The pressure reading have characteristic of small deviation,excellent value precision,good stability and can communication with master computer through RS485 interface.

Based on the character analysis of RS485 interface,the hardware of RS485 network supervisory control system is designed and the operational principle of the system is analyzed in detail.

One control system structure on fieldbus divided into groups in grades and the application method of RS485 interface and MODEBUS protocols in the fieldbus control module is introduced,and the instance of the switch quantity I/O module design with sixteen channels is provided.

Adopting USB-RS485 interface could make up the disadvantage of data-acquisition-systems which adopt single USB bus or the RS485 bus or RS232 bus.

The system can perform network based monitoring and detecting with high accruacy data acquisition by means of these function modules for the SN75LBC184 transmitter/transceiver,USB-RS485 interface, chip controller, data acquisition software and communication protocol supporting, featuring easy, high speed, long distance, multi-point detecting,and hot inserting and pulling operation.

RS-485 standard bus interface is utilized to make the whole network had the capability of intercommunication between the measure instrument and computer.