The selection method of laser particle size analyzer

The selection method of laser particle size analyzer

1. The laser particle size analyzer has a wide measurement range and is suitable for a wide range of applications. Not only do we need to look at the range reported by the instrument, but we also need to consider how to detect small particle scattering<0.5 μ m>that exceeds the area of the main detector.

The approach is to directly detect the entire range, in order to ensure the consistency of background deduction. Mixing different methods of testing and then using a computer to create a graph will definitely bring errors.

2. Laser light sources generally use 2mW lasers. If the power is too low, the scattered light energy will be low, resulting in low sensitivity; In addition, gas light sources have shorter wavelengths and better stability than solid-state light sources. The larger the radius of the laser diffraction ring and the weaker the light intensity, the more likely the detector is to cause a decrease in the signal-to-noise ratio of small particles and miss detection. Therefore, the distribution detection 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 Miller theory of *

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

4. Accuracy and repeatability indicators

The higher the better. Adopting 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 50 watt tungsten lamps) 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 visits or inquiries from 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 to 1000 times per second. Generally speaking, the more times the cyclic scanning test is conducted, the better the accuracy of the average results, 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 also faster because the particles only pass through the sample area once.

The amount of samples that users need to process every day is also a factor that considers speed.

It can automatically align without the need to change lenses and can be automatically calibrated.

7. Ease of use and maintenance

This point is often overlooked before purchase, but in reality, it directly determines the efficiency and lifespan of the instrument. The method of understanding is to understand the structure of the instrument and the feedback from other existing users.

Is disassembly and cleaning convenient? The particle size analyzer is divided into two parts: the main unit and the disperser. The sample flow cell always needs to be cleaned regularly, and the cleaning interval depends on the nature of the sample. The instrument that combines the host and disperser often places the sample cell deep inside the instrument, making it cumbersome to remove and disassemble, and easily damaging the optical system.

8. Must meet the standard standards

The ISO13320 standard is the basic requirement for laser particle size analyzers. The use of non laser diffraction methods in measuring the distribution of submicron particles is not in compliance with standards.