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Description of the three methods of electromagnetic flowmeter anti-interference

The English name of the flow meter is flowmeter, which is defined by the National Scientific and Technical Terminology Committee as a meter indicating the measured flow rate and/or the total amount of fluid in the selected time interval. Simply put, it is a meter used to measure the flow of fluid in a pipe or open channel.

The flowmeter is further divided into a differential pressure flowmeter, a rotameter, a throttle flowmeter, a slit flowmeter, a volumetric flowmeter, an electromagnetic flowmeter, an ultrasonic flowmeter, and the like. Classified by media: liquid flow meter and gas flow meter.

When using electromagnetic flowmeters, you may encounter interference, so how to resist interference? Today, I will introduce you to the three methods of electromagnetic flowmeter anti-interference.

1. Differential interference and power frequency interference cancellation signals often have differential interference and power frequency interference signals at the same time. Low-pass filtering in signal processing circuits is often difficult to completely filter out 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. Simultaneous sampling technique, sampling on

The initial time lags the excitation signal by 1/4 cycle, which adopts the pulse width as an even multiple of the power frequency period, eliminates the differential interference and makes the average value of the power frequency interference in the flow signal potential equal to zero, so as to eliminate the influence of power frequency interference; The frequency fluctuation compensation of the power supply is to ensure the dynamic fluctuation of the frequency. The excitation power supply and the sampling pulse can be adjusted synchronously, and the synchronous sampling technology and the synchronous excitation technology are realized, and the synchronous A/D conversion is realized.

Change, reducing the impact of differential interference and power frequency interference.

2, zero drift eliminates the so-called zero drift, that 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 zero drift

Shift, using the differential circuit input of the three op amps to achieve weak signal acquisition of large internal resistance to suppress the introduction of common mode signals. 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 orthogonal interference generated by the “transformer effect” of the electromagnetic flowmeter sensor, the “transfer zero method” is used to eliminate.

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