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A Practical Guide to Particle Counting for Drinking Water Treatment - Chapter 14

Hiệu chuẩn hạt truy cập là một chủ đề mà có thể điền vào một cuốn sách của riêng mình. Các vấn đề hiệu chuẩn đã trở thành quan trọng hơn như hạt đếm được chấp nhận rộng rãi trong ngành công nghiệp xử lý nước uống. Mong muốn cho các tiêu chuẩn về tính chính xác cụ và qua so sánh các dữ liệu đã đặt một số lượng ngày càng tăng giám sát hiệu chuẩn truy cập hạt như hiện nay thực hành | CHAPTER 14 Calibration Particle counter calibration is a subject which could fill a book in itself. Calibration issues have become more important as particle counting has gained wider acceptance in the drinking water treatment industry. The desire for standards for both instrument accuracy and cross-comparison of data has placed an increasing amount of scrutiny on particle counter calibration as currently practiced. A. CALIBRATION AN INEXACT SCIENCE The foremost thing to keep in mind with regard to particle counter calibration is that it is at best an inexact science. There are several reasons this is so. The first is the nature of the particles being measured with the particle counter. Particles in the range of 1 to 2 pm are difficult enough to measure let alone produce accurate standards for. Particle counters are pushed to the limits of sensitivity just to measure these particles at all unlike turbidimeters which are usually calibrated at a concentration well into the middle of their operating range. The high sensitivity of the particle counter to tiny microscopic particles makes it difficult to avoid contamination. At present only size calibration is performed as a standard practice. The standards used are polystyrene latex PSL beads which can be produced to within a few percent of the desired size. Some of the drawbacks to these materials are that they are perfectly spherical unlike the actual particles found in the water supply and are composed of a substance not found in natural water sources. On the whole these problems are not insurmountable and not even frustrating if one keeps in mind the value of particle counting as a water quality optimization tool. B. CALIBRATION MATERIALS Sizing standards currently in use in drinking water particle counting are PSL spheres. The most prominent supplier of these standards for drinking water treatment 131 2001 by CRC Press LLC 132 A PRACTICAL GUIDE TO PARTICLE COUNTING is Duke Scientific Corp. of Palo Alto CA. These .