Source: China Air Purification Industry Alliance Network

In recent years, there have been frequent occurrences of haze and weather in my country. Air pollution has always affected our health. Air quality issues have attracted great attention from the whole society. With the improvement of people's living standards and the continuous improvement of people's health awareness, air quality monitoring and air purification products have received extensive attention. The remarkable thing is the intelligent extreme experience of air monitoring and purification products, so that clean air is no longer It is extravagant!

Driven by huge market demand, the domestic air purifier market is developing rapidly, and new and old brands are fiercely competing. According to statistics, in 2015, the average price of the ten products most concerned by consumers in my country's air purifier market was 4,566, and seven of them sold for more than 3,000 yuan. Consumers with products higher than 2000 yuan reached 72.2% overall. It can be seen that the mid-to-high-end purifier market will remain the focus of future purifier manufacturers.

Air purifier products are different from air conditioners. As far as ordinary consumers are concerned, it is difficult to establish a very intuitive feeling about whether the air purifier products they buy are effective, and it is necessary to have a fair evaluation of relevant monitoring data. Therefore, the dust sensor has gradually attracted industry attention. Only the dust sensor can evaluate the quality of indoor air. It can sense the concentration of hazardous components in the air and is the most important bridge for establishing a direct connection between air purifier products and users.

In the domestic and international high-end air purifier market, the application of dust sensors has been very extensive, and it is one of the necessary sensors for smart air purifiers. With the rapid growth of the domestic air purifier market, dust sensor technology is also developing rapidly, especially the laser dust sensor has been developed rapidly, and domestic manufacturers have also launched their own laser dust sensors. From 2014 to 2015 was the fastest-growing period of domestic laser dust sensors, and the products were gradually becoming mature, stable and mass-produced.

The domestic dust sensor market is indeed brilliant, and new products are coming out. Which manufacturer does not want to stand out in this great environment? However, chaotic flowers are gradually becoming attractive. From the point of view of the promotion of their products by various manufacturers, they are all focused on rendering the advantages of their own products. This is understandable; but sometimes they are unavoidably biased and lack of objectivity. This article starts with how to choose a suitable dust sensor to help mid- to high-end air purifier products to enhance user experience and create value, and talk about which kind of dust sensor should be used in the air purifier.

Correct understanding of laser dust sensor and infrared dust sensor

When it comes to lasers, the first thing that many people think of is the various and powerful laser weapons in science fiction movies. In fact, in addition to the military field, laser technology is widely used in medical, lighting, ranging, cutting and IT fields. For example, the popularity of VCD, DVD and Blu-ray products in recent years has benefited from the gradual development of laser technology.

The English word LASER for laser comes from the acronym of the English phrase "light amplification by stimulated radiation". Initially, LASER was simply transliterated into a laser in my country. In 1964, it was renamed "laser" under the suggestion of a famous Chinese scientist, Qian Xuesen. So, what exactly is a laser? Laser actually refers to the light generated by the special physical phenomenon of "stimulated radiation produces light amplification". Despite the obscure physics terminology, compared with ordinary visible light, laser has the characteristics of high coherence, strong directivity, good monochromaticity and high power density. To make an analogy, the light produced by the laser light source is like a chorus. All the voices are in a single tone and rhythmical; the light produced by the ordinary visible light source is like the noise of the tea shop, scum, no mess sequence. Therefore, the laser can be converged into a very concentrated parallel beam, and can maintain a small diffusion angle and a high power density over a long distance. Common lasers are generally divided into three categories: solid-state lasers, gas lasers, and semiconductor lasers (commonly known as laser LEDs). In the field of instrument-level laser particle counters, (helium-neon) gas lasers are generally used as light sources. In the field of dust sensors, due to cost constraints, laser LEDs are generally used as light sources. Infrared LEDs are light-emitting diodes with emission wavelengths in the infrared range. Common wavelengths are generally around 850nm to 940nm, and are widely used in medical, security, communications, remote control and sensing fields. Because the infrared LED emission wavelength is outside the visible spectrum, with the receiver of a specific spectrum, the impact of ambient light on the received signal can be greatly reduced. Thanks to the continuous maturity of infrared LED technology in recent years, infrared LED has the characteristics of long life, high emission efficiency, good monochromaticity and good directionality. This makes infrared LEDs widely used in the sensor field, especially in the dust sensor industry.

In the current PM 2.5 detection field of dust particles, two kinds of dust sensors are mainly used: infrared dust sensors and laser dust sensors. Some friends have questions about the difference between the two. Here, I will briefly introduce to you from five aspects.

1. Structure and principle

The structure and circuit of the dust sensor of infrared principle is relatively simple. The light source is an infrared LED light source. The airflow inlet and outlet are mainly heated by resistance to obtain hot airflow, and high levels are output when particles pass through. The output signal is only the PWM model.

The structure and circuit of the laser sensor are relatively complicated. The light source is a laser diode. The sampled air is driven by a fan or a blower, and is detected through a complex designed air duct. When the fine particles in the air enter the area where the laser beam is located, the laser light will be scattered; the scattered light is radiated at 360° in space. We placed the photodetector in an appropriate position so that it only receives the scattered light, and then passes the photodetector The photoelectric effect generates a current signal, and after the circuit is amplified and processed, the concentration value of fine particles can be obtained. The output signal is generally a serial output.

Second, price and cost

Infrared dust sensor has been maturely applied in the industry for many years, the market price is about 35-50 yuan, and the laser dust sensor is in the market price of 90-180 yuan.

The cost gap between the two is mainly due to the fact that the latter's material cost adds mechanisms such as laser generators and fans and requires complex circuit structures, and has a high technical threshold.

Three, measurement accuracy

The infrared principle dust sensor can only detect particles above 1 um, and the measurement accuracy is insufficient. Because the particle signal of infrared LED light scattering is weak, it only responds to large particles larger than 1 um, and only uses a heating resistor to drive the sample airflow. The number of samples is small, and the data calculation is completely handed over to the upper computer. The laser dust sensor can detect particles above 0.3 um. Because it comes with a high-performance CPU, it uses a fan or a blower to collect a large amount of data and analyze it through a professional particle counting algorithm. In summary, it has advantages over infrared dust sensors in terms of sampling number, data source, and algorithm.

4. Application

Due to insufficient accuracy, the infrared principle sensor is mainly used for industrial and mining dust, the detection object is large particle size, high concentration dust, the detection level is mg/m3, and the concentration of PM2.5 cannot be accurately measured.

The laser principle sensor is mainly used in the field of PM2.5 detection to quantify the quality of PM2.5 with precision. Can be embedded in household (car, handheld) air detectors, air purifiers. In addition, the laser principle sensor is also used in the fields of Internet of things data collection, environmental quality detection and other fields.

V. Development trend

Before the laser dust sensor entered the civilian field, infrared dust sensors were widely used in air purifiers. However, with the development of the air purifier industry and the large-scale production of laser dust sensors by some major manufacturers, the cost of laser dust sensors is gradually reduced, and the requirements of end customers for accurate measurement of air quality are also increasing. The use of laser principle sensors and accurate quantification of PM2.5 quality is an industry-recognized trend.