Permanent magnetism type excitation method in use for electromagnetic flowmeter

Abstract

The invention discloses a permanent magnet excitation method for electromagnetic flow meter. Said method includes the following steps: the permanent magnet can produce working magnetic field which is respectively perpendicular to conductive fluid flow-rate direction and electrode connected-wire direction, flow signal can be detected by electrode and fed into preamplifier portion, the preamplifier portion can be used for making impedance matching and differential amplification, then the obtained signal is fed into signal processing finally the processed signal can be fed into microprocessor portion, said microprocessor can be used for making calculation of flow, said flow value can be fed into display portion to display said flow value. It is simple in structure, can effectively detect flow signal and can effectively raise response speed of electromagnetic flow meter.

Description

technical field [0001] The invention relates to an excitation method for an electromagnetic flowmeter, in particular to a permanent magnet excitation method for an electromagnetic flowmeter. Background technique [0002] The electromagnetic flowmeter is based on Faraday's law of electromagnetic induction. Its working principle is that when the conductive fluid moves and cuts the magnetic field lines in the working magnetic field, an induced electric potential e is generated at both ends of the fluid. Its direction is determined by the right-hand rule, and its magnitude is related to the magnetic induction of the magnetic field. The strength B is proportional to the length L of the fluid in the magnetic field and the moving speed u of the conductor. If B, L and u are perpendicular to each other, then e=Blu. [0003] The normal operation of the electromagnetic flowmeter requires a certain strength of the magnetic field. At present, there are three main methods of generating m...

AI Technical Summary

Problems solved by technology

[0007] The low-frequency rectangular wave excitation technology has changed the morphological characteristics of power frequency interference. Using power frequency synchronous sampling technology, the electromagnetic flowmeter has a better ability to resist power frequency interference, and the measurement accuracy and zero point stability are higher. However, the frequency of low-frequency rectangular wave excitation Generally, it is 1 / 2 to 1 / 32 of the power frequency, which sacrifices the response speed of the electromagnetic flowmeter while obtaining zero point stability

[0008] The excitation current signal frequency of the three-value low-frequency rectangular wave excitation technology is 1 / 8 of the power frequency frequency, and adopts the law of positive-zero-negative-zero-positive. Its biggest feature is to correct the zero point when the excitation current is zero, so it has Excellent zero point stability, but the response speed of the electromagnetic flowmeter is low

However, the dual-frequency excitation technology is complex and costly, and currently only a few manufacturers have mastered it

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