1, luminous intensity detection Light intensity, the intensity of light, refers to the amount of light emitted at a particular angle. Due to the concentrated light of the LED, the inverse square law is not applicable in the close range. The CIE127 standard specifies two measurement averaging methods: measurement condition A (far field condition) and measurement condition B (near field condition) for the measurement of light intensity. In the case of light intensity, the detector area of ​​both conditions is 1 cm 2 . Normally, the luminous intensity is measured using standard condition B. 2, luminous flux and light efficiency detection The luminous flux is the sum of the amount of light emitted by the light source, that is, the amount of luminescence. The detection methods mainly include the following two types: (1) Integration method. The standard lamp and the lamp to be tested are sequentially ignited in the integrating sphere, and their readings in the photoelectric converter are recorded as Es and ED, respectively. The standard lamp flux is known as Φs, then the luminous flux of the lamp under test is ΦD=ED×Φs/Es. The integral method utilizes the principle of "point source", and the operation is simple, but it is affected by the deviation of the color temperature of the standard lamp and the lamp under test, and the measurement error is large. (2) Spectroscopic method. The luminous flux is calculated from the spectral energy P(λ) distribution. Using a monochromator, the spectrum of the standard lamp from 380 nm to 780 nm is measured in the integrating sphere, and then the spectrum of the lamp under test is measured under the same conditions, and the luminous flux of the lamp to be measured is calculated and compared. The luminous efficiency is the ratio of the luminous flux emitted by the light source to the power consumed by it, and the luminous efficacy of the LED is usually measured by a constant current method. 3. Spectral characteristics detection The spectral characteristic detection of the LED includes spectral power distribution, color coordinates, color temperature, color rendering index and the like. The spectral power distribution indicates that the light of the light source is composed of a plurality of different wavelengths of color radiation, and the radiation power of each wavelength is also different. This difference is sequentially arranged with the wavelength, which is called the spectral power distribution of the light source. The light source is obtained by comparison measurement using a spectrophotometer (monochromator) and a standard lamp. The color coordinate is a digital representation of the amount of illuminating color of the light source on the graph. The coordinate graph representing the color has a variety of coordinate systems, usually in the X, Y coordinate system. The color temperature is an amount indicating a light source color table (appearance color appearance) seen by the human eye. When the light emitted by the light source is the same as the color of the light emitted by the absolute black body at a certain temperature, the temperature is the color temperature. In the field of illumination, color temperature is an important parameter describing the optical properties of a light source. The related theory of color temperature is derived from blackbody radiation, which can be obtained from the color coordinates of the black body trajectory by the color coordinates of the light source. The color rendering index indicates the amount of light emitted by the light source that correctly reflects the color of the object, usually expressed by the general color rendering index Ra, which is the arithmetic mean of the color rendering index of the eight color samples. Color rendering index is an important parameter of light source quality, which determines the application range of light source. Improving the color rendering index of white LED is one of the important tasks of LED research and development. 4, light intensity distribution test The relationship between the light intensity and the spatial angle (direction) is called the pseudo-light intensity distribution, and the closed curve formed by such a distribution is called the light intensity distribution curve. Since there are many measuring points and each point is processed by data, it is usually measured by an automatic distribution photometer. 5. Effect of temperature effect on optical characteristics of LED Temperature affects the optical properties of the LED. A large number of experiments can explain that the temperature affects the LED emission spectrum and color coordinates. 6, surface brightness measurement The brightness of the light source in a certain direction is the luminous intensity of the light source in the projected area of ​​the light source. Generally, the surface brightness meter and the aiming brightness meter are used to measure the surface brightness, and there are two parts of the aiming light path and the measuring light path.
Take a deep breath, close your eyes, the world has the freshest oxygen ... Yu Quan's "Deep Breath" is well known to us, but as the environmental problems become more and more serious, the haze sky also increases, PM2.5 PM10 and so on Vocabulary has also been mentioned more and more, and air purifiers have quickly become popular on the market with this "air quality" trend. Along with this, the air-clean brand has sprung up, and various technologies are dazzling. Which ones are indeed effective and which are just tasteless propaganda? How does the Air Purifier bother us to get rid of pollution? And look at the editors for you.
Analysis of air purifier
The critical value of PM2.5 content is 75 μg / m3
The pollutants in the air mainly include soot, total suspended particulates, inhalable particulates (PM2.5) and fine particulates (PM10). The smaller the diameter of the particulates, the deeper the part that can enter the respiratory tract. 10 micron diameter particles It is deposited in the upper respiratory tract, and particles below 2 microns can penetrate 100% into the bronchiole and alveoli.
1k-5k air purifier prices vary greatly
The air purifier products on the market not only have various functions, but also have prices ranging from thousand yuan to tens of thousands. The pricing of imported products is generally higher than that of domestic brands. Except for the core technology of many brands, the promotion of purification effects is similar, and consumers need to choose according to demand.
The air quality standard of 74 key cities is only 4.1%
According to the data of the press conference held by the State Council Information Office on June 4, according to the new "Ambient Air Quality Standards", the six pollutants SO2, NO2, PM10, PM2.5, CO and O3 were evaluated, 74 new standards In the first phase of monitoring and implementation, the proportion of cities that met the ambient air quality standards was only 4.1%, and the other 256 cities implemented the old air quality standards, and the proportion of cities that met the standards was 69.5%.
Air purifier sales increased by 90.5% compared with last year
According to a report recently released by the China Electronics and Information Industry Development Institute, due to the haze weather, air purifiers have become the most concerned home appliance products, with sales of nearly 2.4 million units nationwide last year, a year-on-year increase of 90.5%; retail The amount reached 5.6 billion yuan, a year-on-year increase of 105.9%.
HEPA filter needs to be replaced in March
The filter of the air purifier is the same as the filter of the water purifier, and it is not effective for a long time. After long-term use, the accumulation of dust on the surface of the filter will also cause the filter to gradually fail. Therefore, when the haze is more serious, the non-washable HEPA filter needs to be replaced every three months.
Merchants claim that the purification rate is more than 99% for the concept of stealing
99% or even 99.99% seems to have become a slogan for many air purifiers on the market. Many brands of products promote their high removal rate of PM2.5 and formaldehyde. In fact, this kind of publicity is more of a kind. The slogan of stealing the concept, the removal rate of 99% is the effect of the material itself on PM2.5 and formaldehyde, not the effect of actually running in space.
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