窄带滤波微流量电磁流量计的相关技术

Related technologies of narrowband filter low-velocity flow electromagnetic flowmeter

微流量信号是叠加着多种噪声干扰的弱信号,为了准确提取流速信号,在电磁流量计中采用窄带滤波信号调理技术,滤除高次谐波,取出信号基波,再经相敏解调、低通滤波消除微分噪声和同相噪声,提高微流量信号的信噪比.根据窄带滤波对交变磁场的要求,提出并制作每个周期内激磁电流平均值恒定的恒均值电流源.对其在环境温度、电网电压发生变化时的稳定性进行了理论分析和实测验证.实际应用证明,可将电磁流量计测量下限扩展到0.002m3/h,实现微流量准确测量.

To extract the low-velocity flow signal accurately, we adopted the narrowband filter in signal processing in the electromagnetic flowmeter to filter out high-order harmonic and extract fundamental wave. Then we used phase sensitive demodulation and low-pass filter to reduce differential noise and phase noise, which improved the signal-to-noise ratio （SNR） of the low-velocity flow signal. According to the requirement of narrowband filter for ahemating magnetic field, we manufactured the invariable average value current source. Its stability was validated by theoretical analysis and actual measurement when the ambient temperature and electric network voltage changed. Application proves that this technology can expand the measurement limit of flowmeter to 0. 002 m^3/h and achieve accurate measurement of low-velocity flow.