自动化仪表课件1.pdf

Vol. 41 ~(). 5 第41 岳第5 期 哈尔滨工业大学学报 2 009 年5 月 JOURNAL OF HARBIN INSTlTUTE OF TECHNOLOGY May 2009 窄带滤波微流 电磁流 计的相关技术 牛滨，陈松景，庞兵，梁原华 (哈尔演理 l 大学测控技术与通信[程(:院，阶尔滨 15∞80 ， niubir而205@ 126. (om) 摘 要做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，在电磁流量计中是用窄带滤 波信号调理技术，滤除高攻谐波，取出信号基渍，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Ho 根据窄带滤波对吏变磁场的要求，提出井制作每个周期内激磁电流平均值恒定的恒均值 电流却对其在环境温度、电网电压发生变化时的稳定性进行了理论分析如实测验证实际应用证明.可将电 磁流量计测量下限扩展歪1 0 ∞2 旷/h ，实现做进量准确测量 关键词·窄带滤波:微流量测量，电磁流量叶，激瞌 t\è流辉 中图分类号， TH814 文献标识码 A 文章编号: 0367 -6234(2ω9)05 -0148-04 Related technologies of narrowband filter low-velocity flow electromagnetic flowmeter NIU Bin , CHEN Song-jin日， PANG Bing , LIANG Yuan-hua ( ColI ~g俨 of Measure-control Technology and Communicalion Engineering , Harbin University ()f Science and Technology , Harbin 15∞80 ， China , niubin0205@ 126ωm) Abstract: To extract the low-velocity f1 0w signal accurately , we adopted the narrowband filter in signal pro- cessing in the electromagnetic flowmeter 10 filtt号r out high-order harrnonic and extraet funclamental wave. Then we used phase sensitive demodulation and low-pa脑 filter to reduce differential noise and phase noi町， which improved the signal-to-noise ratio (SNR) of the low-velocity flow signal. Aceording to the requirement of nar rowband filter for alternating magnetie field , we manufactured the invariable average value current source. Its 叫ahility was validated by theoretical analysis and actual measurement when the ambient temperature and el时­ tric network voltage changed. Application proves that this technology can expand the measurement limit