Research And Design Of Electromagnetic Flowmeter Excited By Alternate Dual Frequency Wave

As a main type of flow measurement instruments, electromagnetic flowmeter has been widely used in various fields, such as in the flied of water supply and drainage, petroleum, chemical, food, medical, environmental protection, aviation, navigation and agricultural irrigation, besides, the demand in domestic market is growing dramatically. Low frequency square wave excitation is the main stream of electromagnetic flowmeter at home and abroad, this kind of electromagnetic flowmeter is poor in noise immunity and it’s output exists swing phenomenon. So designing an electromagnetic flowmeter that can measure the liquid-solid two-phase flow is very significant.On the basis of analyzing some principles of electromagnetic flowmeter, this paper proposes a solution which is based on STM32 MCU with dual frequency excitation. In order to achieve dual frequency precise excitation, designs the circuit of constant-current control based on linear power, controlling excitation drive was completed by H bridge circuit, and uses internal PWM timer of STM32 produce excitation control pulse. Aiming at measured signal is millivolt level and has all kinds of interference, etc. This paper designs signal processing circuit with high precision, high performance instrumentation amplifier and A/D converter, which could achieve signal conversion, and improve the testing precision of electromagnetic flowmeter. In order to meet the network requirements, designs the CAN interface and USB interface. Using the USB interface can realize local transmission and the CAN interface could build network in industrial field can achieve network control. The software part uses the modularization method and software flowcharts are illustrated. Upon the premise of hardware and software design finished, all kinds of interferences in this system are analyzed, and then the solution of anti-interference is put forward.The electromagnetic flowmeter excited by dual frequency, designed in this paper, can improve the stability of zero effectively; meanwhile, strengthen anti-interference performance and improve the response speed. The one could be applied in serious environment such as the pulp measurement and coal-water slurry measurements. Therefore, the electromagnetic flowmeter this paper designed has a practical application value and development prospect.