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Electromagnetic flowmeter anti-interference solution introduction

How does the electromagnetic flowmeter resist interference? The sensor brings a lot of help to people, but when it comes to electromagnetic flowmeters, it is also widely used in the practical application of sensors.

1. Differential interference and elimination of power frequency interference

Differential interference and power frequency interference signals are often present in the signal, and low-pass filtering in the signal processing circuit is often difficult to completely filter out the power frequency interference. The company adopts synchronous sampling and power frequency compensation technology to suppress the power frequency interference caused by mixed power frequency interference and power frequency power frequency fluctuation in the flow signal potential, and effectively eliminate differential interference. Synchronous sampling technology, the sampling start time lags the excitation signal by 1/4 cycle, and the pulse width is an even multiple of the power frequency period. The differential interference is eliminated and the average value of the power frequency interference in the flow signal potential is equal to zero to eliminate the power frequency interference. The effect of frequency fluctuation compensation of power frequency power supply is to ensure the dynamic fluctuation of frequency, the excitation power supply and sampling pulse can be adjusted synchronously, realizing synchronous sampling technology and synchronous excitation technology, synchronous A/D conversion, reducing differential interference and power frequency The impact of interference.

2, zero drift elimination

The so-called zero drift is when the input signal of the sensor is zero, the output of the amplifier is not zero. The zero-drift signal will be transmitted between the circuits of each stage of amplification. After multi-stage amplification, it becomes a larger signal at the output. Because the useful signal output from the sensor is weak, the zero drift may overwhelm the useful signal, making the circuit impossible. normal work. Therefore, in order to suppress the zero drift, the differential circuit input of the three op amps is used to realize the weak signal acquisition of the large internal resistance to suppress the introduction of the common mode signal. The first-stage amplifier circuit uses a DC blocking capacitor to filter out the zero drift of the baseline to prevent the DC signal from being too large and exceeds the input range of the A/D conversion.

3. Other measures to remove interference

For the quadrature interference generated by the "transformer effect" of the electromagnetic flowmeter sensor, the "transfer zeroing method" is used to eliminate.

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