The contrast of dust infrared sensor and laser sensor

    At present,there are two main types of civil dust detection sensor.They respectively are infrared sensor(Shinyei,GE,Sharp)and laser sensor(Nova Fitness,Cubic Optoelectronics,Plantower).The former price range from 20 to 40 yuan,the latter is generally around 1 hundred yuan.So what is the difference between the two types of sensors?This article will analysis in detail.

Structure

    The structure of the infrared sensor is as follows:

    As can be seen from the figure look out,it's structure and circuit are very simple.The light source is the infrared led ligth source ,the inlet is also very simple without complex air duct design.Sampling the air by heating the resistance .The output is only the PWM,so simply to say the output is high level if there's particle through.  

Compare to infrared sensor the laser sensor is much more complex.The light source is laser diode,there's special design for the air flow in and out.Sampling the air through the fan or blower.The output is serial port output such as SDS011 and PWM output.

Data contrast

The data comparison among the dust sensor（PPD42NS）,laser detector(Dylos1100pro)and professional instrument of the scientific research .

Source

http://www.takingspace.org/make-your-own-aircasting-particle-monitor/

It's obvious that there's a great difference between the data of infrared sensor and the laser sensor.And the laser detecting data is very close to the professional instrument.

Here is the comparison data of the SDM805 and Thermo Scientific 5030(using for scientific reseach),shows a great correlation.However,the former is hundreds of yuan while the latter is worth 200 thousand yaun.

Analysis

    We can seen from the curve that the data of the laser sensor with good quality is credible ,but the data of the traditional infrared sensor shows a big difference.Because of using the source of led ,the infrared sensor can only scatter the big particles and only push sampling flow with heating resistance,sample number is less. Data calculation copletely depend on the upper mashine.However,the laser sensor with high performance CPU,collect a large amount data using a fan or blower.Through the professional particle counting algorithm analysis,so the sampling numbers ,data sources and the algorithm will gap away the infrared sensor.To be sure that the laser sensor can get a ore credible numerical,however the infrared sensor has a large error,even can not measure the PM2.5 particles,only can be seen as a toy.Now most of the purifier has adopt the infrared sensor ,but usually the ca only display a quality level not the value,even the quality levels of measurement are less accurate.The Synrad purifier has adopt laser sensor ,it's a trend.