How to judge the advantages and disadvantages of laser particle size analyzer?

To judge the pros and cons of the laser particle size analyzer, mainly look at the following aspects:

1. The particle size measurement range is wide, suitable for a wide range of applications. Not only depends on the range reported by its instrument, but also on how to detect the small particle scattering <0.5μm> beyond the area of ​​the main detector.

The best way is to directly detect the full range, so as to ensure the consistency of the background deduction. The mixed test of different methods, and then fitted into a map by computer, will definitely bring errors.

2. The laser light source generally uses a 2mW laser. If the power is too small, the scattered light energy is low, resulting in low sensitivity. In addition, the gas light source has a short wavelength and stability is better than the solid light source. Because the larger the laser diffraction halo radius, the weaker the light intensity, it is easy to miss the signal-to-noise ratio of small particles and miss detection, so the distribution of small particles can reflect the quality of the instrument. The development of the detector has gone through several stages of circle, semicircle and sector.

3. Whether to use complete Mie theory

Because Mie's dispersion theory is very complicated and the amount of data processing is large, some manufacturers ignore the optical properties of the particles themselves such as refraction and absorption, and use the approximate Mie theory, resulting in problems such as limited application range and increased probability of missed detection.

4. Accuracy and repeatability indicators

The higher the better. Adopt NIST standard particle detection.

5. Stability

The stability of the instrument includes the stability of the optical path and the stability of the dispersion system and the influence of the surrounding environment. Generally speaking, gas lasers and optical platforms are used to help stabilize the optical path. Internal heat-generating components (such as a 50-watt tungsten lamp) will affect the environment around the light path.

The stability index is not included in the manufacturer's instrument description. The user can only judge by judging the structure of the instrument and visiting or asking other users who have used it for a long time.

6. Scanning speed

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

Different manufacturers have different scanning speeds, ranging from 1 time / second to 1000 times / second. Generally speaking, the greater the number of cyclic scan tests, the better the accuracy of the average result, so the higher the speed, the better; the spray dry method and spray require higher speed, the better; although the free fall dry method is not fast, but Since the particles only pass through the sample area once, the speed is faster and better.

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

It can be automatically centered, no need to change the lens, and can be corrected automatically.

7. Ease of use and maintenance

On this point, it is often overlooked before buying, but in fact directly determines the efficiency and life of the instrument. The method of understanding is the understanding of the structure of the instrument and the reflection of other existing users.

Is it convenient to disassemble and clean: the particle size analyzer is divided into two parts: the host and the diffuser. The sample flow cell always needs to be cleaned regularly, and the cleaning interval depends on the nature of the sample. For an instrument combining a host and a disperser, the sample cell is often placed deep inside the instrument. It is cumbersome to take out and disassemble, and it is very easy to damage the optical path system.

8. Whether it meets international standards

The ISO13320 standard is the basic requirement for a laser particle size analyzer. But not all manufacturers comply with this standard. In measuring the distribution of submicron particles, the use of non-laser diffraction methods does not meet the standards.

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