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This post was last edited by yuchenchf on 2017-3-31 07:53. As is well known, electromagnetic flowmeters are designed based on Faraday’s law of electromagnetic induction, and electromagnetic interference can affect the accuracy of the measurements taken by these flowmeters. So how can electromagnetic flowmeters resist such interference? I have summarized the following methods for reducing interference in electromagnetic flowmeters; I hope everyone will share their thoughts on this topic. 1. Elimination of differential interference and power-frequency interference Differential interference and power-frequency interference signals often exist simultaneously in a signal. It is often difficult for low-pass filters in signal processing circuits to completely remove the power-frequency interference. Our company employs synchronous sampling and power-frequency compensation techniques to suppress power-frequency interference that enters the potential of the flow signal, as well as interference caused by fluctuations in the power supply frequency, and to effectively eliminate differential interference. The synchronous sampling technique delays the start time of sampling by 1/4 cycle relative to the excitation signal. It uses a pulse width that is an even multiple of the power frequency cycle, thereby eliminating differential interference and ensuring that the average value of the power-frequency interference in the flow signal potential is zero, so as to reduce the impact of such interference. Frequency fluctuation compensation for the power supply ensures that the excitation source and the sampling pulses can be adjusted synchronously despite dynamic frequency variations, thus enabling true synchronous sampling and synchronous excitation as well as synchronous A/D conversion, and reducing the effects of differential and power-frequency interference. 2. Elimination of zero drift Zero drift refers to the situation where, when the input signal to the sensor is zero, the output of the amplifier is not also zero. The signal of zero-point drift is transmitted between the various amplification stages; after going through multiple stages of amplification, it becomes a stronger signal at the output. Since the useful signal generated by the sensor is weak, zero-point drift can overwhelm this useful signal, preventing the circuit from functioning properly. Therefore, to suppress zero-point drift, a three-op-amp differential circuit is used for input, enabling the acquisition of weak signals from high-impedance sources while preventing the introduction of common-mode signals. A DC-blocking capacitor is used after the first-stage amplification circuit to filter out baseline drift and prevent excessive DC signals from exceeding the input range of the A/D converter. 3. Other measures to eliminate interference: For the orthogonal interference caused by the \"transformer effect\" of the electromagnetic flowmeter sensors, the \"transmitter zeroing method\" is used to eliminate it. The above is my summary of the methods for reducing interference in electromagnetic flowmeters. If you have any additional suggestions, feel free to leave a comment so that we can improve together.