Selection method for laser particle size analyzer:

1. Wide measurement range and granularity range, suitable for a wide range of applications

Not only should we look at the range reported by the instrument, but also at the small particle scattering<0.5 that exceeds the area of the main detector μ m> How to detect.

The approach is to conduct full range direct testing to ensure consistency in background deductions. Mixing different methods of testing and then using a computer to synthesize a graph will definitely bring errors.

2. Laser light source

Generally, a 2mW laser is used. If the power is too small, the scattered light energy will be low, resulting in low sensitivity; In addition, gas light sources have longer wavelengths and better stability than solid light sources. The detector, due to the larger radius of the laser diffraction halo and the weaker light intensity, is prone to a decrease in the signal-to-noise ratio of small particles and miss detection. Therefore, detecting the distribution of small particles can reflect the quality of the instrument. The development of detectors has gone through several stages: circular, semi-circular, and fan-shaped.

3. Using the complete Mie's theory

Due to the complexity of the Mie scattering theory and the large amount of data processing, some manufacturers ignore the optical properties of particles such as refraction and absorption, and adopt approximate Mie theory, which limits its applicability and increases the probability of missed detections.

4. Accuracy and repeatability indicators

The higher, the better. Using NIST standard particle detection.

5. Stability

The stability of the instrument includes the stability of the optical path, the stability of the dispersion system, and the influence of the surrounding environment. Generally speaking, choosing a gas laser and using an optical platform can help stabilize the optical path. Internal heating components (such as a 50 watt tungsten lamp) will affect the surrounding environment of the light path.

The stability index is not included in the manufacturer's instrument instructions, and users can only judge based on their judgment of the instrument structure and visiting or inquiring with other users who have used it for a long time.

6. Scanning speed

Fast scanning speed can improve data accuracy, repeatability, and stability.

The scanning speed of instruments from different manufacturers varies, ranging from 1 time/second to 1000 times/second. Generally speaking, the more times a cyclic scan test is conducted, the better the accuracy of the average result, so the higher the speed, the better; Spray dry method and spray require higher speed; Although the free fall dry method is not fast, it is still faster because particles only pass through the sample area once.