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Nối tiếp dữ liệu đầu ra Phần lớn các quầy hạt cung cấp dữ liệu nối tiếp, hoặc sản lượng, kỹ thuật số. Dữ liệu nối tiếp sản lượng cung cấp cho một số lượng lớn hơn nhiều của thông tin được gửi thông qua một đầu ra duy nhất. Nhiều đơn vị có thể chia sẻ một đường dây thông tin liên lạc duy nhất. Đây là loại dữ liệu được thu thập và "giải mã" với một máy tính. | CHAPTER 10 Serial Data Output The majority of particle counters provide serial data or digital output. Serial data output provides for a much greater amount of information to be sent through a single output. Many units can share a single communication line. This type of data is collected and decoded with a computer. A. BASICS OF SERIAL COMMUNICATIONS Serial communications refers to the fact that data are transmitted in sequential order one bit at a time. Each bit is represented by a voltage level which represents a high or low logic state. Bits are arranged into bytes that are arranged in words. This computer jargon can be a bit confusing and is not essential to grasping the ideas presented here. Basically serial means in sequential order or one at a time. In a typical particle counting system several particle counters are connected together on a single twisted shielded-pair cable. This cable is then connected to a computer or other data collection system. The data collection system DCS will collect data from each of the particle counters in sequence. The data are sent out from the particle counter as a stream of bits which is organized or encoded according to a specific pattern or protocol. The DCS can decode the data from this stream of bits and translate the data into particle counts alarms etc. The key to the whole process is the speed at which serial data can be transmitted. The data from 30 or more particle counters can be transmitted sequentially in a matter of a few seconds. Each particle counter is given a unique address which allows the DCS to identify and communicate with it. A particle counter is polled by the DCS at regular intervals usually once every count cycle. The data from each particle counter are then transferred to the DCS to be displayed and archived. Since a lot of data are being transmitted at a high rate of speed it is inevitable that some data will be lost. Data loss can be the result of interference from induced 99 2001 by CRC Press LLC
