An ultra-low emission Cl2 monitoring optical system based on differential optical absorption spectroscopy has been set up. We have found through comparison experiments that UV reflection enhanced aluminum is damaged and the dielectric film mirror is intact under high concentration of Cl2. Then verify the performance characteristics of ultralow Cl2 emission online monitoring device. The maximum absorbance of 50ppm Cl2 exceeds 0.1, while the 30ppm Cl2 reaches 0.063, so the measurement range can be 0-95 mg/m3, which meets the maximum allowable emission concentration of Cl2 required by the new regulations for detection of 65mg/m3.
In this paper, based on the analysis of the shortcomings of three-point comparison odor bag method, gas chromatography method and gas sensor, a malodorous gas monitoring device based on differential optical absorption spectroscopy (DOAS) is designed. This paper focuses on testing six gases, including carbon disulfide, styrene, dimethyl disulfide and so on. The total length of the optical path is 60cm. When the standard deviation is twice, the detection limit of these gases is around 0.10ppm. The results of mixed malodorous by measured show that the interference between components is very small, and the relative error of each component is less than 3% of the full scale by least square method. The odor gas emission monitoring device based on DOAS technology designed in this paper has the advantages of simple device and high measurement accuracy, which can meet the application requirements of field measurement.
This paper describes a set of ultra-low smoke emission monitoring optical devices based on differential absorption spectroscopy (DOAS), which mainly includes a xenon lamp source, a sample cell, a spectrometer for light detection, and a Y-type optical fiber. The device utilizes a newly developed ultraviolet long path gas chamber, the energy of the ultraviolet spectrum is high, and the energy of the xenon lamp in the experiment is only enough to meet the application requirements. As well, based on DOAS optical device it has the advantages of high ultraviolet energy, small volume and high measurement accuracy. Therefore, the system solves the difficult problem of low concentration flue gas emission monitoring. The lower limit of detection of SO2, NO and NO2 concentration was 0.21 mg/m3, 0.13 mg/m3 and 0.61 mg/m3, respectively. Comparison of on-site field monitoring with high temperature FTIR (Fourier Transform Infrared Spectroscopy) flue gas emission monitor, the average concentrations of SO2, NO and NO2 measured by the two instruments were less than 14 mg/m3, 39 mg/m3 and 25 mg/m3 respectively, and the correlations were all above 0.995.
In order to monitor the motor vehicle exhaust effectively, a motor vehicle exhaust telemetry device is set up based on differential optical absorption spectroscopy (DOAS) in this paper. The absorption spectrum of NO and 1,3-butadiene are analyzed quickly, meanwhile, qualitative and quantitative analysis are made simultaneously by the Least Square Method. Moreover, the correlation coefficient of absorbance and concentration reaching more than 0.999, which is obtained by non-linear analysis through polynomial fitting method. Additionally, the minimum detection limits of NO and 1,3-butadiene are 3ppm and 0.5ppm respectively. In order to verify the performance of the system, a set of tests were performed for a long time. So the experimental results show that the relative error of NO is not more than 2%, and the relative error of 1,3-butadiene is less than 2%. In addition, the calculation results of the experiment demonstrate that the repeatability error of NO is better than 1%, and the repeatability errors of 1,3-butadiene is lower than 2%. All the results meet the requirement of the application.
In the paper, an accurate and sensitive system was used to monitor the ambient atmospheric NO2 concentrations. This system utilizes cavity attenuated phase shift spectroscopy(CAPS), a technology related to cavity ring down spectroscopy(CRDS). Advantages of the CAPS system include such as: (1) cheap and easy to control the light source, (2) high accuracy, and (3) low detection limit. The performance of the CAPS system was evaluated by measuring of the stability and response of the system. The minima (~0.08 ppb NO2) in the Allan plots show the optimum average time(~100s) for optimum detection performance of the CAPS system. Over a 20-day-long period of the ambient atmospheric NO2 concentrations monitoring, a comparison of the CAPS system with an extremely accurate and precise chemiluminescence-based NOx analyzer showed that the CAPS system was able to reliably and quantitatively measure both large and small fluctuations in the ambient nitrogen dioxide concentration. The experimental results show that the measuring instrument results correlation is 0.95.
In the paper, an accurate and sensitive cavity attenuated phase shift spectroscopy (CAPS) sensor was used to monitor the
atmospheric visibility. The CAPS system mainly includes a LED light source, a band-pass filter, an optical resonant
cavity (composed of two high mirror, reflectivity is greater than 99.99%), a photoelectric detector and a lock-in amplifier.
The 2L/min flow rate, the optical sensor rise and fall response time is about 15 s, so as to realize the fast measurement of
visibility. An Allan variance analysis was carried out evaluating the optical system stability (and hence the maximum
averaging time for the minimum detection limit) of the CAPS system. The minima (~0.1 Mm-1) in the Allan plots show
the optimum average time (~100s) for optimum detection performance of the CAPS system. During this period, the
extinction coefficient was correlated with PM2.5 mass (0.88), the extinction coefficient was correlated with PM10 mass
(0.85). The atmospheric visibility was correlated with PM2.5 mass (0.74). The atmospheric visibility was correlated with
PM10 mass (0.66).
The CAPS (Cavity Attenuated Phase shift Spectroscopy) system, which detects the extinction coefficients within a 10 nm bandpass centered at 532 nm, comprises a green LED with center wavelength in 532nm, a resonant optical cavity (36 cm length), a Photo Multiplier Tube detector, and a lock in amplifier. The square wave modulated light from the LED passes through the optical cavity and is detected as a distorted waveform which is characterized by a phase shift with respect to the initial modulation. Extinction coefficients are determined from changes in the phase shift of the distorted waveform of the square wave modulated LED light that is transmitted through the optical cavity. The performance of the CAPS system was evaluated by using measurements of the stability and response of the system. The minima (~0.1 Mm-1) in the Allan plots show the optimum average time (~100s) for optimum detection performance of the CAPS system. In the paper, it illustrates that extinction coefficient was correlated with PM2.5 mass (0.91). These figures indicate that this method has the potential to become one of the most sensitive on-line analytical techniques for extinction coefficient detection. This work aims to provide an initial validation of the CAPS extinction monitor in laboratory and field environments. Our initial results presented in this paper show that the CAPS extinction monitor is capable of providing state-of-the-art performance while dramatically reducing the complexity of optical instrumentation for directly measuring the extinction coefficients.
In the paper, an accurate and sensitive cavity attenuated phase shift spectroscopy (CAPS) system was used to monitor the atmospheric visibility coefficient in urban areas. The CAPS system, which detects the atmospheric visibility within a 10 nm bandpass centered at 532 nm, comprises a green LED with center wavelength in 532nm, a resonant optical cavity (36 cm length), a Photo Multiplier Tube detector and a lock in amplifier. The performance of the CAPS system was evaluated by measuring of the stability and response of the system. The minima (~0.06 Mm-1) in the Allan plots show the optimum average time(~80s) for optimum detection performance of the CAPS system. The 2L/min flow rate, the CAPS system rise and fall response time is about 15 s, so as to realize the fast measurement of visibility. By comparing the forward scatter visibility meter measurement results, the CAPS system measurement results are verified reliably, and have high precision measurement. These figures indicate that this method has the potential to become one of the most sensitive on-line analytical techniques for atmospheric visibility detection.
The objective of this work was to attain essential parameters by using a Gompertz model that employed a new approach of wavelength modulation spectroscopy (WMS) to describe the microorganism growth. The measurement method of WMS introduces noninvasive technique instead of complicated invasive microorganism operation analysis and quickly obtains the accurate real-time measurement results. By using the WMS measurement, the specific growth curve of microorganism growth clearly displayed every three minute, which has characteristics of high sensitivity, high spectral resolution, fast time response and overcomes the randomness and error operation of traditional analysis methods. The measurement value of BF and AF in the range of 1.008 to 1.043 and the lower MSE showed that Gompertz model can fit the data well and be capable of describing bacteria growth rate and lag time. The results of experiment data suggested that the specific growth rate of microorganism depends on the temperature. With the increase of temperature ranging from 25 °C to 42 °C , the lag time of bacteria growth has been shortened. And the suitable temperature of bacteria growth is about 37 °C . Judging from the growth rate of microorganisms, we can identify the microbial species, not only to improve the precision and efficiency, but also to provides a rapidly sensitive way for microbial detection. The lag time of microorganism growth also provides a great application prospect for shelf life of the food safety.
In recent years, there has been a rapid rise in the use of pulse cavity ring-down spectroscopy to determine the optical properties of atmospheric aerosols. In the present work ,we describes the design and performance of a CRDS system for measuring extinction coefficients of atmospheric aerosols. CRDS based methods can achieve impressive sensitivity owing to the long effective path lengths involved. More importantly, the method is not affected by laser intensity fluctuations since the rate of attenuation of light is the measured variable rather than absolute irradiance. The extinction coefficient is a function of the cavity ring-down time. Determining an accurate decay time is critical to precise measurements of the extinction coefficients. The average and standard deviation of the decay time (τ0 is measured 6 hours ,cavity filled only with dry nitrogen) is about 42.21μs and 0.16μs, respectively. Moreover, a minimum detectable aerosol extinction coefficient of 0.41Mm-1 is achieved. Allan deviation plots for the value of τ0 measurements, close to a flicker noise. The minima(~5.8x10-4μs) in the Allan plots indicate the optimum average time(~60s) for optimum detection performance. To test the performance of the CRDS system, we monitored the optical properties of ambient aerosols on the campus of the Zhejiang Normal University from January 3rd to January 7th, 2014. During this period, the average value of the extinction coefficient is 816.8Mm-1, a maximum value more than 1800 Mm-1, and a minimum aerosol extinction coefficient of 119.27 Mm-1 is detected.
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