Develop Of Fieldbus-Based Base-Station-Type Instrument For Measurement And Control

DCS system needs to carry on communication through a large number of cables and control rooms, but the cost is relatively high in three stories of structure, can't be interconnected because standards of every company are different. As everyone knows, fieldbus technology is the effective way of solving above-mentioned problems. But the output signals of the scene measurement instrument do not accord with the fieldbus agreement, if change or add the transform interface will cause the cost increase widely. The existing base-station type measures instrument does not still possess the function of control, and not accord with the fieldbus communication protocol. For this reason, this text develops one support international fieldbus control standard intelligent base-station type measurement and control instrument.The job of this text includes developing the software and hardware two parts of measurement and control instrument and control of the host computer. Measurement and control instrument is a one-chip computer system, and there are the functions of measurement and controlled, is regard as putting the lower computer in the scene. A computer of industry and serial communication interface form's the control host computer.Measurement and control the system of this text has 32 analog signal input passways, 32 signals circulates to sample once within 2 seconds. Its measure precision is superior to 0.2%. Each passway is arbitrarily linked the sensors of 5 kinds by established which include Ptl00 thermal resistance: 0-300 degrees Centigrade; thermocouple of the Model K: 100-800 degrees Centigrade; thermocouple of the Model E: 100-800 degrees Centigrade; 4-20mA electric current signal; 1-5V voltage signal. In addition, there is 8 on-off signal data input (DI) passways (24 VDCs light separate); 8 on-off signal isolated data output (DO) passways (contact without power, 1A/220V); 4 analog signal data output passways(4~20mA), every of them can be set as a certain analog signal's close ring control output passway. The systematic load's range is 0 .- 300 . Adopting the serial-bus of RS-485 (two-wires-system), the communication protocol accords with PROFIBUS Fieldbus standard. And this text system have power breakdown protect function, all parameters setting by the upper computer and the state of DO passwaycan be protected when they are in the state of power breakdown. The life-span of the battery is 10 years.Fieldbus-based base-station-type instrument for measurement and control has following virtue; operation simple and convenient, multiple functions, the precision and dependability are relatively high. The systematic fabrication cost is reasonable, economical and practical, especially suitable to use widely in the medium and small-scale power station...