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How to generate a small signal of electromagnetic flowmeter

How is the electromagnetic signal small signal generated?

The electromagnetic flowmeter is based on Faraday's law of electromagnetic induction, which calculates the fluid flow by measuring the induced electromotive force of the conductive fluid in the magnetic field. The electromagnetic flowmeter usually consists of two parts: the transmitter and the converter. After the flow rate of the measured medium is converted into an induced potential by the transmitter, the potential signal is converted into a unified standard signal (4~20mA output) by the converter, so that Use instructions, records, or use with an electric unit combination meter. Electromagnetic flowmeters have errors and are susceptible to interference in actual measurement sites and process flows, such as the "small-signal" phenomenon, mainly because of the following problems in use:

1. Due to external vibration or large magnetic field interference, when there is no medium flow, external vibration and other signals act on the sensor, introducing a “false flow” signal, which is also accumulated when the signal is higher than the metering lower limit of the meter.

2. The surface of the electrode adheres to a layer of insulation, is disturbed by the outside world, or the mA signal sent by the electrode has a zero drift during the amplification and conversion process, causing the signal to deviate from the normal value, thereby causing an error.

3. When the pump starts, the liquid cuts the magnetic lines through the flowmeter to generate the flow signal. These liquids are finally used by the subsequent links. The flow measurement value is valid and should be accumulated; when the pump stops, there will be in the pipeline. A small amount of liquid reflux, reverse cutting magnetic lines of force, also produces small signals, but these liquids are not used by actual production, and the flow meter will still send signals to the PLC for sampling accumulation, which will cause large errors.

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