CN113504167B - Ultra-low concentration particulate matter detection method and detection system thereof - Google Patents
Ultra-low concentration particulate matter detection method and detection system thereof Download PDFInfo
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Abstract
The invention discloses a method and a system for detecting particles with ultra-low concentration, which relate to the detection technology of the concentration of the particles and comprise the following steps: s1, generating a plurality of frequency values through a function; s2, sweeping frequency of each frequency value in sequence, and determining the lowest noise frequency f; s3, generating sine wave modulation laser with frequency f; and S4, collecting the scattered light signals received by the sensor, and carrying out IQ demodulation calculation to obtain the signal quantity related to the particulate matter concentration. The invention can calculate the concentration value of the particulate matter, effectively reduce the measurement error caused by temperature drift and environmental factor change, and can flexibly adjust the integration time, thereby reducing noise, improving the signal-to-noise ratio, greatly improving the stability and reliability of trace scattered light detection, and ensuring the detection precision of the ultra-low particulate matter.
Description
Technical Field
The invention relates to a particulate matter concentration detection technology, in particular to an ultra-low concentration particulate matter detection method and an ultra-low concentration particulate matter detection system.
Background
With the development of social economy, the national requirements on the emission of environmental pollutants are higher and higher, wherein the popularization of ultra-clean emission of particulate matters is wider and wider, which puts higher requirements on a reliable and stable detection technology of ultra-low particulate matter concentration.
The laser front scattering method is one of the most important methods for ultra-low particulate matter detection in the industry at present, and as for a micro-scattering light detection technology, the mainstream method in the industry at present is to modulate laser by using a simple square wave pulse, and only an in-phase component (I-phase) is used for demodulation of a received signal, and the detection method has two obvious defects:
1. at the modulation end, the Fourier frequency spectrum of the square wave contains rich odd harmonic components besides direct current components and same frequency components, and the existence of the odd harmonic components enables the signal-to-noise ratio of the photoelectric signal after collection and demodulation to be low.
2. The demodulation end only uses the in-phase component (I-phase) for demodulation, and lacks the quadrature component (Q-phase), so that the result after the demodulation of the photoelectric signal comprises an initial phase theta related to signal transmission, and the initial phase theta is a variable sensitive to temperature, which directly causes that the detection result is easily affected by environmental changes, thereby generating larger measurement error.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides an ultra-low concentration particulate matter detection method and a detection system thereof, which can solve the problems.
The technical scheme adopted by the invention for solving the technical problems is as follows:
in an ultra-low concentration particulate matter detection method, the improvement comprising the steps of:
s1, generating a plurality of frequency values through a function;
s2, sweeping frequency of each frequency value in sequence, and determining the lowest noise frequency f;
s3, generating sine wave modulation laser with frequency f;
and S4, collecting the scattered light signals received by the sensor, and carrying out IQ demodulation calculation to obtain the signal quantity related to the particulate matter concentration.
As a further improvement of the above technical means, in step S2, the frequency sweep is performed when the laser is turned off or the light is blocked.
As a further improvement of the technical scheme, IQ demodulation or I demodulation is carried out by collecting sensor signals after laser is extinguished or shielded.
As a further improvement of the above technical solution, after performing IQ demodulation or I demodulation, a noise signal value at each frequency point is calculated and acquired.
As a further improvement of the above technical solution, a formula for obtaining a noise signal value is as follows:
in the formula, f is the frequency of the sine wave, T is the period of the sine wave, and T is 1/f.
As a further improvement of the above technical solution, after a noise signal value is obtained, each frequency point is calculated once, and a frequency value f with the minimum noise amplitude is determined.
As a further improvement of the above technical solution, in step S3, before generating the sine wave modulated laser with the frequency f, the laser needs to be turned on to facilitate normal signal measurement.
As a further improvement of the above solution, a sine wave with frequency f is generated by a digital frequency synthesizer or DAC.
As a further improvement of the above technical solution, an ADC is used to collect the sensor signal.
As a further improvement of the above technical solution, after the sensor signal is collected by the ADC, the concentration value of the particulate matter can be calculated, and the amount of the particulate matter scattered light signal is:
Sig(t)＝Acos(2πft+θ)
sig (t) is a function of the same frequency as the laser modulation, where the initial phase θ comes from the phase difference of the received signal after a series of conditioning passes through photoelectric conversion, amplification and filtering.
As a further improvement of the above technical solution, IQ demodulation calculation is performed on sig (t):
in-phase demodulation calculation:
quadrature demodulation calculation:
as a further improvement of the above technical solution, after IQ demodulation calculation is performed on sig (t), the finally obtained amplitude of the scattered light signal is:
wherein, T is a sine wave period, n is an integration number, nT is an integration time, f is a sine wave frequency, and T is 1/f.
The invention also discloses an ultra-low concentration particulate matter detection system, which comprises a detection unit capable of realizing the detection method.
The invention has the beneficial effects that: the method can calculate the concentration value of the particulate matter, effectively reduce the measurement error caused by temperature drift and environmental factor change, and can flexibly adjust the integration time, thereby reducing noise, improving the signal-to-noise ratio, greatly improving the stability and reliability of trace scattered light detection, and ensuring the detection precision of the ultra-low particulate matter.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is an overall flow diagram of the present invention;
fig. 2 is a summary chart of the comparison of different demodulation amplitudes of the Fig1 signal with amplitude of 1.0V according to the present invention.
Detailed Description
The conception, the specific structure, and the technical effects produced by the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings to fully understand the objects, the features, and the effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention. In addition, all the connection/connection relations referred to in the patent do not mean that the components are directly connected, but mean that a better connection structure can be formed by adding or reducing connection auxiliary components according to specific implementation conditions. All technical characteristics in the invention can be interactively combined on the premise of not conflicting with each other.
Example 1
Referring to fig. 1, a method for detecting ultra-low concentration particulate matter includes the following steps:
s1, generating a plurality of frequency values through a function;
s2, sweeping frequency of each frequency value in sequence, and determining the lowest noise frequency f;
s3, generating sine wave modulation laser with frequency f;
and S4, collecting the scattered light signals received by the sensor, and carrying out IQ demodulation calculation to obtain the signal quantity related to the particulate matter concentration.
In the above embodiment, the detection algorithm of the present invention first generates a plurality of frequency values, such as 1KHz, 2KHz, and 3KHz.. multidot.h, through a function, including but not limited to a random function or a pseudo-random function, etc., then performs frequency sweeping on the plurality of frequency values, determines a frequency value f corresponding to the lowest noise, then modulates a laser through a sine wave with the lowest frequency value f, and then performs IQ demodulation calculation through a scattered light signal received by the collection sensor, thereby obtaining a signal quantity related to the particulate matter concentration. The sine wave frequency modulated by the laser is adjusted according to the noise detection result, the signal-to-noise ratio of signal detection is effectively improved, and the ultralow particulate matter concentration value of <1mg/m3 can be reliably and stably detected.
Further, in step S2, the frequency sweep is performed when the laser light needs to be turned off or blocked. And after the laser is extinguished or the light is shielded, acquiring a sensor signal through the ADC to carry out IQ demodulation. And after IQ demodulation or I demodulation, calculating to obtain the noise signal value of each frequency point.
The formula for obtaining the noise signal value is as follows:
in the formula, f is the frequency of the sine wave, T is the period of the sine wave, and T is 1/f.
After the noise signal value is obtained, each frequency point is calculated once, and the frequency value f with the minimum noise amplitude is determined.
In the above embodiment, assuming that one of the frequency values generated in step S1 is f0, and the number of points involved in calculation is N, for example, N is 128, 256, 512, etc., the sampling rate of the ADC acquisition sensor is set to N × f0, and after the ADC acquisition sensor has acquired N data for the sensor signal sig (t), the algorithm is as follows:
similarly, for the other frequency values f1, f2, f3, and the like generated in step S1, the number of points involved in calculation is also N, the sampling rates of the ADC acquisition sensors are set to be N × f1 and N × f2 … …, and after the ADC acquisition sensors acquire N data for the sensor signal sig (t), the algorithm is as follows:
and finally, determining the corresponding frequency according to the minimum amplitude of the noise, namely the minimum noise frequency f.
Still further, in step S3, before generating the sine wave modulated laser with the frequency f, the laser needs to be turned on to facilitate normal signal measurement. A sine wave of frequency f, generated by a digital frequency synthesizer or DAC, can be used to modulate the laser's emitted power.
Finally, in step S4, after the sensor signal is collected by the ADC, the concentration value of the particulate matter can be calculated, and the amount of the particulate matter scattered light signal is:
Sig(t)＝Acos(2πft+θ)
sig (t) is a function of the same frequency as the laser modulation, where the initial phase θ comes from the phase difference of the received signal after a series of conditioning passes through photoelectric conversion, amplification and filtering.
IQ demodulation calculation for Sig (t):
in-phase demodulation calculation:
quadrature demodulation calculation:
in addition, after IQ demodulation calculation is performed on sig (t), the finally obtained amplitude of the scattered light signal is:
wherein, T is a sine wave period, n is an integration number, nT is an integration time, f is a sine wave frequency, and T is 1/f.
Referring to fig. 2, in step S4, based on the lowest noise frequency f, the number of points involved in the calculation is N, for example, N is 128, 256, 512, etc., the sampling rate of the ADC collecting sensor is set to N f, and after the ADC collects N data for the sensor signal sig (t), the algorithm is as follows:
in-phase demodulation calculation
Quadrature demodulation calculation
The final obtained amplitude of the scattered light signal is:
the adjustment of the integration time is realized by changing the number of sampling points N.
The amplitude P finally obtained by IQ demodulation calculation is in positive correlation with the particulate matter concentration value, so that the amplitude P can be used for calculating the particulate matter concentration value; p only has a variable A related to the concentration value of the particulate matter, so the influence of the initial phase theta is eliminated, and the measurement error caused by temperature drift and environmental factor change is effectively reduced.
In addition, the detection method has another advantage that the integration time nT can be flexibly adjusted, and the increase of the integration time can further reduce the system bandwidth, reduce the noise and improve the SNR.
The method can effectively improve the signal-to-noise ratio and eliminate the initial phase theta sensitive to the temperature, so that the stability and the reliability of the detection of the trace scattered light can be greatly improved, and the detection precision of the ultra-low particulate matters is ensured.
Example 2
The present invention further includes another embodiment, specifically, in step S2, I demodulation is performed, and the rest of the steps refer to the content of embodiment 1, it is noted that, with I demodulation, quadrature demodulation calculation is not required, and the quadrature demodulation calculation process in step 4 can be omitted, so as to save calculation time and improve system response capability.
The invention also discloses an ultra-low concentration particulate matter detection system, which comprises a detection unit capable of realizing the detection method.
It should be noted that, since the detection unit in the system provided in the embodiment of the present invention is based on the same concept as the method embodiment of the present invention, the technical effect thereof is the same as the method embodiment of the present invention, and specific contents may refer to the description in the method embodiment of the present invention, and are not described herein again.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (5)
1. The ultra-low concentration particulate matter detection method is characterized by comprising the following steps:
s1, generating a plurality of frequency values through a function;
s2, sweeping frequency of each frequency value in sequence, and determining the lowest noise frequency f;
IQ demodulation or I demodulation is carried out through the acquisition of the sensor signals, after the IQ demodulation or the I demodulation is carried out, the noise signal value of each frequency point is calculated and obtained, and the formula for obtaining the noise signal value is as follows:
in the formula, f is the frequency of the sine wave, T is the period of the sine wave, and T is 1/f;
after a noise signal value is obtained, calculating each frequency point once, and determining a frequency value f with the minimum noise amplitude;
s3, generating sine wave modulation laser with frequency f;
generating a sine wave with the frequency f by a digital frequency synthesizer or a DAC, and collecting a sensor signal by using an ADC (analog-to-digital converter);
s4, collecting the scattered light signals received by the sensor, and carrying out IQ demodulation calculation to obtain the signal quantity related to the concentration of the particulate matters;
after the sensor signal is collected through the ADC, the concentration value of the particulate matter can be calculated, and the signal quantity of the scattered light of the particulate matter is as follows:
Sig(t)＝Acos(2πft+θ)；
sig (t) is a function with the same frequency as the laser modulation, wherein the initial phase theta comes from the phase difference generated after the received signal is subjected to a series of conditioning transmission of photoelectric conversion, amplification and filtering;
IQ demodulation calculation for Sig (t):
in-phase demodulation calculation:
quadrature demodulation calculation:
after IQ demodulation calculation is performed on sig (t), the finally obtained amplitude of the scattered light signal is:
wherein, T is a sine wave period, n is an integration number, nT is an integration time, f is a sine wave frequency, and T is 1/f.
2. The method for detecting particles with ultra-low concentration according to claim 1, wherein in step S2, a frequency sweep is performed under the condition that the laser needs to be extinguished or shielded from light.
3. The method for detecting the ultra-low concentration particulate matter of claim 2, wherein IQ demodulation or I demodulation is performed by collecting a sensor signal after laser light is extinguished or light is blocked.
4. The method for detecting ultra-low concentration particulate matter of claim 1, wherein in step S3, the laser is turned on before the sine wave modulated laser with frequency f is generated to facilitate normal signal measurement.
5. An ultra-low concentration particulate matter detection system, characterized by comprising a detection unit that can implement the detection method of any one of claims 1 to 4.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1095487A (en) * | 1992-05-22 | 1994-11-23 | 奥泰尔公司 | Noise in the fibre system and distortion suppression |
| CN102629859A (en) * | 2012-03-30 | 2012-08-08 | 上海大学 | Digital bandpass filter for narrow-band signal and filter method |
| CN104914024A (en) * | 2015-03-09 | 2015-09-16 | 浙江大学 | Particulate matter mass concentration detection device applied to atmosphere suspended particulate matters, and method thereof |
| DE102015110359A1 (en) * | 2015-06-26 | 2016-12-29 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Method for the detection of radiation-emitting particles |
| CN209387468U (en) * | 2018-12-27 | 2019-09-13 | 深圳市量宇科技有限公司 | Super low concentration particulate matter measuring apparatus |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| AU2003902319A0 (en) * | 2003-05-14 | 2003-05-29 | Garrett Thermal Systems Limited | Laser video detector |
| CN105319183A (en) * | 2015-11-13 | 2016-02-10 | 哈尔滨工程大学 | Detector and detection method for real-time on-line detection of emission smoke intensity of diesel engine |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1095487A (en) * | 1992-05-22 | 1994-11-23 | 奥泰尔公司 | Noise in the fibre system and distortion suppression |
| CN102629859A (en) * | 2012-03-30 | 2012-08-08 | 上海大学 | Digital bandpass filter for narrow-band signal and filter method |
| CN104914024A (en) * | 2015-03-09 | 2015-09-16 | 浙江大学 | Particulate matter mass concentration detection device applied to atmosphere suspended particulate matters, and method thereof |
| DE102015110359A1 (en) * | 2015-06-26 | 2016-12-29 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Method for the detection of radiation-emitting particles |
| CN209387468U (en) * | 2018-12-27 | 2019-09-13 | 深圳市量宇科技有限公司 | Super low concentration particulate matter measuring apparatus |
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