HART Multiplexer Research And Hardware System Design

HART smart devices are world widely used relying on its advantage of compatible with (4～20)mA analog signals and digital communication capability. The capability of digital communication allows it tof achieve online monitoring, diagnosis, calibration and so on. Constructing HART digital communication network, realizing centralized management of HART device, could make full use of device’s intelligent functions, and could improve the efficiency of equipment management. This is effective means to protect system reliably operation. Therefore, developing the I/O of digital communication network, HART multiplexer, has great significance.Researching a variety of smart intelligent device and I/O module, accesses to their methods of communicating with HART multiplexer and packet format; studying several companies HART multiplexer products, gets its working principles and methods. Describe the comparison of different product’s parameters. Describe the detail design of HART multiplexer hardware circuit; include the isolation circuit of the analog and HART signal, the multiplexer, and so on. Give the sampling time distribution of the HART multiplexer. Give a simple description of the power system and RS-485module.Under the premise of complete hardware system, a HART multiplexer proposed software architecture was described. Describe the data stream of the software in the (4-20)mA analog signal channel and in HART digital channel. Introduce the Timing Diagram of the work between the ADC and multiplexers in the analog channel. A flow chart describes the HART physical layer.In order to ensure HART multiplexer hardware systems meet the design requirements, and finally did a test on the hardware circuit, including power stability test, the accuracy of the analog channel signal value test, HART path normal testing. The final test results show that the HART multiplexer hardware system can complete the acquisition of the analog signal and the HART communication between PC and HART instruments, the design has achieved initial results.