Electromagnetic flowmeter anti-electrochemical interference technology introduction

The measures taken by the electromagnetic flowmeter to improve the anti-electrochemical interference capability are mainly low-frequency rectangular wave excitation and dual-frequency excitation technology. The low-frequency rectangular wave excitation has the characteristics of DC excitation technology not generating eddy current effect and transformer effect (orthogonal interference), and has the power frequency sine wave excitation basically does not produce polarization effect, which is convenient for amplifying signal processing, and can avoid DC amplifier zero drift. , noise, stability and other issues, have better anti-interference performance. Low-frequency rectangular wave excitation has excellent zero stability. However, it is impossible to overcome mud interference and fluid noise interference when measuring the flow rate of liquid-solid two-phase conductive fluid containing fibers and solid particles such as mud and pulp. Research analysis shows that mud interference and flow noise have a spectral characteristic of 1/f. The amplitude is large at low frequencies and the amplitude is small at high frequencies. If high frequency low frequency rectangular wave excitation is used, the magnitude of mud interference can be greatly reduced. Therefore, increasing the excitation frequency helps to reduce mud interference and flow noise, and improves the signal-to-noise ratio of the sensor output signal. In summary, to ensure the zero stability of the electromagnetic flowmeter, it is best to use low-frequency rectangular wave excitation; in order to accurately measure the flow of liquid-solid two-phase conductive fluid and low-conductivity fluid, higher frequency must be used. Rectangular wave excitation. The method of using the dual-frequency rectangular wave excitation shown in Fig. 1 is the best solution.