CN115598184A - Measuring method and detecting device of detecting system - Google Patents
Measuring method and detecting device of detecting system Download PDFInfo
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Abstract
A measuring method of an air quality detection system relates to the field of gas detection. The single chip microcomputer is connected with the temperature and humidity sensor and the gas sensor, the temperature and humidity sensor is used for acquiring temperature and humidity information, the gas sensor is used for acquiring VOC concentration of air, and after the temperature and humidity information and the VOC concentration are acquired by the single chip microcomputer, the VOC concentration of the air is compensated and calibrated according to the temperature and humidity information; on the basis that the single chip microcomputer obtains temperature and humidity information and gas VOC concentration, the invention further has the following advantages that: in the aspect that the moisture content influences the measurement of the VOC concentration, the single chip microcomputer further performs compensation operation on the gas VOC concentration based on temperature and humidity information, so that the single chip microcomputer obtains a more accurate gas VOC concentration value after operation, and the accuracy of a system result is improved; the invention also discloses a detection device.
Description
Technical Field
The present invention relates to the field of gas detection, and more particularly, to a measurement method and a detection apparatus for a detection system.
Background
The resistance value of the gas sensitive material in the gas sensor changes along with the change of the content (concentration) of VOC in the mixed gas at high temperature, and the content (concentration) of VOC is indirectly obtained by measuring the resistance value (gas sensitive resistor) of the gas sensitive material, but in practical application, the gas sensitive resistor is also influenced by the content of moisture in the mixed gas.
Disclosure of Invention
The present invention is directed to overcoming at least one of the above-mentioned deficiencies in the prior art and providing a method and apparatus for measuring a detection system, which enables a single-chip microcomputer to obtain a more accurate VOC concentration.
The technical scheme adopted by the invention is that,
the measuring method of the air quality detection system comprises a single chip microcomputer, a temperature and humidity sensor and a gas sensor, wherein the single chip microcomputer is connected with the temperature and humidity sensor and the gas sensor, the temperature and humidity sensor is used for acquiring temperature and humidity information, the gas sensor is used for acquiring the VOC concentration of air, and after the temperature and humidity information and the VOC concentration are acquired by the single chip microcomputer, the VOC concentration of air is compensated and calibrated according to the temperature and humidity informationAnd the gas sensor comprises a gas sensitive resistor Rs and a heating resistor R HEAT ；
The measuring method of the gas resistance Rs comprises the following steps:
based on the characteristic curve of the gas resistance Rs:
R X ＝R 0 *EXP(-K*C X ) Where K is the sensitivity coefficient, C X Is the gas concentration, R 0 Gas sensitive resistor Rs value, R, for cleaning air X Is VOC of C X The gas-sensitive resistance Rs value under concentration;
the following measurement formula is obtained for obtaining the resistance value of the gas sensitive resistor Rs:
C x within 1ppm, y = 1/(A) x *K x ) Fitting, wherein K x ＝R x /R 1 When 0.1ppm =1/10, namely A 0.1 *(R 0.1 /R 1 ) =10; then A is 0.1 ＝10/K 0.1 ；
When R is X >R 0.1 That is, the range y of the gas concentration below 0.1ppm is calculated as follows:
y＝1/(A 0.1 *K x )；
when R is 1 <R X <R 0.1 Namely, the range y of the gas concentration between 0.1ppm and 1ppm is calculated as follows:
y＝1/(A x *K x ) (ii) a Wherein A is x ＝1+(A 0.1 -1)*(R x -R 1 )/(R 0.1 -R 1 )；
When R is X <R 1 Namely, the range y of the gas concentration between 1ppm and 10ppm is calculated as follows:
y＝1+9*(R 1 -R x )/(R 1 -R 10 )；
wherein R is 0.1 Is concentration C 0.1 Resistance value at =0.1ppm, R 1 Is concentration C 1 Resistance value at 1ppm, R 10 Is concentration C 10 A resistance value at 10ppm, and a is an adjustment factor coefficient.
According to the invention, the characteristic curve of the gas-sensitive resistor Rs is simplified, and R0.1 can be calculated only by calibrating R1 and R10 (namely 1ppm and 10 ppm), so that the VOC concentration in the range of 0-10 ppm can be calculated; by adopting the algorithm, the production efficiency of the sensor can be greatly improved, and meanwhile, good support is provided for zero point self calibration of a user; on the basis that the single chip microcomputer obtains temperature and humidity information and gas VOC concentration, the invention further has the following advantages that: in the aspect of measuring the VOC concentration influenced by the moisture content, the single chip microcomputer further performs compensation operation on the gas VOC concentration based on the temperature and humidity information, so that the single chip microcomputer obtains a more accurate gas VOC concentration value after operation, and the accuracy of a system result is improved.
As an alternative embodiment, the heating resistor R HEAT The single chip microcomputer comprises an IO interface connected with the heating resistor R HEAT For the heating resistor R HEAT Current regulation of (2); the single chip microcomputer comprises an ADC interface, the ADC interface is connected with the gas-sensitive resistor Rs, and the single chip microcomputer acquires the resistance value change of the gas-sensitive resistor Rs through the ADC interface.
As an optional implementation manner, the device further includes a resistor R3, one end of the resistor R3 is connected to the IO interface, and the other end of the resistor R3 is connected in series to the heating resistor R HEAT The single chip microcomputer controls the heating resistor R by controlling the IO interface HEAT The current of (a); or, the resistance value of the resistor R3 is 200 to 500 Ω, and preferably, the resistance value of the resistor R3 is 300 Ω.
The invention changes the heating resistor R by setting the IO port of the singlechip and controlling the high and low level of the IO port HEAT The current of the sensor accelerates the preheating, provides a proper high-temperature environment for the operating environment of the gas-sensitive resistor Rs, and simultaneously, the rapid preheating effect is realized by controlling the level of the IO interface end, so that the operating efficiency of the system is improved; meanwhile, the current in the circuit is limited to a certain extent due to the device operation requirement of the single chip microcomputer, so that the resistor R3 is added, and the heating resistor R is adjusted through the resistor R3 HEAT The preheating process is accelerated.
As an alternative embodiment, the heating resistance R of the gas sensor HEAT The device is also connected with a resistor R4, and one end of the resistor R4 is grounded; or, the gas sensingHaving one end connected to ground; or the resistance value of the resistor R4 is 50-100 omega, preferably, the resistance value of R4 is 68 omega, and R4 is taken as the heating resistor R HEAT A main fixed current.
The resistor R4 and the resistor R3 in the invention and the heating resistor R HEAT In series, wherein a resistor R4 is part of the heating circuit, adapted to the heating resistor R HEAT 。
As an alternative embodiment, the gas sensing resistor Rs is connected in series with a voltage dividing resistor R1.
As an optional embodiment, the resistance value of the voltage dividing resistor R1 is 50K Ω to 150K Ω, and preferably, the resistance value of R1 is 100K Ω.
In the invention, the voltage dividing resistor R1 and the gas sensitive resistor Rs form a voltage dividing circuit, the ADC interface is connected to the voltage dividing circuit to perform ADC sampling gas sensitive resistor Rs voltage division, so as to obtain a voltage signal and resistance value change of the gas sensitive resistor Rs, and the VOC concentration can be measured through the relation between the gas sensitive resistor Rs and the VOC concentration.
As an optional implementation manner, a power supply data interface is provided, and the power supply data interface is used for inputting a 5V power supply to the single chip microcomputer.
As an optional implementation manner, the power supply data interface is connected in parallel with a resistor R5 and a resistor R6, and the resistance ranges of the resistor R5 and the resistor R6 are 5k Ω to 15k Ω; preferably, the resistors R5 and R6 are selected to have a resistance of 10k Ω.
The two resistors are arranged in the invention, so that the IIC has a determined high and low level during communication, the communication is more stable, and the bus requirements of the IIC protocol are matched.
As an optional implementation manner, the power supply data interface is connected with an IIC bus, the IIC bus uses a standard IIC protocol for communication, the IIC bus is used for connecting an external device, and the external device reads the data of the single chip microcomputer through the IIC bus and the standard IIC protocol.
As an optional implementation manner, the power supply data interface includes an LDO linear regulator, a power supply voltage passing through the LDO linear regulator is 3.0V, and the power supply is input to the temperature and humidity sensor and the gas sensor.
In an alternative embodiment, the LDO linear regulator is connected in parallel with a filter capacitor to provide a smoother voltage.
In an optional implementation manner, one end of the filter capacitor is connected in parallel with the LDO linear regulator, and the other end is grounded.
As an optional implementation manner, the filter capacitor includes a first capacitor, a second capacitor, and a third capacitor.
As an optional implementation manner, the single chip microcomputer includes an IIC interface, the IIC interface is connected to the temperature and humidity sensor, and the single chip microcomputer acquires temperature and humidity data measured by the temperature and humidity sensor through the IIC interface.
As an optional implementation manner, the temperature and humidity sensor and the single chip microcomputer communicate with each other by using an IIC communication protocol, or pull-up resistors R8 and R9 are arranged between the temperature and humidity sensor and the IIC interface.
As an optional implementation manner, the resistance values of the pull-up resistors R8 and R9 are 1k Ω to 15k Ω; preferably, the resistance values of R8 and R9 are 10k Ω.
In the invention, the addition of the pull-up resistor enables the IIC bus to have a determined level state during communication, and the singlechip is connected with the temperature and humidity sensor or the IIC communication is stable during data reading.
As an optional implementation manner, the device comprises a PCB, wherein the gas sensor, the temperature and humidity sensor and the single chip are integrated on the PCB, the PCB comprises at least one isolation island, through holes are formed around the isolation island, and the gas sensor or the temperature and humidity sensor is arranged on the isolation island.
As an optional implementation manner, the through hole is of a C-shaped structure, and an opening of the through hole is communicated with the PCB to form the isolation island.
As an optional implementation manner, the PCB board is provided with two isolation islands, and the opening directions of the two isolation islands are opposite to each other and are disposed at two ends of the PCB board.
A temperature and humidity compensation method is used for compensation measurement of the gas-sensitive resistor Rs in the detection system, the singlechip realizes temperature and humidity compensation by adopting the following algorithm,
in the formula, TVOC is the raw data VOC concentration to its temperature and humidity compensation, TVOCx is the VOC concentration after temperature and humidity compensation, RH is relative humidity, and T is the temperature.
A detection device utilizes the measurement method and/or the temperature and humidity compensation method to detect air quality.
Compared with the prior art, the invention has the following beneficial effects:
in the invention, the VOC gas sensor needs to be heated, heat can be generated, and the measurement of the temperature and humidity sensor is seriously influenced, so the PCB layout design needs to be considered, and the heat source conduction path is changed by the PCB layout in an isolation island mode; therefore, in a limited size, the influence of a heating source on the temperature and humidity sensor is greatly reduced, preferably, two isolation island structures are arranged in a mode of reducing the influence as much as possible, the structure is provided with an annular C-shaped through hole structure, the contact area between the structure and a PCB (printed circuit board) can be reduced to the greatest extent, and the heating resistor R in the gas sensor is enabled to be HEAT The influence of the heat transferred out on the board is minimal; meanwhile, a better scheme is that two isolation island structures are arranged, and a gas sensor and a temperature and humidity sensor are respectively arranged, so that the influence of the sensors on the PCB during measurement is further reduced, and the mutual measurement is not influenced; it may also be a inferior solution, only one isolation island is provided for placing the gas sensor.
Drawings
FIG. 1 is an overall structural view of the present invention.
FIG. 2 is a schematic diagram of a PCB board of the present invention.
In the figure, a temperature and humidity sensor 100, a gas sensor 200 and a power supply data interface 300 are shown.
Detailed Description
The drawings are only for purposes of illustration and are not to be construed as limiting the invention. For a better understanding of the following embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
Example 1
As shown in fig. 1, a measurement method of an air quality detection system includes a single chip microcomputer, a temperature and humidity sensor 100 and a gas sensor 200, the single chip microcomputer is connected with the temperature and humidity sensor 100 and the gas sensor 200, the temperature and humidity sensor 100 is used for acquiring temperature and humidity information, the gas sensor 200 is used for acquiring a VOC concentration of air, after the temperature and humidity information and the VOC concentration are acquired by the single chip microcomputer, the VOC concentration of air is compensated and calibrated according to the temperature and humidity information, and the gas sensor 200 includes a gas sensitive resistor Rs and a heating resistor R HEAT ，。
On the basis that the temperature and humidity information and the gas VOC concentration are obtained by the single chip microcomputer, the invention further has the following advantages that: in the aspect of measuring the VOC concentration influenced by the moisture content, the single chip microcomputer further performs compensation operation on the gas VOC concentration based on the temperature and humidity information, so that the single chip microcomputer obtains a more accurate gas VOC concentration value after operation, and the accuracy of a system result is improved.
As an optional implementation mode, the single chip microcomputer comprises an IO interface, and the IO interface is connected with the heating resistor R HEAT For heating the resistance R HEAT Current regulation of (3); the single chip microcomputer comprises an ADC interface, the ADC interface is connected with the gas-sensitive resistor Rs, and the single chip microcomputer acquires the resistance value change of the gas-sensitive resistor Rs through the ADC interface.
As an optional implementation manner, the IO interface further includes a resistor R3, one end of the resistor R3 is connected to the IO interface, and the other end of the resistor R3 is connected in series to the heating resistor R HEAT The single chip microcomputer controls the heating resistor R by controlling the IO interface HEAT The current of (a); or the resistance value of the resistor R3 is 200-500 omega, preferablyOptionally, the resistance of the resistor R3 is 300 Ω.
The invention changes the heating resistor R by setting the IO port of the singlechip and controlling the high and low level of the IO port HEAT The current of the sensor accelerates the preheating, provides a proper high-temperature environment for the operating environment of the gas-sensitive resistor Rs, and simultaneously, the rapid preheating effect is realized by controlling the level of the IO interface end, so that the operating efficiency of the system is improved; meanwhile, the current in the circuit is limited to a certain extent due to the device operation requirement of the single chip microcomputer, so that the resistor R3 is added, and the heating resistor R is adjusted through the resistor R3 HEAT The preheating process is accelerated.
As an alternative embodiment, the gas sensor 200 is further connected with a resistor R4, and one end of the resistor R4 is grounded; alternatively, the gas sensor 200 has one end connected to ground; or the resistance value of the resistor R4 is 50-100 omega, preferably, the resistance value of R4 is 68 omega, and R4 is taken as the heating resistor R HEAT A main fixed current.
The resistor R4 and the resistor R3 in the invention and the heating resistor R HEAT In series, wherein a resistor R4 is part of the heating circuit, adapting the heating resistor R HEAT 。
As an alternative embodiment, the gas sensing resistor Rs is connected in series with a voltage dividing resistor R1.
As an optional embodiment, the resistance value of the voltage dividing resistor R1 is 10K Ω to 150K Ω, and preferably, the resistance value of R1 is 100K Ω.
In the invention, the voltage dividing resistor R1 and the gas sensitive resistor Rs form a voltage dividing circuit, an ADC interface is connected to the voltage dividing circuit to divide the voltage of the ADC sampling gas sensitive resistor Rs, so that a voltage signal and resistance value change of the gas sensitive resistor Rs are obtained, and the VOC concentration can be measured through the relation between the gas sensitive resistor Rs and the VOC concentration.
As an optional implementation manner, a power supply data interface 300 is provided, and the power supply data interface 300 is used for inputting a 5V power supply to the single chip microcomputer.
As an optional implementation manner, the power supply data interface 300 is connected in parallel with a resistor R5 and a resistor R6, and the resistance ranges of the resistor R5 and the resistor R6 are 1k Ω to 15k Ω; preferably, the resistors R5 and R6 are selected to have a resistance of 10k Ω.
The two resistors are arranged in the invention, so that the IIC has a determined high and low level during communication, the communication is more stable, and the bus requirements of the IIC protocol are matched.
As an optional implementation manner, the power supply data interface 300 is connected to an IIC bus, the IIC bus uses a standard IIC protocol for communication, the IIC bus is used for connecting an external device, and the external device reads the data of the single chip microcomputer through the IIC bus and the standard IIC protocol.
As an optional implementation manner, the power supply data interface 300 is provided with an LDO linear regulator, the power supply voltage passing through the LDO linear regulator is 3.0V, and the power supply is input to the temperature and humidity sensor 100 and the gas sensor 200.
In an alternative embodiment, the LDO linear regulator is connected in parallel with a filter capacitor for providing a smoother voltage.
In an optional implementation manner, one end of the filter capacitor is connected in parallel with the LDO linear regulator, and the other end is grounded.
As an optional implementation manner, the filter capacitor includes a first capacitor, a second capacitor, and a third capacitor.
As an optional implementation manner, the single chip microcomputer includes an IIC interface, the IIC interface is connected to the temperature and humidity sensor 100, and the single chip microcomputer obtains temperature and humidity data measured by the temperature and humidity sensor 100 through the IIC interface.
As an optional implementation manner, the temperature and humidity sensor 100 and the single chip microcomputer communicate with each other using an IIC communication protocol, or pull-up resistors R8 and R9 are provided between the temperature and humidity sensor 100 and the IIC interface.
As an optional implementation manner, the resistance values of the pull-up resistors R8 and R9 are 1k Ω to 15k Ω; preferably, the resistance values of R8 and R9 are 10k Ω.
In the invention, the addition of the pull-up resistor enables the IIC bus to have a determined level state during communication, and the single chip microcomputer is connected with the temperature and humidity sensor 100 or the IIC communication is stable during data reading.
As an optional implementation manner, as shown in fig. 2, the temperature and humidity sensor device includes a PCB, the gas sensor 200, the temperature and humidity sensor 100, and the single chip are integrated on the PCB, the PCB includes at least one isolation island, through holes are provided around the isolation island, and the gas sensor 200 or the temperature and humidity sensor 100 is provided on the isolation island.
As an optional implementation manner, the through hole is a C-shaped structure, and an opening of the through hole is communicated with the PCB to form the isolation island.
As an optional implementation manner, the PCB board is provided with two isolation islands, and the opening directions of the two isolation islands are opposite to each other and are disposed at two ends of the PCB board.
A measurement method for measurement of the gas-sensitive resistor Rs in the detection system, based on a characteristic curve of the gas-sensitive resistor Rs:
R X ＝R 0 *EXP(-K*C X ) Wherein K is the sensitivity coefficient, C X Is the gas concentration, R 0 Gas sensitive resistors Rs, R for cleaning air X Is VOC of C X The gas-sensitive resistance Rs value under concentration;
the following measurement formula is obtained for obtaining the resistance value of the gas sensitive resistor Rs:
C x within 1ppm, y = 1/(A) x *K x ) Fitting, wherein K x ＝R x /R 1 When 0.1ppm =1/10, namely A 0.1 *(R 0.1 /R 1 ) =10; then A is 0.1 ＝10/K 0.1 ；
When R is X >R 0.1 That is, the range of the gas concentration below 0.1ppm is calculated as follows:
y＝1/(A 0.1 *K x )；
when R is 1 <R X <R 0.1 Namely, the range of the gas concentration between 0.1ppm and 1ppm is calculated as follows:
y＝1/(A x *K x ) (ii) a Wherein A is x ＝1+(A 0.1 -1)*(R x -R 1 )/(R 0.1 -R 1 )。
When R is X <R 1 Namely, the range of the gas concentration between 1ppm and 10ppm is calculated as follows:
y＝1+9*(R 1 -R x )/(R 1 -R 10 )；
wherein R is 0.1 Is concentration C 0.1 Resistance value at =0.1ppm, R 1 Is concentration C 1 Resistance value at 1ppm, R 10 Is concentration C 10 A resistance value at 10ppm, and a is an adjustment factor coefficient.
According to the invention, the characteristic curve of the gas-sensitive resistor Rs is simplified, and R0.1 can be calculated only by calibrating R1 and R10 (namely 1ppm and 10 ppm), so that the VOC concentration in the range of 0-10 ppm can be calculated; by adopting the algorithm, the production efficiency of the sensor can be greatly improved, and meanwhile, good support is provided for zero point self-calibration of a user.
A temperature and humidity compensation method is used for compensation measurement of the gas-sensitive resistor Rs in the detection system, the singlechip realizes temperature and humidity compensation by adopting the following algorithm,
in the formula, TVOC is the raw data VOC concentration to its temperature and humidity compensation, TVOCx is the VOC concentration after temperature and humidity compensation, RH is relative humidity, and T is the temperature.
A detection device utilizes the measurement method and/or the temperature and humidity compensation method to detect air quality.
In particular, the method comprises the following steps of,
according to experiments and related theories, the gas-sensitive resistance Rs characteristic model accords with an exponential relationship, and fitting can be performed by applying NTC characteristics.
R X ＝R 0 *EXP(-K*C X )
Wherein K is the sensitivity coefficient, C X Is the gas concentration, R 0 Gas-sensitive electric apparatus for cleaning airResistance Rs, R X C as a VOC X Gas sensitive resistance Rs at concentration.
R 0.1 ＝R 0 *EXP(-K*C 0.1 )
R 1 ＝R 0 *EXP(-K*C 1 )
R 10 ＝R 0 *EXP(-K*C 10 )
In the formula R 0.1 Is concentration C 0.1 Resistance value at =0.1ppm, R 1 Is concentration C 1 Resistance value at 1ppm, R 10 Is concentration C 10 Resistance value at 10ppm
Can obtain
LOG(R 0.1 /R 0 )/LOG(R 1 /R 0 )＝C 0.1 /C 1 ＝LOG(R 1 /R 0 )/LOG(R 10 /R 0 )＝C 1 /C 10
Therefore it has the advantages of
(LOG(R 1 /R 0 )) 2 ＝LOG(R 0.1 /R 0 )*LOG(R 10 /R 0 )
Under the condition of low precision requirement, the precision requirement can be simplified to
(R 1 /R 0.1 ) 2 ＝(R 10 /R 0.1 )
Let K = R 10 /R 1 Then simplify the order R 1 /R 0.1 K, this is the critical point,
cx is fit to within 1ppm using y = 1/(Ax. Kx), where Kx = R x /R 1 When 0.1ppm =1/10, namely A 0.1 *(R 0.1 /R 1 ) =10; then A is 0.1 ＝10/K 0.1 ；
When R is X >R 0.1 That is, the range of the gas concentration below 0.1ppm is calculated as follows:
y＝1/(A 0.1 *Kx)；
when R is 1 <R X <R 0.1 That is, the range of the gas concentration between 0.1ppm and 1ppm is calculated as follows:
y = 1/(Ax × Kx); wherein A is x ＝1+(A 0.1 -1)*(R x -R 1 )/(R 0.1 -R 1 )。
When R is X <R 1 Namely, the range of the gas concentration between 1ppm and 10ppm is calculated as follows:
y＝1+9*(R 1 -R x )/(R 1 -R 10 )；
wherein R is 0.1 Is resistance value at concentration C0.1=0.1ppm, R 1 The resistance at a concentration of C1=1ppm, R10 the resistance at a concentration of C10=10ppm, and a the adjustment factor coefficient.
In the invention, the VOC gas sensor 200 generates heat when being heated, and has serious influence on the measurement of the temperature and humidity sensor 100, so the PCB layout needs to be considered, and the PCB layout changes the heat source conduction path in an isolation island mode; therefore, in a limited size, the influence of a heating source on the temperature and humidity sensor 100 is greatly reduced, preferably, two isolation island structures are arranged in a mode of reducing the influence as much as possible, the structure is provided with an annular C-shaped through hole structure, the contact area between the structure and a PCB (printed circuit board) can be reduced to the greatest extent, and the heating resistor R in the gas sensor 200 is enabled to be heated HEAT The influence of the heat transferred out on the board is minimal; meanwhile, a better scheme is that two isolation island structures are arranged, and the gas sensor 200 and the temperature and humidity sensor 100 are respectively placed, so that the influence of the sensors on the PCB during measurement is further reduced, and the mutual measurement is not influenced; it may also be a less preferred solution to provide only one isolated island for placement of the gas sensor 200.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific embodiments of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention claims should be included in the protection scope of the present invention claims.
Claims (10)
1. A measurement method of an air quality detection system, the air quality detection system comprising:
the device comprises a single chip microcomputer, a temperature and humidity sensor and a gas sensor, wherein the single chip microcomputer is connected with the temperature and humidity sensor and the gas sensor, the temperature and humidity sensor is used for acquiring temperature and humidity information, the gas sensor is used for acquiring the VOC concentration of air,
the gas sensor is characterized in that after the single chip microcomputer obtains the temperature and humidity information and the VOC concentration, the VOC concentration of air is compensated and calibrated according to the temperature and humidity information, and the gas sensor comprises a gas sensitive resistor Rs and a heating resistor R HEAT ，
The measurement method is used for measuring the gas resistance Rs and comprises the following steps:
based on the characteristic curve of the gas resistance Rs:
R X ＝R 0 *EXP(-K*C X ) Wherein K is the sensitivity coefficient, C X Is the gas concentration, R 0 Gas sensitive resistor Rs value, R, for cleaning air X Is VOC of C X The gas-sensitive resistance Rs value under concentration;
the following measurement formula is obtained for obtaining the resistance value of the gas sensitive resistor Rs:
C x within 1ppm, y = 1/(A) x *K x ) Fitting, wherein K x ＝R x /R 1 When 0.1ppm =1/10, namely A 0.1 *(R 0.1 /R 1 ) =10; then A is 0.1 ＝10/K 0.1 ；
When R is X >R 0.1 That is, the range y of the gas concentration below 0.1ppm is calculated as follows:
y＝1/(A 0.1 *K x )；
when R is 1 <R X <R 0.1 That is, the range y of the gas concentration between 0.1ppm and 1ppm is calculated as follows:
y＝1/(A x *K x ) (ii) a Wherein A is x ＝1+(A 0.1 -1)*(R x -R 1 )/(R 0.1 -R 1 )；
When R is X <R 1 Namely, the range y of the gas concentration between 1ppm and 10ppm is calculated as follows:
y＝1+9*(R 1 -R x )/(R 1 -R 10 )；
wherein R is 0.1 Is concentration C 0.1 Resistance value at =0.1ppm, R 1 Is concentration C 1 Resistance value at 1ppm, R 10 Is concentration C 10 A resistance value at 10ppm, and a is an adjustment factor coefficient.
2. The measuring method of the air quality detecting system according to claim 1, characterized by comprising a PCB board, wherein the gas sensor, the temperature and humidity sensor and the single chip microcomputer are integrated on the PCB board, the PCB board comprises at least one isolation island, through holes are arranged around the isolation island, and the gas sensor or the temperature and humidity sensor is arranged on the isolation island.
3. The measuring method of an air quality detecting system according to claim 2, wherein the through hole is a C-shaped structure, and an opening of the through hole is communicated with the PCB board to form the isolation island.
4. The measuring method of the air quality detecting system according to claim 3, wherein the PCB is provided with two isolation islands, and the two isolation islands are provided at two ends of the PCB with opposite opening directions.
5. The measuring method of the air quality detection system according to claim 1, wherein the single chip microcomputer comprises an IO interface, and the IO interface is connected with the heating resistor R HEAT For the heating resistor R HEAT Current regulation of (2); the single chip microcomputer further comprises an ADC interface, the ADC interface is connected with the gas sensitive resistor Rs, and the single chip microcomputer acquires the resistance value change of the gas sensitive resistor Rs through the ADC interface.
6. The measuring method of the air quality detecting system according to claim 5, further comprising a resistor R3, wherein one end of the resistor R3 is connected to the IO interface, and the other end is connected in series with the heating resistor R HEAT The single chip microcomputer controls the heating power by controlling the IO interfaceResistance R HEAT Of the current of (c).
7. The method as claimed in claim 2, wherein the gas sensing resistor Rs is connected in series with a voltage dividing resistor R1.
8. The measuring method of the air quality detecting system according to claim 6, further comprising a resistor R3 having a resistance of 200 to 500 Ω.
9. The method as claimed in claim 6, wherein the gas sensor 200 is further connected to a resistor R4, the other end of the resistor R4 is grounded, and the resistance of the resistor R4 is 50 Ω to 100 Ω.
10. A test device for air quality testing using the method of any one of claims 1 to 9.
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