The Design Of Electromagnetic Flowmeter Based On ADuC812 Chip

As a tool for measuring liquid flow, electromagnetic flowmeter (EMF) is widely used in industrial production. We have some achievements in the research of electromagnetic flowmeter. But the skill we produce the transducer of the electromagnetic flowmeter is not versed enough. The network communication interfaces generally is RS485 or RS232 serial interface, networking and communication ability was poor.To fund fieldbus industry control system, it demands that all of the system should have the function of fieldbus controlling. The HART protocol provides a backward compatible solution for smart instrument communication as both analog and digital communication signals are transmitted simultaneously on the same wiring. Research HART protocol applied to the electromagnetic flowmeter is necessary. It is important for us to raise the level of control of electromagnetic flowmeter. On the base of studying, analyzing and comparing the key technologies of electromagnetic flowmeter. We present the design of electromagnetic flowmeter which is based on HART protocol.This thesis first introduces the working principle of electromagnetic flowmeter. Based on the analysis of flow measurement, we study the main issues to be resolved in the design process deeply. Such as the choice of excitation frequency; stable signal reference point; serial mode interference and frequency interference suppression; flow measurement point selection and so on.Introducing the design of the electromagnetic flowmeter hardware system, lays stress on analyzing the conversion and amplifying circuit, wave occurring circuit, the analog-digital conversion circuit, the keyboard display interface circuit, the communicating interface circuit and the anti-interference circuit. Focus on the hardware circuit in the signal acquisition amplifying circuitry, excitation amplifier circuit, communication interface circuit system anti-jamming circuit. Select ADuC812 data acquisition chip for the micro-controller to realize the control of each functional module. Adopt a synchronization V/F conversion chip (AD652) to gather the voltage signal from transducer, so that we can get high precision. In the communicating circuit, choosing HART signal proprietary modem chip (HT2015) to realize the digital signal communication, not disturbing 4~20mA simulate signals. Realize the intelligent and bus-based instrument.After complete the design, we debug various functional modules of the system, and give the results. Basically realized the expected functions and requirements and completed the design of intelligent electromagnetic flowmeter system.