
3. the calculating system of gas response sensitivity under non-oxygen environment as claimed in claim 1, is characterized in that: also comprise display module, is connected with microprocessor, for showing the V that microprocessor exports airand V gasnumerical value.
4. the measuring method of gas response sensitivity under non-oxygen environment, is characterized in that, comprise the steps:
The air chamber of S1, acquisition vacuum environment;
S2, by VOC gas sensor and divider resistance R lcompose in series bleeder circuit;
S3, distribution;
S4, measurement divider resistance R loutput voltage, output voltage V in tested gas when calculating the absorption of VOC gas sensor gas;
S5, make VOC gas sensor desorption, measure divider resistance R loutput voltage, aerial output voltage V after calculating VOC gas sensor desorption air;
S6, computing obtain gas response sensitivity S;
S7, change and pass into the concentration of unstripped gas in air chamber, repeat step S2-S6;
S8, change the kind passing into unstripped gas in air chamber, repeat step S1-S7.
5. the measuring method of gas response sensitivity under non-oxygen environment as claimed in claim 4, it is characterized in that, the computing formula of computing gas response sensitivity is:
For P type VOC gas sensor, gas response sensitivity S is the element ratio of resistance after resistance and element adsorbed gas in atmosphere:
S = R g R a
For N-type VOC gas sensor, gas response sensitivity S is defined as the element ratio of resistance after resistance and element adsorbed gas in atmosphere:
S = R a R g
Wherein, R a = V - V air V air R L , R g = V - V gas V gas R L ; V airand V gasoutput voltage when aerial output voltage and VOC gas sensor adsorb after being respectively VOC gas sensor desorption in tested gas, V is the supply voltage of bleeder circuit, R lfor divider resistance.
6. the measuring method of gas response sensitivity under non-oxygen environment as claimed in claim 4, is characterized in that, the method that the air chamber obtaining vacuum environment adopts be following in one:
(1) use aspiration pump by the air extracting method in air chamber: the injection port of aspiration pump seal, from the bleeding point of air chamber, the air in air chamber extracted out, the rubber tube of bleeding point shrink become flat after, air chamber is interior is vacuum environment or close to vacuum;
(2) inert gas degassing method: pass into inert gas in air chamber, wherein, helium and neon use downward degassing method to be filled with air chamber, and argon gas, Krypton and xenon use upwards degassing method to be filled with air chamber.
7. the method as described in claim 4 or 5, it is characterized in that, the step of described distribution is: the unstripped gas of a certain amount of gaseous state or steam-like is added in the air chamber of known volume, after being filled with carrier gas, tested gas is made in mixing, described unstripped gas is the mixed gas of pure gas or concentration known, wherein, the method obtaining the concentration of unstripped gas be following in one:
(1) when passing into unstripped gas directly to air chamber, the amount of the unstripped gas that service property (quality) flowmeter survey passes into;
(2) when the unstripped gas used is for liquid state, extract in the heating arrangement of a certain amount of liquid material gas injected gas indoor, making liquid state heat vaporized is gaseous state, is learnt the concentration value of the unstripped gas after gasification by following formulae discovery;
ρ×v×ω％/M＝c×V L/(22.4×(273+T)/273)
v＝(273/(273+T))×V L×c×M/(22.4×ρ×ω％)
In formula, ρ is the density of organic liquid, and ω % is the massfraction of tested composition in organic liquid, and M is the molal weight of tested gas, the Celsius temperature in T air chamber, V lfor the volume of air chamber.
8. the measuring method of gas response sensitivity under non-oxygen environment as claimed in claim 4, is characterized in that: the method obtaining gas response sensitivity is:
The V that bleeder circuit in step S4 and step S5 exports by A/D modular converter airand V gasvoltage analog signal be converted to voltage digital signal;
Microprocessor receives the V after the conversion of A/D modular converter airand V gasvoltage digital signal;
The V that data transmission module makes microprocessor export airand V gasdigital data transmission to host computer;
Display module shows the V that microprocessor exports in real time airand V gasnumerical value;
Host computer receives the V of data transmission module transmission airand V gasdigital signal, obtain the air-sensitive responsiveness of VOC gas sensor in tested gas under non-oxygen environment according to the formula operation in claim 5.
9. the measuring method of gas response sensitivity under non-oxygen environment as claimed in claim 8, is characterized in that: host computer also draws out V airand V gasreal-time change curve, the resistance signal Rg of display VOC sensor, and draw out resistance change curves; Also draw out the air-sensitive response sensitivity change curve of VOC gas sensor, demonstrate the real time value of air-sensitive response sensitivity.
CN201410578622.2A 2014-10-24 2014-10-24 Measuring system and method of gas response sensitivity in oxygen-free environment Expired - Fee Related CN104297297B (en)

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CN110057870A (en) * 2019-05-06 2019-07-26 宁波大学 Intelligent liquid vaporation-type VOC gas test characterization instrument based on STM32
CN110057871A (en) * 2019-05-06 2019-07-26 宁波大学 Intelligent liquid vaporation-type VOC gas test method based on STM32

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