CN111089941A - Formaldehyde detection device and detection method thereof - Google Patents
Formaldehyde detection device and detection method thereof Download PDFInfo
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- CN111089941A CN111089941A CN201911236049.6A CN201911236049A CN111089941A CN 111089941 A CN111089941 A CN 111089941A CN 201911236049 A CN201911236049 A CN 201911236049A CN 111089941 A CN111089941 A CN 111089941A
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0062—General constructional details of gas analysers, e.g. portable test equipment concerning the measuring method, e.g. intermittent, or the display, e.g. digital
- G01N33/0067—General constructional details of gas analysers, e.g. portable test equipment concerning the measuring method, e.g. intermittent, or the display, e.g. digital by measuring the rate of variation of the concentration
Abstract
The invention discloses a formaldehyde detection device and a detection method thereof, wherein the detection method comprises the following steps: the measuring sensor is sensitive to formaldehyde and is used for detecting the concentration of the formaldehyde and outputting a measured AD value AD 1; the reference sensor comprises a measuring sensor and a formaldehyde filtering membrane arranged on the measuring sensor, wherein the formaldehyde filtering membrane is used for filtering formaldehyde in the measured gas, detecting the concentration of VOC (volatile organic compounds) which cause interference to the formaldehyde in the air and outputting a reference AD value AD 2; and the processor processes the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm, wherein the AD difference value H is AD1-AD2 so as to obtain the formaldehyde concentration value C. The formaldehyde detection device disclosed by the invention can reduce the influence of VOC (volatile organic compounds) on formaldehyde detection in a detected environment, can also eliminate the influence of a measurement sensor and a reference sensor on alcohol response difference, and has high measurement result precision.
Description
Technical Field
The invention relates to the technical field of formaldehyde detection, in particular to a formaldehyde detection device and a detection method thereof.
Background
Common formaldehyde concentration detection methods comprise spectrophotometry, chromatography, fluorescence and polarography, but formaldehyde detection devices manufactured by the methods are high in cost and complex in operation, and are not suitable for large-scale application in the fields of air purifiers, heating ventilation air conditioners and the like. At present, the formaldehyde concentration is generally detected by adopting an electrochemical principle, wherein the principle is that oxygen and formaldehyde are subjected to oxidation-reduction reaction on an electrode to generate a signal in direct proportion to the formaldehyde concentration, and the formaldehyde concentration is calculated according to the signal. The detection method has the defects of high response speed and short service life, and the formaldehyde concentration detection result is interfered by alcohols such as perfume, alcohol and the like because the formaldehyde sensor reacts to the alcohol interference gases such as perfume, alcohol and the like.
In order to solve the technical problem, chinese patent CN107990512A discloses an air conditioning equipment and a formaldehyde detection device thereof, wherein the formaldehyde detection device includes a formaldehyde sensor and a pair of VOC sensors, and determines whether there is a sudden increase of interfering gas according to whether the formaldehyde sensor and the VOC sensors suddenly change, if there is no sudden increase of interfering gas, the formaldehyde detection value at the current moment is directly output, and if there is a sudden increase of interfering gas, the formaldehyde detection value before sudden change is output. Although the scheme can identify the interference gas suddenly increased in the tested environment, the method has the defects that the interference gas existing in the tested environment cannot be identified, the influence of the interference gas existing in the background on the detection result cannot be eliminated, and the anti-interference performance is limited.
In order to eliminate the influence of interference gas on formaldehyde detection, chinese patent CN104614423B discloses a technical scheme of obtaining a formaldehyde gas concentration signal in an actual environment by subtracting an output signal difference of a reference formaldehyde sensor from an output signal of a measurement formaldehyde sensor, wherein the measurement formaldehyde sensor and the reference formaldehyde sensor are two formaldehyde sensors of the same type, and a semipermeable membrane capable of filtering formaldehyde is arranged on the reference formaldehyde sensor. The method can reduce the influence of the interference factors in the environment on the detection precision. But it does not identify the presence of a sudden increase in ambient interfering gases, nor does it eliminate the effect of the difference between the two sensors on the measurement.
Disclosure of Invention
The invention aims to provide a formaldehyde detection device and a detection method thereof, which can effectively reduce the interference of interfering gas and accurately test the actual concentration of formaldehyde, aiming at the defects in the prior art.
The invention relates to a formaldehyde detection device, which comprises:
the measuring sensor is sensitive to formaldehyde and is used for detecting the concentration of the formaldehyde and outputting a measured AD value AD 1;
the device comprises a reference sensor and a formaldehyde filtering membrane, wherein the reference sensor comprises a measuring sensor and the formaldehyde filtering membrane is arranged on the measuring sensor, and the formaldehyde filtering membrane is used for filtering formaldehyde in the measured gas, detecting the concentration of VOC (volatile organic compounds) which cause interference to the formaldehyde in the air and outputting a reference AD value AD 2;
and the processor is respectively connected with the measurement sensor and the reference sensor, receives the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor, and processes the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm, namely AD1-AD2 to obtain a formaldehyde concentration value C.
Further, processing the AD difference H-AD 1-AD2 between the measured AD value AD1 and the reference AD value AD2 according to a preset algorithm to obtain a formaldehyde concentration value C, comprising: under the pure formaldehyde environment, simultaneously detecting formaldehyde with known concentration by using a measuring sensor and a reference sensor, and calibrating the relation between the reference AD and the AD difference H of the measuring AD and the formaldehyde concentration according to the detection result, thereby obtaining the relation C1-f (AD1-AD2) -K1-H between the formaldehyde concentration value C and the AD difference H output by the two sensors under different formaldehyde environment concentrationsn+K2*Hn-1+…+Kn*H+b,n≥1。
Further, processing the AD difference H of the measured AD value AD1 and the reference AD value AD 2-AD 1-AD2 according to a preset algorithm to obtain a formaldehyde concentration value C, comprising: under the pure VOC environment, a measuring sensor and a reference sensor are used for detecting VOC with known concentration, and the relation between AD difference H and VOC concentration of reference AD and measurement AD is calibrated according to the detection result, so that the AD difference AD3 (AD2) caused by VOC is obtained under different VOC concentrations.
Further, processing the measured AD value AD1 and the reference AD value AD2 according to a preset algorithm to obtain an AD difference H ═ AD1-AD2, so as to obtain a formaldehyde concentration value C, including:
the processor carries out mutation judgment on the reference AD value AD2 at the current sampling moment to determine whether alcohol exists in the tested environment;
if the rising amplitude of the reference AD value AD2 exceeds the first threshold value a1, the reference AD value AD2 continuously and monotonically increases within a certain time, and the rising rate is greater than the second threshold value a2, the alcohol in the tested environment is indicated.
Further, the processor confirms that there is alcohol interference, locks the formaldehyde concentration C before mutation, quits mutation judgment after meeting the quit mutation judgment condition, and the quit mutation judgment is also divided into three conditions:
(1) the reference AD value AD2 begins to decrease and the formaldehyde detection AD value H ═ AD1-AD2 begins to decrease, which shows that the mutation is close to the complete and begins to gradually tend to be smooth, and then the mutation is quitted and locked to enter the concentration output;
(2) the reference AD value AD2 tends to be stable and the formaldehyde detection AD value H (AD1-AD2) tends to be stable, which indicates that the current environment is stable, and the current environment is quitted from mutation and is judged to enter concentration output;
(3) and judging whether the current formaldehyde concentration is less than a3 times of the formaldehyde concentration when locking, if so, quitting mutation judgment, and processing the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm, namely AD1-AD2 to obtain a formaldehyde concentration value C.
Further, the processor processes the AD difference H AD1-AD2 between the measurement AD value AD1 outputted by the measurement sensor and the reference AD value AD2 outputted by the reference sensor according to a preset algorithm to obtain the formaldehyde concentration value C, which is divided into the following cases:
(1) when the mutation does not exist, outputting the concentration of the formaldehyde calculated at the current moment in real time;
(2) after mutation occurs, locking the formaldehyde concentration C (t0) calculated before mutation, further judging whether the difference value between the formaldehyde concentration C (t) calculated at the current moment and the formaldehyde concentration C (t0) calculated before mutation is greater than a third threshold value a4, and if the difference value is greater than the third threshold value a4, slowly changing the formaldehyde output concentration from C (t0) to C (t); and if the concentration is larger than the third threshold value a4, outputting the concentration of the formaldehyde calculated at the current moment in real time.
The formaldehyde detection method using the formaldehyde detection device is characterized by comprising the following steps of: and processing the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm to obtain a formaldehyde concentration value C.
Further, processing the AD difference H between the measured AD value AD1 and the reference AD value AD2 according to a preset algorithm to obtain a formaldehyde concentration value C, including: under the pure formaldehyde environment, simultaneously using a measuring sensor and a reference sensor to detect formaldehyde with known concentration, and calibrating the relation between the reference AD and the AD difference H of the measuring AD and the formaldehyde concentration according to the detection result, thereby obtaining the relation C-K1H between the formaldehyde concentration value C and the AD difference H output by the two sensors under different formaldehyde environment concentrationsn+K2*Hn-1+``````+Kn*H+b,n≥1。
Further, the processing the AD difference H between the measured AD value AD1 and the reference AD value AD2 according to a preset algorithm, which is AD1-AD2, to obtain the formaldehyde concentration value C, includes: under the pure VOC environment, a measuring sensor and a reference sensor are used for detecting VOC with known concentration, and the relation between AD difference H and VOC concentration of reference AD and measurement AD is calibrated according to the detection result, so that the AD difference AD3 (AD2) caused by VOC is obtained under different VOC concentrations.
Further, the processing the measured AD value AD1 and the reference AD value AD2 according to a preset algorithm to obtain an AD difference H ═ AD1-AD2, so as to obtain a formaldehyde concentration value C, includes:
the processor carries out mutation judgment on the reference AD value AD2 at the current sampling moment to determine whether alcohol exists in the tested environment;
if the rising amplitude of the reference AD value AD2 exceeds the first threshold value a1, the reference AD value AD2 continuously and monotonically increases within a certain time, and the rising rate is greater than the second threshold value a2, the alcohol in the tested environment is indicated.
Further, the processor confirms that there is alcohol interference, locks the formaldehyde concentration C before mutation, quits mutation judgment after meeting the quit mutation judgment condition, and the quit mutation judgment is also divided into three conditions:
(1) the reference AD value AD2 begins to decrease and the formaldehyde detection AD value H ═ AD1-AD2 begins to decrease, which shows that the mutation is close to the complete and begins to gradually tend to be smooth, and then the mutation is quitted and locked to enter the concentration output;
(2) the reference AD value AD2 tends to be stable and the formaldehyde detection AD value H (AD1-AD2) tends to be stable, which indicates that the current environment is stable, and the current environment is quitted from mutation and is judged to enter concentration output;
(3) and judging whether the current formaldehyde concentration is less than a3 times of the formaldehyde concentration when locking, if so, quitting mutation judgment, and processing the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm, namely AD1-AD2 to obtain a formaldehyde concentration value C.
Further, the processor processes the AD difference H between the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor, AD1-AD2, according to a preset algorithm, to obtain the formaldehyde concentration value C, which is divided into the following cases:
(1) when the mutation does not exist, outputting the concentration of the formaldehyde calculated at the current moment in real time;
(2) after the mutation has occurred, the concentration of formaldehyde C (t) calculated before the mutation is locked in0) Further judging the concentration C (t) of formaldehyde calculated at the current moment and the concentration C (t) of formaldehyde calculated before mutation0) Whether the difference is larger than a third threshold value a4, and if the difference is larger than the third threshold value a4, the formaldehyde output concentration is from C (t)0) Slowly to c (t); and if the concentration is larger than the third threshold value a4, outputting the concentration of the formaldehyde calculated at the current moment in real time.
The formaldehyde detection device disclosed by the invention can reduce the influence of VOC on formaldehyde detection in a detected environment, can also eliminate the influence of a measurement sensor and a reference sensor on alcohol response difference, and has high measurement result precision.
Drawings
FIG. 1 is a schematic structural diagram of a formaldehyde detecting apparatus according to the present invention;
FIG. 2 is a schematic flow chart of a formaldehyde detection method according to the present invention;
FIG. 3 is a schematic view of the mutation determination process according to the present invention;
FIG. 4 is a graph of formaldehyde concentration C versus measured AD1, reference AD2, and AD difference H for one embodiment of the present invention;
FIG. 5 is a graph of AD difference H versus formaldehyde concentration C according to one embodiment of the present invention.
Detailed Description
The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.
As shown in fig. 1 and 2, a formaldehyde detecting apparatus of the present invention includes:
the measuring sensor is sensitive to formaldehyde and is used for detecting the concentration of the formaldehyde and outputting a measured AD value AD 1;
the reference sensor comprises a measuring sensor and a formaldehyde filtering membrane arranged on the measuring sensor, wherein the formaldehyde filtering membrane is used for filtering formaldehyde in the measured gas, detecting the concentration of VOC (volatile organic compounds) which cause interference to the formaldehyde in the air and outputting a reference AD value AD 2;
and the processor is respectively connected with the measurement sensor and the reference sensor, receives the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor, and processes the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm, namely AD1-AD2 to obtain a formaldehyde concentration value C.
In the process of measuring the formaldehyde concentration of the environment, the device is provided with the measuring sensor and the reference sensor, one sensor is sensitive to formaldehyde and gas which interferes with the formaldehyde in the detected gas, the other sensor is only sensitive to the gas which interferes with the formaldehyde in the detected gas, and then the concentration of the formaldehyde can be obtained through the difference between the detection values output by the measuring sensor and the reference sensor, so that the influence of alcohol on the sensor to measure the formaldehyde in the detected environment can be reduced.
Further, the processor processes the AD difference H between the measured AD value AD1 and the reference AD value AD2 according to a preset algorithm to obtain the formaldehyde concentration value C, and includes: under the environment of pure formaldehyde, simultaneously using a measuring sensor and a reference sensor to detect formaldehyde with known concentration, and calibrating the relation between the AD difference H of the reference AD and the AD of the measured AD and the formaldehyde concentration according to the detection result, thereby obtaining the relation between the formaldehyde concentration value C and the AD difference H output by the two sensors under different formaldehyde environment concentrations, wherein the relation is C-K1Hn+K2*Hn-1+``````+Kn*H+b,n≥1。
The relation C ═ K1 ═ H obtained heren+K2*Hn-1The method comprises the following steps of preparing a plurality of groups of H and C data, wherein the K1, the K2, the K and the B are constants in n which is not less than 1, testing the formaldehyde detection device for a plurality of times in formaldehyde environments with different concentrations and stable to obtain a plurality of groups of H and C data, and then obtaining specific values of K1, K2, the K and the B through fitting.
For example: in this embodiment, the following data table 1 is obtained by detecting a formaldehyde detecting device:
TABLE 1
As shown in fig. 4, by fitting: the relation between the concentration C and the AD difference H is found to be AD1-AD2 and R2 is found to be 0.997, while the relation between the AD difference and the concentration C is found to be 0.00071159H-0.01043507, i.e. K1 is found to be 0.00071159 and b is found to be-0.01043507 by fitting, as shown in fig. 5.
Since there are no measurement sensors and no reference sensors on the market that have the same sensitivity to alcohol, the AD difference H of the measurement AD value AD1 and the reference AD value AD2, AD1-AD2, is processed according to a preset algorithm to obtain the formaldehyde concentration value C, which includes: under the pure VOC environment, a measuring sensor and a reference sensor are used for detecting VOC with known concentration, and the relation between AD difference H and VOC concentration of reference AD and measurement AD is calibrated according to the detection result, so that the AD difference AD3 (AD2) caused by VOC is obtained under different VOC concentrations.
And calibrating the sensitivity of the measuring sensor and the reference sensor to alcohol when the measured environment is in a pure VOC environment, and obtaining a corresponding compensation value T under different alcohol concentrations, namely AD1 (AD2+ AD3) under the pure alcohol environment.
It is clear that the difference in sensitivity to alcohol between the measurement sensor and the reference sensor of a formaldehyde detection unit is also different at different alcohol concentrations, so that the AD3 value is not a fixed value here, and the gradient of the change at different alcohol concentrations with respect to the AD3 value is also different between each formaldehyde detection unit.
In this embodiment, the difference between the sensitivities of the measurement sensor and the reference sensor of the formaldehyde detection device to alcohol is specifically detected, and the following data table 2 is obtained:
TABLE 2
And (3) testing and verifying data of a stable alcohol environment, substituting H in the stable alcohol environment into the linear formula C-0.00071159H-0.01043507, and calculating the influence of alcohol on formaldehyde measured by the sensor, wherein the influence coefficient does not exceed 1.0%.
In order to completely eliminate the influence of alcohol on the formaldehyde measured by the sensor, before detection, the formaldehyde detection device of the invention is placed in alcohol environments with different alcohol concentrations, the difference value H between AD1 and AD2 is obtained, a detailed reference table is formed, in an actual detection environment, when the reference sensor detects that the alcohol concentration in the environment is a certain value, the difference value H corresponding to the sensitivity of the measurement sensor and the reference sensor to alcohol can be correspondingly found in the reference table, namely, in the reference table, the H value corresponding to the alcohol concentration, namely the AD3 value is obtained, and in the calculation of the formaldehyde detection value H in the actual environment, the H is AD1- (AD2+ AD3), wherein the AD3 can be a positive number or a negative number.
It is to be noted here that the relationship between formaldehyde concentration and H and the relationship between AD difference H and VOC concentration for reference AD and for measured AD are calibrated, not in sequence here.
Further, the step of processing the measured AD value AD1 and the reference AD value AD2 according to a preset algorithm to obtain an AD difference H between the measured AD value AD1 and the reference AD value AD2, which is AD1-AD2, so as to obtain a formaldehyde concentration value C, includes:
as shown in fig. 3, the processor performs mutation judgment on the measurement AD value AD1, the reference AD value AD2 and the formaldehyde detection AD value H ═ AD1-AD2 at the current sampling time to determine whether alcohol exists in the tested environment;
if the rising amplitude of the reference AD value AD2 exceeds the first threshold value a1, the reference AD value AD2 continuously and monotonically increases within a certain time, and the rising rate is greater than the second threshold value a2, the alcohol in the tested environment is indicated.
Meanwhile, whether the latest multiple reference AD detection values AD2 are all larger than the corresponding detection values in the specified first set is judged; the elements in the first set comprise a plurality of latest reference AD detection values AD2 in the rest detection values, except the latest reference AD detection values AD2, in the reference AD detection value AD2 data of the current corresponding cache, if the latest reference AD detection values AD2 are larger than the latest reference AD detection values AD2, the mutation occurs in the reference A detection value AD2(t) at the current sampling moment, and if the latest reference AD detection values AD2(t) are not larger than the latest reference AD detection values AD2, the mutation does not occur in the reference A detection value AD 36.
Further, when the processor confirms that alcohol interference exists, the formaldehyde concentration C before mutation is locked, mutation judgment is quitted after the condition of quitting mutation judgment is met, and the quitting mutation judgment is also divided into three conditions:
(1) the reference AD value AD2 begins to decrease and the formaldehyde detection AD value H ═ AD1-AD2 begins to decrease, which shows that the mutation is close to the complete and begins to gradually tend to be smooth, and then the mutation is quitted and locked to enter the concentration output;
(2) the reference AD value AD2 tends to be stable and the formaldehyde detection AD value H (AD1-AD2) tends to be stable, which indicates that the current environment is stable, and the current environment is quitted from mutation and is judged to enter concentration output;
(3) and judging whether the current formaldehyde concentration is less than a3 times of the formaldehyde concentration when locking, if so, quitting mutation judgment, and processing the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm, namely AD1-AD2 to obtain a formaldehyde concentration value C.
Further, the processor processes the AD difference H between the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor, AD1-AD2, according to a preset algorithm, to obtain the formaldehyde concentration value C, which is divided into the following cases:
(1) when the mutation does not exist, outputting the concentration of the formaldehyde calculated at the current moment in real time;
(2) after mutation occurs, locking the formaldehyde concentration C (t0) calculated before mutation, further judging whether the difference value between the formaldehyde concentration C (t) calculated at the current moment and the formaldehyde concentration C (t0) calculated before mutation is greater than a third threshold value a4, and if the difference value is greater than the third threshold value a4, slowly changing the formaldehyde output concentration from C (t0) to C (t); and if the concentration is larger than the third threshold value a4, outputting the concentration of the formaldehyde calculated at the current moment in real time.
A formaldehyde detection method using the formaldehyde detection device comprises the following steps: and processing the AD difference value H of the AD value AD1 output by the measurement sensor and the AD value AD2 output by the reference sensor according to a preset algorithm to obtain a formaldehyde concentration value C, wherein the AD difference value H is AD1-AD 2.
Further, processing the AD difference H between the measured AD value AD1 and the reference AD value AD 2-AD 1-AD2 according to a preset algorithm to obtain the formaldehyde concentration value C, including: under the pure formaldehyde environment, simultaneously using a measuring sensor and a reference sensor to detect formaldehyde with known concentration, and according to the detection result, comparing reference AD and AD difference value H of measured AD with firstThe relationship between the aldehyde concentration is calibrated, so that the relationship C-K1H between the formaldehyde concentration value C and the AD value difference H output by the two sensors under different formaldehyde environmental concentrations is obtainedn+K2*Hn-1+``````+Kn*H+b,n≥1。
Furthermore, processing the AD difference H between the measured AD value AD1 and the reference AD value AD2, AD1-AD2, according to a preset algorithm, to obtain a formaldehyde concentration value C, comprising: under the pure VOC environment, a measuring sensor and a reference sensor are used for detecting VOC with known concentration, and the relation between AD difference H and VOC concentration of reference AD and measurement AD is calibrated according to the detection result, so that the AD difference AD3 (AD2) caused by VOC is obtained under different VOC concentrations.
Further, the step of processing the measured AD value AD1 and the reference AD value AD2 according to a preset algorithm to obtain an AD difference H between the measured AD value AD1 and the reference AD value AD2, which is AD1-AD2, so as to obtain a formaldehyde concentration value C, includes:
the processor carries out mutation judgment on a measurement AD value AD1, a reference AD value AD2 and a formaldehyde detection AD value H which are AD1-AD2 at the current sampling moment so as to determine whether alcohol exists in the detected environment;
if the rising amplitude of the reference AD value AD2 exceeds the first threshold value a1, the reference AD value AD2 continuously and monotonically increases within a certain time, and the rising rate is greater than the second threshold value a2, the alcohol in the tested environment is indicated.
As shown in fig. 3, further, the processor confirms that there is alcohol interference, locks the formaldehyde concentration C before mutation, and exits mutation judgment after meeting the exit mutation judgment condition, and the exit mutation judgment is also divided into three cases:
(1) the reference AD value AD2 begins to decrease and the formaldehyde detection AD value H ═ AD1-AD2 begins to decrease, which shows that the mutation is close to the complete and begins to gradually tend to be smooth, and then the mutation is quitted and locked to enter the concentration output;
(2) the reference AD value AD2 tends to be stable and the formaldehyde detection AD value H (AD1-AD2) tends to be stable, which indicates that the current environment is stable, and the current environment is quitted from mutation and is judged to enter concentration output;
(3) and judging whether the current formaldehyde concentration is less than a3 times of the formaldehyde concentration when locking, if so, quitting mutation judgment, and processing the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm, namely AD1-AD2 to obtain a formaldehyde concentration value C.
Further, the processor processes the AD difference H between the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor, AD1-AD2, according to a preset algorithm, to obtain the formaldehyde concentration value C, which is divided into the following cases:
(1) when the mutation does not exist, outputting the concentration of the formaldehyde calculated at the current moment in real time;
(2) after the mutation has occurred, the concentration of formaldehyde C (t) calculated before the mutation is locked in0) Further judging the concentration C (t) of formaldehyde calculated at the current moment and the concentration C (t) of formaldehyde calculated before mutation0) Whether the difference is larger than a third threshold value a4, and if the difference is larger than the third threshold value a4, the formaldehyde output concentration is from C (t)0) Slowly to c (t); and if the concentration is larger than the third threshold value a4, outputting the concentration of the formaldehyde calculated at the current moment in real time.
Wherein the processor may be a commercially available product such as: STM32F series single-chip microcomputer.
The measuring sensor may be a formaldehyde sensor, and the reference sensor may be a formaldehyde sensor and a formaldehyde filtering membrane disposed at an air inlet of the formaldehyde sensor, wherein the formaldehyde sensor may be a commercially available product.
The above is not relevant and is applicable to the prior art.
While certain specific embodiments of the present invention have been described in detail by way of illustration, it will be understood by those skilled in the art that the foregoing is illustrative only and is not limiting of the scope of the invention, as various modifications or additions may be made to the specific embodiments described and substituted in a similar manner by those skilled in the art without departing from the scope of the invention as defined in the appending claims. It should be understood by those skilled in the art that any modifications, equivalents, improvements and the like made to the above embodiments in accordance with the technical spirit of the present invention are included in the scope of the present invention.
Claims (12)
1. A formaldehyde detection device, comprising:
the measuring sensor is sensitive to formaldehyde and is used for detecting the concentration of the formaldehyde and outputting a measured AD value AD 1; the device comprises a reference sensor and a formaldehyde filtering membrane, wherein the reference sensor comprises a measuring sensor and the formaldehyde filtering membrane is arranged on the measuring sensor, and the formaldehyde filtering membrane is used for filtering formaldehyde in the measured gas, detecting the concentration of VOC (volatile organic compounds) which cause interference to the formaldehyde in the air and outputting a reference AD value AD 2;
and the processor is respectively connected with the measurement sensor and the reference sensor, receives the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor, and processes the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm, namely AD1-AD2 to obtain a formaldehyde concentration value C.
2. The formaldehyde detecting apparatus as claimed in claim 1, wherein the processing of the AD difference H-AD 1-AD2 between the measured AD1 and the reference AD2 according to a predetermined algorithm to obtain the formaldehyde concentration value C comprises: under the pure formaldehyde environment, simultaneously detecting formaldehyde with known concentration by using a measuring sensor and a reference sensor, and calibrating the relation between the reference AD and the AD difference H of the measuring AD and the formaldehyde concentration according to the detection result, thereby obtaining the relation C1-f (AD1-AD2) -K1-H between the formaldehyde concentration value C and the AD difference H output by the two sensors under different formaldehyde environment concentrationsn+K2*Hn-1+…+Kn*H+b，n≥1。
3. The formaldehyde detecting device as claimed in claim 2, wherein the processing of the AD difference H-AD 1-AD2 between the measured AD value AD1 and the reference AD value AD2 according to a predetermined algorithm to obtain the formaldehyde concentration value C comprises: under the pure VOC environment, a measuring sensor and a reference sensor are used for detecting VOC with known concentration, and the relation between AD difference H and VOC concentration of reference AD and measurement AD is calibrated according to the detection result, so that the AD difference AD3 (AD2) caused by VOC is obtained under different VOC concentrations.
4. The formaldehyde detecting device as claimed in claim 3, wherein the processing of the measured AD value AD1 and the reference AD value AD2 according to a predetermined algorithm to obtain an AD difference H ═ AD1-AD2, so as to obtain the formaldehyde concentration value C comprises:
the processor carries out mutation judgment on the reference AD value AD2 at the current sampling moment so as to determine whether alcohol exists in the tested environment;
if the rising amplitude of the reference AD value AD2 exceeds the first threshold value a1, the reference AD value AD2 continuously and monotonically increases within a certain time, and the rising rate is greater than the second threshold value a2, the alcohol in the tested environment is indicated.
5. The formaldehyde detecting device according to claim 4, wherein the processor confirms that there is alcohol interference, locks the formaldehyde concentration C before mutation, exits mutation judgment after meeting the conditions for exiting mutation judgment, and the exiting mutation judgment is also divided into three cases:
(1) the reference AD value AD2 begins to decrease and the formaldehyde detection AD value H ═ AD1-AD2 begins to decrease, which shows that the mutation is close to the complete and begins to gradually tend to be smooth, and then the mutation is quitted and locked to enter the concentration output;
(2) the reference AD value AD2 tends to be stable and the formaldehyde detection AD value H (AD1-AD2) tends to be stable, which indicates that the current environment is stable, and the current environment is quitted from mutation and is judged to enter concentration output;
(3) and judging whether the current formaldehyde concentration is less than a3 times of the formaldehyde concentration when locking, if so, quitting mutation judgment, and processing the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm, namely AD1-AD2 to obtain a formaldehyde concentration value C.
6. The formaldehyde detecting device as claimed in claim 5, wherein the processor processes the AD difference H-AD 1-AD2 between the measured AD1 output from the measuring sensor and the reference AD2 output from the reference sensor according to a predetermined algorithm to obtain the formaldehyde concentration value C as follows:
(1) when the mutation does not exist, outputting the concentration of the formaldehyde calculated at the current moment in real time;
(2) after mutation occurs, locking the formaldehyde concentration C (t0) calculated before mutation, further judging whether the difference value between the formaldehyde concentration C (t) calculated at the current moment and the formaldehyde concentration C (t0) calculated before mutation is greater than a third threshold value a4, and if the difference value is greater than the third threshold value a4, slowly changing the formaldehyde output concentration from C (t0) to C (t); and if the concentration is larger than the third threshold value a4, outputting the concentration of the formaldehyde calculated at the current moment in real time.
7. A formaldehyde detecting method using the formaldehyde detecting apparatus according to any one of claims 1 to 6, comprising the steps of: and processing the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm to obtain a formaldehyde concentration value C.
8. The formaldehyde detection method of claim 7, wherein processing the AD difference H-AD 1-AD2 between the measured AD value AD1 and the reference AD value AD2 according to a predetermined algorithm to obtain the formaldehyde concentration value C comprises: under the pure formaldehyde environment, simultaneously using a measuring sensor and a reference sensor to detect formaldehyde with known concentration, and calibrating the relation between the reference AD and the AD difference H of the measuring AD and the formaldehyde concentration according to the detection result, thereby obtaining the relation C-K1H between the formaldehyde concentration value C and the AD difference H output by the two sensors under different formaldehyde environment concentrationsn+K2*Hn-1+``````+Kn*H+b,n≥1。
9. The formaldehyde detecting method according to claim 8, wherein the processing the AD difference H-AD 1-AD2 between the measured AD value AD1 and the reference AD value AD2 according to a predetermined algorithm to obtain the formaldehyde concentration value C comprises: under the pure VOC environment, a measuring sensor and a reference sensor are used for detecting VOC with known concentration, and the relation between AD difference H and VOC concentration of reference AD and measurement AD is calibrated according to the detection result, so that the AD difference AD3 (AD2) caused by VOC is obtained under different VOC concentrations.
10. The formaldehyde detecting method as claimed in claim 9, wherein the processing the measured AD value AD1 and the reference AD value AD2 according to a predetermined algorithm to obtain an AD difference H ═ AD1-AD2, so as to obtain the formaldehyde concentration value C, comprises:
the processor carries out mutation judgment on the reference AD value AD2 at the current sampling moment to determine whether alcohol exists in the tested environment;
if the rising amplitude of the reference AD value AD2 exceeds the first threshold value a1, the reference AD value AD2 continuously and monotonically increases within a certain time, and the rising rate is greater than the second threshold value a2, the alcohol in the tested environment is indicated.
11. The formaldehyde detecting method according to claim 10, wherein the processor confirms the presence of alcohol interference, locks the formaldehyde concentration C before mutation, exits mutation judgment after meeting the condition for exiting mutation judgment, and the exiting mutation judgment is also divided into three cases:
(1) the reference AD value AD2 begins to decrease and the formaldehyde detection AD value H ═ AD1-AD2 begins to decrease, which shows that the mutation is close to the complete and begins to gradually tend to be smooth, and then the mutation is quitted and locked to enter the concentration output;
(2) the reference AD value AD2 tends to be stable and the formaldehyde detection AD value H (AD1-AD2) tends to be stable, which indicates that the current environment is stable, and the current environment is quitted from mutation and is judged to enter concentration output;
(3) and judging whether the current formaldehyde concentration is less than a3 times of the formaldehyde concentration when locking, if so, quitting mutation judgment, and processing the AD difference value H of the measurement AD value AD1 output by the measurement sensor and the reference AD value AD2 output by the reference sensor according to a preset algorithm, namely AD1-AD2 to obtain a formaldehyde concentration value C.
12. The formaldehyde detecting method as claimed in claim 11, wherein the processor processes the AD difference H-AD 1-AD2 between the measured AD1 output from the measuring sensor and the reference AD2 output from the reference sensor according to a predetermined algorithm to obtain the formaldehyde concentration value C as follows:
(1) when the mutation does not exist, outputting the concentration of the formaldehyde calculated at the current moment in real time;
(2) after the mutation has occurred, the concentration of formaldehyde C (t) calculated before the mutation is locked in0) Further judging the concentration C (t) of formaldehyde calculated at the current moment and the concentration C (t) of formaldehyde calculated before mutation0) Whether the difference is larger than a third threshold value a4, and if the difference is larger than the third threshold value a4, the formaldehyde output concentration is from C (t)0) Slowly to c (t); and if the concentration is larger than the third threshold value a4, outputting the concentration of the formaldehyde calculated at the current moment in real time.
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