We all know that PM2.5 is widely used in daily life, so do you know which band of laser diode is used to detect PM2.5 on traditional equipment? Let's take a look at it together.

Why does everyone love to use 650nm red light?

The scattering ability of 650nm is moderate, the wavelength is too long, the scattering is too weak, no fine particles can be seen, the wavelength is too short, the absorption is high, the cost is high, and it is not easy to do. 650nm belongs to a just right position, and the scattering effect is particularly obvious for particles of the size of PM2.5

It is also simple to equip the receiver with photodiode, and the red detector is easy to choose, with good response, low noise and low module cost.

Then why are people using 780nm or 850nm?

There are two main benefits of infrared laser:

The penetration is stronger, the scattering is more uniform, and the infrared stability will be better for some scenes with particularly discrete particle distribution.

The detector can use cheaper large-area silicon photodiode.

But the disadvantages are also obvious:

Scattering is weaker than red light. When the particles are very small, the sensitivity will decrease, and the signal processing will be more detailed. Some manufacturers' algorithms are not suitable for infrared band.

The above is the mainstream laser diode used in PM2.5 on the market. I hope it will help you after reading it.