Laser particle size analyzer is recognized as the most advanced and fastest particle testing instrument in the world. There are many manufacturers of laser particle size analyzer at home and abroad, and there are many kinds of products. How can we choose a suitable laser particle size analyzer?
1、 Understand your needs:
The items to be clarified are as follows:
(1) According to the amount of money at our disposal, we can decide whether to choose imported equipment or domestic equipment: generally, the price of imported equipment is more than 400000 yuan. The price of domestic products ranges from tens of thousands to hundreds of thousands.
(2) According to the nature of the tested sample, determine whether to buy dry or wet particle size analyzer: the dispersion mode of laser particle size analyzer is divided into dry method and wet method. If a suitable dispersion medium (water or other liquid) can not react with the tested sample, it is recommended to use wet particle size analyzer, with stable test results and low price. If it is difficult to find a suitable dispersing medium due to the special properties of the sample, the dry particle size analyzer is recommended.
(3) According to the general distribution range of test samples, choose the instrument model suitable for the test range of your own samples: the larger the test range, the higher the price. Generally speaking, if you choose an instrument slightly wider than the sample distribution range, you can. Most of the laser particle sizers on the market span 3-4 orders of magnitude, but the sample distribution of most industrial tests is only within one order of magnitude. If the sample distribution is narrow and the test range of ultra wide range is selected, the accuracy will be reduced just like weighing a bean on a scale. Some domestic manufacturers have developed products for grading test, which can adjust the gear according to the sample situation to solve this problem to a certain extent.
(4) According to the use, choose the type of particle size analyzer: users should not blindly follow the trend, choose high-end models, if only put into the factory for routine product testing, you do not need to buy the latest products, old products often after years of improvement, mature structure, stable test results, and low price. If the test task is heavy, we should choose automatic intelligent products, which can greatly reduce the workload of testers. Most of the high-end products are prepared for research-oriented customers such as universities or scientific research institutes. Most of these products are widely distributed, with high precision and complex structure, and they are often expensive.
2、 Select the manufacturer with technical strength:
Laser particle size analyzer is a kind of high-tech instrument products, which requires high technical strength of manufacturers. Before selecting products, manufacturers should be selected. Generally, manufacturers with technical foundation, R & D ability and strong professionalism are more reliable. Generally, small-scale manufacturers are not recommended. They are not only immature in technology, but also likely to close down in a few years, Without after-sales maintenance, the instrument is a pile of scrap iron.
3、 Several key test points of the product:
Laser particle sizer has several key test points
(1) Laser selection: one of the important components of laser particle size analyzer, mainly He-Ne laser and semiconductor laser. Among them, the performance of He-Ne laser is better than that of semiconductor laser, and the cost is much higher than that of semiconductor laser. The problem of poor unidirectionality of semiconductor laser has a great influence on the stability of test results. Therefore, it is recommended that users choose He-Ne laser.
(2) Photodetectors: the types of photodetectors used in domestic products are similar, generally half ring type, dot matrix type, etc. the advantage of half ring type is that it can achieve high detection accuracy with less channels. Moreover, when the ring is broken, it can be operated temporarily, which has little influence on the test results. The dot matrix detector is an old detector type, which is less used now.
(3) Instrument structure topic: it is mainly divided into integral type and split type. Integral type is to integrate the distributed system and the test system into one and operate cooperatively. Split type is that the distributed system is independent of the test system. The tester needs to operate the distributed system first, disperse the samples, and then lead the dispersed samples into the test system through the pipeline for testing. The disadvantage is that the collaborative manipulation is not good, the heavier particles are easy to precipitate in the pipeline, the cleaning is inconvenient and has a certain impact on the test results. Now the integral structure of the instrument is the development direction, most of the imported products use the integral structure, and the domestic products are slowly developing to the integral structure.
(4) Optical path design topic: optical path design is the basis for the development of laser particle size analyzer. The advantage of imported products is not only in the manufacturing process, but also in the design level of optical path. Most domestic manufacturers now use simple parallel optical path design. It is understood that the products launched by Jinan micro nano company use convergent Fourier transform optical path. This kind of light path is a more advanced light path, which can obtain a wider scattering angle and has a certain advantage in improving the test accuracy.
4、 Basic knowledge of particle testing
In the actual test, the accuracy is relative, and the repeatability is perfect: in the actual particle test, we can not evaluate the “correct” or “incorrect” of the laser particle size analyzer test results, because the samples are irregular shape, and the test results compared with them are only obtained by another kind of instrument, We can only say that the test result of instrument a is correct compared with that of instrument B, but we can’t say that the test result of instrument a is correct or incorrect. Many testers always like to compare with Marvin’s. as long as it is consistent, it is correct, and if it is not, it is incorrect. This is really a misunderstanding. The standard to consider whether the instrument is good or bad is repeatability. For a certain kind of sample, if the difference between the previous and the next test results is small, it means that the instrument is stable and has good repeatability. If the difference is large, it means that the test effect of the instrument is not good.
5、 Field test
It is best to send samples for field test before selection. Due to the different properties of samples, some instruments are not versatile and may have large deviation for some samples.
Editor in charge: GT