1, particle size measurement range The particle size range is wide, suitable for a wide range of applications. Not only to look at the range reported by their instruments, but to see how the small particle scattering 〈0.5μm〉 beyond the area of the main detector is detected.
The best route is full-range direct detection, which ensures the consistency of background deduction. The mixture of different methods of testing, and then computer fitting to synthesize a map, certainly bring errors.
2, the laser light source is generally used 2mW laser, 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, the stability is better than the solid light source. Detector because the larger the radius of the laser diffraction halo, the weaker the light intensity, it is very easy to cause small particles to reduce the signal-to-noise ratio and leakage detection, so the distribution of small particles to detect the instrument can be reflected in the good or bad. The development of the detector has gone through several stages of circular, semi-circular and fan-shaped.
3, whether to use the full Mie theory
Because the Mie theory of light dispersion is very complex, the amount of data processing, so some manufacturers ignore the particles themselves refractive and absorption and other optical properties, the use of approximate Mie theory, resulting in the scope of application of the limitations of the probability of leakage detection increased and so on.
4, accuracy and repeatability indicators
The higher the better. NIST standard particle detection is used.
5, stability
Instrument stability, including the stability of the optical path and the stability of the dispersion system and the impact of the surrounding environment. Generally speaking, the selection of gas lasers, the use of optical platforms to help the stability of the optical path. Internal heat-generating components (e.g., 50-watt tungsten lamp) will affect the light path surrounding environment.
Stability indicators in the manufacturer's instrument description is not available, the user can only rely on the structure of the instrument to judge and visit or ask other long-time users to judge.
6, scanning speed
Scanning speed can improve data accuracy, repeatability and stability.
Different manufacturers of instruments with different scanning speeds, from 1 time / second to 1000 times / second. Generally speaking, the more cycle scanning test times, the better the accuracy of the average results, so the higher the speed is better; jet dry and spray even more demanding the higher the speed is better; free-fall dry method is not fast, but due to the particles only through the sample area once, the speed is also faster than some of the good.
The amount of samples a user needs to process per day is also a factor in considering speed.
It can be auto-centered without the need to change lenses and can be auto-corrected.
7, ease of use and maintenance
On this point, before the purchase is often overlooked, but in fact directly determines the use of the instrument efficiency and life. The way to understand is to understand the structure of the instrument and the reflection of other existing users.
Disassembly, cleaning is convenient: particle size instrument is divided into the host and disperser two parts. And the sample flow cell always need regular cleaning, cleaning interval depends on the nature of the sample. The host and disperser into one instrument will often be the sample cell deep inside the instrument, remove and disassemble are very cumbersome, and very easy to touch the optical system.
8, whether in line with international standards
ISO13320 standard is the basic requirements of the laser particle size analyzer. But not all manufacturers in accordance with the implementation of the standard. In the process of measuring the distribution of submicron particles, the use of non-laser diffraction method is not in line with the standard.
Summary: from the world's production of laser particle sizer product performance, the British Malvern company's recognition of the product is relatively high, but the high price of the product, taking into account the cost-effective, domestic particle sizer manufacturers such as Zhuhai Europe and the United States, such as the company's production of the product is enough to meet the user's requirements, the price is cheaper than the foreign products, as a reference to the user's choice.