Tìm hiểu công nghệ Trong phần này của cuốn sách chúng ta chuyển sự chú ý của chúng tôi để một cái nhìn sâu hơn tại quầy hạt, từ việc xây dựng cơ bản của thiết bị với các tính năng của hệ thống hoàn chỉnh đếm hạt. Quầy hạt được trình bày tổng quát trong phần này, trong khi ở Phần III cung cấp sản phẩm nhà sản xuất thực tế được trình bày. Các chương Phần II và III được thiết kế để chạy song song, cho phép crossreference dễ dàng. . | PART II Understanding the Technology In this part of the book we turn our attention to a more in-depth look at particle counters from the basic construction of the instrument to the features of the complete particle counting system. Particle counters are presented generically in this part while in Part III the actual manufacturer s product offerings are presented. The chapters for Parts II and III are designed to run in parallel to allow for easy crossreference. 73 2001 by CRC Press LLC CHAPTER 6 Specifications All instruments are designed for a specific task. Specifications are the measure of how well the instrument performs the various parts of that task. Some specifications are common to all types of instruments dimensions weight power requirements etc. and are easily understood. Specialized instruments have specifications that are unique to the task for which they are designed. In many cases common specification terms such as resolution and sensitivity must be understood in relation to the unique properties of the application. In this section the primary specifications employed for evaluating particle counter performance are defined and discussed. Understanding of these few specification parameters is essential to making informed decisions about particle counters. If these are not clear at first reading readers should refer back to this section as they continue through the book. It will become evident that these specification parameters are interrelated and will only be understood completely when the whole picture of particle counting is clear. A. SENSITIVITY Sensitivity is the smallest measurable amount that an instrument can detect. In the case of the particle counter this refers to the smallest particle size that can be reliably detected. The general rule in the industry is that a particle can be reliably detected and measured if it produces a signal with a minimum 2 to 1 signal-to-noise ratio. B. SIGNAL-TO-NOISE RATIO All electronic instruments are subject
