The working principle of electromagnetic flowmeter is Faraday's law of electromagnetic induction. The conductive liquid flows in the magnetic field and cuts the magnetic field lines, creating an induced electric potential. The expression is: E=KBLv. In the formula, B is the magnetic induction intensity; L is the distance between the measuring electrodes; v is the average velocity of the fluid to be measured moving in the magnetic field; K is the proportionality constant.
Electromagnetic flowmeter is mainly composed of transmitter (also known as primary device, detector or sensor), converter (also known as secondary device or converter) and flow display instrument. The transmitter converts the flow rate of the liquid to be measured into the corresponding induced potential. The function of the converter is to amplify and convert the millivolt level voltage signal proportional to the flow rate output by the electromagnetic flow transmitter into a standard DC current, voltage or pulse signal output that can be received by the industrial instrument, so as to cooperate with the instrument and the regulator. , to realize the indication, recording and calculation of the flow.
The first comment in this paper is how to complete the intelligentization of the electromagnetic flowmeter converter, and the interface between the converter and the HART communication protocol. Once the traditional electromagnetic flowmeter is turned on, it can automatically carry out successive measurements, but the outside world cannot control its operation status. It can only operate according to the normal operation method at the time of production, so the function is relatively simple and the operation is relatively rigid, which cannot satisfy the sensitivity of modern measurement. real-time demand. The so-called intelligence of electromagnetic flowmeter means that after the flowmeter is turned on, it can measure in the form of procedural rules, and during operation, it can withstand external intentions and make corresponding adjustments at any time according to external instructions. The function of the flowmeter is relatively complete, and can be controlled by humans, and the operation is relatively sensitive. For example, when the electromagnetic flowmeter is measured at the excitation frequency of 30 Hz, the measuring person wants to change the excitation frequency to 60 Hz according to the actual situation of the flow, and he can press a certain button of the electromagnetic flowmeter according to the product manual. In order to make the appearance according to his intention to change, and traditional flow meter can not do this. Of course, the completion of this intelligence is based on the single-chip system. The purpose of the so-called HART protocol is to integrate various types of surfaces on the basis of intelligence, and the same command can control multiple surfaces, so that the surfaces can communicate with each other and work harmoniously.