抄録
Being capable of highly accurate measurement, P.D. flowmeters have been used conventionally in such applications as custody transfer and meter proving. For more accurate measurements, servo P.D. flowmeters, in which the serve motor drives the rotors so that the pressure difference across the rotors are appropriately controlled, have taken over ordinary P.D. flowmeters. Further requirements on these meters are, however, becoming tough year after year. Demands on high precision measurement of multiple liquid types with different properties, wider range-ability, and higher response are recently required.
