基于WorldFIP现场总线的智能差压变送器的研发

Development of Smart Pressure Transmitter Based on WorldFIP Fieldbus Technology

为了将WorldFIP现场总线技术引进到现场测量控制仪表通信中,以现场底层测量控制仪表差压变送器为代表,介绍了具有现场总线通信机制的智能化仪表的开发方法.首先介绍了现场总线智能差压变送器相对与传统4～20mA差压变送器各方面具有的优势,然后对该差压变送器工作原理、整体结构做出详细介绍.其次分析了电容膜盒式差压传感器的测量特点,并针对这种传感器设计了测量模块的电路,根据测量精度和微控制器接口的要求,利用可编程逻辑器件实现设计要求.最后将支持WorldFIP现场总线协议的通信微控制器MICROFIP为核心的通信圆卡的硬件结构特点作出介绍.实验证明,测量电路的测量功能满足设计要求,输出测量脉冲稳定,同时通信圆卡可以实现基于WorldFIP总线协议机制的变量传送功能,设计达到预期目的.

In order to introduce WorldFIP fieldbus protocol to the communication among real-time measuring and controlling instruments, this paper presents a development approach of intelligent instruments with fieldbus communication by taking the pressure difference transmitter for realtime controlling and measuring instruments as an exampie. At first this paper highlights the advantages of fieldbus intelligent pressure difference transmitter over traditional ones communicating with 4-20mA signals, and then introduces the operational principle and its overall structure. Next this paper analyses the measuring principle of capacitance cell pressure difference sensor and designs the measuring circuit module for the sensor. The main circuit is a Complex Programmable Logic Device that satisfies the requests of measuring precision and temporal logic of MCU interface. In the end the paper presents the communication round card which consists of MICROFIP and communication controller obeying WorldFIP fieldbus protocol, as the core. Experiments prove that the measuring circuit meets the designing requirement and the communication rotmd card can transmit variables based on WorldFIP fieldbus protocol.