WhichofthefollowingstatementsaboutflowmetersisFALSE?以下关于流量计的哪种说法是错误的?()ATheVenturimeterhasfixedcrosssectionareas，butvaryingpressuredrop;whilerotameteristheopposite文丘里管利用恒定的横截面积和变动的压降来测量流量；转子流量计则相反