Information collection also is called data collection. It is an interface that collects data produced outside the system and transmits them into the system. Data collection technology is widely used in various fields.

As regard to data collection system, the collected data has been transformed into various physical quantity indicated in electrical signal, such as temperature, water level, wind speed, pressure, and so on. The electrical signal representing physical quantity can be analog signal or digital signal. Data is collected through sampling. Sampling can be described as repeated collecting data from the same point at fixed space of time. The collected data can be instantaneous value, or eigenvalue produced within a given period of time. Accurate sampling is the foundation of data collection. Sampling can be carried out in the form of contact type or non-contact type. There are many detecting component available for you to use in sampling. To guarantee the correctness of collected data, no matter what type of detecting device or sampling method is chosen, the precondition for selection is the state of measurand and the ambience of the measurand should not be influenced. Regarding petrochemical industry, the main data collection methods applied include:

For a device in which DCS system is applied, the DCS system is used as center of the device and LAN (local area network) is used as the foundation of the device. In most cases, each such device is equipped with a server that is used in real –time data collection. Relevant process data of the DCS system is collected and saved in the form of OPC (OLE for process control).A real-time database main server is placed in network central equipment room which is used for storing real-time process data produced by all devices. A web server is also required which can be used as real-time data release center. Any computer user who has been authorized to be connected with LAN can browse real-time production information of device via browser.

For decentralized assistant production equipment, a remote I/O station can be positioned in operation field. Process signal to be monitored can be transmitted to relevant signal card of remote I/O station with reference to type of signal. Then, these signals are transmitted to PLC in the equipment room via optical fiber. During the transmission, MOBUS and FROFIBUS protocol are applied. At last, with the help of PLC monitoring software, these real-time process data is transmitted to data collection network of the device in the form of OPC

For situation where few sampling points is limited scattered in a wide area, the data collected in field can be directly transmitted to control room. Monitoring is realized on a computer. And the computer will transmit data into network in higher level via serial port and in the form of DDE.