Data acquisition system soft DCSPLC - Solutions - Huaqiang Electronic Network

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The data acquisition system simply collects the live signal into the control computer, and there is no loop control function block in the computer. It is only for the display of the human machine interface. It should be said that it is relatively simple. On the hardware structure, it can be divided into *** or two levels. They are I/O boards, controllers, and human-machine interfaces. Simple I/O board and human machine interface. However, some industries have some special requirements. For example, the control system of a power plant often separates the boiler control and data acquisition systems. Boiler control uses dcs, while others use data acquisition systems (DAS). There are also many manufacturers in the world that produce data acquisition systems. In general, the data acquisition system is technically no problem, but there are some special requirements in the power plant. There are some points in the power plant that need to record the sequence of events. There is a fast interrupt function (usually 2 hours). The number of such points is small, and the amount of switching is about 100 points. The resolution of the tablet should be on the order of milliseconds. Its difficulty is event sequence recording (SOE). There should be a function to store historical data on the tablet. When the display unit is called up, the time sequence of the events can be displayed. SOE (SEQUENCEOFEVENT) is manufactured by a special manufacturer. Some DCS systems dedicated to power plants also have such functions.
The more widely used data acquisition system is the OPTO22 product of the United States, with one small module and one small module with switching quantity (DI, DO) and analog quantity (AI, AO). There are 42 small modules with different voltage levels for users to choose. When in use, the small module is mounted on a large board (ie, B1 board, B2 board), analog quantity 8 pieces/block board, switch quantity 16 pieces/block board, B1, B2 board except these small modules, Serial communication port. Install the two boards on a shelf and install the shelves in the cabinet. The CRT-based human-machine interface runs on the WINDOWS platform. The monitoring software with Modbus driver software is installed. Previously, the PAREGON software was used. Now there are fewer people. Now I use FIX and INTOUCH. The human-machine interface can read the I/O signals from the small modules and display them on the CRT. . More than 20 plants in the United States produce this similar product. It is the same grade as the STD bus. The products of the STD bus are gradually withdrawing from the market due to the large amount of engineering work of the user.
In some purely collected systems, OPTO products are used more. The main advantage is the low maintenance. If closed-loop control is required, a controller similar to a PC (LC4) is added between the HMI and the I/O. There are some function blocks in the controller that can be configured with various control strategies. In general, because the number of function blocks is relatively small, there are still relatively few OPTO22s as large control systems with thousands of I/O points.
The most widely used module for OPTO switching is the isolation module that acts as a DCS switching input module. Keep the DCS itself from lightning strikes. Due to the relatively simple manufacturing process, the domestic module users are also very useful, but the price is less than half of the import.
In the early 1990s, due to the development of computer technology, it was suggested that ordinary microcomputers (PCs) were very mature, and both the computing speed and the memory could meet the control requirements. It is divided into front and back operations. DCS or plc do not need a controller, the function code and ladder diagram in DCS and PLC controller are transplanted into the PC of NT operating system, and software migration is quite difficult. It is directly connected to the I/O board by the microcomputer. Because the control algorithm already exists in the PC, the PC acts both as a human-machine interface and as a controller. Some people call them soft DCS and soft PLC. American AB company has a soft PLC. Each PC is connected by Ethernet. So far, the application is still not very broad. Some small systems use SOFTDCS and SOFTPLC.