200-560-000-113 VM600 VIBRO振动监测器

200-560-000-113 VM600  VIBRO振动监测器

200-560-000-113 VM600  VIBRO振动监测器

PLC的程序一般不能按事先设定的循环周期运行。PLC程序使从头到尾执行一次后又从头开始执行。（现在一些***PLC有所改进，不过对任务周期的数量还是有限制）而DCS可以设定任务周期。比如，快速任务等。同样是传感器的采样，压力传感器的变化时间很短，我们可以用200ms的任务周期采样，而温度传感器的滞后时间很大，我们可以用2s的任务采样周期。这样，DCS可以合理的调度控制器的资源。一般来讲，DCS惯常使用两层网络结构，一层为过程级网络，大部分DCS使用自己的总线协议，比如横河的Modbus、西门子和ABB的Profibus、ABB的CANbus等，这些协议均建立在标准串口传输协议RS232或RS485协议的基础上。现场IO模块，特别是模拟量的采样数据十分庞大，同时现场干扰因素较多，因此应该采用数据吞吐量大、抗干扰能力强的网络标准。基于RS485串口异步通讯方式的总线结构，符合现场通讯的要求。IO的采样数据经CPU转换后变为整型数据或实型数据，在操作级网络（***层网络）上传输。因此操作级网络可以采用数据吞吐量适中、传输速度快、连接方便的网路标准，同时因操作级网络一般布置在控制室内，对抗干扰的要求相对较低。因此采用标准以太网是选择。TCP/IP协议是一种标准以太网协议，一般我们采用100Mbit/s的通讯速率。PLC系统的工作任务相对简单，因此需要传输的数据量一般不会太大，所以常见的PLC系统为一层网络结构。过程级网络和操作级网络要么合并在一起，要不过程级网络简化成模块之间的内部链接。PLC不会或很少使用以太网。 从应用对象的规模上来说： PLC一般用在小型自控场所，比如设备的控制或少量的模拟量的控制及连锁，而大型的应用一般都是DCS。当然，这个概念不准确，但很直观，习惯上我们把大于600点的系统成为DCS，小于这个规模叫做PLC。

200-560-000-113 VM600  VIBRO振动监测器

Generally, the program of PLC can't run according to the preset cycle. The PLC program is executed once from the beginning to the end and then from the beginning. (Now some * * * PLCs have been improved, but there are still restrictions on the number of task cycles) and DCS can set task cycles. For example, quick tasks, etc. The same is the sampling of sensors. The change time of pressure sensor is very short, so we can sample with a duty cycle of 200ms, while the lag time of temperature sensor is very large, so we can sample with a duty cycle of 2 s.. In this way, DCS can reasonably schedule the resources of the controller. Generally speaking, DCS usually use two-layer network structure, one is process-level network, and most DCS use their own bus protocols, such as Modbus of Yokogawa, Profibus of Siemens and ABB, CANbus of ABB, etc. These protocols are based on standard serial port transmission protocol RS232 or RS485. The sampling data of the field IO module, especially the analog quantity, is huge, and there are many interference factors in the field, so the network standard with large data throughput and strong anti-interference ability should be adopted. The bus structure based on RS485 serial asynchronous communication mode meets the requirements of field communication. The sampled data of IO is converted into integer data or real data by CPU, and transmitted on the operation level network (* * * layer network). Therefore, the network standard of moderate data throughput, fast transmission speed and convenient connection can be adopted in the operation level network, and the requirements for anti-interference are relatively low because the operation level network is generally arranged in the control room. Therefore, adopting standard Ethernet is an option. TCP/IP protocol is a standard Ethernet protocol. Generally, we use the communication rate of 100 Mbit/s.. The task of PLC system is relatively simple, so the amount of data to be transmitted is generally not too large, so the common PLC system is a one-layer network structure. The process-level network and the operation-level network are either merged together, or the process-level network is simplified as an internal link between modules. PLC does not or seldom use Ethernet. From the scale of application objects: PLC is generally used in small automatic control places, such as equipment control or a small amount of analog control and interlocking, while large-scale applications are generally DCS. Of course, this concept is not accurate, but it is intuitive. Traditionally, we call a system larger than 600 points DCS, and a system smaller than this size PLC.

200-560-000-113 VM600  VIBRO振动监测器